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Issue ImGui API calls inside app render pass #6

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Merged
merged 1 commit into from
Mar 24, 2025
Merged

Issue ImGui API calls inside app render pass #6

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6 changes: 6 additions & 0 deletions guide/src/dear_imgui/imgui_integration.md
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Original file line number Diff line number Diff line change
Expand Up @@ -33,9 +33,15 @@ Start a new ImGui frame after resetting the render fence, and show the demo wind
m_device->resetFences(*render_sync.drawn);
m_imgui->new_frame();

// ...
render_sync.command_buffer.beginRendering(rendering_info);
ImGui::ShowDemoWindow();
// draw stuff here.
render_sync.command_buffer.endRendering();
```

ImGui doesn't draw anything here (the actual draw command requires the Command Buffer), it's just a good customization point to use indirection at later.

We use a separate render pass for Dear ImGui, again for isolation, and to enable us to change the main render pass later, eg by adding a depth buffer attachment (`DearImGui` is setup assuming its render pass will only use a single color attachment).

```cpp
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3 changes: 1 addition & 2 deletions src/app.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -183,8 +183,6 @@ void App::main_loop() {
m_device->resetFences(*render_sync.drawn);
m_imgui->new_frame();

ImGui::ShowDemoWindow();

auto command_buffer_bi = vk::CommandBufferBeginInfo{};
// this flag means recorded commands will not be reused.
command_buffer_bi.setFlags(
Expand Down Expand Up @@ -222,6 +220,7 @@ void App::main_loop() {
.setLayerCount(1);

render_sync.command_buffer.beginRendering(rendering_info);
ImGui::ShowDemoWindow();
// draw stuff here.
render_sync.command_buffer.endRendering();

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