imgui/examples/imgui_impl_glfw.cpp

// ImGui GLFW binding with OpenGL3 + shaders
// (GLFW is a cross-platform general purpose library for handling windows, inputs, OpenGL/Vulkan graphics context creation, etc.)
// (GL3W is a helper library to access OpenGL functions since there is no standard header to access modern OpenGL functions easily. Alternatives are GLEW, Glad, etc.)

// Implemented features:
//  [X] User texture binding. Cast 'GLuint' OpenGL texture identifier as void*/ImTextureID. Read the FAQ about ImTextureID in imgui.cpp.
//  [X] Gamepad navigation mapping. Enable with 'io.NavFlags |= ImGuiNavFlags_EnableGamepad'.

// You can copy and use unmodified imgui_impl_* files in your project. See main.cpp for an example of using this.
// If you use this binding you'll need to call 4 functions: ImGui_ImplXXXX_Init(), ImGui_ImplXXXX_NewFrame(), ImGui::Render() and ImGui_ImplXXXX_Shutdown().
// If you are new to ImGui, see examples/README.txt and documentation at the top of imgui.cpp.
// https://github.com/ocornut/imgui

// CHANGELOG
// (minor and older changes stripped away, please see git history for details)
//  2018-02-16: Misc: Obsoleted the io.RenderDrawListsFn callback and exposed ImGui_ImplGlfwGL3_RenderDrawData() in the .h file so you can call it yourself.
//  2018-02-06: Misc: Removed call to ImGui::Shutdown() which is not available from 1.60 WIP, user needs to call CreateContext/DestroyContext themselves.
//  2018-02-06: Inputs: Added mapping for ImGuiKey_Space.
//  2018-01-25: Inputs: Added gamepad support if ImGuiNavFlags_EnableGamepad is set.
//  2018-01-25: Inputs: Honoring the io.WantMoveMouse by repositioning the mouse by using navigation and ImGuiNavFlags_MoveMouse is set.
//  2018-01-20: Inputs: Added Horizontal Mouse Wheel support.
//  2018-01-18: Inputs: Added mapping for ImGuiKey_Insert.
//  2018-01-07: OpenGL: Changed GLSL shader version from 330 to 150. (Also changed GL context from 3.3 to 3.2 in example's main.cpp)
//  2017-09-01: OpenGL: Save and restore current bound sampler. Save and restore current polygon mode.
//  2017-08-25: Inputs: MousePos set to -FLT_MAX,-FLT_MAX when mouse is unavailable/missing (instead of -1,-1).
//  2017-05-01: OpenGL: Fixed save and restore of current blend function state.
//  2016-10-15: Misc: Added a void* user_data parameter to Clipboard function handlers.
//  2016-09-05: OpenGL: Fixed save and restore of current scissor rectangle.
//  2016-04-30: OpenGL: Fixed save and restore of current GL_ACTIVE_TEXTURE.

#include "imgui.h"
#include "imgui_impl_glfw.h"

// GL3W/GLFW
#include <GLFW/glfw3.h>
#ifdef _WIN32
#undef APIENTRY
#define GLFW_EXPOSE_NATIVE_WIN32
#include <GLFW/glfw3native.h> // for glfwGetWin32Window
#endif

// Data
static GLFWwindow*  g_Window = NULL;
static double       g_Time = 0.0f;
static bool         g_MouseJustPressed[3] = { false, false, false };

static const char* ImGui_ImplGlfwGL3_GetClipboardText(void* user_data)
{
    return glfwGetClipboardString((GLFWwindow*)user_data);
}

static void ImGui_ImplGlfwGL3_SetClipboardText(void* user_data, const char* text)
{
    glfwSetClipboardString((GLFWwindow*)user_data, text);
}

void ImGui_ImplGlfw_MouseButtonCallback(GLFWwindow*, int button, int action, int /*mods*/)
{
    if (action == GLFW_PRESS && button >= 0 && button < 3)
        g_MouseJustPressed[button] = true;
}

void ImGui_ImplGlfw_ScrollCallback(GLFWwindow*, double xoffset, double yoffset)
{
    ImGuiIO& io = ImGui::GetIO();
    io.MouseWheelH += (float)xoffset;
    io.MouseWheel += (float)yoffset;
}

void ImGui_ImplGlfw_KeyCallback(GLFWwindow*, int key, int, int action, int mods)
{
    ImGuiIO& io = ImGui::GetIO();
    if (action == GLFW_PRESS)
        io.KeysDown[key] = true;
    if (action == GLFW_RELEASE)
        io.KeysDown[key] = false;

