imgui

imgui_impl_opengl2.cpp (13115B)

---

 // dear imgui: Renderer Backend for OpenGL2 (legacy OpenGL, fixed pipeline)
 // This needs to be used along with a Platform Backend (e.g. GLFW, SDL, Win32, custom..)
 
 // Implemented features:
 //  [X] Renderer: User texture binding. Use 'GLuint' OpenGL texture identifier as void*/ImTextureID. Read the FAQ about ImTextureID!
 
 // You can copy and use unmodified imgui_impl_* files in your project. See examples/ folder for examples of using this.
 // If you are new to Dear ImGui, read documentation from the docs/ folder + read the top of imgui.cpp.
 // Read online: https://github.com/ocornut/imgui/tree/master/docs
 
 // **DO NOT USE THIS CODE IF YOUR CODE/ENGINE IS USING MODERN OPENGL (SHADERS, VBO, VAO, etc.)**
 // **Prefer using the code in imgui_impl_opengl3.cpp**
 // This code is mostly provided as a reference to learn how ImGui integration works, because it is shorter to read.
 // If your code is using GL3+ context or any semi modern OpenGL calls, using this is likely to make everything more
 // complicated, will require your code to reset every single OpenGL attributes to their initial state, and might
 // confuse your GPU driver.
 // The GL2 code is unable to reset attributes or even call e.g. "glUseProgram(0)" because they don't exist in that API.
 
 // CHANGELOG
 // (minor and older changes stripped away, please see git history for details)
 //  2021-05-19: OpenGL: Replaced direct access to ImDrawCmd::TextureId with a call to ImDrawCmd::GetTexID(). (will become a requirement)
 //  2021-01-03: OpenGL: Backup, setup and restore GL_SHADE_MODEL state, disable GL_STENCIL_TEST and disable GL_NORMAL_ARRAY client state to increase compatibility with legacy OpenGL applications.
 //  2020-01-23: OpenGL: Backup, setup and restore GL_TEXTURE_ENV to increase compatibility with legacy OpenGL applications.
 //  2019-04-30: OpenGL: Added support for special ImDrawCallback_ResetRenderState callback to reset render state.
 //  2019-02-11: OpenGL: Projecting clipping rectangles correctly using draw_data->FramebufferScale to allow multi-viewports for retina display.
 //  2018-11-30: Misc: Setting up io.BackendRendererName so it can be displayed in the About Window.
 //  2018-08-03: OpenGL: Disabling/restoring GL_LIGHTING and GL_COLOR_MATERIAL to increase compatibility with legacy OpenGL applications.
 //  2018-06-08: Misc: Extracted imgui_impl_opengl2.cpp/.h away from the old combined GLFW/SDL+OpenGL2 examples.
 //  2018-06-08: OpenGL: Use draw_data->DisplayPos and draw_data->DisplaySize to setup projection matrix and clipping rectangle.
 //  2018-02-16: Misc: Obsoleted the io.RenderDrawListsFn callback and exposed ImGui_ImplOpenGL2_RenderDrawData() in the .h file so you can call it yourself.
 //  2017-09-01: OpenGL: Save and restore current polygon mode.
 //  2016-09-10: OpenGL: Uploading font texture as RGBA32 to increase compatibility with users shaders (not ideal).
 //  2016-09-05: OpenGL: Fixed save and restore of current scissor rectangle.
 
 #include "imgui.h"
 #include "imgui_impl_opengl2.h"
 #if defined(_MSC_VER) && _MSC_VER <= 1500 // MSVC 2008 or earlier
 #include <stddef.h>     // intptr_t
 #else
 #include <stdint.h>     // intptr_t
 #endif
 
 // Include OpenGL header (without an OpenGL loader) requires a bit of fiddling
 #if defined(_WIN32) && !defined(APIENTRY)
 #define APIENTRY __stdcall                  // It is customary to use APIENTRY for OpenGL function pointer declarations on all platforms.  Additionally, the Windows OpenGL header needs APIENTRY.
 #endif
 #if defined(_WIN32) && !defined(WINGDIAPI)
 #define WINGDIAPI __declspec(dllimport)     // Some Windows OpenGL headers need this
 #endif
 #if defined(__APPLE__)
 #define GL_SILENCE_DEPRECATION
 #include <OpenGL/gl.h>
 #else
 #include <GL/gl.h>
 #endif
 
 // OpenGL Data
 static GLuint       g_FontTexture = 0;
 
