ImDrawData: Added FramebufferScale field (currently a copy of the value from io.DisplayFramebufferScale).

This is to allow render functions being written without pulling any data from ImGuiIO, allowing incoming multi-viewport feature to behave on Retina display and with multiple displays. If you are not using a custom binding, please update your render function code ahead of time, and use draw_data->FramebufferScale instead of io.DisplayFramebufferScale. (#2306, #1676)
Examples: Metal, OpenGL2, OpenGL3: Fixed offsetting of clipping rectangle with ImDrawData::DisplayPos != (0,0) when the display frame-buffer scale scale is not (1,1). While this doesn't make a difference when using master branch, this is effectively fixing support for multi-viewport with Mac Retina Displays on those examples. (#2306) Also using ImDrawData::FramebufferScale instead of io.DisplayFramebufferScale.
Examples: Clarified the use the ImDrawData::DisplayPos to offset clipping rectangles.

docs/CHANGELOG.txt

@@ -39,6 +39,11 @@ Breaking Changes:
 
 Other Changes:
 - Added .editorconfig file for text editors to standardize using spaces. (#2038) [@kudaba]
+- ImDrawData: Added FramebufferScale field (currently a copy of the value from io.DisplayFramebufferScale).
+  This is to allow render functions being written without pulling any data from ImGuiIO, allowing incoming
+  multi-viewport feature to behave on Retina display and with multiple displays.
+  If you are not using a custom binding, please update your render function code ahead of time,
+  and use draw_data->FramebufferScale instead of io.DisplayFramebufferScale. (#2306, #1676)
 - InputText: Fixed a bug where ESCAPE would not restore the initial value in all situations. (#2321) [@relick]
 - InputText: Fixed a bug where ESCAPE would be first captured by the Keyboard Navigation code. (#2321, #787)
 - InputText: Fixed redo buffer exhaustion handling (rare) which could corrupt the undo character buffer. (#2333)
@@ -65,6 +70,11 @@ Other Changes:
 - ImFontAtlas: FreeType: Added support for imgui allocators + custom FreeType only SetAllocatorFunctions. (#2285) [@Vuhdo]
 - ImFontAtlas: FreeType: Fixed using imgui_freetype.cpp in unity builds. (#2302)
 - Demo: Fixed "Log" demo not initializing properly, leading to the first line not showing before a Clear. (#2318) [@bluescan]
+- Examples: Metal, OpenGL2, OpenGL3: Fixed offsetting of clipping rectangle with ImDrawData::DisplayPos != (0,0) when
+  the display frame-buffer scale scale is not (1,1). While this doesn't make a difference when using master branch,
+  this is effectively fixing support for multi-viewport with Mac Retina Displays on those examples. (#2306) [@rasky, @ocornut]
+  Also using ImDrawData::FramebufferScale instead of io.DisplayFramebufferScale.
+- Examples: Clarified the use the ImDrawData::DisplayPos to offset clipping rectangles.
 - Examples: Win32: Using GetForegroundWindow()+IsChild() instead of GetActiveWindow() to be compatible with windows created
   in a different thread or parent. (#1951, #2087, #2156, #2232) [many people]
 - Examples: Win32: Added support for XInput games (if ImGuiConfigFlags_NavEnableGamepad is enabled).

examples/example_apple_opengl2/main.mm

@@ -92,13 +92,14 @@
 	[[self openGLContext] makeCurrentContext];
 
     ImGuiIO& io = ImGui::GetIO();
-    GLsizei width  = (GLsizei)(io.DisplaySize.x * io.DisplayFramebufferScale.x);
-    GLsizei height = (GLsizei)(io.DisplaySize.y * io.DisplayFramebufferScale.y);
+    ImDrawData* draw_data = ImGui::GetDrawData();
+    GLsizei width  = (GLsizei)(draw_data->DisplaySize.x * draw_data->FramebufferScale.x);
+    GLsizei height = (GLsizei)(draw_data->DisplaySize.y * draw_data->FramebufferScale.y);
     glViewport(0, 0, width, height);
 
 	glClearColor(clear_color.x, clear_color.y, clear_color.z, clear_color.w);
 	glClear(GL_COLOR_BUFFER_BIT);
-	ImGui_ImplOpenGL2_RenderDrawData(ImGui::GetDrawData());
+	ImGui_ImplOpenGL2_RenderDrawData(draw_data);
 
