[vlc-devel] [PATCH] win32/drawable: process the WM_SIZE asynchronously

[Alexandre Janniaux]

Hi,

How does resizing work with asynchronous posting? I had the
feeling that win32 API needed synchronous resizing to be able
to achieve smooth resizing, is it wrong or unrelated here?

Regards,
--
Alexandre Janniaux
Videolabs

On Mon, Feb 22, 2021 at 08:25:30AM +0100, Steve Lhomme wrote:
> The vout_window_ReportSize call may make changes in underlying HWND's which in
> turn might make reentrant calls to WinVoutEventProc, which might in turn call
> WM_SIZE in the same stack (when resizing quickly).
>
> vout_window_ReportSize() is not reentrant so we should avoid calling it in
> calls that might be reentrant (WM_SIZE in this case).
>
> We keep the latest WM_SIZE so when the asynchronous call is done, we already
> have the most up to date value.
> ---
>  modules/video_output/win32/drawable.c | 10 +++++++++-
>  1 file changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/modules/video_output/win32/drawable.c b/modules/video_output/win32/drawable.c
> index 90106558848..c6f2f573a2f 100644
> --- a/modules/video_output/win32/drawable.c
> +++ b/modules/video_output/win32/drawable.c
> @@ -77,6 +77,8 @@ struct drawable_sys
>      HWND hWnd;
>      HWND embed_hwnd;
>      RECT rect_parent;
> +
> +    unsigned int width, height;
>  };
>
>  static LRESULT CALLBACK WinVoutEventProc(HWND hwnd, UINT message,
> @@ -131,7 +133,13 @@ static LRESULT CALLBACK WinVoutEventProc(HWND hwnd, UINT message,
>          return 0;
>
>      case WM_SIZE:
> -        vout_window_ReportSize(wnd, LOWORD(lParam), HIWORD(lParam));
> +        sys->width  = LOWORD(lParam);
> +        sys->height = HIWORD(lParam);
> +        PostMessage(hwnd, WM_USER, 0, lParam);
> +        return 0;
> +
> +    case WM_USER:
> +        vout_window_ReportSize(wnd, sys->width, sys->height);
>          return 0;
>
>      default:
> --
> 2.29.2
>
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