imgui/imgui_internal.h

// dear imgui, v1.54 WIP
// (internals)

// You may use this file to debug, understand or extend ImGui features but we don't provide any guarantee of forward compatibility!
// Set:
//   #define IMGUI_DEFINE_MATH_OPERATORS
// To implement maths operators for ImVec2 (disabled by default to not collide with using IM_VEC2_CLASS_EXTRA along with your own math types+operators)

#pragma once

#ifndef IMGUI_VERSION
#error Must include imgui.h before imgui_internal.h
#endif

#include <stdio.h>      // FILE*
#include <math.h>       // sqrtf, fabsf, fmodf, powf, floorf, ceilf, cosf, sinf
#include <limits.h>     // INT_MIN, INT_MAX

#ifdef _MSC_VER
#pragma warning (push)
#pragma warning (disable: 4251) // class 'xxx' needs to have dll-interface to be used by clients of struct 'xxx' // when IMGUI_API is set to__declspec(dllexport)
#endif

#ifdef __clang__
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wunused-function"        // for stb_textedit.h
#pragma clang diagnostic ignored "-Wmissing-prototypes"     // for stb_textedit.h
#pragma clang diagnostic ignored "-Wold-style-cast"
#endif

//-----------------------------------------------------------------------------
// Forward Declarations
//-----------------------------------------------------------------------------

struct ImRect;
struct ImGuiColMod;
struct ImGuiStyleMod;
struct ImGuiGroupData;
struct ImGuiMenuColumns;
struct ImGuiDrawContext;
struct ImGuiTextEditState;
struct ImGuiMouseCursorData;
struct ImGuiPopupRef;
struct ImGuiWindow;
struct ImGuiWindowSettings;

typedef int ImGuiLayoutType;        // enum: horizontal or vertical             // enum ImGuiLayoutType_
typedef int ImGuiButtonFlags;       // flags: for ButtonEx(), ButtonBehavior()  // enum ImGuiButtonFlags_
typedef int ImGuiItemFlags;         // flags: for PushItemFlag()                // enum ImGuiItemFlags_
typedef int ImGuiNavHighlightFlags; // flags: for RenderNavHighlight()          // enum ImGuiNavHighlightFlags_
typedef int ImGuiSeparatorFlags;    // flags: for Separator() - internal        // enum ImGuiSeparatorFlags_
typedef int ImGuiSliderFlags;       // flags: for SliderBehavior()              // enum ImGuiSliderFlags_

//-------------------------------------------------------------------------
// STB libraries
//-------------------------------------------------------------------------

namespace ImGuiStb
{

#undef STB_TEXTEDIT_STRING
#undef STB_TEXTEDIT_CHARTYPE
#define STB_TEXTEDIT_STRING             ImGuiTextEditState
#define STB_TEXTEDIT_CHARTYPE           ImWchar
#define STB_TEXTEDIT_GETWIDTH_NEWLINE   -1.0f
#include "stb_textedit.h"

} // namespace ImGuiStb

//-----------------------------------------------------------------------------
// Context
//-----------------------------------------------------------------------------

#ifndef GImGui
extern IMGUI_API ImGuiContext* GImGui;  // Current implicit ImGui context pointer
#endif

//-----------------------------------------------------------------------------
// Helpers
//-----------------------------------------------------------------------------

#define IM_PI           3.14159265358979323846f

// Helpers: UTF-8 <> wchar
IMGUI_API int           ImTextStrToUtf8(char* buf, int buf_size, const ImWchar* in_text, const ImWchar* in_text_end);      // return output UTF-8 bytes count
IMGUI_API int           ImTextCharFromUtf8(unsigned int* out_char, const char* in_text, const char* in_text_end);          // return input UTF-8 bytes count
IMGUI_API int           ImTextStrFromUtf8(ImWchar* buf, int buf_size, const char* in_text, const char* in_text_end, const char** in_remaining = NULL);   // return input UTF-8 bytes count
IMGUI_API int           ImTextCountCharsFromUtf8(const char* in_text, const char* in_text_end);                            // return number of UTF-8 code-points (NOT bytes count)
IMGUI_API int           ImTextCountUtf8BytesFromStr(const ImWchar* in_text, const ImWchar* in_text_end);                   // return number of bytes to express string as UTF-8 code-points

// Helpers: Misc
IMGUI_API ImU32         ImHash(const void* data, int data_size, ImU32 seed = 0);    // Pass data_size==0 for zero-terminated strings
IMGUI_API void*         ImFileLoadToMemory(const char* filename, const char* file_open_mode, int* out_file_size = NULL, int padding_bytes = 0);
IMGUI_API FILE*         ImFileOpen(const char* filename, const char* file_open_mode);
static inline bool      ImCharIsSpace(int c)            { return c == ' ' || c == '\t' || c == 0x3000; }
static inline bool      ImIsPowerOfTwo(int v)           { return v != 0 && (v & (v - 1)) == 0; }
static inline int       ImUpperPowerOfTwo(int v)        { v--; v |= v >> 1; v |= v >> 2; v |= v >> 4; v |= v >> 8; v |= v >> 16; v++; return v; }

// Helpers: Geometry
IMGUI_API ImVec2        ImLineClosestPoint(const ImVec2& a, const ImVec2& b, const ImVec2& p);
IMGUI_API bool          ImTriangleContainsPoint(const ImVec2& a, const ImVec2& b, const ImVec2& c, const ImVec2& p);
IMGUI_API ImVec2        ImTriangleClosestPoint(const ImVec2& a, const ImVec2& b, const ImVec2& c, const ImVec2& p);
IMGUI_API void          ImTriangleBarycentricCoords(const ImVec2& a, const ImVec2& b, const ImVec2& c, const ImVec2& p, float& out_u, float& out_v, float& out_w);

// Helpers: String
IMGUI_API int           ImStricmp(const char* str1, const char* str2);
IMGUI_API int           ImStrnicmp(const char* str1, const char* str2, size_t count);
IMGUI_API void          ImStrncpy(char* dst, const char* src, size_t count);
IMGUI_API char*         ImStrdup(const char* str);
IMGUI_API char*         ImStrchrRange(const char* str_begin, const char* str_end, char c);
IMGUI_API int           ImStrlenW(const ImWchar* str);
IMGUI_API const ImWchar*ImStrbolW(const ImWchar* buf_mid_line, const ImWchar* buf_begin); // Find beginning-of-line
IMGUI_API const char*   ImStristr(const char* haystack, const char* haystack_end, const char* needle, const char* needle_end);
IMGUI_API int           ImFormatString(char* buf, size_t buf_size, const char* fmt, ...) IM_FMTARGS(3);
IMGUI_API int           ImFormatStringV(char* buf, size_t buf_size, const char* fmt, va_list args) IM_FMTLIST(3);

// Helpers: Math
// We are keeping those not leaking to the user by default, in the case the user has implicit cast operators between ImVec2 and its own types (when IM_VEC2_CLASS_EXTRA is defined)
#ifdef IMGUI_DEFINE_MATH_OPERATORS
static inline ImVec2 operator*(const ImVec2& lhs, const float rhs)              { return ImVec2(lhs.x*rhs, lhs.y*rhs); }
static inline ImVec2 operator/(const ImVec2& lhs, const float rhs)              { return ImVec2(lhs.x/rhs, lhs.y/rhs); }
static inline ImVec2 operator+(const ImVec2& lhs, const ImVec2& rhs)            { return ImVec2(lhs.x+rhs.x, lhs.y+rhs.y); }
static inline ImVec2 operator-(const ImVec2& lhs, const ImVec2& rhs)            { return ImVec2(lhs.x-rhs.x, lhs.y-rhs.y); }
static inline ImVec2 operator*(const ImVec2& lhs, const ImVec2& rhs)            { return ImVec2(lhs.x*rhs.x, lhs.y*rhs.y); }
static inline ImVec2 operator/(const ImVec2& lhs, const ImVec2& rhs)            { return ImVec2(lhs.x/rhs.x, lhs.y/rhs.y); }
static inline ImVec2& operator+=(ImVec2& lhs, const ImVec2& rhs)                { lhs.x += rhs.x; lhs.y += rhs.y; return lhs; }
static inline ImVec2& operator-=(ImVec2& lhs, const ImVec2& rhs)                { lhs.x -= rhs.x; lhs.y -= rhs.y; return lhs; }
static inline ImVec2& operator*=(ImVec2& lhs, const float rhs)                  { lhs.x *= rhs; lhs.y *= rhs; return lhs; }
static inline ImVec2& operator/=(ImVec2& lhs, const float rhs)                  { lhs.x /= rhs; lhs.y /= rhs; return lhs; }
static inline ImVec4 operator+(const ImVec4& lhs, const ImVec4& rhs)            { return ImVec4(lhs.x+rhs.x, lhs.y+rhs.y, lhs.z+rhs.z, lhs.w+rhs.w); }
static inline ImVec4 operator-(const ImVec4& lhs, const ImVec4& rhs)            { return ImVec4(lhs.x-rhs.x, lhs.y-rhs.y, lhs.z-rhs.z, lhs.w-rhs.w); }
static inline ImVec4 operator*(const ImVec4& lhs, const ImVec4& rhs)            { return ImVec4(lhs.x*rhs.x, lhs.y*rhs.y, lhs.z*rhs.z, lhs.w*rhs.w); }
#endif

