[cairo] pixman: Branch 'master'

[Carl Worth]

On Fri, 29 Feb 2008 15:48:29 -0800 (PST), Søren wrote:
> +  - Moving to 24.8 coordinates. This is tricky because X is still
> +    defined as 16.16 and will be basically forever. It's possible we
> +    could do this by adding extra offset_x/y parameters to the
> +    trapezoid calls. The X server could then just call the API with
> +    (0, 0). Cairo would have to make sure that the delta *within* a
> +    batch of trapezoids does not exceed 16 bit.

I'm not sure that the offset idea will cut it.

One of the first justifications that Mozilla gave for wanting to do
larger-than-16-bit coordinates was for a giant scrollable region that
greatly exceeds the current pixmap. Obviously they'll draw only items
that are actually visible on the current region of interest, but one
of those items can be a full-size background-color rectangle.

So in that case, there's a single trapezoid with top and bottom
coordinates that don't fit into the 16-bit limit.

Meanwhile, I really don't see why changing pixman will cause any
problem for the X server. I mean, it's not as if the Render protocol
guarantees that all trapezoids will be accurately rendered within a
16-bit sub-pixel grid, (that doesn't even make sense with only 8 bits
of alpha per pixel, for example).

-Carl
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