Added PushStyleVar(),PopStyleVar() helpers.

BeginChild() allows to specify negative sizes to specify "use remaining minus xx".
Added a simple example console into the demo window.

imgui.cpp

@@ -548,12 +548,18 @@ static void ImConvertColorHSVtoRGB(float h, float s, float v, float& out_r, floa
 
 //-----------------------------------------------------------------------------
 
-struct ImGuiColMod  // Color/style modifier, backup of modified data so we can restore it
+struct ImGuiColMod       // Color modifier, backup of modified data so we can restore it
 {
     ImGuiCol    Col;
     ImVec4      PreviousValue;
 };
 
+struct ImGuiStyleMod    // Style modifier, backup of modified data so we can restore it
+{
+    ImGuiStyleVar Var;
+    ImVec2      PreviousValue;
+};
+
 struct ImGuiAabb    // 2D axis aligned bounding-box
 {
     ImVec2      Min;
@@ -597,6 +603,7 @@ struct ImGuiDrawContext
     ImVector<float>         ItemWidth;
     ImVector<float>         TextWrapPos;
     ImVector<ImGuiColMod>   ColorModifiers;
+    ImVector<ImGuiStyleMod> StyleModifiers;
     ImGuiColorEditMode      ColorEditMode;
     ImGuiStorage*           StateStorage;
     int                     OpenNextNode;
@@ -1963,17 +1970,19 @@ void BeginChild(const char* str_id, ImVec2 size, bool border, ImGuiWindowFlags e
 
     ImGuiWindowFlags flags = ImGuiWindowFlags_NoTitleBar|ImGuiWindowFlags_NoMove|ImGuiWindowFlags_NoResize|ImGuiWindowFlags_ChildWindow;
 
-    const ImVec2 content_max = window->Pos + ImGui::GetWindowContentRegionMax();
+    const ImVec2 content_max = window->Pos + ImGui::GetContentRegionMax();
     const ImVec2 cursor_pos = window->Pos + ImGui::GetCursorPos();
     if (size.x <= 0.0f)
     {
-        size.x = ImMax(content_max.x - cursor_pos.x, g.Style.WindowMinSize.x);
+        if (size.x == 0.0f)
             flags |= ImGuiWindowFlags_ChildWindowAutoFitX;
+        size.x = ImMax(content_max.x - cursor_pos.x, g.Style.WindowMinSize.x) - fabsf(size.x);
     }
     if (size.y <= 0.0f)
     {
-        size.y = ImMax(content_max.y - cursor_pos.y, g.Style.WindowMinSize.y);
+        if (size.y == 0.0f)
             flags |= ImGuiWindowFlags_ChildWindowAutoFitY;
+        size.y = ImMax(content_max.y - cursor_pos.y, g.Style.WindowMinSize.y) - fabsf(size.y);
     }
     if (border)
         flags |= ImGuiWindowFlags_ShowBorders;
@@ -2330,6 +2339,7 @@ bool Begin(const char* name, bool* open, ImVec2 size, float fill_alpha, ImGuiWin
         window->DC.TextWrapPos.resize(0);
         window->DC.TextWrapPos.push_back(-1.0f); // disabled
         window->DC.ColorModifiers.resize(0);
+        window->DC.StyleModifiers.resize(0);
         window->DC.ColorEditMode = ImGuiColorEditMode_UserSelect;
         window->DC.ColumnCurrent = 0;
         window->DC.ColumnsCount = 1;
@@ -2528,6 +2538,73 @@ void PopStyleColor()
     window->DC.ColorModifiers.pop_back();
 }
 