static inline int    ImMin(int lhs, int rhs)                                    { return lhs < rhs ? lhs : rhs; }
static inline int    ImMax(int lhs, int rhs)                                    { return lhs >= rhs ? lhs : rhs; }
static inline float  ImMin(float lhs, float rhs)                                { return lhs < rhs ? lhs : rhs; }
static inline float  ImMax(float lhs, float rhs)                                { return lhs >= rhs ? lhs : rhs; }
static inline ImVec2 ImMin(const ImVec2& lhs, const ImVec2& rhs)                { return ImVec2(ImMin(lhs.x,rhs.x), ImMin(lhs.y,rhs.y)); }
static inline ImVec2 ImMax(const ImVec2& lhs, const ImVec2& rhs)                { return ImVec2(ImMax(lhs.x,rhs.x), ImMax(lhs.y,rhs.y)); }
static inline int    ImClamp(int v, int mn, int mx)                             { return (v < mn) ? mn : (v > mx) ? mx : v; }
static inline float  ImClamp(float v, float mn, float mx)                       { return (v < mn) ? mn : (v > mx) ? mx : v; }
static inline ImVec2 ImClamp(const ImVec2& f, const ImVec2& mn, ImVec2 mx)      { return ImVec2(ImClamp(f.x,mn.x,mx.x), ImClamp(f.y,mn.y,mx.y)); }
static inline float  ImSaturate(float f)                                        { return (f < 0.0f) ? 0.0f : (f > 1.0f) ? 1.0f : f; }
static inline void   ImSwap(int& a, int& b)                                     { int tmp = a; a = b; b = tmp; }
static inline void   ImSwap(float& a, float& b)                                 { float tmp = a; a = b; b = tmp; }
static inline int    ImLerp(int a, int b, float t)                              { return (int)(a + (b - a) * t); }
static inline float  ImLerp(float a, float b, float t)                          { return a + (b - a) * t; }
static inline ImVec2 ImLerp(const ImVec2& a, const ImVec2& b, float t)          { return ImVec2(a.x + (b.x - a.x) * t, a.y + (b.y - a.y) * t); }
static inline ImVec2 ImLerp(const ImVec2& a, const ImVec2& b, const ImVec2& t)  { return ImVec2(a.x + (b.x - a.x) * t.x, a.y + (b.y - a.y) * t.y); }
static inline ImVec4 ImLerp(const ImVec4& a, const ImVec4& b, float t)          { return ImVec4(a.x + (b.x - a.x) * t, a.y + (b.y - a.y) * t, a.z + (b.z - a.z) * t, a.w + (b.w - a.w) * t); }
static inline float  ImLengthSqr(const ImVec2& lhs)                             { return lhs.x*lhs.x + lhs.y*lhs.y; }
static inline float  ImLengthSqr(const ImVec4& lhs)                             { return lhs.x*lhs.x + lhs.y*lhs.y + lhs.z*lhs.z + lhs.w*lhs.w; }
static inline float  ImInvLength(const ImVec2& lhs, float fail_value)           { float d = lhs.x*lhs.x + lhs.y*lhs.y; if (d > 0.0f) return 1.0f / sqrtf(d); return fail_value; }
static inline float  ImFloor(float f)                                           { return (float)(int)f; }
static inline ImVec2 ImFloor(const ImVec2& v)                                   { return ImVec2((float)(int)v.x, (float)(int)v.y); }
static inline float  ImDot(const ImVec2& a, const ImVec2& b)                    { return a.x * b.x + a.y * b.y; }
static inline ImVec2 ImRotate(const ImVec2& v, float cos_a, float sin_a)        { return ImVec2(v.x * cos_a - v.y * sin_a, v.x * sin_a + v.y * cos_a); }
static inline float  ImLinearSweep(float current, float target, float speed)    { if (current < target) return ImMin(current + speed, target); if (current > target) return ImMax(current - speed, target); return current; }
static inline ImVec2 ImMul(const ImVec2& lhs, const ImVec2& rhs)                { return ImVec2(lhs.x * rhs.x, lhs.y * rhs.y); }

// We call C++ constructor on own allocated memory via the placement "new(ptr) Type()" syntax.
// Defining a custom placement new() with a dummy parameter allows us to bypass including <new> which on some platforms complains when user has disabled exceptions.
struct ImNewPlacementDummy {};
inline void* operator   new(size_t, ImNewPlacementDummy, void* ptr) { return ptr; }
inline void  operator   delete(void*, ImNewPlacementDummy, void*)   {} // This is only required so we can use the symetrical new()
#define IM_PLACEMENT_NEW(_PTR)              new(ImNewPlacementDummy(), _PTR)
#define IM_NEW(_TYPE)                       new(ImNewPlacementDummy(), ImGui::MemAlloc(sizeof(_TYPE))) _TYPE
template <typename T> void IM_DELETE(T*& p) { if (p) { p->~T(); ImGui::MemFree(p); p = NULL; } }

//-----------------------------------------------------------------------------
// Types
//-----------------------------------------------------------------------------

// Internal Drag and Drop payload types. String starting with '_' are reserved for Dear ImGui.
#define IMGUI_PAYLOAD_TYPE_DOCKABLE         "_IMDOCK"   // ImGuiWindow* // [Internal] Docking/tabs

enum ImGuiButtonFlags_
{
    ImGuiButtonFlags_Repeat                 = 1 << 0,   // hold to repeat
    ImGuiButtonFlags_PressedOnClickRelease  = 1 << 1,   // return true on click + release on same item [DEFAULT if no PressedOn* flag is set]
    ImGuiButtonFlags_PressedOnClick         = 1 << 2,   // return true on click (default requires click+release)
    ImGuiButtonFlags_PressedOnRelease       = 1 << 3,   // return true on release (default requires click+release)
    ImGuiButtonFlags_PressedOnDoubleClick   = 1 << 4,   // return true on double-click (default requires click+release)
    ImGuiButtonFlags_FlattenChildren        = 1 << 5,   // allow interactions even if a child window is overlapping
    ImGuiButtonFlags_AllowItemOverlap       = 1 << 6,   // require previous frame HoveredId to either match id or be null before being usable, use along with SetItemAllowOverlap()
    ImGuiButtonFlags_DontClosePopups        = 1 << 7,   // disable automatically closing parent popup on press // [UNUSED]
    ImGuiButtonFlags_Disabled               = 1 << 8,   // disable interactions
    ImGuiButtonFlags_AlignTextBaseLine      = 1 << 9,   // vertically align button to match text baseline - ButtonEx() only // FIXME: Should be removed and handled by SmallButton(), not possible currently because of DC.CursorPosPrevLine
    ImGuiButtonFlags_NoKeyModifiers         = 1 << 10,  // disable interaction if a key modifier is held
    ImGuiButtonFlags_NoHoldingActiveID      = 1 << 11,  // don't set ActiveId while holding the mouse (ImGuiButtonFlags_PressedOnClick only)
    ImGuiButtonFlags_PressedOnDragDropHold  = 1 << 12,  // press when held into while we are drag and dropping another item (used by e.g. tree nodes, collapsing headers)
    ImGuiButtonFlags_NoNavFocus             = 1 << 13   // don't override navigation focus when activated
};

enum ImGuiSliderFlags_
{
    ImGuiSliderFlags_Vertical               = 1 << 0
};

enum ImGuiColumnsFlags_
{
    // Default: 0
    ImGuiColumnsFlags_NoBorder              = 1 << 0,   // Disable column dividers
    ImGuiColumnsFlags_NoResize              = 1 << 1,   // Disable resizing columns when clicking on the dividers
    ImGuiColumnsFlags_NoPreserveWidths      = 1 << 2,   // Disable column width preservation when adjusting columns
    ImGuiColumnsFlags_NoForceWithinWindow   = 1 << 3,   // Disable forcing columns to fit within window
    ImGuiColumnsFlags_GrowParentContentsSize= 1 << 4    // (WIP) Restore pre-1.51 behavior of extending the parent window contents size but _without affecting the columns width at all_. Will eventually remove.
};

enum ImGuiSelectableFlagsPrivate_
{
    // NB: need to be in sync with last value of ImGuiSelectableFlags_
    ImGuiSelectableFlags_Menu               = 1 << 3,   // -> PressedOnClick
    ImGuiSelectableFlags_MenuItem           = 1 << 4,   // -> PressedOnRelease
    ImGuiSelectableFlags_Disabled           = 1 << 5,
    ImGuiSelectableFlags_DrawFillAvailWidth = 1 << 6
};

enum ImGuiSeparatorFlags_
{
    ImGuiSeparatorFlags_Horizontal          = 1 << 0,   // Axis default to current layout type, so generally Horizontal unless e.g. in a menu bar
    ImGuiSeparatorFlags_Vertical            = 1 << 1
};

