Windows OS DX11 - Handling Render on Resizing Main Window

[CycloneRing]

Hi,
How can I render on resizing the window, I want to update gui when user resizes the window and avoid black borders.

[thedmd]

Handle WM_PAINT message in your WinProc and render a frame there. This should do the trick.

[CycloneRing]

I did and it gone wrong can you show me some code?

[thedmd]

Basic trick is to put frame rendering in a function and call it while handling WM_PAINT message.

Describe what got wrong.

[rokups]

Does Windows even send WM_PAINT during resize? AFAIK all rendering stops until resize grip is released. It is possible to work this around by rendering a frame on WM_SIZE (untested, actually i do it via SDL on SDL_WINDOWEVENT_RESIZED event), but it is a hack and can cause it's own problems.

[thedmd]

Does Windows even send WM_PAINT during resize?

Yes

[thedmd]

In main function:

    // Main loop
    while (true)
    {
        MSG msg = {};
        while (PeekMessage(&msg, nullptr, 0U, 0U, PM_REMOVE))
        {
            if (msg.message == WM_QUIT)
                return static_cast<int>(msg.wParam);

            TranslateMessage(&msg);
            DispatchMessage(&msg);

            if (IsIconic(hWnd))
                Sleep(16);
        }

        ImGui_Frame(hWnd);

        Sleep(16);
    }

In WinProc:

        case WM_PAINT:
            ImGui_Frame(hWnd);
            return 0;

And my ImGui_Frame function is more or less:

void ImGui_Frame(HWND hWnd)
{
    if (g_InFrame)
        return;

    g_InFrame = true;

    ImGuiStyle& style = ImGui::GetStyle();

    ImGui_ImplDX11_NewFrame();
    ImGui_ImplWin32_NewFrame();
    ImGui::NewFrame();

    ImGui::Text("Hello World");

    // Rendering
    g_pd3dDeviceContext->OMSetRenderTargets(1, &g_mainRenderTargetView, nullptr);
    g_pd3dDeviceContext->ClearRenderTargetView(g_mainRenderTargetView, (float*)&style.Colors[ImGuiCol_WindowBg]);
    ImGui::Render();
    ImGui_ImplDX11_RenderDrawData(ImGui::GetDrawData());

    g_pSwapChain->Present(1, 0); // Present with vsync

    g_InFrame = false;
}