[vlc-devel] [vlc-commits] opengl: forward the error code from the resize callback

Steve Lhomme robux4 at ycbcr.xyz
Fri Jan 18 10:50:39 CET 2019

On 18/01/2019 10:38, Rémi Denis-Courmont wrote:
> You cannot have direct rendering with invalid pictures. The vout 
> wrapper will force non-DR in the later case.


> And all I'm saying is that resizing a display cannot fail, at least 
> not on X11 and Win32. 

But the patches (and following ones) are about "window less" rendering, 
in an external texture or whatever you want.

> If you cannot handle a given size, you have to ensure that the window 
> provider will never report it, by whatever means.

In OpenGL it may work to ignore what a client app does, but in D3D9 and 
D3D11 it will not work. So I could return an error in the general 
callback and ignore it for OpenGL (even though it seems wrong to me).

> Le 18 janvier 2019 10:39:31 GMT+02:00, Steve Lhomme <robux4 at ycbcr.xyz> 
> a écrit :
>     On 17/01/2019 17:06, Rémi Denis-Courmont wrote:
>         Le torstaina 17. tammikuuta 2019, 17.46.15 EET Steve Lhomme a
>         écrit :
>             On 16/01/2019 12:41, Rémi Denis-Courmont wrote:
>                 This is obviously wrong since it ends with an
>                 assertion failure at opengl/display.c:228. And thus
>                 the commits before it make no sense. 
>             It asserts there because it's not meant to handle
>             VOUT_DISPLAY_RESET_PICTURES. And it receives that because
>             during a
>             PLAY_CHANGE_ZOOM it returned an error from a call to
>             vlc_gl_Resize(). If the code is not ready to handle such
>             an error (why it occurs for you is another thing to look
>             at) then it will also assert on the call right after:
>             if(vlc_gl_MakeCurrent(sys->gl)!=VLC_SUCCESS)
>             returnVLC_EGENERIC; So I don't see how the commit is
>             wrong. Either the DISPLAY_CHANGE_* events can never return
>             an error from there, or the code needs to be ready to
>             handle it. 
>         Returning an error from those controls just means you need to
>         reset the display input format, 
>     This wasn't clear to me.
>         and the pool if the display was not ported yet. 
>     The display pool ? What if direct rendering is on ? That means the
>     decoder pool as well. Right now the comment you added says "internal
>     buffers" that's rather vague.
>     >
>         Returning an error does *not* mean that you reject the change.
>         You *cannot* reject the change. It simply does not work and
>         cannot that way. Since the control is dispatched
>         asynchronously, it is too late to reject the change. I am
>         planning to address that for other reasons than error
>         handling, but even then, most (all except maybe Wayland)
>         windowing systems lack provisions for rejecting a window size
>         change. So if you have a failure at that stage, then you have
>         two options: - render wrong going forward, or - stop rendering
>         and discard pictures until further notice. Either way, you
>         don't need to return an error to the core. 
>     That would be true if OpenGL wasn't handled in the core. But this
>     function clearly returns whether the surface dimensions were succesfully
>     changed:
>     http://git.videolan.org/?p=vlc.git;a=blob;f=src/video_output/opengl.c;h=c288fd83b429dfeaabdef4432dfacc96650e5c80;hb=HEAD#l173
>     Telling it that it worked when it didn't will not do any good.
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