// FIXME: this is in development, not exposed/functional as a generic feature yet.
enum ImGuiLayoutType_
{
    ImGuiLayoutType_Vertical,
    ImGuiLayoutType_Horizontal
};

enum ImGuiAxis
{
    ImGuiAxis_None = -1,
    ImGuiAxis_X = 0,
    ImGuiAxis_Y = 1
};

enum ImGuiPlotType
{
    ImGuiPlotType_Lines,
    ImGuiPlotType_Histogram
};

enum ImGuiDataType
{
    ImGuiDataType_Int,
    ImGuiDataType_Float,
    ImGuiDataType_Float2
};

enum ImGuiInputSource
{
    ImGuiInputSource_None = 0,
    ImGuiInputSource_Mouse,
    ImGuiInputSource_Nav,
    ImGuiInputSource_Count_,
};

enum ImGuiDir
{
    ImGuiDir_None    = -1,
    ImGuiDir_Left    = 0,
    ImGuiDir_Right   = 1,
    ImGuiDir_Up      = 2,
    ImGuiDir_Down    = 3,
    ImGuiDir_Count_
};

enum ImGuiNavHighlightFlags_
{
    ImGuiNavHighlightFlags_TypeDefault  = 1 << 0,
    ImGuiNavHighlightFlags_TypeThin     = 1 << 1,
    ImGuiNavHighlightFlags_AlwaysDraw   = 1 << 2
};

// 2D axis aligned bounding-box
// NB: we can't rely on ImVec2 math operators being available here
struct IMGUI_API ImRect
{
    ImVec2      Min;    // Upper-left
    ImVec2      Max;    // Lower-right

    ImRect()                                        : Min(FLT_MAX,FLT_MAX), Max(-FLT_MAX,-FLT_MAX)  {}
    ImRect(const ImVec2& min, const ImVec2& max)    : Min(min), Max(max)                            {}
    ImRect(const ImVec4& v)                         : Min(v.x, v.y), Max(v.z, v.w)                  {}
    ImRect(float x1, float y1, float x2, float y2)  : Min(x1, y1), Max(x2, y2)                      {}

    ImVec2      GetCenter() const                   { return ImVec2((Min.x + Max.x) * 0.5f, (Min.y + Max.y) * 0.5f); }
    ImVec2      GetSize() const                     { return ImVec2(Max.x - Min.x, Max.y - Min.y); }
    float       GetWidth() const                    { return Max.x - Min.x; }
    float       GetHeight() const                   { return Max.y - Min.y; }
    ImVec2      GetTL() const                       { return Min; }                   // Top-left
    ImVec2      GetTR() const                       { return ImVec2(Max.x, Min.y); }  // Top-right
    ImVec2      GetBL() const                       { return ImVec2(Min.x, Max.y); }  // Bottom-left
    ImVec2      GetBR() const                       { return Max; }                   // Bottom-right
    bool        Contains(const ImVec2& p) const     { return p.x     >= Min.x && p.y     >= Min.y && p.x     < Max.x && p.y     < Max.y; }
    bool        Contains(const ImRect& r) const     { return r.Min.x >= Min.x && r.Min.y >= Min.y && r.Max.x < Max.x && r.Max.y < Max.y; }
    bool        Overlaps(const ImRect& r) const     { return r.Min.y <  Max.y && r.Max.y >  Min.y && r.Min.x < Max.x && r.Max.x > Min.x; }
    void        Add(const ImVec2& p)                { if (Min.x > p.x)     Min.x = p.x;     if (Min.y > p.y)     Min.y = p.y;     if (Max.x < p.x)     Max.x = p.x;     if (Max.y < p.y)     Max.y = p.y; }
    void        Add(const ImRect& r)                { if (Min.x > r.Min.x) Min.x = r.Min.x; if (Min.y > r.Min.y) Min.y = r.Min.y; if (Max.x < r.Max.x) Max.x = r.Max.x; if (Max.y < r.Max.y) Max.y = r.Max.y; }
    void        Expand(const float amount)          { Min.x -= amount;   Min.y -= amount;   Max.x += amount;   Max.y += amount; }
    void        Expand(const ImVec2& amount)        { Min.x -= amount.x; Min.y -= amount.y; Max.x += amount.x; Max.y += amount.y; }
    void        Translate(const ImVec2& v)          { Min.x += v.x; Min.y += v.y; Max.x += v.x; Max.y += v.y; }
    void        ClipWith(const ImRect& r)           { if (Min.x < r.Min.x) Min.x = r.Min.x; if (Min.y < r.Min.y) Min.y = r.Min.y; if (Max.x > r.Max.x) Max.x = r.Max.x; if (Max.y > r.Max.y) Max.y = r.Max.y; }
    void        Floor()                             { Min.x = (float)(int)Min.x; Min.y = (float)(int)Min.y; Max.x = (float)(int)Max.x; Max.y = (float)(int)Max.y; }
    void        FixInverted()                       { if (Min.x > Max.x) ImSwap(Min.x, Max.x); if (Min.y > Max.y) ImSwap(Min.y, Max.y); }
    bool        IsFinite() const                    { return Min.x != FLT_MAX; }
};

// Stacked color modifier, backup of modified data so we can restore it
struct ImGuiColMod
{
    ImGuiCol    Col;
    ImVec4      BackupValue;
};

// Stacked style modifier, backup of modified data so we can restore it. Data type inferred from the variable.
struct ImGuiStyleMod
{
    ImGuiStyleVar   VarIdx;
    union           { int BackupInt[2]; float BackupFloat[2]; };
    ImGuiStyleMod(ImGuiStyleVar idx, int v)     { VarIdx = idx; BackupInt[0] = v; }
    ImGuiStyleMod(ImGuiStyleVar idx, float v)   { VarIdx = idx; BackupFloat[0] = v; }
    ImGuiStyleMod(ImGuiStyleVar idx, ImVec2 v)  { VarIdx = idx; BackupFloat[0] = v.x; BackupFloat[1] = v.y; }
};

// Stacked data for BeginGroup()/EndGroup()
struct ImGuiGroupData
{
    ImVec2      BackupCursorPos;
    ImVec2      BackupCursorMaxPos;
    float       BackupIndentX;
    float       BackupGroupOffsetX;
    float       BackupCurrentLineHeight;
    float       BackupCurrentLineTextBaseOffset;
    float       BackupLogLinePosY;
    bool        BackupActiveIdIsAlive;
    bool        AdvanceCursor;
};

// Simple column measurement currently used for MenuItem() only. This is very short-sighted/throw-away code and NOT a generic helper.
struct IMGUI_API ImGuiMenuColumns
{
    int         Count;
    float       Spacing;
    float       Width, NextWidth;
    float       Pos[4], NextWidths[4];

    ImGuiMenuColumns();
    void        Update(int count, float spacing, bool clear);
    float       DeclColumns(float w0, float w1, float w2);
    float       CalcExtraSpace(float avail_w);
};

// Internal state of the currently focused/edited text input box
struct IMGUI_API ImGuiTextEditState
{
    ImGuiID             Id;                         // widget id owning the text state
    ImVector<ImWchar>   Text;                       // edit buffer, we need to persist but can't guarantee the persistence of the user-provided buffer. so we copy into own buffer.
    ImVector<char>      InitialText;                // backup of end-user buffer at the time of focus (in UTF-8, unaltered)
    ImVector<char>      TempTextBuffer;
    int                 CurLenA, CurLenW;           // we need to maintain our buffer length in both UTF-8 and wchar format.
    int                 BufSizeA;                   // end-user buffer size
    float               ScrollX;
    ImGuiStb::STB_TexteditState   StbState;
    float               CursorAnim;
    bool                CursorFollow;
    bool                SelectedAllMouseLock;

    ImGuiTextEditState()                            { memset(this, 0, sizeof(*this)); }
    void                CursorAnimReset()           { CursorAnim = -0.30f; }                                   // After a user-input the cursor stays on for a while without blinking
    void                CursorClamp()               { StbState.cursor = ImMin(StbState.cursor, CurLenW); StbState.select_start = ImMin(StbState.select_start, CurLenW); StbState.select_end = ImMin(StbState.select_end, CurLenW); }
    bool                HasSelection() const        { return StbState.select_start != StbState.select_end; }
    void                ClearSelection()            { StbState.select_start = StbState.select_end = StbState.cursor; }
    void                SelectAll()                 { StbState.select_start = 0; StbState.select_end = CurLenW; StbState.cursor = StbState.select_end; StbState.has_preferred_x = false; }
    void                OnKeyPressed(int key);
};

// Data saved in imgui.ini file
struct ImGuiWindowSettings
{
    char*       Name;
    ImGuiID     Id;
    ImVec2      Pos;
    ImVec2      Size;
    bool        Collapsed;

    ImGuiWindowSettings() { Name = NULL; Id = 0; Pos = Size = ImVec2(0,0); Collapsed = false; }
};

struct ImGuiSettingsHandler
{
    const char* TypeName;   // Short description stored in .ini file. Disallowed characters: '[' ']'  
    ImGuiID     TypeHash;   // == ImHash(TypeName, 0, 0)
    void*       (*ReadOpenFn)(ImGuiContext* ctx, ImGuiSettingsHandler* handler, const char* name);
    void        (*ReadLineFn)(ImGuiContext* ctx, ImGuiSettingsHandler* handler, void* entry, const char* line);
    void        (*WriteAllFn)(ImGuiContext* ctx, ImGuiSettingsHandler* handler, ImGuiTextBuffer* out_buf);
    void*       UserData;

