[FFmpeg-devel] [PATCH v3 1/1] avdevice/gdigrab: Add use_captureblt option for disable or use CAPTUREBLT flag, when useing the bitblt function with CAPTUREBLT it caused the mouse cursor flicker. most time we don't need this flag to capture window

[Marton Balint]

On Mon, 30 Dec 2019, fgodtdev at hotmail.com wrote:

> From: FgoDt <fgodtdev at hotmail.com>

The commit description should go here, not in the commit title.

>
> Signed-off-by: fgodt <fgodtdev at hotmail.com>
> ---
> doc/indevs.texi       |  6 ++++++
> libavdevice/gdigrab.c | 10 +++++++++-
> 2 files changed, 15 insertions(+), 1 deletion(-)
>
> diff --git a/doc/indevs.texi b/doc/indevs.texi
> index 92bc65be41..43b0bd0465 100644
> --- a/doc/indevs.texi
> +++ b/doc/indevs.texi
> @@ -748,6 +748,12 @@ When capturing a region with @var{video_size}, set the distance from the top edg
> 
> Note that the offset calculation is from the top left corner of the primary monitor on Windows. If you have a monitor positioned above your primary monitor, you will need to use a negative @var{offset_y} value to move the region to that monitor.
> 
> + at item use_captureblt
> +When use gdigrab to capture window or desktop, the mouse cursor will flicker.

Why? Does this happen with every windows version? This does not seem like 
the right fix. In fact, I dont't see how this can work, because mouse is 
drawn upon the captured video "manually" in paint_mouse_pointer. Could you 
dig deeper what is the main cause of the issue?

> +Disable CAPTUREBLT FLAG by set value @code{0} to fix cursor flickering. Default value is @code{1}
> +

Doesn't this change what is captured when the user captures a single 
window and something is dragged on top? That alone might be a useful 
addition, but the documentation as is would be totally misleading.

> +Note the value @code{1} is essential to capture specific  window
> +
> @end table
> 
> @section iec61883
> diff --git a/libavdevice/gdigrab.c b/libavdevice/gdigrab.c
> index f4444406fa..658719e929 100644
> --- a/libavdevice/gdigrab.c
> +++ b/libavdevice/gdigrab.c
> @@ -53,6 +53,8 @@ struct gdigrab {
>     int        offset_x;    /**< Capture x offset (private option) */
>     int        offset_y;    /**< Capture y offset (private option) */
> 
> +    int        use_captureblt; /**< Capture gdi window with CAPTUREBLT flag (private option) */
> +
>     HWND       hwnd;        /**< Handle of the window for the grab */
>     HDC        source_hdc;  /**< Source device context */
>     HDC        dest_hdc;    /**< Destination, source-compatible DC */
> @@ -542,6 +544,8 @@ static int gdigrab_read_packet(AVFormatContext *s1, AVPacket *pkt)
>
>     int64_t curtime, delay;
> 
> +    unsigned long flag = SRCCOPY;
> +
>     /* Calculate the time of the next frame */
>     time_frame += INT64_C(1000000);
> 
> @@ -570,12 +574,15 @@ static int gdigrab_read_packet(AVFormatContext *s1, AVPacket *pkt)
>         return AVERROR(ENOMEM);
>     pkt->pts = curtime;
> 
> +    if(gdigrab->use_captureblt)
> +        flag |= CAPTUREBLT;
> +
>     /* Blit screen grab */
>     if (!BitBlt(dest_hdc, 0, 0,
>                 clip_rect.right - clip_rect.left,
>                 clip_rect.bottom - clip_rect.top,
>                 source_hdc,
> -                clip_rect.left, clip_rect.top, SRCCOPY | CAPTUREBLT)) {
> +                clip_rect.left, clip_rect.top, flag)) {
>         WIN32_API_ERROR("Failed to capture image");
>         return AVERROR(EIO);
>     }
> @@ -639,6 +646,7 @@ static const AVOption options[] = {
>     { "video_size", "set video frame size", OFFSET(width), AV_OPT_TYPE_IMAGE_SIZE, {.str = NULL}, 0, 0, DEC },
>     { "offset_x", "capture area x offset", OFFSET(offset_x), AV_OPT_TYPE_INT, {.i64 = 0}, INT_MIN, INT_MAX, DEC },
>     { "offset_y", "capture area y offset", OFFSET(offset_y), AV_OPT_TYPE_INT, {.i64 = 0}, INT_MIN, INT_MAX, DEC },
> +    { "use_captureblt", "capture gdi window use CAPTTUREBLT flag", OFFSET(use_captureblt), AV_OPT_TYPE_INT, {.i64 = 1}, 0, 1, DEC },
>     { NULL },
> };
>

Regards,
Marton