If window quads need to be generated after the wl_surface is destroyed,
the SurfaceItemWayland::mapToBuffer() function will return wrong values.
In order to fix that, we need to store the last surface-to-buffer matrix
in SurfaceItem.
QPainter::setWindow() doesn't work as we expect if the device pixel
ratio of the paint device is less than 1, for example 0.5 or 0.75.
QPainter only allows the effective device pixel ratios that are greater
than or equal to 1. This restriction probably has to be lifted.
For the time being, this change introduces a helper function that can be
used to determine the scale factor by which QPainter::window() must be
multiplied.
BUG: 432766
Once in a while, we receive complaints from other fellow KDE developers
about the file organization of kwin. This change addresses some of those
complaints by moving all of source code in a separate directory, src/,
thus making the project structure more traditional. Things such as tests
are kept in their own toplevel directories.
This change may wreak havoc on merge requests that add new files to kwin,
but if a patch modifies an already existing file, git should be smart
enough to figure out that the file has been relocated.
We may potentially split the src/ directory further to make navigating
the source code easier, but hopefully this is good enough already.
