Bug 123338 – Re-enable simple line layout on non-Mac platforms

• Component: Layout and Rendering
• Status: RESOLVED FIXED

[Antti Koivisto]

It hits

ASSERT(run.charactersLength() >= run.length()) 

in textWidth().

for example:
http://build.webkit.org/builders/GTK%20Linux%2064-bit%20Debug%20WK1/builds/4983
http://build.webkit.org/builders/EFL%20Linux%2064-bit%20Release%20WK1/builds/2321

[Antti Koivisto]

Some

[Antti Koivisto]

It is not obvious from code what the difference is between Mac and other platforms.

[Zan Dobersek]

Non-Mac platforms don't define ENABLE_8BIT_TEXTRUN to 1, so the TextRun constructor implicitly converts the character data to a WTF::String. The length parameter that's passed to the TextRun constructor is then ignored, and the length of the complete string is used.

[Zan Dobersek]

(In reply to comment #3)
> The length parameter that's passed to the TextRun constructor is then ignored, and the length of the complete string is used.

The length parameter is actually used as the xpos value rather than the length.

Anyway, enabling the 8-bit text runs works for the GTK port. Modifying the TextRun construction in the textWidth function would likely work equally well.

The 8-bit TextRun was introduced in bug #96979, but was only enabled for the Mac port because code of other platforms needed additional modifications to properly support the introduced optimization.
https://bugs.webkit.org/show_bug.cgi?id=96979#c9

The GTK port doesn't seem affected when running the tests with the support for 8-bit text runs enabled, so simply enabling the feature define would work. I'd also like to see people test out the feature on other ports and provide the proper changes so the define can be removed entirely.

[Antti Koivisto]

Ah ok. Thanks for looking into this. We should really make String(const char*) explicit to avoid bugs like this.

[Csaba Osztrogonác]

ENABLE_8BIT_TEXTRUN guards were removed by
https://trac.webkit.org/changeset/163478

So let's go ahead.

[Csaba Osztrogonác]

Created attachment 223334 [details]
Patch

[Csaba Osztrogonác]

Comment on attachment 223334 [details]
Patch

Clearing flags on attachment: 223334

Committed r163537: <http://trac.webkit.org/changeset/163537>

[Csaba Osztrogonác]

All reviewed patches have been landed.  Closing bug.