Freeglut OpenGL2 example

examples/freeglut_opengl2_example/README.md

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+# imgui Freeglut example
+
+```
+imgui_impl_glut.h
+imgui_impl_glut.cpp
+```
+
+Above two files implemente imgui freeglut bindings, which come from a github project [imgui_freeglut](https://github.com/azer89/imgui_freeglut).
+
+```
+main.cpp
+```
+
+This simple file demostrates how to integrate imgui with freeglut. Fixed window updating and mouse scroll binding bugs.
+
+

examples/freeglut_opengl2_example/bulid_win32.bat

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+
+@REM Build for Visual Studio compiler. Run your copy of vcvars32.bat or vcvarsall.bat to setup command-line compiler.
+mkdir Debug
+cl /EHsc /nologo /Zi /MD /I ..\.. /I ..\libs\freeglut3.0.0\include\GL *.cpp ..\..\*.cpp /FeDebug/opengl2_example.exe /FoDebug/ /link /LIBPATH:..\libs\freeglut3.0.0\lib freeglut.lib opengl32.lib gdi32.lib shell32.lib

examples/freeglut_opengl2_example/imgui_impl_glut.cpp

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+// ImGui Glut binding with OpenGL
+// You can copy and use unmodified imgui_impl_* files in your project.
+// If you use this binding you'll need to call 4 functions: ImGui_ImplXXXX_Init(), ImGui_ImplXXXX_NewFrame(), ImGui::Render() and ImGui_ImplXXXX_Shutdown().
+// See main.cpp for an example of using this.
+// https://github.com/ocornut/imgui
+
+
+#include "imgui.h"
+#include "imgui_impl_glut.h"
+
+#include "freeglut.h"
+
+#include <iostream>
+
+// Data
+static int          oldTimeSinceStart = 0;
+static bool         g_MousePressed[3] = { false, false, false };
+static float        g_MouseWheel = 0.0f;
+static GLuint       g_FontTexture = 0;
+
+// This is the main rendering function that you have to implement and provide to ImGui (via setting up 'RenderDrawListsFn' in the ImGuiIO structure)
+// If text or lines are blurry when integrating ImGui in your engine:
+// - in your Render function, try translating your projection matrix by (0.5f,0.5f) or (0.375f,0.375f)
+void ImGui_ImplGLUT_RenderDrawLists(ImDrawData* draw_data)
+{
+    // Avoid rendering when minimized, scale coordinates for retina displays (screen coordinates != framebuffer coordinates)
+    ImGuiIO& io = ImGui::GetIO();
+    int fb_width = (int)(io.DisplaySize.x * io.DisplayFramebufferScale.x);
+    int fb_height = (int)(io.DisplaySize.y * io.DisplayFramebufferScale.y);
+    if (fb_width == 0 || fb_height == 0)
+        return;
+    draw_data->ScaleClipRects(io.DisplayFramebufferScale);
+
+    // We are using the OpenGL fixed pipeline to make the example code simpler to read!
+    // Setup render state: alpha-blending enabled, no face culling, no depth testing, scissor enabled, vertex/texcoord/color pointers.
+    GLint last_texture; glGetIntegerv(GL_TEXTURE_BINDING_2D, &last_texture);
+    GLint last_viewport[4]; glGetIntegerv(GL_VIEWPORT, last_viewport);
+    glPushAttrib(GL_ENABLE_BIT | GL_COLOR_BUFFER_BIT | GL_TRANSFORM_BIT);
+    glEnable(GL_BLEND);
+    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
+    glDisable(GL_CULL_FACE);
+    glDisable(GL_DEPTH_TEST);
+    glEnable(GL_SCISSOR_TEST);
+    glEnableClientState(GL_VERTEX_ARRAY);
+    glEnableClientState(GL_TEXTURE_COORD_ARRAY);
+    glEnableClientState(GL_COLOR_ARRAY);
