Re: Image transformations

[Alan Third]

On Thu, Jun 13, 2019 at 10:47:38PM +0300, Eli Zaretskii wrote:
> > Date: Thu, 13 Jun 2019 20:27:24 +0100
> > From: Alan Third <address@hidden>
> > Cc: address@hidden
> > 
> > Or storing the basic crop and scaling information separately so you
> > don’t have to worry about the matrices at all.
> 
> I'm beginning to think we should do this on all platforms, and leave
> the matrix calculation, if needed, to the terminal-specific back-ends
> (xterm.c, w32term.c, etc.).  It sounds like we gain nothing by
> spilling XRender-specific stuff in image.c and letting all the other
> platforms adapt.

I think you have a fundamental misunderstanding of how the
transformation matrix is being used. It’s not specific to XRender.
Aside from a few short‐circuits the only XRender specific code is in
image_set_transform, and XRender, NS and Cairo all have their own code
in there, and use the same transformation matrix.

We could even use the same matrix with ImageMagick with a bit of work.

If we were to throw out that shared matrix code and put it into each
backend we would be simply duplicating the code. Even using a
toolkit’s built‐in crop/rotate/resize functions is probably recreating
the exact same transformation matrix in the background.
-- 
Alan Third