[FFmpeg-devel] [PATCH v4 1/1] avdevice/gdigrab add use_captureblt option

[fgodt]

On 2020/1/17 上午2:00, Calvin Walton wrote:
> On Thu, 2020-01-16 at 09:08 +0800, fgodt wrote:
>
>>> By default, this is set to @code{1}, which means that gdigrab will
>>> use
>>> the CAPTUREBLT flag when grabbing images of a window. With this
>>> flag
>>> set, gdigrab will capture the entire contents of a window even if
>>> it is
>>> covered by other windows on the screen.
>>>
>>> If this option is set to @code{0}, the image captured will match
>>> what
>>> you see on the screen: the contents of any windows covering the
>>> selected window will be visible in the capture.
>>>
>>> Depending on your Windows version and graphics settings, you may
>>> see
>>> the mouse cursor flicker on your screen while capturing with this
>>> option set to @code{1}. If that happens, you can disable CAPTUREBLT
>>> by
>>> setting this option to @code{0}.
>>>
>> Thanks for you suggestion, but there is issue, without the
>> CAPTUREBLT
>> flag not change any thing for normal window in captured video, the
>> worke
>> same like use CAPTUREBLT flag. So the can capture window even if it
>> is
>> covered.
> Ah, fun, this is based on a misinterpretation of the windows
> documentation:
>
> CAPTUREBLT
> Includes any windows that are layered on top of your window in the
> resulting image. By default, the image only contains your window.
>
> But according to this StackOverflow response:
> https://stackoverflow.com/a/4646999
>
> What that actually means is that CAPTUREBLT includes windows with the
> "WS_EX_LAYERED" window style that overlap the window, not *any* window.
>
> Layered windows are described in:
> https://docs.microsoft.com/en-us/windows/win32/winmsg/window-features#layered-windows
>
>
> I think we should unconditionally remove the CAPTUREBLT flag, there's
> no need for any options or documentation changes.
>
Thanks, if we remove CAPTUREBLT flag the user may can't capture layered 
window(use WS_EX_LAYERED extended), it is ok for this?

fgodt