Turns out that the comment from `set_root_movie` was right all along!
`set_root_movie` should not be used when replacing the root movie,
because it will leave out unclosed resources.
This patch introduces `replace_root_movie`, which is dedicated to be
used when replacing (instead of just setting) the root movie.
The best solution would be to use RAII, e.g. destroy and recreate
the whole Player instance, but this patch is a first step towards
proper resource control.
Not thread-safe WinitAsyncExecutor was wrapped with a Mutex, making
any access to the instance exclusive. It was problematic, because
when a task was awoken from within another task, it resulted in
a deadlock, because the mutex was not reentrant.
This patch makes WinitAsyncExecutor thread-safe and changes how tasks
are locked. Specifically, instead of locking all tasks, only
the currently executed task is being locked. This allows waking any
other task from within it.
Currently when clicking in a textbox, the cursor will only be placed
correctly if you click exactly on top of a letter. The basic purpose of
this commit is to make it so that clicking in the surrounding margin
will put the cursor in the closest available position, as in Flash Player.
The logic is a bit complex because a single row of text can contain
multiple layout boxes, each with a different Y offset (but all with the
same Y extent). To be accurate, we need to treat each layout box in the
row "as if" it had the same Y offset that the tallest box in its row has.
This commit also contains a fix for an issue where lower_from_text_spans
was passing the wrong text strings and indexes to fixup_line for
newlines, which needed to be fixed in order to be able to click to place
the cursor in an empty row that was created by newlines.