Rendering big images in QML1 with GLWidget

[Martin Gräßlin]

On Monday 03 March 2014 21:25:59 Shantanu Tushar Jha wrote:
> Hi folks,
> 
> In PMC, we have this fragment of code which (from what I understand) uses
> an OpenGL canvas to draw stuff -
> 
>         QGLWidget *glWidget = new QGLWidget;
>         glWidget->setAutoFillBackground(false);
>         view->setViewport(glWidget);
> 
> While this gives improved video playback performance and quality
> (antialiasing etc), this leads to the QML1 Image element rendering a black
> area for images more than a specific size (Somewhat more than 4000x3000 px).
> 
> The Image renders fine if I remove the GLWidget, has anyone encountered
> this before and/or can suggest a solution?

you try to render an image which is larger than most likely your max texture 
size of your GPU. You can check the actual limits with glxinfo -l.

This is a common problem we have run into in KWin and we post IIRC a warning 
and disable OpenGL compositing. For your usecase it also sounds like a good 
idea to check the limits and just disable the GLWidget if the image is larger 
than the limit.

Cheers
Martin
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