+static float* GetStyleVarFloatAddr(ImGuiStyleVar idx)
+{
+    ImGuiState& g = GImGui;
+    switch (idx)
+    {
+    case ImGuiStyleVar_Alpha: return &g.Style.Alpha;
+    case ImGuiStyleVar_TreeNodeSpacing: return &g.Style.TreeNodeSpacing;
+    case ImGuiStyleVar_ColumnsMinSpacing: return &g.Style.ColumnsMinSpacing;
+    }
+    return NULL;
+}
+
+static ImVec2* GetStyleVarVec2Addr(ImGuiStyleVar idx)
+{
+    ImGuiState& g = GImGui;
+    switch (idx)
+    {
+    case ImGuiStyleVar_WindowPadding: return &g.Style.WindowPadding;
+    case ImGuiStyleVar_FramePadding: return &g.Style.FramePadding;
+    case ImGuiStyleVar_ItemSpacing: return &g.Style.ItemSpacing;
+    case ImGuiStyleVar_ItemInnerSpacing: return &g.Style.ItemInnerSpacing;
+    }
+    return NULL;
+}
+
+void PushStyleVar(ImGuiStyleVar idx, float val)
+{
+    ImGuiState& g = GImGui;
+    ImGuiWindow* window = GetCurrentWindow();
+
+    float* pvar = GetStyleVarFloatAddr(idx);
+    IM_ASSERT(pvar != NULL); // Called wrong function?
+    ImGuiStyleMod backup;
+    backup.Var = idx;
+    backup.PreviousValue = ImVec2(*pvar, 0.0f);
+    window->DC.StyleModifiers.push_back(backup);
+    *pvar = val;
+}
+
+
+void PushStyleVar(ImGuiStyleVar idx, const ImVec2& val)
+{
+    ImGuiState& g = GImGui;
+    ImGuiWindow* window = GetCurrentWindow();
+
+    ImVec2* pvar = GetStyleVarVec2Addr(idx);
+    IM_ASSERT(pvar != NULL); // Called wrong function?
+    ImGuiStyleMod backup;
+    backup.Var = idx;
+    backup.PreviousValue = *pvar;
+    window->DC.StyleModifiers.push_back(backup);
+    *pvar = val;
+}
+
+void PopStyleVar()
+{
+    ImGuiState& g = GImGui;
+    ImGuiWindow* window = GetCurrentWindow();
+
+    ImGuiStyleMod& backup = window->DC.StyleModifiers.back();
+    if (float* pvar = GetStyleVarFloatAddr(backup.Var))
+        *pvar = backup.PreviousValue.x;
+    else if (ImVec2* pvar = GetStyleVarVec2Addr(backup.Var))
+        *pvar = backup.PreviousValue;
+    window->DC.StyleModifiers.pop_back();
+}
+
 const char* GetStyleColorName(ImGuiCol idx)
 {
     // Create switch-case from enum with regexp: ImGuiCol_{.*}, --> case ImGuiCol_\1: return "\1";
@@ -6260,6 +6337,8 @@ void ShowStyleEditor(ImGuiStyle* ref)
 // SAMPLE CODE
 //-----------------------------------------------------------------------------
 
+static void ShowExampleConsole(bool* open);
+
 // Demonstrate ImGui features (unfortunately this makes this function a little bloated!)
 void ShowTestWindow(bool* open)
 {
@@ -6760,6 +6839,15 @@ void ShowTestWindow(bool* open)
         }
     }
 
+    if (ImGui::CollapsingHeader("App Examples"))
+    {
+        static bool show_console = false;
+        ImGui::Checkbox("Console", &show_console);
+
+        if (show_console)
+            ShowExampleConsole(&show_console);
+    }
+
     if (ImGui::CollapsingHeader("Long text"))
     {
         static ImGuiTextBuffer log;
@@ -6781,6 +6869,83 @@ void ShowTestWindow(bool* open)
 
     ImGui::End();
 }
+
+static void ShowExampleConsole(bool* open)
+{
+    if (!ImGui::Begin("Example: Console", open, ImVec2(520,600)))
+    {
+        ImGui::End();
+        return;
+    }
+
+    ImGui::TextWrapped("This example implement a simple console. A more elaborate implementation may want to store individual entries along with extra data such as timestamp, emitter, etc. Here we automatically set focus on the text edition fields when hovering them.");
+
+    // TODO: display from bottom
+    // TODO: clip manually
+    // TODO: history
+    // TODO: completion
+
+    static ImVector<char*> items;
+    static char input[256] = "";
+    static bool new_items = false;
+
+    if (ImGui::SmallButton("Add Dummy Text")) { items.push_back(ImStrdup("some text\nsome more text")); new_items = true; }
+    ImGui::SameLine(); 
+    if (ImGui::SmallButton("Add Dummy Error")) { items.push_back(ImStrdup("[error] something went wrong")); new_items = true; }
+    ImGui::SameLine(); 
+    if (ImGui::SmallButton("Clear all")) { for (size_t i = 0; i < items.size(); i++) ImGui::MemFree(items[i]); items.clear(); }
+    ImGui::Separator();
+
+    ImGui::PushStyleVar(ImGuiStyleVar_FramePadding, ImVec2(0,0));
+    static ImGuiTextFilter filter;
+    filter.Draw("Filter (\"incl,-excl\") (\"error\")", 180);
+    if (ImGui::IsItemHovered()) ImGui::SetKeyboardFocusHere(-1); // Auto focus on hover
+    ImGui::PopStyleVar();
+    ImGui::Separator();
+
+    ImGui::BeginChild("ScrollingRegion", ImVec2(0,-ImGui::GetTextLineSpacing()*2));
+
+    // Display every line as a separate entry so we can change their color or add custom widgets. If you only want raw text you can use ImGui::TextUnformatted(log.begin(), log.end());
+    // NB- if you have lots of text this approach may be too inefficient. You can seek and display only the lines that are on display using a technique similar to what TextUnformatted() does,
+    // or faster if your entries are already stored into a table.
+    ImGui::PushStyleVar(ImGuiStyleVar_ItemSpacing, ImVec2(4,1)); // tighten spacing
+    ImGui::GetStyle().ItemSpacing.y = 1; // tighten spacing
+    for (size_t i = 0; i < items.size(); i++)
+    {
+        const char* item = items[i];
+        if (!filter.PassFilter(item))
+            continue;
+        ImVec4 col(1,1,1,1);
+        if (strstr(item, "[error]")) col = ImVec4(1.0f,0.4f,0.4f,1.0f);
+        else if (strncmp(item, "# ", 2) == 0) col = ImVec4(1.0f,0.8f,0.6f,1.0f);
+        ImGui::PushStyleColor(ImGuiCol_Text, col);
+        ImGui::TextUnformatted(item);
+        ImGui::PopStyleColor();
+    }
+    ImGui::PopStyleVar();
+    if (new_items)
+    {
+        ImGui::SetScrollPosHere();
+        new_items = false;
+    }
+    ImGui::EndChild();
+
+    ImGui::Separator();
+    if (ImGui::InputText("Input", input, IM_ARRAYSIZE(input), ImGuiInputTextFlags_EnterReturnsTrue))
+    {
+        new_items = true;
+        char buf[256];
+        ImFormatString(buf, IM_ARRAYSIZE(buf), "# %s\n", input);
+        items.push_back(ImStrdup(buf));
+        ImFormatString(buf, IM_ARRAYSIZE(buf), "Unknown command '%s'\n", input);
+        items.push_back(ImStrdup(buf));
+        strcpy(input, "");
+    }
+    if (ImGui::IsItemHovered()) ImGui::SetKeyboardFocusHere(-1); // Auto focus on hover
+
+    ImGui::End();
+}
+
 // End of Sample code
 
