Added basic SDL2 example.

examples/opengl_example/sdl2_example/main.cpp

@@ -0,0 +1,201 @@
+#define STB_IMAGE_IMPLEMENTATION
+#include "stb_image.h"                  // for .png loading
+#include "../../../imgui.h"
+
+// glew & glfw
+//#define GLEW_STATIC
+#include <GL/glew.h>
+#include <SDL2/SDL.h>
+
+#include <iostream>
+
+static SDL_Window* window;
+static SDL_GLContext context;
+static GLuint fontTex;
+static bool mousePressed[4] = { false, false };
+static ImVec2 mousePosScale(1.0f, 1.0f);
+
+// 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)
+// - try adjusting ImGui::GetIO().PixelCenterOffset to 0.5f or 0.375f
+static void ImImpl_RenderDrawLists(ImDrawList** const cmd_lists, int cmd_lists_count)
+{
+  if (cmd_lists_count == 0)
+    return;
+
+  // We are using the OpenGL fixed pipeline to make the example code simpler to read!
+  // A probable faster way to render would be to collate all vertices from all cmd_lists into a single vertex buffer.
+  // Setup render state: alpha-blending enabled, no face culling, no depth testing, scissor enabled, vertex/texcoord/color pointers.
+  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);
+
+  // Setup texture
+  glBindTexture(GL_TEXTURE_2D, fontTex);
+  glEnable(GL_TEXTURE_2D);
+
+  // Setup orthographic projection matrix
+  const float width = ImGui::GetIO().DisplaySize.x;
+  const float height = ImGui::GetIO().DisplaySize.y;
+  glMatrixMode(GL_PROJECTION);
+  glLoadIdentity();
+  glOrtho(0.0f, width, height, 0.0f, -1.0f, +1.0f);
+  glMatrixMode(GL_MODELVIEW);
+  glLoadIdentity();
+
+  // Render command lists
+  for (int n = 0; n < cmd_lists_count; n++)
+  {
+    const ImDrawList* cmd_list = cmd_lists[n];
+    const unsigned char* vtx_buffer = (const unsigned char*)cmd_list->vtx_buffer.begin();
+    glVertexPointer(2, GL_FLOAT, sizeof(ImDrawVert), (void*)(vtx_buffer));
+    glTexCoordPointer(2, GL_FLOAT, sizeof(ImDrawVert), (void*)(vtx_buffer+8));
+    glColorPointer(4, GL_UNSIGNED_BYTE, sizeof(ImDrawVert), (void*)(vtx_buffer+16));
+
+    int vtx_offset = 0;
+    const ImDrawCmd* pcmd_end = cmd_list->commands.end();
+    for (const ImDrawCmd* pcmd = cmd_list->commands.begin(); pcmd != pcmd_end; pcmd++)
+    {
+      glScissor((int)pcmd->clip_rect.x, (int)(height - pcmd->clip_rect.w), (int)(pcmd->clip_rect.z - pcmd->clip_rect.x), (int)(pcmd->clip_rect.w - pcmd->clip_rect.y));
+      glDrawArrays(GL_TRIANGLES, vtx_offset, pcmd->vtx_count);
+      vtx_offset += pcmd->vtx_count;
+    }
+  }
+  glDisable(GL_SCISSOR_TEST);
+  glDisableClientState(GL_COLOR_ARRAY);
+  glDisableClientState(GL_TEXTURE_COORD_ARRAY);
+  glDisableClientState(GL_VERTEX_ARRAY);
+}
+
+void InitGL()
+{
+  SDL_GL_SetAttribute(SDL_GL_RED_SIZE, 8);
+  SDL_GL_SetAttribute(SDL_GL_GREEN_SIZE, 8);
+  SDL_GL_SetAttribute(SDL_GL_BLUE_SIZE, 8);
+  SDL_GL_SetAttribute(SDL_GL_ALPHA_SIZE, 8);
+  SDL_GL_SetAttribute(SDL_GL_BUFFER_SIZE, 32);
+  SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
+  SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK,
+      SDL_GL_CONTEXT_PROFILE_CORE);
+
+  SDL_Init(SDL_INIT_EVERYTHING);
+
+  window = SDL_CreateWindow("SDL IMGui Example.",
+      SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED, 1280, 720,
+      SDL_WINDOW_OPENGL);
+  context = SDL_GL_CreateContext(window);
+
+  glewExperimental = GL_TRUE;
+  GLenum status = glewInit();
+  if (status != GLEW_OK) {
+    printf("Could not initialize GLEW!\n");
+  }
+}
+
+void InitImGui()
+{
+  int w, h;
+  int fb_w, fb_h;
+  SDL_GetWindowSize(window, &w, &h);
+  SDL_GetWindowSize(window, &fb_w, &fb_h); // Needs to be corrected for SDL Framebuffer
+  mousePosScale.x = (float)fb_w / w;
+  mousePosScale.y = (float)fb_h / h;
+
+  ImGuiIO& io = ImGui::GetIO();
+  io.DisplaySize = ImVec2((float)fb_w, (float)fb_h);  // Display size, in pixels. For clamping windows positions.