    ImGuiSettingsHandler() { memset(this, 0, sizeof(*this)); }
};

// Mouse cursor data (used when io.MouseDrawCursor is set)
struct ImGuiMouseCursorData
{
    ImGuiMouseCursor    Type;
    ImVec2              HotOffset;
    ImVec2              Size;
    ImVec2              TexUvMin[2];
    ImVec2              TexUvMax[2];
};

// Storage for current popup stack
struct ImGuiPopupRef
{
    ImGuiID             PopupId;        // Set on OpenPopup()
    ImGuiWindow*        Window;         // Resolved on BeginPopup() - may stay unresolved if user never calls OpenPopup()
    ImGuiWindow*        ParentWindow;   // Set on OpenPopup()
    ImGuiID             ParentMenuSet;  // Set on OpenPopup()
    ImVec2              PopupPosOnOpen; // Preferred popup position (typically == MousePosOnOpen when using mouse)
    ImVec2              MousePosOnOpen; // Copy of mouse position at the time of opening popup

    ImGuiPopupRef(ImGuiID id, ImGuiWindow* parent_window, ImGuiID parent_menu_set, const ImVec2& popup_pos, const ImVec2& mouse_pos) { PopupId = id; Window = NULL; ParentWindow = parent_window; ParentMenuSet = parent_menu_set; PopupPosOnOpen = popup_pos; MousePosOnOpen = mouse_pos; }
};

struct ImGuiColumnData
{
    float               OffsetNorm;         // Column start offset, normalized 0.0 (far left) -> 1.0 (far right)
    float               OffsetNormBeforeResize;
    ImGuiColumnsFlags   Flags;              // Not exposed
    ImRect              ClipRect;

    ImGuiColumnData()   { OffsetNorm = OffsetNormBeforeResize = 0.0f; Flags = 0; }
};

struct ImGuiColumnsSet
{
    ImGuiID             ID;
    ImGuiColumnsFlags   Flags;
    bool                IsFirstFrame;
    bool                IsBeingResized;
    int                 Current;
    int                 Count;
    float               MinX, MaxX;
    float               StartPosY;
    float               StartMaxPosX;       // Backup of CursorMaxPos
    float               CellMinY, CellMaxY;
    ImVector<ImGuiColumnData> Columns;

    ImGuiColumnsSet()   { Clear(); }
    void Clear()
    {
        ID = 0;
        Flags = 0;
        IsFirstFrame = false;
        IsBeingResized = false;
        Current = 0;
        Count = 1;
        MinX = MaxX = 0.0f;
        StartPosY = 0.0f;
        StartMaxPosX = 0.0f;
        CellMinY = CellMaxY = 0.0f;
        Columns.clear();
    }
};

struct ImDrawListSharedData
{
    ImVec2          TexUvWhitePixel;            // UV of white pixel in the atlas
    ImFont*         Font;                       // Current/default font (optional, for simplified AddText overload)
    float           FontSize;                   // Current/default font size (optional, for simplified AddText overload)
    float           CurveTessellationTol;
    ImVec4          ClipRectFullscreen;         // Value for PushClipRectFullscreen()

    // Const data
    // FIXME: Bake rounded corners fill/borders in atlas
    ImVec2          CircleVtx12[12];

    ImDrawListSharedData();
};

// Storage for SetNexWindow** functions
struct ImGuiNextWindowData
{
    ImGuiCond               PosCond;
    ImGuiCond               SizeCond;
    ImGuiCond               ContentSizeCond;
    ImGuiCond               CollapsedCond;
    ImGuiCond               SizeConstraintCond;
    ImGuiCond               FocusCond;
    ImVec2                  PosVal;
    ImVec2                  PosPivotVal;
    ImVec2                  SizeVal;
    ImVec2                  ContentSizeVal;
    bool                    CollapsedVal;
    ImRect                  SizeConstraintRect;                 // Valid if 'SetNextWindowSizeConstraint' is true
    ImGuiSizeCallback       SizeCallback;
    void*                   SizeCallbackUserData;

    ImGuiNextWindowData()
    {
        PosCond = SizeCond = ContentSizeCond = CollapsedCond = SizeConstraintCond = FocusCond = 0;
        PosVal = PosPivotVal = SizeVal = ImVec2(0.0f, 0.0f);
        ContentSizeVal = ImVec2(0.0f, 0.0f);
        CollapsedVal = false;
        SizeConstraintRect = ImRect();
        SizeCallback = NULL;
        SizeCallbackUserData = NULL;
    }

    void    Clear()
    {
        PosCond = SizeCond = ContentSizeCond = CollapsedCond = SizeConstraintCond = FocusCond = 0;
    }
};

// Main state for ImGui
struct ImGuiContext
{
    bool                    Initialized;
    ImGuiIO                 IO;
    ImGuiStyle              Style;
    ImFont*                 Font;                               // (Shortcut) == FontStack.empty() ? IO.Font : FontStack.back()
    float                   FontSize;                           // (Shortcut) == FontBaseSize * g.CurrentWindow->FontWindowScale == window->FontSize(). Text height for current window.
    float                   FontBaseSize;                       // (Shortcut) == IO.FontGlobalScale * Font->Scale * Font->FontSize. Base text height.
    ImDrawListSharedData    DrawListSharedData;

    float                   Time;
    int                     FrameCount;
    int                     FrameCountEnded;
    int                     FrameCountRendered;
    ImVector<ImGuiWindow*>  Windows;
    ImVector<ImGuiWindow*>  WindowsSortBuffer;
    ImVector<ImGuiWindow*>  CurrentWindowStack;
    ImGuiStorage            WindowsById;
    int                     WindowsActiveCount;
    ImGuiWindow*            CurrentWindow;                      // Being drawn into
    ImGuiWindow*            HoveredWindow;                      // Will catch mouse inputs
    ImGuiWindow*            HoveredRootWindow;                  // Will catch mouse inputs (for focus/move only)
    ImGuiID                 HoveredId;                          // Hovered widget
    bool                    HoveredIdAllowOverlap;
    ImGuiID                 HoveredIdPreviousFrame;
    float                   HoveredIdTimer;
    ImGuiID                 ActiveId;                           // Active widget
    ImGuiID                 ActiveIdPreviousFrame;
    float                   ActiveIdTimer;
    bool                    ActiveIdIsAlive;                    // Active widget has been seen this frame
    bool                    ActiveIdIsJustActivated;            // Set at the time of activation for one frame
    bool                    ActiveIdAllowOverlap;               // Active widget allows another widget to steal active id (generally for overlapping widgets, but not always)
    int                     ActiveIdAllowNavDirFlags;           // Active widget allows using directional navigation (e.g. can activate a button and move away from it)
    ImVec2                  ActiveIdClickOffset;                // Clicked offset from upper-left corner, if applicable (currently only set by ButtonBehavior)
    ImGuiWindow*            ActiveIdWindow;
    ImGuiInputSource        ActiveIdSource;                     // Activating with mouse or nav (gamepad/keyboard)
    ImGuiWindow*            MovingWindow;                       // Track the child window we clicked on to move a window.
    ImGuiID                 MovingWindowMoveId;                 // == MovingWindow->MoveId
    ImVector<ImGuiColMod>   ColorModifiers;                     // Stack for PushStyleColor()/PopStyleColor()
    ImVector<ImGuiStyleMod> StyleModifiers;                     // Stack for PushStyleVar()/PopStyleVar()
    ImVector<ImFont*>       FontStack;                          // Stack for PushFont()/PopFont()
    ImVector<ImGuiPopupRef> OpenPopupStack;                     // Which popups are open (persistent)
    ImVector<ImGuiPopupRef> CurrentPopupStack;                  // Which level of BeginPopup() we are in (reset every frame)
    ImGuiNextWindowData     NextWindowData;                     // Storage for SetNextWindow** functions
    bool                    NextTreeNodeOpenVal;                // Storage for SetNextTreeNode** functions
    ImGuiCond               NextTreeNodeOpenCond;

