There was a performance problem with the old flicker fixing
approach. For moved windows we copied the window data to the double
buffer pixmap and then back to the window with the rest of the
expose data. In some cases the copy from window data to pixmap was
very slow because the pixmap was allocated in system memory and
the window in video memory.
The new approach is to delay all window moves and then replay them
after the expose has drawn to the double buffer pixmap but before
drawing it to the window. Furthermore, we remove all exposed areas
from the destination of the delayed moves so we won't copy something
just to then immediately draw over it.
This makes scrolling in firefox fast, and it makes tests/flicker not
show any (detectable) flicker.
We return the raw window drawable, so its likely the app will do some
weird stuff to it, like draw using non-gdk operations. We don't want
the app to see any half-drawn state, so flush everything.
This fixes a scroll issue in firefox at least.
This is basically the same fix as was done for
gdk_window_move_resize_internal. We make sure not to move the native
child window contents twice and we don't copy data that was overwritten
by the moving of the native child windows.
Whenever a native window is moved this causes an immediate change in
the window (the window content is copied). This change conflicts can
conflict with outstanding moves or other cached changed, so we need
to flush all outstanding moves in the related windows.
To simplify the code for window move/resize the toplevel version was
split out to its own function.
Move native windows after recomputing so that we get the right new
shape before moving (and the implied copy). This means we're not
copying too much data.
Take into account the area of a moved window that contains native
subwindows, as these affect things in two ways:
First of all we shouldn't copy the original window location, as that
is copied by the native window move.
Secondly, we can't copy things that would end up copying from the
native window move destination, as the data that used to be there is
now destroyed by the native window move.
It can happen that another native window is re-shaped over the region to
be moved, this will not destroy the data (since we're unsetting the background
when we reshape), but it will mean we need to read from this window.
We already used INCLUDE_INFERIORS, but that only handle subwindows. We fix
this by doing the copy on the toplevel, offsetting the copy to compensate for
this.
There is no need to do all these computations when moving toplevels
as that can't really change any visible regions. Nor will it cause
any exposes we need to handle.
move_region_on_impl() - doesn't need to copy anything if dx/dy == 0
Ensure that we queue an update when invalidating an empty area but we have outstanding moves
Temporarily unset background when moving native child windows
