Custom DX9: backend: certain Widgets do not get clipped inside the Window properly

[ClonkAndre]

Version/Branch of Dear ImGui:

Version: 1.89.8 (18980)
Branch: master

Back-end/Renderer/Compiler/OS

Back-ends: imgui_impl_win32 + custom imgui_impl_dx9 (Was modified to use shaders instead of fixed function DX9)
Compiler: VS2022 MSVC
Operating System: Windows 11

My Issue/Question:

I'm using a dx9 device end scene hook with a custom imgui_impl_dx9 backend to get Dear ImGui to work with GTA IV.
It all works fine, except that some Widgets (Like the Listbox and the items inside the Listbox) will not stay inside the Window when you scroll. Basically the whole clipping behaviour is acting weird.

A video of that behaviour can be seen below where i'm testing this with the demo window.

Any help would be appreciated! Thanks!

Screenshots/Video

imgui.mp4

Code

My OnBeforeD3D9DeviceEndScene Method

	static void OnBeforeD3D9DeviceEndScene(IDirect3DDevice9* d3d9Device)
	{
		// Initialize ImGui if not initialized yet
		InitializeImGui(d3d9Device);

		// ImGui is not initialized, return.
		//if (!ImGuiStates::s_bIsImGuiInitialized)
		//	return;

		// Get ImGuiIO
		ImGuiIO& io = ImGui::GetIO(); (void)io;

		// Get the main viewport of ImGui
		/*ImGuiViewport* vp = ImGui::GetMainViewport();*/

		// Show cursor and disable mouse forever for testing
		io.MouseDrawCursor = true;
		ImGuiStates::s_bImGuiWantsMouseDisabled = true;

		// Create new ImGui Frame
		ImGui_ImplDX9_NewFrame();
		ImGui_ImplWin32_NewFrame();
		ImGui::NewFrame();

		ImGui::ShowDemoWindow();

		// End ImGui Frame and draw
		ImGui::EndFrame();
		ImGui::Render();
		ImGui_ImplDX9_RenderDrawData(ImGui::GetDrawData());
	}

The InitializeImGui Method

	static void InitializeImGui(IDirect3DDevice9* d3d9Device)
	{
		if (ImGuiStates::s_bIsImGuiInitialized)
			return;
		if (ImGuiStates::s_bStopTryingToInitializeImGui)
			return;

		D3DDEVICE_CREATION_PARAMETERS creationParams;
		d3d9Device->GetCreationParameters(&creationParams);

		// Setup ImGui stuff
		IMGUI_CHECKVERSION();
		ImGui::CreateContext();
		ImGuiIO& io = ImGui::GetIO(); (void)io;
		io.IniFilename = NULL;

		// Initialize the win32 backend
		ImGui_ImplWin32_Init(creationParams.hFocusWindow);

		// Initialize the dx9 backend
		ImGui_ImplDX9_Init(d3d9Device);

		ImGuiStates::s_bIsImGuiInitialized = true;
	}

[ocornut]

Your rendering backend is not honoring the ImDrawCmd::ClipRect field correctly.
Perhaps the SetScissorRect() call has no effect in your situation for some reason, in spite of bd->pd3dDevice->SetRenderState(D3DRS_SCISSORTESTENABLE, TRUE); being called. I don't know the reason. Perhaps you can replicate scissoring in the vertex shader.

There's a DX9+Shader backend at #3874 which didn't seem to mention this issue.

This is not our backend nor our code so we can't really provide support for it.