Re: [PATCH 2/2] gdi32: Clip font glyphs to fit within text metrics.

[Dmitry Timoshkov]

Sam Edwards <cfsworks(a)gmail.com> wrote:
> This change only affects malformed fonts that have glyphs with splines 
> that go above the maximum ascent as specified in the font's hhea/os2 
> table. For that reason, any tests for this change would have to include 
> a malformed font, so I did not write tests. If we want in-tree tests, 
> we'll need to figure out how to include a malformed font to test against.

Please add a test case, Wine test suite already includes custom fonts,
you can either use an existing font, or add a new one.

-- 
Dmitry.

[PATCH 2/2] gdi32: Clip font glyphs to fit within text metrics.

[Max TenEyck Woodbury]

On 04/19/2013 02:46 AM, Dmitry Timoshkov wrote:
> Sam Edwards <cfsworks(a)gmail.com> wrote:
> > This change only affects malformed fonts that have glyphs with splines
> > that go above the maximum ascent as specified in the font's hhea/os2
> > table. For that reason, any tests for this change would have to include
> > a malformed font, so I did not write tests. If we want in-tree tests,
> > we'll need to figure out how to include a malformed font to test against.
>
> Please add a test case, Wine test suite already includes custom fonts,
> you can either use an existing font, or add a new one.

As I understand it, some fonts deliberately have glyphs larger than
their metrics bounding boxes.  Clipping them is almost certainly not a
good idea.

[PATCH 2/2] gdi32: Clip font glyphs to fit within text metrics.

[Sam Edwards]

On 04/19/2013 10:32 AM, Max TenEyck Woodbury wrote:
> As I understand it, some fonts deliberately have glyphs larger than
> their metrics bounding boxes.  Clipping them is almost certainly not a
> good idea.

Forgive my disbelief, but can you provide an example? It seems like 
Windows has the same clipping behavior (see my test 
http://source.winehq.org/patches/data/95792).

 From my understanding, the intent of the ascent metric is that it 
indicates the maximum ascender on any glyph in the font (and likewise 
for descent), so the only real reason for the ascent/descent metrics to 
be wrong is if the font designer made a mistake. (And some tools, like 
FontForge, will automatically set the ascent/descent metrics correctly 
for you on export.)

I can't think of any reason why a font author would want to create a 
font with an invalid ascent/descent metric.

P.S. This is a resend because I accidentally sent this to wine-patches 
the first time... Sorry! That was dumb of me. :)