     // Present
     [[self openGLContext] flushBuffer];

examples/imgui_impl_allegro5.cpp

@@ -122,8 +122,9 @@ void ImGui_ImplAllegro5_RenderDrawData(ImDrawData* draw_data)
             indices = (const int*)cmd_list->IdxBuffer.Data;
         }
 
+        // Render command lists
         int idx_offset = 0;
-        ImVec2 pos = draw_data->DisplayPos;
+        ImVec2 clip_off = draw_data->DisplayPos;
         for (int cmd_i = 0; cmd_i < cmd_list->CmdBuffer.Size; cmd_i++)
         {
             const ImDrawCmd* pcmd = &cmd_list->CmdBuffer[cmd_i];
@@ -134,7 +135,7 @@ void ImGui_ImplAllegro5_RenderDrawData(ImDrawData* draw_data)
             else
             {
                 ALLEGRO_BITMAP* texture = (ALLEGRO_BITMAP*)pcmd->TextureId;
-                al_set_clipping_rectangle(pcmd->ClipRect.x - pos.x, pcmd->ClipRect.y - pos.y, pcmd->ClipRect.z - pcmd->ClipRect.x, pcmd->ClipRect.w - pcmd->ClipRect.y);
+                al_set_clipping_rectangle(pcmd->ClipRect.x - clip_off.x, pcmd->ClipRect.y - clip_off.y, pcmd->ClipRect.z - pcmd->ClipRect.x, pcmd->ClipRect.w - pcmd->ClipRect.y);
                 al_draw_prim(&vertices[0], g_VertexDecl, texture, idx_offset, idx_offset + pcmd->ElemCount, ALLEGRO_PRIM_TRIANGLE_LIST);
             }
             idx_offset += pcmd->ElemCount;

examples/imgui_impl_dx10.cpp

@@ -199,7 +199,7 @@ void ImGui_ImplDX10_RenderDrawData(ImDrawData* draw_data)
     // Render command lists
     int vtx_offset = 0;
     int idx_offset = 0;
-    ImVec2 pos = draw_data->DisplayPos;
+    ImVec2 clip_off = draw_data->DisplayPos;
     for (int n = 0; n < draw_data->CmdListsCount; n++)
     {
         const ImDrawList* cmd_list = draw_data->CmdLists[n];
@@ -214,7 +214,7 @@ void ImGui_ImplDX10_RenderDrawData(ImDrawData* draw_data)
             else
             {
                 // Apply scissor/clipping rectangle
-                const D3D10_RECT r = { (LONG)(pcmd->ClipRect.x - pos.x), (LONG)(pcmd->ClipRect.y - pos.y), (LONG)(pcmd->ClipRect.z - pos.x), (LONG)(pcmd->ClipRect.w - pos.y)};
+                const D3D10_RECT r = { (LONG)(pcmd->ClipRect.x - clip_off.x), (LONG)(pcmd->ClipRect.y - clip_off.y), (LONG)(pcmd->ClipRect.z - clip_off.x), (LONG)(pcmd->ClipRect.w - clip_off.y)};
                 ctx->RSSetScissorRects(1, &r);
 