    // Navigation data (for gamepad/keyboard)
    ImGuiWindow*            NavWindow;                          // Focused window for navigation. Could be called 'FocusWindow'
    ImGuiID                 NavId;                              // Focused item for navigation
    ImGuiID                 NavActivateId;                      // ~~ IsNavInputPressed(ImGuiNavInput_PadActivate) ? NavId : 0, also set when calling ActivateItem()
    ImGuiID                 NavActivateDownId;                  // ~~ IsNavInputPressed(ImGuiNavInput_PadActivate) ? NavId : 0
    ImGuiID                 NavInputId;                         // ~~ IsNavInputPressed(ImGuiNavInput_PadInput) ? NavId : 0
    ImGuiID                 NavJustTabbedId;                    // Just tabbed to this id.
    ImGuiID                 NavNextActivateId;                  // Set by ActivateItem(), queued until next frame
    ImGuiID                 NavJustMovedToId;                   // Just navigated to this id (result of a successfully MoveRequest)
    ImRect                  NavScoringRectScreen;               // Rectangle used for scoring, in screen space. Based of window->DC.NavRefRectRel[], modified for directional navigation scoring.
    ImGuiWindow*            NavWindowingTarget;
    float                   NavWindowingDisplayAlpha;
    bool                    NavWindowingToggleLayer;
    int                     NavLayer;                           // Layer we are navigating on. For now the system is hard-coded for 0=main contents and 1=menu/title bar, may expose layers later.
    int                     NavIdTabCounter;                    // == NavWindow->DC.FocusIdxTabCounter at time of NavId processing
    bool                    NavIdIsAlive;                       // Nav widget has been seen this frame ~~ NavRefRectRel is valid
    bool                    NavMousePosDirty;
    bool                    NavDisableHighlight;                // When user starts using mouse, we hide gamepad/keyboard highlight (nb: but they are still available, which is why NavDisableHighlight isn't always != NavDisableMouseHover)
    bool                    NavDisableMouseHover;               // When user starts using gamepad/keyboard, we hide mouse hovering highlight until mouse is touched again.
    bool                    NavAnyRequest;                      // ~~ NavMoveRequest || NavInitRequest
    bool                    NavInitRequest;                     // Init request for appearing window to select first item
    ImGuiID                 NavInitResultId;
    ImRect                  NavInitResultRectRel;
    bool                    NavInitResultExplicit;              // Whether the result was explicitly requested with SetItemDefaultFocus()
    bool                    NavMoveFromClampedRefRect;          // Set by manual scrolling, if we scroll to a point where NavId isn't visible we reset navigation from visible items
    bool                    NavMoveRequest;                     // Move request for this frame
    int                     NavMoveRequestForwardStep;          // 0: no forward, 1: forward request, 2: forward result (this is used to navigate sibling parent menus from a child menu)
    ImGuiDir                NavMoveDir;                         // Direction of the move request (left/right/up/down)
    ImGuiDir                NavMoveDirLast;                     // Direction of the previous move request
    ImGuiID                 NavMoveResultId;                    // Best move request candidate
    ImGuiID                 NavMoveResultParentId;              //
    float                   NavMoveResultDistBox;               // Best move request candidate box distance to current NavId
    float                   NavMoveResultDistCenter;            // Best move request candidate center distance to current NavId
    float                   NavMoveResultDistAxial;
    ImRect                  NavMoveResultRectRel;               // Best move request candidate bounding box in window relative space

    // Render
    ImDrawData              RenderDrawData;                     // Main ImDrawData instance to pass render information to the user
    ImVector<ImDrawList*>   RenderDrawLists[3];
    float                   ModalWindowDarkeningRatio;
    ImDrawList              OverlayDrawList;                    // Optional software render of mouse cursors, if io.MouseDrawCursor is set + a few debug overlays
    ImGuiMouseCursor        MouseCursor;
    ImGuiMouseCursorData    MouseCursorData[ImGuiMouseCursor_Count_];

    // Drag and Drop
    bool                    DragDropActive;
    ImGuiDragDropFlags      DragDropSourceFlags;
    int                     DragDropMouseButton;
    ImGuiPayload            DragDropPayload;
    ImRect                  DragDropTargetRect;
    ImGuiID                 DragDropTargetId;
    float                   DragDropAcceptIdCurrRectSurface;
    ImGuiID                 DragDropAcceptIdCurr;               // Target item id (set at the time of accepting the payload)
    ImGuiID                 DragDropAcceptIdPrev;               // Target item id from previous frame (we need to store this to allow for overlapping drag and drop targets)
    int                     DragDropAcceptFrameCount;           // Last time a target expressed a desire to accept the source
    ImVector<unsigned char> DragDropPayloadBufHeap;             // We don't expose the ImVector<> directly
    unsigned char           DragDropPayloadBufLocal[8];

    // Widget state
    ImGuiTextEditState      InputTextState;
    ImFont                  InputTextPasswordFont;
    ImGuiID                 ScalarAsInputTextId;                // Temporary text input when CTRL+clicking on a slider, etc.
    ImGuiColorEditFlags     ColorEditOptions;                   // Store user options for color edit widgets
    ImVec4                  ColorPickerRef;
    float                   DragCurrentValue;                   // Currently dragged value, always float, not rounded by end-user precision settings
    ImVec2                  DragLastMouseDelta;
    float                   DragSpeedDefaultRatio;              // If speed == 0.0f, uses (max-min) * DragSpeedDefaultRatio
    float                   DragSpeedScaleSlow;
    float                   DragSpeedScaleFast;
    ImVec2                  ScrollbarClickDeltaToGrabCenter;    // Distance between mouse and center of grab box, normalized in parent space. Use storage?
    int                     TooltipOverrideCount;
    ImVector<char>          PrivateClipboard;                   // If no custom clipboard handler is defined
    ImVec2                  OsImePosRequest, OsImePosSet;       // Cursor position request & last passed to the OS Input Method Editor

    // Settings
    float                          SettingsDirtyTimer;          // Save .ini Settings on disk when time reaches zero
    ImVector<ImGuiWindowSettings>  SettingsWindows;             // .ini settings for ImGuiWindow
    ImVector<ImGuiSettingsHandler> SettingsHandlers;            // List of .ini settings handlers

    // Logging
    bool                    LogEnabled;
    FILE*                   LogFile;                            // If != NULL log to stdout/ file
    ImGuiTextBuffer*        LogClipboard;                       // Else log to clipboard. This is pointer so our GImGui static constructor doesn't call heap allocators.
    int                     LogStartDepth;
    int                     LogAutoExpandMaxDepth;

    // Misc
    float                   FramerateSecPerFrame[120];          // calculate estimate of framerate for user
    int                     FramerateSecPerFrameIdx;
    float                   FramerateSecPerFrameAccum;
    int                     WantCaptureMouseNextFrame;          // explicit capture via CaptureInputs() sets those flags
    int                     WantCaptureKeyboardNextFrame;
    int                     WantTextInputNextFrame;
    char                    TempBuffer[1024*3+1];               // temporary text buffer

    ImGuiContext() : OverlayDrawList(NULL)
    {
        Initialized = false;
        Font = NULL;
        FontSize = FontBaseSize = 0.0f;

        Time = 0.0f;
        FrameCount = 0;
        FrameCountEnded = FrameCountRendered = -1;
        WindowsActiveCount = 0;
        CurrentWindow = NULL;
        HoveredWindow = NULL;
        HoveredRootWindow = NULL;
        HoveredId = 0;
        HoveredIdAllowOverlap = false;
        HoveredIdPreviousFrame = 0;
        HoveredIdTimer = 0.0f;
        ActiveId = 0;
        ActiveIdPreviousFrame = 0;
        ActiveIdTimer = 0.0f;
        ActiveIdIsAlive = false;
        ActiveIdIsJustActivated = false;
        ActiveIdAllowOverlap = false;
        ActiveIdAllowNavDirFlags = 0;
        ActiveIdClickOffset = ImVec2(-1,-1);
        ActiveIdWindow = NULL;
        ActiveIdSource = ImGuiInputSource_None;
        MovingWindow = NULL;
        MovingWindowMoveId = 0;

        NextTreeNodeOpenVal = false;
        NextTreeNodeOpenCond = 0;

        NavWindow = NULL;
        NavId = NavActivateId = NavActivateDownId = NavInputId = 0;
        NavJustTabbedId = NavJustMovedToId = NavNextActivateId = 0;
        NavScoringRectScreen = ImRect();
        NavWindowingTarget = NULL;
        NavWindowingDisplayAlpha = 0.0f;
        NavWindowingToggleLayer = false;
        NavLayer = 0;
        NavIdTabCounter = INT_MAX;
        NavIdIsAlive = false;
        NavMousePosDirty = false;
        NavDisableHighlight = true;
        NavDisableMouseHover = false;
        NavAnyRequest = false;
        NavInitRequest = false;
        NavInitResultId = 0;
        NavInitResultExplicit = false;
        NavMoveFromClampedRefRect = false;
        NavMoveRequest = false;
        NavMoveRequestForwardStep = 0;
        NavMoveDir = NavMoveDirLast = ImGuiDir_None;
        NavMoveResultId = 0;
        NavMoveResultParentId = 0;
        NavMoveResultDistBox = NavMoveResultDistCenter = NavMoveResultDistAxial = 0.0f;

        DragDropActive = false;
        DragDropSourceFlags = 0;
        DragDropMouseButton = -1;
        DragDropTargetId = 0;
        DragDropAcceptIdPrev = DragDropAcceptIdCurr = 0;
        DragDropAcceptFrameCount = -1;
        memset(DragDropPayloadBufLocal, 0, sizeof(DragDropPayloadBufLocal));

        ScalarAsInputTextId = 0;
        ColorEditOptions = ImGuiColorEditFlags__OptionsDefault;
        DragCurrentValue = 0.0f;
        DragLastMouseDelta = ImVec2(0.0f, 0.0f);
        DragSpeedDefaultRatio = 1.0f / 100.0f;
        DragSpeedScaleSlow = 1.0f / 100.0f;
        DragSpeedScaleFast = 10.0f;
        ScrollbarClickDeltaToGrabCenter = ImVec2(0.0f, 0.0f);
        TooltipOverrideCount = 0;
        OsImePosRequest = OsImePosSet = ImVec2(-1.0f, -1.0f);

