574908 - [DW] rendering of font with bitmap glyphs is different when the font-style is italic or oblique

Status: NEW

(Core :: Graphics, defect)

Description

[Masayuki Nakano [:masayuki] (he/him)(JST, +0900)]

Attachment: Screenshot (left is GDI, right is DW)

See the testcase.

> data:text/html;charset=utf-8,<p style="font-family: MS PGothic; font-size:16px;"><span style="font-style: normal;">これはMS PGothicで表示されています</span><br><span style="font-style: italic;">これはMS PGothicで表示されています</span><br><span style="font-style: oblique;">これはMS PGothicで表示されています</span></p>

MS PGothic is rendered by bitmap glyphs at font-size: 16px. However, if the font-style is italic or oblique, the bitmap glyphs are not used.

The testcase may look better for you, however, in following case, it doesn't looks good.

> <p style="font-family: MS PGothic;">There <em>are</em> some words.</p>

The "are" is only rendered with anti-aliasing. It feels no good.

I'm not sure this is DirectWrite's spec or not. We should check the IE9's behavior.

Comment 1

[Joe Drew (not getting mail)]

We should check on IE9 here.

Comment 2

[Jeff Muizelaar [:jrmuizel]]

IE9 has the same rendering as we do.

Comment 3

[Joe Drew (not getting mail)]

I won't block on this for now, because it's not clear to me that we're doing the wrong thing here.

Comment 4

[Masayuki Nakano [:masayuki] (he/him)(JST, +0900)]

I think that if IE9 *final* renders the testcase same as us, this bug should be marked as INVA.

Comment 5

[John Daggett (:jtd)]

It looks to me like the Cleartype/GDI rendering uses the outline version of the font, *not* the bitmap glyphs.  MS PGothic has no italic face so that makes sense.  Note how some of the stems are clearly thicker than the bitmap case, that would not happen via manual obliquing.  So the comparison here is really between a poorly hinted TrueType font rendering in Cleartype/GDI vs. DirectWrite.

Rather than just following IE, I think we should base the choice on whether or not text at a given size becomes unreadable when rendered with DirectWrite instead of Cleartype/GDI.  Zooming in and out on the testcase I don't see any size where the Cleartype/GDI rendering appears more readable.  It looks like crap at all sizes! ;)

I think this should be marked invalid unless we can find a case where DirectWrite rendering is clearly worse.