Closed Bug 1097128 Opened 5 years ago Closed 5 years ago

turn on the compile-time switch for vertical writing-mode support


(Core :: Layout, defect)

Not set





(Reporter: jfkthame, Assigned: jfkthame)


(Blocks 1 open bug)



(1 file, 1 obsolete file)

We have both a compile-time switch in WritingModes.h that completely disables support for vertical writing modes, and a runtime pref that determines whether the CSS writing-mode, text-orientation, and text-combine-upright properties are actually recognized.

At this point, I think we should consider landing the patch to enable the compile-time switch on Nightly (we might want to keep it disabled on release for now). As long as the runtime vertical-text pref remains off, this should have no impact on behavior, but it becomes possible to start testing vertical modes in standard nightly builds by just toggling a pref.

This will mean that key low-level mozilla::WritingMode methods such as IsVertical() will actually be testing something, rather than returning a hard-coded value, and so we'll need to watch for any performance impact; the compiler will no longer be able to optimize away various tests, conversion codepaths, etc., throughout Layout.

I've tried pushing such a patch to tryserver recently, and looking at the Tp numbers;[1] I couldn't see any consistent difference compared to a standard mozilla-central build, but we still need to be alert for any significant regression.

[1] See That push also enabled the runtime vertical-text pref, which currently results in the unit test oranges seen there; the compile-time switch alone will not cause this.
WDYT - are we far enough along that it's worth throwing the switch here, both to check for any perf impact and to make it easier for people to start experimenting?
Attachment #8520736 - Flags: review?(smontagu)
Assignee: nobody → jfkthame
Oops, sorry for the noise - I forgot to make it conditional on #ifndef RELEASE_BUILD. For now.
Attachment #8520738 - Flags: review?(smontagu)
Attachment #8520736 - Attachment is obsolete: true
Attachment #8520736 - Flags: review?(smontagu)
Comment on attachment 8520738 [details] [diff] [review]
Enable compile-time support for vertical writing modes.

Review of attachment 8520738 [details] [diff] [review]:

It is time.
Attachment #8520738 - Flags: review?(smontagu) → review+
OK, let's see how this goes... I'm hopeful this will stick without problems, but we do need to be alert for possible regressions.
Target Milestone: --- → mozilla36
Closed: 5 years ago
Resolution: --- → FIXED
Depends on: 1104905
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