LCD, pan, randr1.2, and pan-to-downscale

Thomas Hellström thomas at
Sun Apr 15 05:30:13 PDT 2007

Austin Yuan wrote:
> Hi!
> I know if configuring a screen size larger than the physical size of a
> LCD, pan will occur, and users need to scroll to view the far edges of
> the desktop.
> Pan-to-downscale here means when the screen size is bigger than LCD
> size, downscale screen content in order to fit its whole content into
> the viewable area. Pan-to-downscale is useful for those small LCD with
> lower resolution (such as 800x480) on small devices,so that user can
> view more content larger than LCD size without scrolling.
> Pan-to-downscale currently needs to do some ugly hacking in the video
> driver to achieve it. I saw randr1.2 has many significantly changes
> compared with version 1.1, and there are some discussion about
> pan-and-scan. I am curious whether randr1.2 has addressed this
> pan-to-downscale feature, and will it support it in future?
Wouldn't it be possible to add an extra "rotation" flag, similar to the 
reflect flags (called RR_Scale), and set up the
composite transformation matrix accordingly? The RandR code would 
automatically allocate a new buffer matching the
LCD size and the rotation code would handle scaling, rotation and 
reflect automatically. Drivers with composite hooks would
automatically do accelerated scaling.

Useful also for upscaling for hardware that doesn't have a panel fitter.


> Thanks,
> Austin
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