    (void)mods; // Modifiers are not reliable across systems
    io.KeyCtrl = io.KeysDown[GLFW_KEY_LEFT_CONTROL] || io.KeysDown[GLFW_KEY_RIGHT_CONTROL];
    io.KeyShift = io.KeysDown[GLFW_KEY_LEFT_SHIFT] || io.KeysDown[GLFW_KEY_RIGHT_SHIFT];
    io.KeyAlt = io.KeysDown[GLFW_KEY_LEFT_ALT] || io.KeysDown[GLFW_KEY_RIGHT_ALT];
    io.KeySuper = io.KeysDown[GLFW_KEY_LEFT_SUPER] || io.KeysDown[GLFW_KEY_RIGHT_SUPER];
}

void ImGui_ImplGlfw_CharCallback(GLFWwindow*, unsigned int c)
{
    ImGuiIO& io = ImGui::GetIO();
    if (c > 0 && c < 0x10000)
        io.AddInputCharacter((unsigned short)c);
}

bool    ImGui_ImplGlfw_Init(GLFWwindow* window, bool install_callbacks)
{
    g_Window = window;

    ImGuiIO& io = ImGui::GetIO();
    io.KeyMap[ImGuiKey_Tab] = GLFW_KEY_TAB;                         // Keyboard mapping. ImGui will use those indices to peek into the io.KeyDown[] array.
    io.KeyMap[ImGuiKey_LeftArrow] = GLFW_KEY_LEFT;
    io.KeyMap[ImGuiKey_RightArrow] = GLFW_KEY_RIGHT;
    io.KeyMap[ImGuiKey_UpArrow] = GLFW_KEY_UP;
    io.KeyMap[ImGuiKey_DownArrow] = GLFW_KEY_DOWN;
    io.KeyMap[ImGuiKey_PageUp] = GLFW_KEY_PAGE_UP;
    io.KeyMap[ImGuiKey_PageDown] = GLFW_KEY_PAGE_DOWN;
    io.KeyMap[ImGuiKey_Home] = GLFW_KEY_HOME;
    io.KeyMap[ImGuiKey_End] = GLFW_KEY_END;
    io.KeyMap[ImGuiKey_Insert] = GLFW_KEY_INSERT;
    io.KeyMap[ImGuiKey_Delete] = GLFW_KEY_DELETE;
    io.KeyMap[ImGuiKey_Backspace] = GLFW_KEY_BACKSPACE;
    io.KeyMap[ImGuiKey_Space] = GLFW_KEY_SPACE;
    io.KeyMap[ImGuiKey_Enter] = GLFW_KEY_ENTER;
    io.KeyMap[ImGuiKey_Escape] = GLFW_KEY_ESCAPE;
    io.KeyMap[ImGuiKey_A] = GLFW_KEY_A;
    io.KeyMap[ImGuiKey_C] = GLFW_KEY_C;
    io.KeyMap[ImGuiKey_V] = GLFW_KEY_V;
    io.KeyMap[ImGuiKey_X] = GLFW_KEY_X;
    io.KeyMap[ImGuiKey_Y] = GLFW_KEY_Y;
    io.KeyMap[ImGuiKey_Z] = GLFW_KEY_Z;

    io.SetClipboardTextFn = ImGui_ImplGlfwGL3_SetClipboardText;
    io.GetClipboardTextFn = ImGui_ImplGlfwGL3_GetClipboardText;
    io.ClipboardUserData = g_Window;
#ifdef _WIN32
    io.ImeWindowHandle = glfwGetWin32Window(g_Window);
#endif

    if (install_callbacks)
    {
        glfwSetMouseButtonCallback(window, ImGui_ImplGlfw_MouseButtonCallback);
        glfwSetScrollCallback(window, ImGui_ImplGlfw_ScrollCallback);
        glfwSetKeyCallback(window, ImGui_ImplGlfw_KeyCallback);
        glfwSetCharCallback(window, ImGui_ImplGlfw_CharCallback);
    }

    return true;
}

void ImGui_ImplGlfw_Shutdown()
{
}

void ImGui_ImplGlfw_NewFrame()
{
    ImGuiIO& io = ImGui::GetIO();
    IM_ASSERT(io.Fonts->IsBuilt());     // Font atlas needs to be built, call renderer _NewFrame() function e.g. ImGui_ImplOpenGL3_NewFrame() 

    // Setup display size
    int w, h;
    int display_w, display_h;
    glfwGetWindowSize(g_Window, &w, &h);
    glfwGetFramebufferSize(g_Window, &display_w, &display_h);
    io.DisplaySize = ImVec2((float)w, (float)h);
    io.DisplayFramebufferScale = ImVec2(w > 0 ? ((float)display_w / w) : 0, h > 0 ? ((float)display_h / h) : 0);

