[Pixman] [PATCH v3] test: Add cover-test

Pekka Paalanen ppaalanen at gmail.com
Mon Sep 7 02:19:04 PDT 2015

On Fri, 04 Sep 2015 14:29:22 +0100
"Ben Avison" <bavison at riscosopen.org> wrote:

> On Fri, 04 Sep 2015 11:18:03 +0100, Pekka Paalanen <ppaalanen at gmail.com> wrote:
> > I think we may have a problem with sizes/coordinates.
> >
> > With 64 kB page size, the minimum fenced image width for r5g6b5 image
> > is 32768 pixels. GDB tells me src_img->bits.width << 16 is negative.
> >
> > Similarly the minimum width of an a8 image becomes 64k pixels. These
> > coordinates do not fit in pixman_fixed_t.
> This is a good point.
> However, I have thought of a workaround. Only the image width is
> constrained to be < 65536 (or < 32768 if we want to avoid signed issues,
> since pixman_fixed_t is defined to be a signed quantity). The *stride*
> isn't.

> In the case where the page size is much larger than a row, this amounts to
> alternating protected and unprotected pages. Then we set the stride to
> the distance between protected pages, and set image->bits.bits such that
> either the left or right edge of each row lines up with the page boundary.

> Obviously that would require work to the fence image code as well as to
> cover-test, so I thought I'd ask for opinions - is it worth the added
> complexity, or should we just bail out if the page size is > 32K as Pekka
> suggests?

My opinion is that let's get this test landed now with skip on too
large page size, and enchance it later if wanted.

Ben, shall I add the skips and bikeshed with style and send the
cover-test patch to the list once more?

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