+  io.PixelCenterOffset = 0.0f;                        // Align OpenGL texels
+
+  io.RenderDrawListsFn = ImImpl_RenderDrawLists;
+
+  // Load font texture
+  glGenTextures(1, &fontTex);
+  glBindTexture(GL_TEXTURE_2D, fontTex);
+  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
+  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
+
+  // Default font (embedded in code)
+  const void* png_data;
+  unsigned int png_size;
+  ImGui::GetDefaultFontData(NULL, NULL, &png_data, &png_size);
+  int tex_x, tex_y, tex_comp;
+  void* tex_data = stbi_load_from_memory((const unsigned char*)png_data, (int)png_size, &tex_x, &tex_y, &tex_comp, 0);
+  IM_ASSERT(tex_data != NULL);
+
+  glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, tex_x, tex_y, 0, GL_RGBA, GL_UNSIGNED_BYTE, tex_data);
+  stbi_image_free(tex_data);
+}
+
+void UpdateImGui()
+{
+  ImGuiIO& io = ImGui::GetIO();
+
+  SDL_PumpEvents();
+
+  // Setup inputs
+  // (we already got mouse wheel, keyboard keys & characters from glfw callbacks polled in glfwPollEvents())
+  int mouse_x, mouse_y;
+  SDL_GetMouseState(&mouse_x, &mouse_y);
+
+  io.MousePos = ImVec2((float)mouse_x * mousePosScale.x, (float)mouse_y * mousePosScale.y);      // Mouse position, in pixels (set to -1,-1 if no mouse / on another screen, etc.)
+
+  io.MouseDown[0] = mousePressed[0] || (SDL_GetMouseState(NULL, NULL) & SDL_BUTTON(SDL_BUTTON_LEFT));
+  io.MouseDown[1] = mousePressed[1] || (SDL_GetMouseState(NULL, NULL) & SDL_BUTTON(SDL_BUTTON_RIGHT));
+
+  // Start the frame
+  ImGui::NewFrame();
+}
+
+// Application code
+int main(int argc, char** argv)
+{
+  InitGL();
+  InitImGui();
+
+  bool running = true;
+  while (running) {
+    ImGuiIO& io = ImGui::GetIO();
+    mousePressed[0] = mousePressed[1] = false;
+    io.MouseWheel = 0;
+
+    SDL_Event event;
+    while (SDL_PollEvent(&event)) {
+      if (event.type == SDL_QUIT) {
+        running = false;
+      }
+    }
+
+    UpdateImGui();
+
+    ImGui::Begin("Debug");
+    ImGui::Text("Hello, world %d", 123);
+    if (ImGui::Button("OK")) {
+      std::cout << "Button clicked!\n";
+    }
+    ImGui::End();
+
+    // Rendering
+    glClearColor(0.8f, 0.6f, 0.6f, 1.0f);
+    glClear(GL_COLOR_BUFFER_BIT);
+
+    ImGui::Render();
+
+    GLenum error = glGetError();
+    if (error != GL_NO_ERROR) {
+      std::cout << gluErrorString(error) << std::endl;
+    }
+
+    SDL_GL_SwapWindow(window);
+  }
+
+  ImGui::Shutdown();
+  SDL_GL_DeleteContext(context);
+  SDL_DestroyWindow(window);
+  SDL_Quit();
+  return 0;
+}