 // Functions
 bool    ImGui_ImplOpenGL2_Init()
 {
     // Setup backend capabilities flags
     ImGuiIO& io = ImGui::GetIO();
     io.BackendRendererName = "imgui_impl_opengl2";
     return true;
 }
 
 void    ImGui_ImplOpenGL2_Shutdown()
 {
     ImGui_ImplOpenGL2_DestroyDeviceObjects();
 }
 
 void    ImGui_ImplOpenGL2_NewFrame()
 {
     if (!g_FontTexture)
         ImGui_ImplOpenGL2_CreateDeviceObjects();
 }
 
 static void ImGui_ImplOpenGL2_SetupRenderState(ImDrawData* draw_data, int fb_width, int fb_height)
 {
     // Setup render state: alpha-blending enabled, no face culling, no depth testing, scissor enabled, vertex/texcoord/color pointers, polygon fill.
     glEnable(GL_BLEND);
     glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
     //glBlendFuncSeparate(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA, GL_ONE, GL_ONE_MINUS_SRC_ALPHA); // In order to composite our output buffer we need to preserve alpha
     glDisable(GL_CULL_FACE);
     glDisable(GL_DEPTH_TEST);
     glDisable(GL_STENCIL_TEST);
     glDisable(GL_LIGHTING);
     glDisable(GL_COLOR_MATERIAL);
     glEnable(GL_SCISSOR_TEST);
     glEnableClientState(GL_VERTEX_ARRAY);
     glEnableClientState(GL_TEXTURE_COORD_ARRAY);
     glEnableClientState(GL_COLOR_ARRAY);
     glDisableClientState(GL_NORMAL_ARRAY);
     glEnable(GL_TEXTURE_2D);
     glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);
     glShadeModel(GL_SMOOTH);
     glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);
 
     // If you are using this code with non-legacy OpenGL header/contexts (which you should not, prefer using imgui_impl_opengl3.cpp!!),
     // you may need to backup/reset/restore other state, e.g. for current shader using the commented lines below.
     // (DO NOT MODIFY THIS FILE! Add the code in your calling function)
     //   GLint last_program;
     //   glGetIntegerv(GL_CURRENT_PROGRAM, &last_program);
     //   glUseProgram(0);
     //   ImGui_ImplOpenGL2_RenderDrawData(...);
     //   glUseProgram(last_program)
     // There are potentially many more states you could need to clear/setup that we can't access from default headers.
     // e.g. glBindBuffer(GL_ARRAY_BUFFER, 0), glDisable(GL_TEXTURE_CUBE_MAP).
 
     // Setup viewport, orthographic projection matrix
     // Our visible imgui space lies from draw_data->DisplayPos (top left) to draw_data->DisplayPos+data_data->DisplaySize (bottom right). DisplayPos is (0,0) for single viewport apps.
     glViewport(0, 0, (GLsizei)fb_width, (GLsizei)fb_height);
     glMatrixMode(GL_PROJECTION);
     glPushMatrix();
     glLoadIdentity();
     glOrtho(draw_data->DisplayPos.x, draw_data->DisplayPos.x + draw_data->DisplaySize.x, draw_data->DisplayPos.y + draw_data->DisplaySize.y, draw_data->DisplayPos.y, -1.0f, +1.0f);
     glMatrixMode(GL_MODELVIEW);
     glPushMatrix();
     glLoadIdentity();
 }
 
 // OpenGL2 Render function.
 // Note that this implementation is little overcomplicated because we are saving/setting up/restoring every OpenGL state explicitly.
 // This is in order to be able to run within an OpenGL engine that doesn't do so.
 void ImGui_ImplOpenGL2_RenderDrawData(ImDrawData* draw_data)
 {
     // Avoid rendering when minimized, scale coordinates for retina displays (screen coordinates != framebuffer coordinates)
     int fb_width = (int)(draw_data->DisplaySize.x * draw_data->FramebufferScale.x);
     int fb_height = (int)(draw_data->DisplaySize.y * draw_data->FramebufferScale.y);
     if (fb_width == 0 || fb_height == 0)
         return;
 
     // Backup GL state
     GLint last_texture; glGetIntegerv(GL_TEXTURE_BINDING_2D, &last_texture);
     GLint last_polygon_mode[2]; glGetIntegerv(GL_POLYGON_MODE, last_polygon_mode);
     GLint last_viewport[4]; glGetIntegerv(GL_VIEWPORT, last_viewport);
     GLint last_scissor_box[4]; glGetIntegerv(GL_SCISSOR_BOX, last_scissor_box);
     GLint last_shade_model; glGetIntegerv(GL_SHADE_MODEL, &last_shade_model);
     GLint last_tex_env_mode; glGetTexEnviv(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, &last_tex_env_mode);
     glPushAttrib(GL_ENABLE_BIT | GL_COLOR_BUFFER_BIT | GL_TRANSFORM_BIT);
 
     // Setup desired GL state
     ImGui_ImplOpenGL2_SetupRenderState(draw_data, fb_width, fb_height);
 
     // Will project scissor/clipping rectangles into framebuffer space
     ImVec2 clip_off = draw_data->DisplayPos;         // (0,0) unless using multi-viewports
     ImVec2 clip_scale = draw_data->FramebufferScale; // (1,1) unless using retina display which are often (2,2)
 