                 // Bind texture, Draw

examples/imgui_impl_dx11.cpp

@@ -204,7 +204,7 @@ void ImGui_ImplDX11_RenderDrawData(ImDrawData* draw_data)
     // Render command lists
     int vtx_offset = 0;
     int idx_offset = 0;
-    ImVec2 pos = draw_data->DisplayPos;
+    ImVec2 clip_off = draw_data->DisplayPos;
     for (int n = 0; n < draw_data->CmdListsCount; n++)
     {
         const ImDrawList* cmd_list = draw_data->CmdLists[n];
@@ -219,7 +219,7 @@ void ImGui_ImplDX11_RenderDrawData(ImDrawData* draw_data)
             else
             {
                 // Apply scissor/clipping rectangle
-                const D3D11_RECT r = { (LONG)(pcmd->ClipRect.x - pos.x), (LONG)(pcmd->ClipRect.y - pos.y), (LONG)(pcmd->ClipRect.z - pos.x), (LONG)(pcmd->ClipRect.w - pos.y) };
+                const D3D11_RECT r = { (LONG)(pcmd->ClipRect.x - clip_off.x), (LONG)(pcmd->ClipRect.y - clip_off.y), (LONG)(pcmd->ClipRect.z - clip_off.x), (LONG)(pcmd->ClipRect.w - clip_off.y) };
                 ctx->RSSetScissorRects(1, &r);
 
                 // Bind texture, Draw

examples/imgui_impl_dx12.cpp

@@ -199,7 +199,7 @@ void ImGui_ImplDX12_RenderDrawData(ImDrawData* draw_data, ID3D12GraphicsCommandL
     // Render command lists
     int vtx_offset = 0;
     int idx_offset = 0;
-    ImVec2 pos = draw_data->DisplayPos;
+    ImVec2 clip_off = draw_data->DisplayPos;
     for (int n = 0; n < draw_data->CmdListsCount; n++)
     {
         const ImDrawList* cmd_list = draw_data->CmdLists[n];
@@ -212,7 +212,7 @@ void ImGui_ImplDX12_RenderDrawData(ImDrawData* draw_data, ID3D12GraphicsCommandL
             }
             else
             {
-                const D3D12_RECT r = { (LONG)(pcmd->ClipRect.x - pos.x), (LONG)(pcmd->ClipRect.y - pos.y), (LONG)(pcmd->ClipRect.z - pos.x), (LONG)(pcmd->ClipRect.w - pos.y) };
+                const D3D12_RECT r = { (LONG)(pcmd->ClipRect.x - clip_off.x), (LONG)(pcmd->ClipRect.y - clip_off.y), (LONG)(pcmd->ClipRect.z - clip_off.x), (LONG)(pcmd->ClipRect.w - clip_off.y) };
                 ctx->SetGraphicsRootDescriptorTable(1, *(D3D12_GPU_DESCRIPTOR_HANDLE*)&pcmd->TextureId);
                 ctx->RSSetScissorRects(1, &r);
                 ctx->DrawIndexedInstanced(pcmd->ElemCount, 1, idx_offset, vtx_offset, 0);

examples/imgui_impl_dx9.cpp

@@ -166,7 +166,7 @@ void ImGui_ImplDX9_RenderDrawData(ImDrawData* draw_data)
     // Render command lists
     int vtx_offset = 0;
     int idx_offset = 0;
-    ImVec2 pos = draw_data->DisplayPos;
+    ImVec2 clip_off = draw_data->DisplayPos;
     for (int n = 0; n < draw_data->CmdListsCount; n++)
     {
         const ImDrawList* cmd_list = draw_data->CmdLists[n];
@@ -179,7 +179,7 @@ void ImGui_ImplDX9_RenderDrawData(ImDrawData* draw_data)
             }
             else
             {
-                const RECT r = { (LONG)(pcmd->ClipRect.x - pos.x), (LONG)(pcmd->ClipRect.y - pos.y), (LONG)(pcmd->ClipRect.z - pos.x), (LONG)(pcmd->ClipRect.w - pos.y) };
+                const RECT r = { (LONG)(pcmd->ClipRect.x - clip_off.x), (LONG)(pcmd->ClipRect.y - clip_off.y), (LONG)(pcmd->ClipRect.z - clip_off.x), (LONG)(pcmd->ClipRect.w - clip_off.y) };
                 const LPDIRECT3DTEXTURE9 texture = (LPDIRECT3DTEXTURE9)pcmd->TextureId;
                 g_pd3dDevice->SetTexture(0, texture);
                 g_pd3dDevice->SetScissorRect(&r);

examples/imgui_impl_marmalade.cpp

@@ -3,6 +3,8 @@
 
 // Implemented features:
 //  [X] Renderer: User texture binding. Use 'CIwTexture*' as ImTextureID. Read the FAQ about ImTextureID in imgui.cpp.
+// Missing features:
+//  [ ] Renderer: Clipping rectangles are not honored.
 