+    glEnable(GL_TEXTURE_2D);
+    //glUseProgram(0); // You may want this if using this code in an OpenGL 3+ context
+
+    // Setup viewport, orthographic projection matrix
+    glViewport(0, 0, (GLsizei)fb_width, (GLsizei)fb_height);
+    glMatrixMode(GL_PROJECTION);
+    glPushMatrix();
+    glLoadIdentity();
+    glOrtho(0.0f, io.DisplaySize.x, io.DisplaySize.y, 0.0f, -1.0f, +1.0f);
+    glMatrixMode(GL_MODELVIEW);
+    glPushMatrix();
+    glLoadIdentity();
+
+    // Render command lists
+    #define OFFSETOF(TYPE, ELEMENT) ((size_t)&(((TYPE *)0)->ELEMENT))
+    for (int n = 0; n < draw_data->CmdListsCount; n++)
+    {
+        const ImDrawList* cmd_list = draw_data->CmdLists[n];
+        const unsigned char* vtx_buffer = (const unsigned char*)&cmd_list->VtxBuffer.front();
+        const ImDrawIdx* idx_buffer = &cmd_list->IdxBuffer.front();
+        glVertexPointer(2, GL_FLOAT, sizeof(ImDrawVert), (void*)(vtx_buffer + OFFSETOF(ImDrawVert, pos)));
+        glTexCoordPointer(2, GL_FLOAT, sizeof(ImDrawVert), (void*)(vtx_buffer + OFFSETOF(ImDrawVert, uv)));
+        glColorPointer(4, GL_UNSIGNED_BYTE, sizeof(ImDrawVert), (void*)(vtx_buffer + OFFSETOF(ImDrawVert, col)));
+
+        for (int cmd_i = 0; cmd_i < cmd_list->CmdBuffer.size(); cmd_i++)
+        {
+            const ImDrawCmd* pcmd = &cmd_list->CmdBuffer[cmd_i];
+            if (pcmd->UserCallback)
+            {
+                pcmd->UserCallback(cmd_list, pcmd);
+            }
+            else
+            {
+                glBindTexture(GL_TEXTURE_2D, (GLuint)(intptr_t)pcmd->TextureId);
+                glScissor((int)pcmd->ClipRect.x, (int)(fb_height - pcmd->ClipRect.w), (int)(pcmd->ClipRect.z - pcmd->ClipRect.x), (int)(pcmd->ClipRect.w - pcmd->ClipRect.y));
+                glDrawElements(GL_TRIANGLES, (GLsizei)pcmd->ElemCount, sizeof(ImDrawIdx) == 2 ? GL_UNSIGNED_SHORT : GL_UNSIGNED_INT, idx_buffer);
+            }
+            idx_buffer += pcmd->ElemCount;
+        }
+    }
+    #undef OFFSETOF
+
+    // Restore modified state
+    glDisableClientState(GL_COLOR_ARRAY);
+    glDisableClientState(GL_TEXTURE_COORD_ARRAY);
+    glDisableClientState(GL_VERTEX_ARRAY);
+    glBindTexture(GL_TEXTURE_2D, (GLuint)last_texture);
+    glMatrixMode(GL_MODELVIEW);
+    glPopMatrix();
+    glMatrixMode(GL_PROJECTION);
+    glPopMatrix();
+    glPopAttrib();
+    glViewport(last_viewport[0], last_viewport[1], (GLsizei)last_viewport[2], (GLsizei)last_viewport[3]);
+}
+
+static const char* ImGui_ImplGLUT_GetClipboardText()
+{
+    std::cerr << "ImGui_ImplGLUT_GetClipboardText not implemented\n";
+    return "";
+}
+
+static void ImGui_ImplGLUT_SetClipboardText(const char* text)
+{
+}
+
+bool ImGui_ImplGLUT_CreateDeviceObjects()
+{
+    // Build texture atlas
+    ImGuiIO& io = ImGui::GetIO();
+    unsigned char* pixels;
+    int width, height;
+    io.Fonts->GetTexDataAsAlpha8(&pixels, &width, &height);
+
+    // Upload texture to graphics system
+    GLint last_texture;
+    glGetIntegerv(GL_TEXTURE_BINDING_2D, &last_texture);
+    glGenTextures(1, &g_FontTexture);
+    glBindTexture(GL_TEXTURE_2D, g_FontTexture);
+    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
+    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
