This extension allows us to get font hint metrics without having to create and
destroy cairo font options structs. Since this is used in loops, this will
improve performance, especially in documents which have many text segments.
Since these are just interpreted comments, there's 0 impact on actual code.
This removes all lines that match /* vim: set(.*)tw=80: */ with S&R -- there are
a few others scattered around which will be removed manually in a second part.
This gets rid of platform-dependent hard-coded defaults, but keeps
build-time blocking if there is no GL provider (in which case layers
acceleration almost certainly won't work because it needs a GL
compositor and would likely crash without)
New prefs are
- layers.acceleration.enabled to enable HWA
- layers.acceleration.force to force it enabled (requires .enabled to be
set as well)
This is the platform part of this issue. The rest will be front-end work
(Preference UI integration and pref migration)
Mozilla tried to enable XRENDER support with backends other than Cairo
in 286348:e13aaaaf1962 /
https://hg.mozilla.org/mozilla-central/rev/e13aaaaf1962 - at least until
they decided to completely remove XRENDER support.
The change looked innocent enough, but actually turned out to do exactly
the opposite: it forcefully enabled image offscreen surfaces with GTK2
when it was previously disabled (since
gfxPrefs::UseImageOffscreenSurfaces() will always return true) and, by
extension, disabled the XRENDER-based functionality by creating a
non-Xlib surface.
Interestingly, a previously enabled double buffering check was also
disabled by this, but since the comment for this was diverging with the
code, that behavior just sounds like yet another bug.
Instead of disabling image offscreen surfaces (at least when using the
GTK2 backend), let's force the creation of Xlib-based image surfaces
when XRENDER support is enabled. This will let UXP use the more
common/modern code paths, but also make scrolling much faster again. Too
fast scrolling may induce tearing (if not smoothed), but on the other
hand performs much better in remote computing contexts.
As an added benefit, GTK3-based builds should roughly behave the same
way. Further tests with the GTK3-backend enabled will be required in the
future.
This creates a number of stubs and leaves some surrounding code that may be irrelevant (eg. recorded time stamps, status variables).
Stub resolution/removal should be a follow-up to this.