 // You can copy and use unmodified imgui_impl_* files in your project. See main.cpp for an example of using this.
 // If you are new to dear imgui, read examples/README.txt and read the documentation at the top of imgui.cpp.
@@ -38,10 +40,6 @@ static ImVec2       g_RenderScale = ImVec2(1.0f,1.0f);
 // (this used to be set in io.RenderDrawListsFn and called by ImGui::Render(), but you can now call this directly from your main loop)
 void ImGui_Marmalade_RenderDrawData(ImDrawData* draw_data)
 {
-    // Handle cases of screen coordinates != from framebuffer coordinates (e.g. retina displays)
-    ImGuiIO& io = ImGui::GetIO();
-    draw_data->ScaleClipRects(io.DisplayFramebufferScale);
-
     // Render command lists
     for (int n = 0; n < draw_data->CmdListsCount; n++)
     {
@@ -54,7 +52,7 @@ void ImGui_Marmalade_RenderDrawData(ImDrawData* draw_data)
 
         for (int i = 0; i < nVert; i++)
         {
-            // TODO: optimize multiplication on gpu using vertex shader/projection matrix.
+            // FIXME-OPT: optimize multiplication on GPU using vertex shader/projection matrix.
             pVertStream[i].x = cmd_list->VtxBuffer[i].pos.x * g_RenderScale.x;
             pVertStream[i].y = cmd_list->VtxBuffer[i].pos.y * g_RenderScale.y;
             pUVStream[i].x = cmd_list->VtxBuffer[i].uv.x;
@@ -76,6 +74,7 @@ void ImGui_Marmalade_RenderDrawData(ImDrawData* draw_data)
             }
             else
             {
+                // FIXME: Not honoring ClipRect fields.
                 CIwMaterial* pCurrentMaterial = IW_GX_ALLOC_MATERIAL();
                 pCurrentMaterial->SetShadeMode(CIwMaterial::SHADE_FLAT);
                 pCurrentMaterial->SetCullMode(CIwMaterial::CULL_NONE);

examples/imgui_impl_metal.mm

@@ -10,6 +10,7 @@
 
 // CHANGELOG
 // (minor and older changes stripped away, please see git history for details)
+//  2019-02-11: Metal: 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.
 //  2018-07-05: Metal: Added new Metal backend implementation.
 
@@ -401,12 +402,10 @@ void ImGui_ImplMetal_DestroyDeviceObjects()
         commandEncoder:(id<MTLRenderCommandEncoder>)commandEncoder
 {
     // Avoid rendering when minimized, scale coordinates for retina displays (screen coordinates != framebuffer coordinates)
-    ImGuiIO &io = ImGui::GetIO();
-    int fb_width = (int)(drawData->DisplaySize.x * io.DisplayFramebufferScale.x);
-    int fb_height = (int)(drawData->DisplaySize.y * io.DisplayFramebufferScale.y);
+    int fb_width = (int)(drawData->DisplaySize.x * draw_data->FramebufferScale.x);
+    int fb_height = (int)(drawData->DisplaySize.y * draw_data->FramebufferScale.y);
     if (fb_width <= 0 || fb_height <= 0 || drawData->CmdListsCount == 0)
         return;
-    drawData->ScaleClipRects(io.DisplayFramebufferScale);
 
     [commandEncoder setCullMode:MTLCullModeNone];
     [commandEncoder setDepthStencilState:g_sharedMetalContext.depthStencilState];
@@ -450,9 +449,13 @@ void ImGui_ImplMetal_DestroyDeviceObjects()
 
     [commandEncoder setVertexBuffer:vertexBuffer.buffer offset:0 atIndex:0];
 
