[vlc-devel] [PATCH] vout/opengl: Store and restore last viewport

[Marvin Scholz]

On 12 Aug 2019, at 9:37, Thomas Guillem wrote:

> On Sat, Aug 10, 2019, at 19:56, Marvin Scholz wrote:
>> Between the call to vout_display_opengl_Viewport and the call to
>> vout_display_opengl_Display the viewport can be changed by the OS
>> causing the picture to render incorrectly.
>>
>> To prevent that, store the last set viewport and restore it in the
>> display function.
>>
>> Fix #21357
>> Fix #22209
>> ---
>>  modules/video_output/opengl/vout_helper.c | 17 +++++++++++++++++
>>  1 file changed, 17 insertions(+)
>>
>> diff --git a/modules/video_output/opengl/vout_helper.c
>> b/modules/video_output/opengl/vout_helper.c
>> index b37b653257..2a8ec9cc12 100644
>> --- a/modules/video_output/opengl/vout_helper.c
>> +++ b/modules/video_output/opengl/vout_helper.c
>> @@ -166,6 +166,13 @@ struct vout_display_opengl_t {
>>      float f_fovy; /* to avoid recalculating them when needed.      
>> */
>>      float f_z;    /* Position of the camera on the shpere radius
>> vector */
>>      float f_sar;
>> +
>> +    struct {
>> +        GLint i_x;
>> +        GLint i_y;
>> +        GLint i_width;
>> +        GLint i_height;
>> +    } last_viewport;
>>  };
>>
>>  static const vlc_fourcc_t gl_subpicture_chromas[] = {
>> @@ -1021,6 +1028,10 @@ void
>> vout_display_opengl_SetWindowAspectRatio(vout_display_opengl_t *vgl,
>>  void vout_display_opengl_Viewport(vout_display_opengl_t *vgl, int x,
>> int y,
>>                                    unsigned width, unsigned height)
>>  {
>> +    vgl->last_viewport.i_x = x;
>> +    vgl->last_viewport.i_y = y;
>> +    vgl->last_viewport.i_width = width;
>> +    vgl->last_viewport.i_height = height;
>>      vgl->vt.Viewport(x, y, width, height);
>
> So, why not removing this vgl->vt.Viewport(x, y, width, height) call ?
>

The reason for this was that I wasn't sure if something would call
vout_display_opengl_Viewport with the intention to set the viewport
immediately and not call vout_display_opengl_Display later.
After checking the uses of vout_display_opengl_Viewport again it seems
thats nowhere the case right now though so I could indeed remove that.

>>  }
>>
>> @@ -1564,6 +1575,12 @@ int
>> vout_display_opengl_Display(vout_display_opengl_t *vgl,
>>  {
>>      GL_ASSERT_NOERROR();
>>
>> +    // Restore Viewport
>> +    vgl->vt.Viewport(vgl->last_viewport.i_x,
>> +                     vgl->last_viewport.i_y,
>> +                     vgl->last_viewport.i_width,
>> +                     vgl->last_viewport.i_height);
>
>
> And set the viewport only here.
>
>> +
>>      /* Why drawing here and not in Render()? Because this way, the
>>         OpenGL providers can call vout_display_opengl_Display to 
>> force redraw.
>>         Currently, the OS X provider uses it to get a smooth window 
>> resizing */
>> -- 
>> 2.19.1
>>
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