Examples: Using IM_OFFSETOF macro. + Comments

examples/allegro5_example/imgui_impl_a5.cpp

@@ -28,8 +28,6 @@ static double                   g_Time = 0.0;
 static ALLEGRO_MOUSE_CURSOR*    g_MouseCursorInvisible = NULL;
 static ALLEGRO_VERTEX_DECL*     g_VertexDecl = NULL;
 
-#define OFFSETOF(TYPE, ELEMENT) ((size_t)&(((TYPE *)0)->ELEMENT))
-
 struct ImDrawVertAllegro
 {
     ImVec2 pos;
@@ -162,9 +160,9 @@ bool ImGui_ImplA5_Init(ALLEGRO_DISPLAY* display)
     // We still use a custom declaration to use 'ALLEGRO_PRIM_TEX_COORD' instead of 'ALLEGRO_PRIM_TEX_COORD_PIXEL' else we can't do a reliable conversion.
     ALLEGRO_VERTEX_ELEMENT elems[] =
     {
-        { ALLEGRO_PRIM_POSITION, ALLEGRO_PRIM_FLOAT_2, OFFSETOF(ImDrawVertAllegro, pos) },
-        { ALLEGRO_PRIM_TEX_COORD, ALLEGRO_PRIM_FLOAT_2, OFFSETOF(ImDrawVertAllegro, uv) },
-        { ALLEGRO_PRIM_COLOR_ATTR, 0, OFFSETOF(ImDrawVertAllegro, col) },
+        { ALLEGRO_PRIM_POSITION, ALLEGRO_PRIM_FLOAT_2, IM_OFFSETOF(ImDrawVertAllegro, pos) },
+        { ALLEGRO_PRIM_TEX_COORD, ALLEGRO_PRIM_FLOAT_2, IM_OFFSETOF(ImDrawVertAllegro, uv) },
+        { ALLEGRO_PRIM_COLOR_ATTR, 0, IM_OFFSETOF(ImDrawVertAllegro, col) },
         { 0, 0, 0 }
     };
     g_VertexDecl = al_create_vertex_decl(elems, sizeof(ImDrawVertAllegro));

examples/apple_example/imguiex-ios/imgui_impl_ios.mm

@@ -793,11 +793,10 @@ bool ImGui_ImplIOS_CreateDeviceObjects()
     glEnableVertexAttribArray(g_AttribLocationUV);
     glEnableVertexAttribArray(g_AttribLocationColor);
     
-#define OFFSETOF(TYPE, ELEMENT) ((size_t)&(((TYPE *)0)->ELEMENT))
-    glVertexAttribPointer(g_AttribLocationPosition, 2, GL_FLOAT, GL_FALSE, sizeof(ImDrawVert), (GLvoid*)OFFSETOF(ImDrawVert, pos));
-    glVertexAttribPointer(g_AttribLocationUV, 2, GL_FLOAT, GL_FALSE, sizeof(ImDrawVert), (GLvoid*)OFFSETOF(ImDrawVert, uv));
-    glVertexAttribPointer(g_AttribLocationColor, 4, GL_UNSIGNED_BYTE, GL_TRUE, sizeof(ImDrawVert), (GLvoid*)OFFSETOF(ImDrawVert, col));
-#undef OFFSETOF
+    glVertexAttribPointer(g_AttribLocationPosition, 2, GL_FLOAT, GL_FALSE, sizeof(ImDrawVert), (GLvoid*)IM_OFFSETOF(ImDrawVert, pos));
+    glVertexAttribPointer(g_AttribLocationUV, 2, GL_FLOAT, GL_FALSE, sizeof(ImDrawVert), (GLvoid*)IM_OFFSETOF(ImDrawVert, uv));
+    glVertexAttribPointer(g_AttribLocationColor, 4, GL_UNSIGNED_BYTE, GL_TRUE, sizeof(ImDrawVert), (GLvoid*)IM_OFFSETOF(ImDrawVert, col));
+
     glBindVertexArray(0);
     glBindBuffer(GL_ARRAY_BUFFER, 0);
     

examples/opengl2_example/imgui_impl_glfw.cpp

@@ -77,15 +77,14 @@ void ImGui_ImplGlfwGL2_RenderDrawLists(ImDrawData* draw_data)
     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 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 + OFFSETOF(ImDrawVert, pos)));
-        glTexCoordPointer(2, GL_FLOAT, sizeof(ImDrawVert), (const GLvoid*)((const char*)vtx_buffer + OFFSETOF(ImDrawVert, uv)));
-        glColorPointer(4, GL_UNSIGNED_BYTE, sizeof(ImDrawVert), (const GLvoid*)((const char*)vtx_buffer + OFFSETOF(ImDrawVert, col)));
+        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++)
         {
@@ -103,7 +102,6 @@ void ImGui_ImplGlfwGL2_RenderDrawLists(ImDrawData* draw_data)
             idx_buffer += pcmd->ElemCount;
         }
     }
-    #undef OFFSETOF
 
     // Restore modified state
     glDisableClientState(GL_COLOR_ARRAY);

examples/opengl3_example/imgui_impl_glfw_gl3.cpp

@@ -269,11 +269,9 @@ bool ImGui_ImplGlfwGL3_CreateDeviceObjects()
     glEnableVertexAttribArray(g_AttribLocationUV);
     glEnableVertexAttribArray(g_AttribLocationColor);
 