 } // namespace ImGui

imgui.h

@@ -33,6 +33,7 @@ typedef unsigned int ImU32;
 typedef unsigned short ImWchar;
 typedef ImU32 ImGuiID;
 typedef int ImGuiCol;               // enum ImGuiCol_
+typedef int ImGuiStyleVar;          // enum ImGuiStyleVar_
 typedef int ImGuiKey;               // enum ImGuiKey_
 typedef int ImGuiColorEditMode;     // enum ImGuiColorEditMode_
 typedef int ImGuiWindowFlags;       // enum ImGuiWindowFlags_
@@ -145,7 +146,7 @@ namespace ImGui
     // Window
     IMGUI_API bool          Begin(const char* name = "Debug", bool* open = NULL, ImVec2 size = ImVec2(0,0), float fill_alpha = -1.0f, ImGuiWindowFlags flags = 0);    // return false when window is collapsed, so you can early out in your code.
     IMGUI_API void          End();
-    IMGUI_API void          BeginChild(const char* str_id, ImVec2 size = ImVec2(0,0), bool border = false, ImGuiWindowFlags extra_flags = 0);
+    IMGUI_API void          BeginChild(const char* str_id, ImVec2 size = ImVec2(0,0), bool border = false, ImGuiWindowFlags extra_flags = 0);                         // size==0.0f: use remaining window size, size<0.0f: use remaining window size minus abs(size). on each axis.
     IMGUI_API void          EndChild();
     IMGUI_API bool          GetWindowIsFocused();
     IMGUI_API ImVec2        GetWindowSize();
@@ -172,6 +173,9 @@ namespace ImGui
     IMGUI_API void          PopAllowKeyboardFocus();
     IMGUI_API void          PushStyleColor(ImGuiCol idx, const ImVec4& col);
     IMGUI_API void          PopStyleColor();
+    IMGUI_API void          PushStyleVar(ImGuiStyleVar idx, float val);
+    IMGUI_API void          PushStyleVar(ImGuiStyleVar idx, const ImVec2& val);
+    IMGUI_API void          PopStyleVar();
     IMGUI_API void          PushTextWrapPos(float wrap_pos_x);                                  // word-wrapping for Text*() commands. < 0.0f: no wrapping; 0.0f: wrap to end of window (or column); > 0.0f: wrap at 'wrap_pos_x' position in window local space.
     IMGUI_API void          PopTextWrapPos();
 
@@ -345,6 +349,7 @@ enum ImGuiKey_
     ImGuiKey_COUNT,
 };
 
+// Enumeration for PushStyleColor() / PopStyleColor()
 enum ImGuiCol_
 {
     ImGuiCol_Text,
@@ -387,6 +392,19 @@ enum ImGuiCol_
     ImGuiCol_COUNT,
 };
 
+// Enumeration for PushStyleVar() / PopStyleVar()
+// NB: the enum only refers to fields of ImGuiStyle() which makes sense to be pushed/poped in UI code. Feel free to add others.
+enum ImGuiStyleVar_
+{
+    ImGuiStyleVar_Alpha,             // float
+    ImGuiStyleVar_WindowPadding,     // ImVec2
+    ImGuiStyleVar_FramePadding,      // ImVec2
+    ImGuiStyleVar_ItemSpacing,       // ImVec2
+    ImGuiStyleVar_ItemInnerSpacing,  // ImVec2
+    ImGuiStyleVar_TreeNodeSpacing,   // float
+    ImGuiStyleVar_ColumnsMinSpacing, // float 
+};
+
 enum ImGuiColorEditMode_
 {
     ImGuiColorEditMode_UserSelect = -1,