+    // 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
     size_t vertexBufferOffset = 0;
     size_t indexBufferOffset = 0;
-    ImVec2 pos = drawData->DisplayPos;
     for (int n = 0; n < drawData->CmdListsCount; n++)
     {
         const ImDrawList* cmd_list = drawData->CmdLists[n];
@@ -473,7 +476,13 @@ void ImGui_ImplMetal_DestroyDeviceObjects()
             }
             else
             {
-                ImVec4 clip_rect = ImVec4(pcmd->ClipRect.x - pos.x, pcmd->ClipRect.y - pos.y, pcmd->ClipRect.z - pos.x, pcmd->ClipRect.w - pos.y);
+                // 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

examples/imgui_impl_opengl2.cpp

@@ -18,6 +18,7 @@
 
 // CHANGELOG
 // (minor and older changes stripped away, please see git history for details)
+//  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.
@@ -76,12 +77,10 @@ void    ImGui_ImplOpenGL2_NewFrame()
 void ImGui_ImplOpenGL2_RenderDrawData(ImDrawData* draw_data)
 {
     // Avoid rendering when minimized, scale coordinates for retina displays (screen coordinates != framebuffer coordinates)
-    ImGuiIO& io = ImGui::GetIO();
-    int fb_width = (int)(draw_data->DisplaySize.x * io.DisplayFramebufferScale.x);
-    int fb_height = (int)(draw_data->DisplaySize.y * io.DisplayFramebufferScale.y);
+    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;
-    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, polygon fill.
@@ -122,8 +121,11 @@ void ImGui_ImplOpenGL2_RenderDrawData(ImDrawData* draw_data)
     glPushMatrix();
     glLoadIdentity();
 
+    // 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
-    ImVec2 pos = draw_data->DisplayPos;
     for (int n = 0; n < draw_data->CmdListsCount; n++)
     {
         const ImDrawList* cmd_list = draw_data->CmdLists[n];
@@ -143,7 +145,13 @@ void ImGui_ImplOpenGL2_RenderDrawData(ImDrawData* draw_data)
             }
             else
             {
-                ImVec4 clip_rect = ImVec4(pcmd->ClipRect.x - pos.x, pcmd->ClipRect.y - pos.y, pcmd->ClipRect.z - pos.x, pcmd->ClipRect.w - pos.y);
+                // 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

examples/imgui_impl_opengl3.cpp

@@ -11,6 +11,7 @@
 
 // CHANGELOG
 // (minor and older changes stripped away, please see git history for details)
+//  2019-02-11: OpenGL: Projecting clipping rectangles correctly using draw_data->FramebufferScale to allow multi-viewports for retina display.
 //  2019-02-01: OpenGL: Using GLSL 410 shaders for any version over 410 (e.g. 430, 450).
 //  2018-11-30: Misc: Setting up io.BackendRendererName so it can be displayed in the About Window.
 //  2018-11-13: OpenGL: Support for GL 4.5's glClipControl(GL_UPPER_LEFT).
@@ -137,12 +138,10 @@ void    ImGui_ImplOpenGL3_NewFrame()
 void    ImGui_ImplOpenGL3_RenderDrawData(ImDrawData* draw_data)
 {
     // Avoid rendering when minimized, scale coordinates for retina displays (screen coordinates != framebuffer coordinates)
-    ImGuiIO& io = ImGui::GetIO();
-    int fb_width = (int)(draw_data->DisplaySize.x * io.DisplayFramebufferScale.x);
-    int fb_height = (int)(draw_data->DisplaySize.y * io.DisplayFramebufferScale.y);
+    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;
-    draw_data->ScaleClipRects(io.DisplayFramebufferScale);
 
     // Backup GL state
     GLenum last_active_texture; glGetIntegerv(GL_ACTIVE_TEXTURE, (GLint*)&last_active_texture);
@@ -220,8 +219,11 @@ void    ImGui_ImplOpenGL3_RenderDrawData(ImDrawData* draw_data)
     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));
 
