[cairo] Rotated text bug on drawable target

[Carl Worth]

On Thu, 04 Nov 2004 00:00:17 +0800, Steve Chaplin wrote:
> The attached file draws text rotated 90 degrees first to a PNG file and
> then to a drawable. The PNG file looks fine, the text on the drawable is
> unreadable.

Wow, that's a whopper of a bug. Thanks Steve.

I whipped up a quick interactive program and its pretty dramatic to
watch the characters jiggle and slide as the rotation angle changes.

I also checked with cairo-0.1.23 and the behavior is much better
there. With 0.1.23 there is a little bit of jiggling, (as previously
mentioned in the "shaking fonts" thread--and yes, this is a bug rather
than just a hinting problem), but the position of each character is
roughly correct.

But with the code as in CVS the glyphs are positioned quite badly. Looks
like rotations within the 1st quadrant are roughly correct. But
rotations within the 3rd quadrant align the glyphs by their tops rather
than along the baseline. Within the 2nd and 4th quadrants the positions
transitions between the two extremes.

So this looks like a regression due to recent font rework. And it looks
like it's high time to add an Xlib target to our new regression test
suite.

-Carl