        ModalWindowDarkeningRatio = 0.0f;
        OverlayDrawList._Data = &DrawListSharedData;
        OverlayDrawList._OwnerName = "##Overlay"; // Give it a name for debugging
        MouseCursor = ImGuiMouseCursor_Arrow;
        memset(MouseCursorData, 0, sizeof(MouseCursorData));

        SettingsDirtyTimer = 0.0f;

        LogEnabled = false;
        LogFile = NULL;
        LogClipboard = NULL;
        LogStartDepth = 0;
        LogAutoExpandMaxDepth = 2;

        memset(FramerateSecPerFrame, 0, sizeof(FramerateSecPerFrame));
        FramerateSecPerFrameIdx = 0;
        FramerateSecPerFrameAccum = 0.0f;
        WantCaptureMouseNextFrame = WantCaptureKeyboardNextFrame = WantTextInputNextFrame = -1;
        memset(TempBuffer, 0, sizeof(TempBuffer));
    }
};

// Transient per-window flags, reset at the beginning of the frame. For child window, inherited from parent on first Begin().
enum ImGuiItemFlags_
{
    ImGuiItemFlags_AllowKeyboardFocus           = 1 << 0,  // true
    ImGuiItemFlags_ButtonRepeat                 = 1 << 1,  // false    // Button() will return true multiple times based on io.KeyRepeatDelay and io.KeyRepeatRate settings.
    ImGuiItemFlags_Disabled                     = 1 << 2,  // false    // FIXME-WIP: Disable interactions but doesn't affect visuals. Should be: grey out and disable interactions with widgets that affect data + view widgets (WIP) 
    ImGuiItemFlags_NoNav                        = 1 << 3,  // false
    ImGuiItemFlags_NoNavDefaultFocus            = 1 << 4,  // false
    ImGuiItemFlags_SelectableDontClosePopup     = 1 << 5,  // false    // MenuItem/Selectable() automatically closes current Popup window
    ImGuiItemFlags_Default_                     = ImGuiItemFlags_AllowKeyboardFocus
};

// Transient per-window data, reset at the beginning of the frame
// FIXME: That's theory, in practice the delimitation between ImGuiWindow and ImGuiDrawContext is quite tenuous and could be reconsidered.
struct IMGUI_API ImGuiDrawContext
{
    ImVec2                  CursorPos;
    ImVec2                  CursorPosPrevLine;
    ImVec2                  CursorStartPos;
    ImVec2                  CursorMaxPos;           // Used to implicitly calculate the size of our contents, always growing during the frame. Turned into window->SizeContents at the beginning of next frame
    float                   CurrentLineHeight;
    float                   CurrentLineTextBaseOffset;
    float                   PrevLineHeight;
    float                   PrevLineTextBaseOffset;
    float                   LogLinePosY;
    int                     TreeDepth;
    ImGuiID                 LastItemId;
    ImRect                  LastItemRect;
    bool                    LastItemRectHoveredRect;
    bool                    NavHasScroll;           // Set when scrolling can be used (ScrollMax > 0.0f)
    int                     NavLayerCurrent;        // Current layer, 0..31 (we currently only use 0..1)
    int                     NavLayerCurrentMask;    // = (1 << NavLayerCurrent) used by ItemAdd prior to clipping.
    int                     NavLayerActiveMask;     // Which layer have been written to (result from previous frame)
    int                     NavLayerActiveMaskNext; // Which layer have been written to (buffer for current frame)
    bool                    MenuBarAppending;       // FIXME: Remove this
    float                   MenuBarOffsetX;
    ImVector<ImGuiWindow*>  ChildWindows;
    ImGuiStorage*           StateStorage;
    ImGuiLayoutType         LayoutType;
    ImGuiLayoutType         ParentLayoutType;       // Layout type of parent window at the time of Begin()

    // We store the current settings outside of the vectors to increase memory locality (reduce cache misses). The vectors are rarely modified. Also it allows us to not heap allocate for short-lived windows which are not using those settings.
    ImGuiItemFlags          ItemFlags;              // == ItemFlagsStack.back() [empty == ImGuiItemFlags_Default]
    float                   ItemWidth;              // == ItemWidthStack.back(). 0.0: default, >0.0: width in pixels, <0.0: align xx pixels to the right of window
    float                   TextWrapPos;            // == TextWrapPosStack.back() [empty == -1.0f]
    ImVector<ImGuiItemFlags>ItemFlagsStack;
    ImVector<float>         ItemWidthStack;
    ImVector<float>         TextWrapPosStack;
    ImVector<ImGuiGroupData>GroupStack;
    int                     StackSizesBackup[6];    // Store size of various stacks for asserting

    float                   IndentX;                // Indentation / start position from left of window (increased by TreePush/TreePop, etc.)
    float                   GroupOffsetX;
    float                   ColumnsOffsetX;         // Offset to the current column (if ColumnsCurrent > 0). FIXME: This and the above should be a stack to allow use cases like Tree->Column->Tree. Need revamp columns API.
    ImGuiColumnsSet*        ColumnsSet;             // Current columns set

    ImGuiDrawContext()
    {
        CursorPos = CursorPosPrevLine = CursorStartPos = CursorMaxPos = ImVec2(0.0f, 0.0f);
        CurrentLineHeight = PrevLineHeight = 0.0f;
        CurrentLineTextBaseOffset = PrevLineTextBaseOffset = 0.0f;
        LogLinePosY = -1.0f;
        TreeDepth = 0;
        LastItemId = 0;
        LastItemRect = ImRect();
        LastItemRectHoveredRect = false;
        NavHasScroll = false;
        NavLayerActiveMask = NavLayerActiveMaskNext = 0x00;
        NavLayerCurrent = 0;
        NavLayerCurrentMask = 1 << 0;
        MenuBarAppending = false;
        MenuBarOffsetX = 0.0f;
        StateStorage = NULL;
        LayoutType = ParentLayoutType = ImGuiLayoutType_Vertical;
        ItemWidth = 0.0f;
        ItemFlags = ImGuiItemFlags_Default_;
        TextWrapPos = -1.0f;
        memset(StackSizesBackup, 0, sizeof(StackSizesBackup));

        IndentX = 0.0f;
        GroupOffsetX = 0.0f;
        ColumnsOffsetX = 0.0f;
        ColumnsSet = NULL;
    }
};

// Windows data
struct IMGUI_API ImGuiWindow
{
    char*                   Name;
    ImGuiID                 ID;                                 // == ImHash(Name)
    ImGuiWindowFlags        Flags;                              // See enum ImGuiWindowFlags_
    ImVec2                  PosFloat;
    ImVec2                  Pos;                                // Position rounded-up to nearest pixel
    ImVec2                  Size;                               // Current size (==SizeFull or collapsed title bar size)
    ImVec2                  SizeFull;                           // Size when non collapsed
    ImVec2                  SizeFullAtLastBegin;                // Copy of SizeFull at the end of Begin. This is the reference value we'll use on the next frame to decide if we need scrollbars.
    ImVec2                  SizeContents;                       // Size of contents (== extents reach of the drawing cursor) from previous frame. Include decoration, window title, border, menu, etc.
    ImVec2                  SizeContentsExplicit;               // Size of contents explicitly set by the user via SetNextWindowContentSize()
    ImRect                  ContentsRegionRect;                 // Maximum visible content position in window coordinates. ~~ (SizeContentsExplicit ? SizeContentsExplicit : Size - ScrollbarSizes) - CursorStartPos, per axis
    ImVec2                  WindowPadding;                      // Window padding at the time of begin.
    float                   WindowRounding;                     // Window rounding at the time of begin.
    float                   WindowBorderSize;                   // Window border size at the time of begin.
    ImGuiID                 MoveId;                             // == window->GetID("#MOVE")
    ImGuiID                 ChildId;                            // Id of corresponding item in parent window (for child windows)
    ImVec2                  Scroll;
    ImVec2                  ScrollTarget;                       // target scroll position. stored as cursor position with scrolling canceled out, so the highest point is always 0.0f. (FLT_MAX for no change)
    ImVec2                  ScrollTargetCenterRatio;            // 0.0f = scroll so that target position is at top, 0.5f = scroll so that target position is centered
    bool                    ScrollbarX, ScrollbarY;
    ImVec2                  ScrollbarSizes;
    bool                    Active;                             // Set to true on Begin(), unless Collapsed
    bool                    WasActive;
    bool                    WriteAccessed;                      // Set to true when any widget access the current window
    bool                    Collapsed;                          // Set when collapsing window to become only title-bar
    bool                    CollapseToggleWanted;
    bool                    SkipItems;                          // Set when items can safely be all clipped (e.g. window not visible or collapsed)
    bool                    Appearing;                          // Set during the frame where the window is appearing (or re-appearing)
    bool                    CloseButton;                        // Set when the window has a close button (p_open != NULL)
    int                     BeginOrderWithinParent;             // Order within immediate parent window, if we are a child window. Otherwise 0.
    int                     BeginOrderWithinContext;            // Order within entire imgui context. This is mostly used for debugging submission order related issues.
    int                     BeginCount;                         // Number of Begin() during the current frame (generally 0 or 1, 1+ if appending via multiple Begin/End pairs)
    ImGuiID                 PopupId;                            // ID in the popup stack when this window is used as a popup/menu (because we use generic Name/ID for recycling)
    int                     AutoFitFramesX, AutoFitFramesY;
    bool                    AutoFitOnlyGrows;
    int                     AutoFitChildAxises;
    ImGuiDir                AutoPosLastDirection;
    int                     HiddenFrames;
    ImGuiCond               SetWindowPosAllowFlags;             // store condition flags for next SetWindowPos() call.
    ImGuiCond               SetWindowSizeAllowFlags;            // store condition flags for next SetWindowSize() call.
    ImGuiCond               SetWindowCollapsedAllowFlags;       // store condition flags for next SetWindowCollapsed() call.
    ImVec2                  SetWindowPosVal;                    // store window position when using a non-zero Pivot (position set needs to be processed when we know the window size)
    ImVec2                  SetWindowPosPivot;                  // store window pivot for positioning. ImVec2(0,0) when positioning from top-left corner; ImVec2(0.5f,0.5f) for centering; ImVec2(1,1) for bottom right.

