This is enabled by default on Android, because Glutin currently sends mouse
events instead of touch events on Android. It's also useful for testing on
non-touch platforms.
Add an option to dump the layer tree, which activates the previously
unused layer tree debugging code. Also improve the output using the
PrintTree struct.
Prior to this commit, `str_join` would skip empty items at the start of
the `Iterator` until it found a non-empty item. This contradicts
`SliceConcatExt::join` which doesn't skip anything.
Brought up in:
https://github.com/servo/servo/pull/7776#issuecomment-144317281
This allows both boolean and string-type preferences. It
also implements a system where prefs that are read from a
configuration file can be reset back to their initial value,
which is useful in a number of cases e.g. when running tests
to ensure that each test starts with the same values for
the prefs.
Fix#7609, "error: unable to create file tests/ref/hello_a?foo#bar.html
(Invalid argument)" during git checkout on Windows.
Behavior change: passing an nonexistent file name on the command line
now shows a blank page (like network errors)
rather than exit with an error message.
Fail on unrecognized debug option
Refs: https://github.com/servo/servo/issues/7142
Ran some basic functional tests:
```
$ ./mach run -d -Z bubble-widths,disable-canvas-aa,trace-layout tests/ref/blur_ref.html
$ ./mach run -d -Z help
Usage: /Users/greg/servo/target/debug/servo debug option,[options,...]
where options include
Options:
bubble-widths Bubble intrinsic widths separately like other engines.
disable-text-aa Disable antialiasing of rendered text.
disable-canvas-aa Disable antialiasing on the HTML canvas element.
dump-flow-tree Print the flow tree after each layout.
dump-display-list Print the display list after each layout.
dump-display-list-json Print the display list in JSON form.
dump-display-list-optimized Print optimized display list (at paint time).
relayout-event Print notifications when there is a relayout.
profile-tasks Instrument each task, writing the output to a file.
show-compositor-borders Paint borders along layer and tile boundaries.
show-fragment-borders Paint borders along fragment boundaries.
show-parallel-paint Overlay tiles with colors showing which thread painted them.
show-parallel-layout Mark which thread laid each flow out with colors.
paint-flashing Overlay repainted areas with a random color.
trace-layout Write layout trace to an external file for debugging.
validate-display-list-geometry Display an error when display list geometry escapes overflow region.
disable-share-style-cache Disable the style sharing cache.
parallel-display-list-building Build display lists in parallel.
replace-surrogates Replace unpaires surrogates in DOM strings with U+FFFD. See https://github.com/servo/servo/issues/6564
gc-profile Log GC passes and their durations.
$ ./mach run -d -Z blah
error: unrecognized debug option: blah
Servo exited with return value 1
```
Didn't check that setting debug flags actually did anything.
Haven't written much Rust so this feels more verbose than necessary.
Added `disable-canvas-aa` to debug options help.
Should DebugOptions struct derive Clone like Opts does?
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