[cairo] Screen orientation

[Behdad Esfahbod]

On Mon, 2007-12-10 at 08:32 -0500, Jean-Claude Repetto wrote:
> Hello,

Hi,

> I am using Cairo in a handheld device with a LCD screen. The device has 
> a frame buffer, so I am using Cairo image surfaces to draw directly into 
> the frame buffer.
> Unfortunately, some of the devices have been manufactured with a LCD 
> screen rotated of 90 degrees. I have tried to use a Cairo transformation 
> matrix. It works, but it is much slower.

May it be the case that you are rotating around a pixel center instead
of origin?  I doubt that myself.


> Is there a possibility of avoiding the cost of a matrix multiplication ? 
> Changing the orientation requires only a swap between X and Y, and/or a 
> substraction.

No, at least not yet.  You should profile though and see what's being
slow.

> Naturally, I could write two versions of the application, but I'd prefer 
> avoid this solution. A solution with two versions of the Cairo library 
> is acceptable.
> 
> Thanks for your suggestions,
> Jean-Claude

Have fun with cairo!

-- 
behdad
http://behdad.org/

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