+    glTexImage2D(GL_TEXTURE_2D, 0, GL_ALPHA, width, height, 0, GL_ALPHA, GL_UNSIGNED_BYTE, pixels);
+
+    // Store our identifier
+    io.Fonts->TexID = (void *)(intptr_t)g_FontTexture;
+
+    // Restore state
+    glBindTexture(GL_TEXTURE_2D, last_texture);
+
+    return true;
+}
+
+void ImGui_ImplGLUT_InvalidateDeviceObjects()
+{
+    if (g_FontTexture)
+    {
+        glDeleteTextures(1, &g_FontTexture);
+        ImGui::GetIO().Fonts->TexID = 0;
+        g_FontTexture = 0;
+    }
+}
+
+bool ImGui_ImplGLUT_Init()
+{
+    ImGuiIO& io = ImGui::GetIO();
+
+    io.RenderDrawListsFn = ImGui_ImplGLUT_RenderDrawLists;   // Alternatively you can set this to NULL and call ImGui::GetDrawData() after ImGui::Render() to get the same ImDrawData pointer.
+    io.SetClipboardTextFn = ImGui_ImplGLUT_SetClipboardText;
+    io.GetClipboardTextFn = ImGui_ImplGLUT_GetClipboardText;
+
+    io.KeyMap[ImGuiKey_Tab]        = 9;                     // tab
+    io.KeyMap[ImGuiKey_LeftArrow]  = GLUT_KEY_LEFT;         // Left
+    io.KeyMap[ImGuiKey_RightArrow] = GLUT_KEY_RIGHT;        // Right
+    io.KeyMap[ImGuiKey_UpArrow]    = GLUT_KEY_UP;           // Up
+    io.KeyMap[ImGuiKey_DownArrow]  = GLUT_KEY_DOWN;         // Down
+    io.KeyMap[ImGuiKey_PageUp]     = GLUT_KEY_PAGE_UP;      // PageUp
+    io.KeyMap[ImGuiKey_PageDown]   = GLUT_KEY_PAGE_DOWN;    // PageDown
+    io.KeyMap[ImGuiKey_Home]       = GLUT_KEY_HOME;         // Home
+    io.KeyMap[ImGuiKey_End]        = GLUT_KEY_END;          // End
+    io.KeyMap[ImGuiKey_Delete]     = 127;                   // Delete
+    io.KeyMap[ImGuiKey_Backspace]  = 8;                     // Backspace
+    io.KeyMap[ImGuiKey_Enter]      = 13;                    // Enter
+    io.KeyMap[ImGuiKey_Escape]     = 27;                    // Escape
+    io.KeyMap[11]                  = 1;                     // ctrl-A
+    io.KeyMap[12]                  = 3;                     // ctrl-C
+    io.KeyMap[13]                  = 22;                    // ctrl-V
+    io.KeyMap[14]                  = 24;                    // ctrl-X
+    io.KeyMap[15]                  = 25;                    // ctrl-Y
+    io.KeyMap[16]                  = 26;                    // ctrl-Z
+
+    return true;
+}
+
+void ImGui_ImplGLUT_Shutdown()
+{
+    ImGui_ImplGLUT_InvalidateDeviceObjects();
+    ImGui::Shutdown();
+}
+
+void ImGui_ImplGLUT_NewFrame(int w, int h)
+{
+    if (!g_FontTexture)
+        ImGui_ImplGLUT_CreateDeviceObjects();
+
+    ImGuiIO& io = ImGui::GetIO();
+
+    // Setup display size (every frame to accommodate for window resizing)
+    io.DisplaySize = ImVec2((float)w, (float)h);
+
+    // Setup time step
+    int timeSinceStart = glutGet(GLUT_ELAPSED_TIME);
+    float deltaTime = (timeSinceStart - oldTimeSinceStart)/1000.0f;
+
+    io.DeltaTime = deltaTime > 0.0 ? deltaTime : (float)(1.0f / 60.0f);
+    oldTimeSinceStart = timeSinceStart;
+
+    // Start the frame
+    ImGui::NewFrame();
+}

examples/freeglut_opengl2_example/imgui_impl_glut.h

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+// ImGui freeglut binding with OpenGL
+
+// 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
+
+IMGUI_API bool        ImGui_ImplGLUT_Init();
+IMGUI_API void        ImGui_ImplGLUT_NewFrame(int w, int h);
+IMGUI_API void        ImGui_ImplGLUT_Shutdown();