-#define OFFSETOF(TYPE, ELEMENT) ((size_t)&(((TYPE *)0)->ELEMENT))
-    glVertexAttribPointer(g_AttribLocationPosition, 2, GL_FLOAT, GL_FALSE, sizeof(ImDrawVert), (GLvoid*)OFFSETOF(ImDrawVert, pos));
-    glVertexAttribPointer(g_AttribLocationUV, 2, GL_FLOAT, GL_FALSE, sizeof(ImDrawVert), (GLvoid*)OFFSETOF(ImDrawVert, uv));
-    glVertexAttribPointer(g_AttribLocationColor, 4, GL_UNSIGNED_BYTE, GL_TRUE, sizeof(ImDrawVert), (GLvoid*)OFFSETOF(ImDrawVert, col));
-#undef OFFSETOF
+    glVertexAttribPointer(g_AttribLocationPosition, 2, GL_FLOAT, GL_FALSE, sizeof(ImDrawVert), (GLvoid*)IM_OFFSETOF(ImDrawVert, pos));
+    glVertexAttribPointer(g_AttribLocationUV, 2, GL_FLOAT, GL_FALSE, sizeof(ImDrawVert), (GLvoid*)IM_OFFSETOF(ImDrawVert, uv));
+    glVertexAttribPointer(g_AttribLocationColor, 4, GL_UNSIGNED_BYTE, GL_TRUE, sizeof(ImDrawVert), (GLvoid*)IM_OFFSETOF(ImDrawVert, col));
 
     ImGui_ImplGlfwGL3_CreateFontsTexture();
 

examples/sdl_opengl2_example/imgui_impl_sdl.cpp

@@ -70,15 +70,14 @@ void ImGui_ImplSdl_RenderDrawLists(ImDrawData* draw_data)
     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 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 + OFFSETOF(ImDrawVert, pos)));
-        glTexCoordPointer(2, GL_FLOAT, sizeof(ImDrawVert), (const GLvoid*)((const char*)vtx_buffer + OFFSETOF(ImDrawVert, uv)));
-        glColorPointer(4, GL_UNSIGNED_BYTE, sizeof(ImDrawVert), (const GLvoid*)((const char*)vtx_buffer + OFFSETOF(ImDrawVert, col)));
+        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++)
         {
@@ -96,7 +95,6 @@ void ImGui_ImplSdl_RenderDrawLists(ImDrawData* draw_data)
             idx_buffer += pcmd->ElemCount;
         }
     }
-    #undef OFFSETOF
 
     // Restore modified state
     glDisableClientState(GL_COLOR_ARRAY);

examples/sdl_opengl3_example/imgui_impl_sdl_gl3.cpp

@@ -273,11 +273,9 @@ bool ImGui_ImplSdlGL3_CreateDeviceObjects()
     glEnableVertexAttribArray(g_AttribLocationUV);
     glEnableVertexAttribArray(g_AttribLocationColor);
 
-#define OFFSETOF(TYPE, ELEMENT) ((size_t)&(((TYPE *)0)->ELEMENT))
-    glVertexAttribPointer(g_AttribLocationPosition, 2, GL_FLOAT, GL_FALSE, sizeof(ImDrawVert), (GLvoid*)OFFSETOF(ImDrawVert, pos));
-    glVertexAttribPointer(g_AttribLocationUV, 2, GL_FLOAT, GL_FALSE, sizeof(ImDrawVert), (GLvoid*)OFFSETOF(ImDrawVert, uv));
-    glVertexAttribPointer(g_AttribLocationColor, 4, GL_UNSIGNED_BYTE, GL_TRUE, sizeof(ImDrawVert), (GLvoid*)OFFSETOF(ImDrawVert, col));
-#undef OFFSETOF
+    glVertexAttribPointer(g_AttribLocationPosition, 2, GL_FLOAT, GL_FALSE, sizeof(ImDrawVert), (GLvoid*)IM_OFFSETOF(ImDrawVert, pos));
+    glVertexAttribPointer(g_AttribLocationUV, 2, GL_FLOAT, GL_FALSE, sizeof(ImDrawVert), (GLvoid*)IM_OFFSETOF(ImDrawVert, uv));
+    glVertexAttribPointer(g_AttribLocationColor, 4, GL_UNSIGNED_BYTE, GL_TRUE, sizeof(ImDrawVert), (GLvoid*)IM_OFFSETOF(ImDrawVert, col));
 
     ImGui_ImplSdlGL3_CreateFontsTexture();
 

imgui.h

@@ -39,7 +39,7 @@
 #define IM_FMTLIST(FMT)
 #endif
 #define IM_ARRAYSIZE(_ARR)          ((int)(sizeof(_ARR)/sizeof(*_ARR)))
-#define IM_OFFSETOF(_TYPE,_ELM)     ((size_t)&(((_TYPE*)0)->_ELM))
+#define IM_OFFSETOF(_TYPE,_MEMBER)  ((size_t)&(((_TYPE*)0)->_MEMBER))       // Offset of _MEMBER within _TYPE. Standardized as offsetof() in modern C++.
 
 #if defined(__clang__)
 #pragma clang diagnostic push