    ImGuiID                 NavLastIds[2];                      // Last known NavId for this window, per layer (0/1)
    ImRect                  NavRectRel[2];                      // Reference rectangle, in window space

    ImGuiDrawContext        DC;                                 // Temporary per-window data, reset at the beginning of the frame
    ImVector<ImGuiID>       IDStack;                            // ID stack. ID are hashes seeded with the value at the top of the stack
    ImRect                  ClipRect;                           // = DrawList->clip_rect_stack.back(). Scissoring / clipping rectangle. x1, y1, x2, y2.
    ImRect                  WindowRectClipped;                  // = WindowRect just after setup in Begin(). == window->Rect() for root window.
    ImRect                  InnerRect;
    int                     LastFrameActive;
    float                   ItemWidthDefault;
    ImGuiMenuColumns        MenuColumns;                        // Simplified columns storage for menu items
    ImGuiStorage            StateStorage;
    ImVector<ImGuiColumnsSet> ColumnsStorage;
    float                   FontWindowScale;                    // Scale multiplier per-window
    ImDrawList*             DrawList;
    ImGuiWindow*            ParentWindow;                       // If we are a child _or_ popup window, this is pointing to our parent. Otherwise NULL.
    ImGuiWindow*            RootWindow;                         // Generally point to ourself. If we are a child window, this is pointing to the first non-child parent window.
    ImGuiWindow*            RootNonPopupWindow;                 // Generally point to ourself. Used to display TitleBgActive color and for selecting which window to use for NavWindowing
    ImGuiWindow*            RootNavWindow;                      // Generally point to ourself. If we are a child window with the ImGuiWindowFlags_NavFlattenedChild flag, point to parent. Used to display TitleBgActive color and for selecting which window to use for NavWindowing.

    // Navigation / Focus
    // FIXME-NAVIGATION: Merge all this with the new Nav system, at least the request variables should be moved to ImGuiContext
    int                     FocusIdxAllCounter;                 // Start at -1 and increase as assigned via FocusItemRegister()
    int                     FocusIdxTabCounter;                 // (same, but only count widgets which you can Tab through)
    int                     FocusIdxAllRequestCurrent;          // Item being requested for focus
    int                     FocusIdxTabRequestCurrent;          // Tab-able item being requested for focus
    int                     FocusIdxAllRequestNext;             // Item being requested for focus, for next update (relies on layout to be stable between the frame pressing TAB and the next frame)
    int                     FocusIdxTabRequestNext;             // "

public:
    ImGuiWindow(ImGuiContext* context, const char* name);
    ~ImGuiWindow();

    ImGuiID     GetID(const char* str, const char* str_end = NULL);
    ImGuiID     GetID(const void* ptr);
    ImGuiID     GetIDNoKeepAlive(const char* str, const char* str_end = NULL);
    ImGuiID     GetIDFromRectangle(const ImRect& r_abs);

    // We don't use g.FontSize because the window may be != g.CurrentWidow.
    ImRect      Rect() const                            { return ImRect(Pos.x, Pos.y, Pos.x+Size.x, Pos.y+Size.y); }
    float       CalcFontSize() const                    { return GImGui->FontBaseSize * FontWindowScale; }
    float       TitleBarHeight() const                  { return (Flags & ImGuiWindowFlags_NoTitleBar) ? 0.0f : CalcFontSize() + GImGui->Style.FramePadding.y * 2.0f; }
    ImRect      TitleBarRect() const                    { return ImRect(Pos, ImVec2(Pos.x + SizeFull.x, Pos.y + TitleBarHeight())); }
    float       MenuBarHeight() const                   { return (Flags & ImGuiWindowFlags_MenuBar) ? CalcFontSize() + GImGui->Style.FramePadding.y * 2.0f : 0.0f; }
    ImRect      MenuBarRect() const                     { float y1 = Pos.y + TitleBarHeight(); return ImRect(Pos.x, y1, Pos.x + SizeFull.x, y1 + MenuBarHeight()); }
};

// Backup and restore just enough data to be able to use IsItemHovered() on item A after another B in the same window has overwritten the data.  
struct ImGuiItemHoveredDataBackup
{
    ImGuiID     LastItemId;
    ImRect      LastItemRect;
    bool        LastItemRectHoveredRect;

    ImGuiItemHoveredDataBackup() { Backup(); }
    void Backup()        { ImGuiWindow* window = GImGui->CurrentWindow; LastItemId = window->DC.LastItemId; LastItemRect = window->DC.LastItemRect; LastItemRectHoveredRect = window->DC.LastItemRectHoveredRect; }
    void Restore() const { ImGuiWindow* window = GImGui->CurrentWindow; window->DC.LastItemId = LastItemId; window->DC.LastItemRect = LastItemRect; window->DC.LastItemRectHoveredRect = LastItemRectHoveredRect; }
};

//-----------------------------------------------------------------------------
// Internal API
// No guarantee of forward compatibility here.
//-----------------------------------------------------------------------------

namespace ImGui
{
    // We should always have a CurrentWindow in the stack (there is an implicit "Debug" window)
    // If this ever crash because g.CurrentWindow is NULL it means that either
    // - ImGui::NewFrame() has never been called, which is illegal.
    // - You are calling ImGui functions after ImGui::Render() and before the next ImGui::NewFrame(), which is also illegal.
    inline    ImGuiWindow*  GetCurrentWindowRead()      { ImGuiContext& g = *GImGui; return g.CurrentWindow; }
    inline    ImGuiWindow*  GetCurrentWindow()          { ImGuiContext& g = *GImGui; g.CurrentWindow->WriteAccessed = true; return g.CurrentWindow; }
    IMGUI_API ImGuiWindow*  FindWindowByName(const char* name);
    IMGUI_API void          FocusWindow(ImGuiWindow* window);
    IMGUI_API void          BringWindowToFront(ImGuiWindow* window);
    IMGUI_API void          BringWindowToBack(ImGuiWindow* window);
    IMGUI_API bool          IsWindowChildOf(ImGuiWindow* window, ImGuiWindow* potential_parent);

    IMGUI_API void          Initialize();

    IMGUI_API void                  MarkIniSettingsDirty();
    IMGUI_API ImGuiSettingsHandler* FindSettingsHandler(const char* type_name);
    IMGUI_API ImGuiWindowSettings*  FindWindowSettings(ImGuiID id);

    IMGUI_API void          SetActiveID(ImGuiID id, ImGuiWindow* window);
    IMGUI_API ImGuiID       GetActiveID();
    IMGUI_API void          SetFocusID(ImGuiID id, ImGuiWindow* window);
    IMGUI_API void          ClearActiveID();
    IMGUI_API void          SetHoveredID(ImGuiID id);
    IMGUI_API ImGuiID       GetHoveredID();
    IMGUI_API void          KeepAliveID(ImGuiID id);

    IMGUI_API void          ItemSize(const ImVec2& size, float text_offset_y = 0.0f);
    IMGUI_API void          ItemSize(const ImRect& bb, float text_offset_y = 0.0f);
    IMGUI_API bool          ItemAdd(const ImRect& bb, ImGuiID id, const ImRect* nav_bb = NULL);
    IMGUI_API bool          ItemHoverable(const ImRect& bb, ImGuiID id);
    IMGUI_API bool          IsClippedEx(const ImRect& bb, ImGuiID id, bool clip_even_when_logged);
    IMGUI_API bool          FocusableItemRegister(ImGuiWindow* window, ImGuiID id, bool tab_stop = true);      // Return true if focus is requested
    IMGUI_API void          FocusableItemUnregister(ImGuiWindow* window);
    IMGUI_API ImVec2        CalcItemSize(ImVec2 size, float default_x, float default_y);
    IMGUI_API float         CalcWrapWidthForPos(const ImVec2& pos, float wrap_pos_x);
    IMGUI_API void          PushMultiItemsWidths(int components, float width_full = 0.0f);
    IMGUI_API void          PushItemFlag(ImGuiItemFlags option, bool enabled);
    IMGUI_API void          PopItemFlag();

