This errors was reported in #4431: The Tx wasn't rolled back correctly
in case of a Lua error inside the transaction because Lua needs to be
compiled as C++ to avoid longjmps and support stack
unwinding (i.e. calling destructors).
If the user preferences file (aseprite.ini) contained a non-existent
language, the first option of the languages combo box was selected,
which might lead to a confusing situation where just opening the
preferences dialog will change from English to other
language (non-English, the first language in the combobox).
This was mainly found in SpriteSizeJob crash reports. In these reports
deleted image buffers were still used to paint the Editor canvas
because the doc was write-locked in the main thread (same thread where
the canvas is painted). This produced a re-entrant lock in the
Editor::onPaint() as we can still read-lock from the same thread where
we write-locked the doc.
With this change we write-lock the doc from the SpriteJob background
thread (not the main thread) only if it's necessary (i.e. when the doc
is not already locked in the main thread, e.g. when running a script).
This makes that the main thread (Editor::onPaint) cannot read the doc
until we finish the whole SpriteJob transaction/Tx.
One fix that this patch includes for #4367 (crash by unhandled
CannotWriteDocException exception) is when we drag-and-drop a tag
border to resize its limits. This is a fix for that case but we don't
know if this include all cases of #4367 crashes (so we cannot close
the issue).
Anyway we have added some try { } catch in cases where it's better to
avoid propagating the exception, e.g. in
MovingSelectionState::onLeaveState() to avoid throwing exceptions in
Editor::backToPreviousState() which might be problematic in several
cases. (Maybe related to #2829?)
This is to fix the appearance of the icon when Windows is configured
with 125% DPI or 175% DPI. In the past we've done something similar
for 150% DPI (713a2eac80) with a 24x24
icon.
Anyway this code is not used anymore, it was for v1.1 when v1.1 and
v1.2 branches were developed at the same time (layer groups feature
was added in v1.2, so v1.1 just moved groups children to the root).
