WM_PAINT and DX12

In DirectX 12, the handling of the WM_PAINT message is slightly different compared to previous versions of DirectX. DirectX 12 allows more control over the rendering pipeline and introduces a lower-level programming model.

Traditionally, when using DirectX 9 or earlier versions, the WM_PAINT message was used to trigger rendering and present the frame to the screen. This involved retrieving the device context (HDC), creating a swap chain, and performing the rendering operations. However, in DirectX 12, the approach is different due to the more explicit control provided by the API.

In DirectX 12, you typically set up a rendering loop that runs continuously rather than relying on the WM_PAINT message. The loop is responsible for synchronizing with the display refresh rate, updating the game logic, and rendering frames.

Here is a simplified example of a DirectX 12 rendering loop:

cppCopy code
// Game loop

while (!quit)

{

    // Process input, update game logic



    // Render frame

    Render();



    // Present the frame

    Present();

}

Within the Render() function, you would perform the necessary DirectX 12 operations, such as recording command lists, executing commands on the GPU, and rendering the scene.

The Present() function is responsible for presenting the frame to the screen. In DirectX 12, this is typically done by submitting the command lists to the command queue and signaling the frame completion using fences or other synchronization mechanisms.

To integrate this rendering loop with the Windows message pump and handle the WM_PAINT message, you can modify your window procedure accordingly:

cppCopy code
LRESULT CALLBACK WindowProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)

{

    switch (message)

    {

        case WM_PAINT:

        {

            // Process WM_PAINT message

            ValidateRect(hWnd, nullptr);

            Render();

            Present();

            return 0;

        }

        // Other message handling

    }



    return DefWindowProc(hWnd, message, wParam, lParam);

}

In this modified window procedure, the WM_PAINT message triggers the rendering and presentation of the frame. However, note that the game loop (Render and Present calls) should still be handled separately and not be limited solely to the WM_PAINT message.

Remember that this is a simplified example, and the actual implementation may vary depending on your specific requirements and architecture. Additionally, it's worth noting that DirectX 12 programming requires an understanding of the API and its associated concepts, such as command lists, command queues, and synchronization.