OpenGL example: uses offsetof() macros for vertice definition instead of hardcoded offsets

examples/opengl_example/main.cpp

@@ -64,9 +64,9 @@ static void ImImpl_RenderDrawLists(ImDrawList** const cmd_lists, int cmd_lists_c
     {
         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));
+        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)));
 
         int vtx_offset = 0;
         const ImDrawCmd* pcmd_end = cmd_list->commands.end();