[FFmpeg-devel] PATCH: gdigrab work for DPI in windows

[Matt Oliver]

On 5 October 2015 at 20:05, Matt Oliver <protogonoi at gmail.com> wrote:

> On 5 October 2015 at 19:29, Matt Oliver <protogonoi at gmail.com> wrote:
>
>> On 30 September 2015 at 02:48, wm4 <nfxjfg at googlemail.com> wrote:
>>
>>> On Wed, 23 Sep 2015 12:04:43 -0600
>>> Roger Pack <rogerdpack2 at gmail.com> wrote:
>>>
>>> > From 6a972dda58bd5ab31524cd4e5326b4bcdeaeaa8c Mon Sep 17 00:00:00 2001
>>> > From: rogerdpack <rogerpack2005 at gmail.com>
>>> > Date: Wed, 23 Sep 2015 12:03:27 -0600
>>> > Subject: [PATCH] gdigrab: grab right desktop size if DPI in use, based
>>> on
>>> >  patch from Alexander Brotzge
>>> >
>>> > Signed-off-by: rogerdpack <rogerpack2005 at gmail.com>
>>> > ---
>>> >  libavdevice/gdigrab.c | 44
>>> +++++++++++++++++++++++++++++---------------
>>> >  1 file changed, 29 insertions(+), 15 deletions(-)
>>> >
>>> > diff --git a/libavdevice/gdigrab.c b/libavdevice/gdigrab.c
>>> > index 9a185d4..b0faf45 100644
>>> > --- a/libavdevice/gdigrab.c
>>> > +++ b/libavdevice/gdigrab.c
>>> > @@ -235,6 +235,9 @@ gdigrab_read_header(AVFormatContext *s1)
>>> >      AVStream   *st       = NULL;
>>> >
>>> >      int bpp;
>>> > +    int vertres;
>>> > +    int desktopvertres;
>>> > +    float scale;
>>> >      RECT virtual_rect;
>>> >      RECT clip_rect;
>>> >      BITMAP bmp;
>>> > @@ -263,14 +266,34 @@ gdigrab_read_header(AVFormatContext *s1)
>>> >          goto error;
>>> >      }
>>> >
>>> > -    if (hwnd) {
>>> > -        GetClientRect(hwnd, &virtual_rect);
>>> > -    } else {
>>> > +    /* This will get the device context for the selected window, or if
>>> > +     * none, the primary screen */
>>> > +    source_hdc = GetDC(hwnd);
>>> > +    if (!source_hdc) {
>>> > +        WIN32_API_ERROR("Couldn't get window device context");
>>> > +        ret = AVERROR(EIO);
>>> > +        goto error;
>>> > +    }
>>> > +    bpp = GetDeviceCaps(source_hdc, BITSPIXEL);
>>> > +
>>> > +    scale = 1.0;
>>> > +    if (hwnd == NULL) {
>>> > +      /* desktop -- get the right height and width for scaling DPI */
>>> > +      vertres = GetDeviceCaps(source_hdc, VERTRES);
>>> > +      desktopvertres = GetDeviceCaps(source_hdc, DESKTOPVERTRES);
>>> > +      scale = (float) desktopvertres / (float) vertres;
>>> > +    }
>>>
>>
>> This seems a little redundant as scale is only being set when hwnd is
>> null however in the below lines its then being used in the opposite
>> conditional. Since this checks for hwnd essentially being non null then
>> scale is always going to be the inital value of 1.
>>
>>
>>> > +     if (hwnd) {
>>> > +         GetClientRect(hwnd, &virtual_rect);
>>> > +         virtual_rect.right = virtual_rect.right * scale;
>>> > +         virtual_rect.bottom = virtual_rect.bottom * scale;
>>> > +     } else {
>>> >          virtual_rect.left = GetSystemMetrics(SM_XVIRTUALSCREEN);
>>> >          virtual_rect.top = GetSystemMetrics(SM_YVIRTUALSCREEN);
>>> > -        virtual_rect.right = virtual_rect.left +
>>> GetSystemMetrics(SM_CXVIRTUALSCREEN);
>>> > -        virtual_rect.bottom = virtual_rect.top +
>>> GetSystemMetrics(SM_CYVIRTUALSCREEN);
>>> > -    }
>>> > +        virtual_rect.right = (virtual_rect.left +
>>> GetSystemMetrics(SM_CXVIRTUALSCREEN)) * scale;
>>> > +        virtual_rect.bottom = (virtual_rect.top +
>>> GetSystemMetrics(SM_CYVIRTUALSCREEN)) * scale;
>>> > +     }
>>>
>>
>> This if else could be combined with the above if as scale is only a value
>> different to 1 in the 'else' case. Also as wm4 said it would probably be
>> better to keep the scale factors as ints.
>>
>>
>>> >
>>> >      /* If no width or height set, use full screen/window area */
>>> >      if (!gdigrab->width || !gdigrab->height) {
>>> > @@ -299,15 +322,6 @@ gdigrab_read_header(AVFormatContext *s1)
>>> >              goto error;
>>> >      }
>>> >
>>> > -    /* This will get the device context for the selected window, or if
>>> > -     * none, the primary screen */
>>> > -    source_hdc = GetDC(hwnd);
>>> > -    if (!source_hdc) {
>>> > -        WIN32_API_ERROR("Couldn't get window device context");
>>> > -        ret = AVERROR(EIO);
>>> > -        goto error;
>>> > -    }
>>> > -    bpp = GetDeviceCaps(source_hdc, BITSPIXEL);
>>> >
>>> >      if (name) {
>>> >          av_log(s1, AV_LOG_INFO,
>>
>>
>> However I think the basic dpi scaling technique is correct. However I
>> would think it should be more along the lines of the modifications Ive
>> attached.
>>
>
> Woops, allow me to try that again without windows messing up the patches
> line endings.
>

Does anyone have any issues with the updated patch or can it be pushed?