    // Setup time step
    double current_time =  glfwGetTime();
    io.DeltaTime = g_Time > 0.0 ? (float)(current_time - g_Time) : (float)(1.0f/60.0f);
    g_Time = current_time;

    // Setup inputs
    // (we already got mouse wheel, keyboard keys & characters from glfw callbacks polled in glfwPollEvents())
    if (glfwGetWindowAttrib(g_Window, GLFW_FOCUSED))
    {
        if (io.WantMoveMouse)
        {
            glfwSetCursorPos(g_Window, (double)io.MousePos.x, (double)io.MousePos.y);   // Set mouse position if requested by io.WantMoveMouse flag (used when io.NavMovesTrue is enabled by user and using directional navigation)
        }
        else
        {
            double mouse_x, mouse_y;
            glfwGetCursorPos(g_Window, &mouse_x, &mouse_y);
            io.MousePos = ImVec2((float)mouse_x, (float)mouse_y);
        }
    }
    else
    {
        io.MousePos = ImVec2(-FLT_MAX,-FLT_MAX);
    }

    for (int i = 0; i < 3; i++)
    {
        // If a mouse press event came, always pass it as "mouse held this frame", so we don't miss click-release events that are shorter than 1 frame.
        io.MouseDown[i] = g_MouseJustPressed[i] || glfwGetMouseButton(g_Window, i) != 0;
        g_MouseJustPressed[i] = false;
    }

    // Hide OS mouse cursor if ImGui is drawing it
    glfwSetInputMode(g_Window, GLFW_CURSOR, io.MouseDrawCursor ? GLFW_CURSOR_HIDDEN : GLFW_CURSOR_NORMAL);

    // Gamepad navigation mapping [BETA]
    memset(io.NavInputs, 0, sizeof(io.NavInputs));
    if (io.NavFlags & ImGuiNavFlags_EnableGamepad)
    {
        // Update gamepad inputs
        #define MAP_BUTTON(NAV_NO, BUTTON_NO)       { if (buttons_count > BUTTON_NO && buttons[BUTTON_NO] == GLFW_PRESS) io.NavInputs[NAV_NO] = 1.0f; }
        #define MAP_ANALOG(NAV_NO, AXIS_NO, V0, V1) { float v = (axes_count > AXIS_NO) ? axes[AXIS_NO] : V0; v = (v - V0) / (V1 - V0); if (v > 1.0f) v = 1.0f; if (io.NavInputs[NAV_NO] < v) io.NavInputs[NAV_NO] = v; }
        int axes_count = 0, buttons_count = 0;
        const float* axes = glfwGetJoystickAxes(GLFW_JOYSTICK_1, &axes_count);
        const unsigned char* buttons = glfwGetJoystickButtons(GLFW_JOYSTICK_1, &buttons_count);
        MAP_BUTTON(ImGuiNavInput_Activate,   0);     // Cross / A
        MAP_BUTTON(ImGuiNavInput_Cancel,     1);     // Circle / B
        MAP_BUTTON(ImGuiNavInput_Menu,       2);     // Square / X
        MAP_BUTTON(ImGuiNavInput_Input,      3);     // Triangle / Y
        MAP_BUTTON(ImGuiNavInput_DpadLeft,   13);    // D-Pad Left
        MAP_BUTTON(ImGuiNavInput_DpadRight,  11);    // D-Pad Right
        MAP_BUTTON(ImGuiNavInput_DpadUp,     10);    // D-Pad Up
        MAP_BUTTON(ImGuiNavInput_DpadDown,   12);    // D-Pad Down
        MAP_BUTTON(ImGuiNavInput_FocusPrev,  4);     // L1 / LB
        MAP_BUTTON(ImGuiNavInput_FocusNext,  5);     // R1 / RB
        MAP_BUTTON(ImGuiNavInput_TweakSlow,  4);     // L1 / LB
        MAP_BUTTON(ImGuiNavInput_TweakFast,  5);     // R1 / RB
        MAP_ANALOG(ImGuiNavInput_LStickLeft, 0,  -0.3f,  -0.9f);
        MAP_ANALOG(ImGuiNavInput_LStickRight,0,  +0.3f,  +0.9f);
        MAP_ANALOG(ImGuiNavInput_LStickUp,   1,  +0.3f,  +0.9f);
        MAP_ANALOG(ImGuiNavInput_LStickDown, 1,  -0.3f,  -0.9f);
        #undef MAP_BUTTON
        #undef MAP_ANALOG
    }

    // Start the frame. This call will update the io.WantCaptureMouse, io.WantCaptureKeyboard flag that you can use to dispatch inputs (or not) to your application.
    ImGui::NewFrame();
}