     // Render command lists
     for (int n = 0; n < draw_data->CmdListsCount; n++)
     {
         const ImDrawList* cmd_list = draw_data->CmdLists[n];
         const ImDrawVert* vtx_buffer = cmd_list->VtxBuffer.Data;
         const ImDrawIdx* idx_buffer = cmd_list->IdxBuffer.Data;
         glVertexPointer(2, GL_FLOAT, sizeof(ImDrawVert), (const GLvoid*)((const char*)vtx_buffer + IM_OFFSETOF(ImDrawVert, pos)));
         glTexCoordPointer(2, GL_FLOAT, sizeof(ImDrawVert), (const GLvoid*)((const char*)vtx_buffer + IM_OFFSETOF(ImDrawVert, uv)));
         glColorPointer(4, GL_UNSIGNED_BYTE, sizeof(ImDrawVert), (const GLvoid*)((const char*)vtx_buffer + IM_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)
             {
                 // User callback, registered via ImDrawList::AddCallback()
                 // (ImDrawCallback_ResetRenderState is a special callback value used by the user to request the renderer to reset render state.)
                 if (pcmd->UserCallback == ImDrawCallback_ResetRenderState)
                     ImGui_ImplOpenGL2_SetupRenderState(draw_data, fb_width, fb_height);
                 else
                     pcmd->UserCallback(cmd_list, pcmd);
             }
             else
             {
                 // Project scissor/clipping rectangles into framebuffer space
                 ImVec4 clip_rect;
                 clip_rect.x = (pcmd->ClipRect.x - clip_off.x) * clip_scale.x;
                 clip_rect.y = (pcmd->ClipRect.y - clip_off.y) * clip_scale.y;
                 clip_rect.z = (pcmd->ClipRect.z - clip_off.x) * clip_scale.x;
                 clip_rect.w = (pcmd->ClipRect.w - clip_off.y) * clip_scale.y;
 
                 if (clip_rect.x < fb_width && clip_rect.y < fb_height && clip_rect.z >= 0.0f && clip_rect.w >= 0.0f)
                 {
                     // Apply scissor/clipping rectangle
                     glScissor((int)clip_rect.x, (int)(fb_height - clip_rect.w), (int)(clip_rect.z - clip_rect.x), (int)(clip_rect.w - clip_rect.y));
 
                     // Bind texture, Draw
                     glBindTexture(GL_TEXTURE_2D, (GLuint)(intptr_t)pcmd->GetTexID());
                     glDrawElements(GL_TRIANGLES, (GLsizei)pcmd->ElemCount, sizeof(ImDrawIdx) == 2 ? GL_UNSIGNED_SHORT : GL_UNSIGNED_INT, idx_buffer);
                 }
             }
             idx_buffer += pcmd->ElemCount;
         }
     }
 
     // Restore modified GL 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();
     glPolygonMode(GL_FRONT, (GLenum)last_polygon_mode[0]); glPolygonMode(GL_BACK, (GLenum)last_polygon_mode[1]);
     glViewport(last_viewport[0], last_viewport[1], (GLsizei)last_viewport[2], (GLsizei)last_viewport[3]);
     glScissor(last_scissor_box[0], last_scissor_box[1], (GLsizei)last_scissor_box[2], (GLsizei)last_scissor_box[3]);
     glShadeModel(last_shade_model);
     glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, last_tex_env_mode);
 }
 
 bool ImGui_ImplOpenGL2_CreateFontsTexture()
 {
     // Build texture atlas
     ImGuiIO& io = ImGui::GetIO();
     unsigned char* pixels;
     int width, height;
     io.Fonts->GetTexDataAsRGBA32(&pixels, &width, &height);   // Load as RGBA 32-bit (75% of the memory is wasted, but default font is so small) because it is more likely to be compatible with user's existing shaders. If your ImTextureId represent a higher-level concept than just a GL texture id, consider calling GetTexDataAsAlpha8() instead to save on GPU memory.
 
     // 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);
     glPixelStorei(GL_UNPACK_ROW_LENGTH, 0);
     glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, pixels);
 
     // Store our identifier
     io.Fonts->SetTexID((ImTextureID)(intptr_t)g_FontTexture);
 
     // Restore state
     glBindTexture(GL_TEXTURE_2D, last_texture);
 
     return true;
 }
 
 void ImGui_ImplOpenGL2_DestroyFontsTexture()
 {
     if (g_FontTexture)
     {
         ImGuiIO& io = ImGui::GetIO();
         glDeleteTextures(1, &g_FontTexture);
         io.Fonts->SetTexID(0);
         g_FontTexture = 0;
     }
 }
 
 bool    ImGui_ImplOpenGL2_CreateDeviceObjects()
 {
     return ImGui_ImplOpenGL2_CreateFontsTexture();
 }
 
 void    ImGui_ImplOpenGL2_DestroyDeviceObjects()
 {
     ImGui_ImplOpenGL2_DestroyFontsTexture();
 }