    IMGUI_API void          OpenPopupEx(ImGuiID id, bool reopen_existing);
    IMGUI_API void          ClosePopup(ImGuiID id);
    IMGUI_API bool          IsPopupOpen(ImGuiID id);
    IMGUI_API bool          BeginPopupEx(ImGuiID id, ImGuiWindowFlags extra_flags);
    IMGUI_API void          BeginTooltipEx(ImGuiWindowFlags extra_flags, bool override_previous_tooltip = true);

    IMGUI_API void          NavInitWindow(ImGuiWindow* window, bool force_reinit);

    IMGUI_API int           CalcTypematicPressedRepeatAmount(float t, float t_prev, float repeat_delay, float repeat_rate);

    IMGUI_API void          Scrollbar(ImGuiLayoutType direction);
    IMGUI_API void          VerticalSeparator();        // Vertical separator, for menu bars (use current line height). not exposed because it is misleading what it doesn't have an effect on regular layout.
    IMGUI_API bool          SplitterBehavior(ImGuiID id, const ImRect& bb, ImGuiAxis axis, float* size1, float* size2, float min_size1, float min_size2, float hover_extend = 0.0f);

    IMGUI_API bool          BeginDragDropTargetCustom(const ImRect& bb, ImGuiID id);
    IMGUI_API void          ClearDragDrop();
    IMGUI_API bool          IsDragDropPayloadBeingAccepted();

    // FIXME-WIP: New Columns API
    IMGUI_API void          BeginColumns(const char* str_id, int count, ImGuiColumnsFlags flags = 0); // setup number of columns. use an identifier to distinguish multiple column sets. close with EndColumns().
    IMGUI_API void          EndColumns();                                                             // close columns
    IMGUI_API void          PushColumnClipRect(int column_index = -1);

    // NB: All position are in absolute pixels coordinates (never using window coordinates internally)
    // AVOID USING OUTSIDE OF IMGUI.CPP! NOT FOR PUBLIC CONSUMPTION. THOSE FUNCTIONS ARE A MESS. THEIR SIGNATURE AND BEHAVIOR WILL CHANGE, THEY NEED TO BE REFACTORED INTO SOMETHING DECENT.
    IMGUI_API void          RenderText(ImVec2 pos, const char* text, const char* text_end = NULL, bool hide_text_after_hash = true);
    IMGUI_API void          RenderTextWrapped(ImVec2 pos, const char* text, const char* text_end, float wrap_width);
    IMGUI_API void          RenderTextClipped(const ImVec2& pos_min, const ImVec2& pos_max, const char* text, const char* text_end, const ImVec2* text_size_if_known, const ImVec2& align = ImVec2(0,0), const ImRect* clip_rect = NULL);
    IMGUI_API void          RenderFrame(ImVec2 p_min, ImVec2 p_max, ImU32 fill_col, bool border = true, float rounding = 0.0f);
    IMGUI_API void          RenderFrameBorder(ImVec2 p_min, ImVec2 p_max, float rounding = 0.0f);
    IMGUI_API void          RenderColorRectWithAlphaCheckerboard(ImVec2 p_min, ImVec2 p_max, ImU32 fill_col, float grid_step, ImVec2 grid_off, float rounding = 0.0f, int rounding_corners_flags = ~0);
    IMGUI_API void          RenderTriangle(ImVec2 pos, ImGuiDir dir, float scale = 1.0f);
    IMGUI_API void          RenderBullet(ImVec2 pos);
    IMGUI_API void          RenderCheckMark(ImVec2 pos, ImU32 col, float sz);
    IMGUI_API void          RenderNavHighlight(const ImRect& bb, ImGuiID id, ImGuiNavHighlightFlags flags = ImGuiNavHighlightFlags_TypeDefault); // Navigation highlight
    IMGUI_API void          RenderRectFilledRangeH(ImDrawList* draw_list, const ImRect& rect, ImU32 col, float x_start_norm, float x_end_norm, float rounding);
    IMGUI_API const char*   FindRenderedTextEnd(const char* text, const char* text_end = NULL); // Find the optional ## from which we stop displaying text.

    IMGUI_API bool          ButtonBehavior(const ImRect& bb, ImGuiID id, bool* out_hovered, bool* out_held, ImGuiButtonFlags flags = 0);
    IMGUI_API bool          ButtonEx(const char* label, const ImVec2& size_arg = ImVec2(0,0), ImGuiButtonFlags flags = 0);
    IMGUI_API bool          CloseButton(ImGuiID id, const ImVec2& pos, float radius);
    IMGUI_API bool          ArrowButton(ImGuiID id, ImGuiDir dir, ImVec2 padding, ImGuiButtonFlags flags = 0);

    IMGUI_API bool          SliderBehavior(const ImRect& frame_bb, ImGuiID id, float* v, float v_min, float v_max, float power, int decimal_precision, ImGuiSliderFlags flags = 0);
    IMGUI_API bool          SliderFloatN(const char* label, float* v, int components, float v_min, float v_max, const char* display_format, float power);
    IMGUI_API bool          SliderIntN(const char* label, int* v, int components, int v_min, int v_max, const char* display_format);

    IMGUI_API bool          DragBehavior(const ImRect& frame_bb, ImGuiID id, float* v, float v_speed, float v_min, float v_max, int decimal_precision, float power);
    IMGUI_API bool          DragFloatN(const char* label, float* v, int components, float v_speed, float v_min, float v_max, const char* display_format, float power);
    IMGUI_API bool          DragIntN(const char* label, int* v, int components, float v_speed, int v_min, int v_max, const char* display_format);

    IMGUI_API bool          InputTextEx(const char* label, char* buf, int buf_size, const ImVec2& size_arg, ImGuiInputTextFlags flags, ImGuiTextEditCallback callback = NULL, void* user_data = NULL);
    IMGUI_API bool          InputFloatN(const char* label, float* v, int components, int decimal_precision, ImGuiInputTextFlags extra_flags);
    IMGUI_API bool          InputIntN(const char* label, int* v, int components, ImGuiInputTextFlags extra_flags);
    IMGUI_API bool          InputScalarEx(const char* label, ImGuiDataType data_type, void* data_ptr, void* step_ptr, void* step_fast_ptr, const char* scalar_format, ImGuiInputTextFlags extra_flags);
    IMGUI_API bool          InputScalarAsWidgetReplacement(const ImRect& aabb, const char* label, ImGuiDataType data_type, void* data_ptr, ImGuiID id, int decimal_precision);

    IMGUI_API void          ColorTooltip(const char* text, const float* col, ImGuiColorEditFlags flags);
    IMGUI_API void          ColorEditOptionsPopup(const float* col, ImGuiColorEditFlags flags);

    IMGUI_API bool          TreeNodeBehavior(ImGuiID id, ImGuiTreeNodeFlags flags, const char* label, const char* label_end = NULL);
    IMGUI_API bool          TreeNodeBehaviorIsOpen(ImGuiID id, ImGuiTreeNodeFlags flags = 0);                     // Consume previous SetNextTreeNodeOpened() data, if any. May return true when logging
    IMGUI_API void          TreePushRawID(ImGuiID id);

    IMGUI_API void          PlotEx(ImGuiPlotType plot_type, const char* label, float (*values_getter)(void* data, int idx), void* data, int values_count, int values_offset, const char* overlay_text, float scale_min, float scale_max, ImVec2 graph_size);

    IMGUI_API int           ParseFormatPrecision(const char* fmt, int default_value);
    IMGUI_API float         RoundScalar(float value, int decimal_precision);

    // Shade functions
    IMGUI_API void          ShadeVertsLinearColorGradientKeepAlpha(ImDrawVert* vert_start, ImDrawVert* vert_end, ImVec2 gradient_p0, ImVec2 gradient_p1, ImU32 col0, ImU32 col1);
    IMGUI_API void          ShadeVertsLinearAlphaGradientForLeftToRightText(ImDrawVert* vert_start, ImDrawVert* vert_end, float gradient_p0_x, float gradient_p1_x);
    IMGUI_API void          ShadeVertsLinearUV(ImDrawVert* vert_start, ImDrawVert* vert_end, const ImVec2& a, const ImVec2& b, const ImVec2& uv_a, const ImVec2& uv_b, bool clamp);

} // namespace ImGui

// ImFontAtlas internals
IMGUI_API bool              ImFontAtlasBuildWithStbTruetype(ImFontAtlas* atlas);
IMGUI_API void              ImFontAtlasBuildRegisterDefaultCustomRects(ImFontAtlas* atlas);
IMGUI_API void              ImFontAtlasBuildSetupFont(ImFontAtlas* atlas, ImFont* font, ImFontConfig* font_config, float ascent, float descent); 
IMGUI_API void              ImFontAtlasBuildPackCustomRects(ImFontAtlas* atlas, void* spc);
IMGUI_API void              ImFontAtlasBuildFinish(ImFontAtlas* atlas);
IMGUI_API void              ImFontAtlasBuildMultiplyCalcLookupTable(unsigned char out_table[256], float in_multiply_factor);
IMGUI_API void              ImFontAtlasBuildMultiplyRectAlpha8(const unsigned char table[256], unsigned char* pixels, int x, int y, int w, int h, int stride);

#ifdef __clang__
#pragma clang diagnostic pop
#endif

#ifdef _MSC_VER
#pragma warning (pop)
#endif