-    // Draw
-    ImVec2 pos = draw_data->DisplayPos;
+    // 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];
@@ -243,7 +245,13 @@ void    ImGui_ImplOpenGL3_RenderDrawData(ImDrawData* draw_data)
             }
             else
             {
-                ImVec4 clip_rect = ImVec4(pcmd->ClipRect.x - pos.x, pcmd->ClipRect.y - pos.y, pcmd->ClipRect.z - pos.x, pcmd->ClipRect.w - pos.y);
+                // 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

examples/imgui_impl_vulkan.cpp

@@ -289,7 +289,7 @@ void ImGui_ImplVulkan_RenderDrawData(ImDrawData* draw_data, VkCommandBuffer comm
     // Render the command lists:
     int vtx_offset = 0;
     int idx_offset = 0;
-    ImVec2 display_pos = draw_data->DisplayPos;
+    ImVec2 clip_off = draw_data->DisplayPos;
     for (int n = 0; n < draw_data->CmdListsCount; n++)
     {
         const ImDrawList* cmd_list = draw_data->CmdLists[n];
@@ -305,8 +305,8 @@ void ImGui_ImplVulkan_RenderDrawData(ImDrawData* draw_data, VkCommandBuffer comm
                 // Apply scissor/clipping rectangle
                 // FIXME: We could clamp width/height based on clamped min/max values.
                 VkRect2D scissor;
-                scissor.offset.x = (int32_t)(pcmd->ClipRect.x - display_pos.x) > 0 ? (int32_t)(pcmd->ClipRect.x - display_pos.x) : 0;
-                scissor.offset.y = (int32_t)(pcmd->ClipRect.y - display_pos.y) > 0 ? (int32_t)(pcmd->ClipRect.y - display_pos.y) : 0;
+                scissor.offset.x = (int32_t)(pcmd->ClipRect.x - clip_off.x) > 0 ? (int32_t)(pcmd->ClipRect.x - clip_off.x) : 0;
+                scissor.offset.y = (int32_t)(pcmd->ClipRect.y - clip_off.y) > 0 ? (int32_t)(pcmd->ClipRect.y - clip_off.y) : 0;
                 scissor.extent.width = (uint32_t)(pcmd->ClipRect.z - pcmd->ClipRect.x);
                 scissor.extent.height = (uint32_t)(pcmd->ClipRect.w - pcmd->ClipRect.y + 1); // FIXME: Why +1 here?
                 vkCmdSetScissor(command_buffer, 0, 1, &scissor);

imgui.cpp

@@ -3731,6 +3731,7 @@ static void SetupDrawData(ImVector<ImDrawList*>* draw_lists, ImDrawData* draw_da
     draw_data->TotalVtxCount = draw_data->TotalIdxCount = 0;
     draw_data->DisplayPos = ImVec2(0.0f, 0.0f);
     draw_data->DisplaySize = io.DisplaySize;
+    draw_data->FramebufferScale = io.DisplayFramebufferScale;
     for (int n = 0; n < draw_lists->Size; n++)
     {
         draw_data->TotalVtxCount += draw_lists->Data[n]->VtxBuffer.Size;

imgui.h

@@ -1300,7 +1300,7 @@ struct ImGuiIO
     float       FontGlobalScale;                // = 1.0f           // Global scale all fonts
     bool        FontAllowUserScaling;           // = false          // Allow user scaling text of individual window with CTRL+Wheel.
     ImFont*     FontDefault;                    // = NULL           // Font to use on NewFrame(). Use NULL to uses Fonts->Fonts[0].
-    ImVec2      DisplayFramebufferScale;        // = (1.0f,1.0f)    // For hi-dpi/retina display or other situations where window coordinates are different from framebuffer coordinates. User storage only, presently not used by ImGui.
+    ImVec2      DisplayFramebufferScale;        // = (1, 1)         // For retina display or other situations where window coordinates are different from framebuffer coordinates. This generally ends up in ImDrawData::FramebufferScale.
 
     // Miscellaneous options
     bool        MouseDrawCursor;                // = false          // Request ImGui to draw a mouse cursor for you (if you are on a platform without a mouse cursor). Cannot be easily renamed to 'io.ConfigXXX' because this is frequently used by back-end implementations.
@@ -1893,13 +1893,14 @@ struct ImDrawData
     int             TotalVtxCount;          // For convenience, sum of all ImDrawList's VtxBuffer.Size
     ImVec2          DisplayPos;             // Upper-left position of the viewport to render (== upper-left of the orthogonal projection matrix to use)
     ImVec2          DisplaySize;            // Size of the viewport to render (== io.DisplaySize for the main viewport) (DisplayPos + DisplaySize == lower-right of the orthogonal projection matrix to use)
+    ImVec2          FramebufferScale;       // Amount of pixels for each unit of DisplaySize. Based on io.DisplayFramebufferScale. Generally (1,1) on normal display, (2,2) on OSX with Retina display.
 
     // Functions
     ImDrawData()    { Valid = false; Clear(); }
     ~ImDrawData()   { Clear(); }
-    void Clear()    { Valid = false; CmdLists = NULL; CmdListsCount = TotalVtxCount = TotalIdxCount = 0; DisplayPos = DisplaySize = ImVec2(0.f, 0.f); } // The ImDrawList are owned by ImGuiContext!
-    IMGUI_API void  DeIndexAllBuffers();                // Helper to convert all buffers from indexed to non-indexed, in case you cannot render indexed. Note: this is slow and most likely a waste of resources. Always prefer indexed rendering!
-    IMGUI_API void  ScaleClipRects(const ImVec2& sc);   // Helper to scale the ClipRect field of each ImDrawCmd. Use if your final output buffer is at a different scale than ImGui expects, or if there is a difference between your window resolution and framebuffer resolution.
+    void Clear()    { Valid = false; CmdLists = NULL; CmdListsCount = TotalVtxCount = TotalIdxCount = 0; DisplayPos = DisplaySize = FramebufferScale = ImVec2(0.f, 0.f); } // The ImDrawList are owned by ImGuiContext!
+    IMGUI_API void  DeIndexAllBuffers();                    // Helper to convert all buffers from indexed to non-indexed, in case you cannot render indexed. Note: this is slow and most likely a waste of resources. Always prefer indexed rendering!
+    IMGUI_API void  ScaleClipRects(const ImVec2& fb_scale); // Helper to scale the ClipRect field of each ImDrawCmd. Use if your final output buffer is at a different scale than ImGui expects, or if there is a difference between your window resolution and framebuffer resolution.
 };
 
 //-----------------------------------------------------------------------------

imgui_draw.cpp

@@ -1287,8 +1287,10 @@ void ImDrawData::DeIndexAllBuffers()
     }
 }
 
-// Helper to scale the ClipRect field of each ImDrawCmd. Use if your final output buffer is at a different scale than ImGui expects, or if there is a difference between your window resolution and framebuffer resolution.
-void ImDrawData::ScaleClipRects(const ImVec2& scale)
+// Helper to scale the ClipRect field of each ImDrawCmd. 
+// Use if your final output buffer is at a different scale than draw_data->DisplaySize, 
+// or if there is a difference between your window resolution and framebuffer resolution.
+void ImDrawData::ScaleClipRects(const ImVec2& fb_scale)
 {
     for (int i = 0; i < CmdListsCount; i++)
     {
@@ -1296,7 +1298,7 @@ void ImDrawData::ScaleClipRects(const ImVec2& scale)
         for (int cmd_i = 0; cmd_i < cmd_list->CmdBuffer.Size; cmd_i++)
         {
             ImDrawCmd* cmd = &cmd_list->CmdBuffer[cmd_i];
-            cmd->ClipRect = ImVec4(cmd->ClipRect.x * scale.x, cmd->ClipRect.y * scale.y, cmd->ClipRect.z * scale.x, cmd->ClipRect.w * scale.y);
+            cmd->ClipRect = ImVec4(cmd->ClipRect.x * fb_scale.x, cmd->ClipRect.y * fb_scale.y, cmd->ClipRect.z * fb_scale.x, cmd->ClipRect.w * fb_scale.y);
         }
     }
 }