Xcursor loading code has hardcoded search paths, in order to take into
account distros installing app data in a different location,
libwayland-cursor sets the ICONDIR to the icon directory computed based
on the install prefix.
However, that won't work with gitlab CI because it relocates binaries. A
more robust way to find cursors would be to use QStandardPaths to find
all the icon directories on the system.
Another advantage of using own cursor loading code is that it allows us
to reuse cursor images that are symlinks. For example, with
breeze_cursors, almost half of the files in the cursors directory are
symlinks.
The main disadvantage of this approach is that we would have to keep the
search paths up to date. However, on the hand, there are not that many
of them, e.g. ~/.icons, ~/.local/share/icons, /usr/share/icons,
/usr/local/share/icons. The last three are implicitly handled by the
QStandardPaths.
Xcursors don't support hidpi so if a hidpi cursor is needed, kwin will
scale the desired size by the scale factor and ask Xcursor helpers to
load a theme with the given name and the size.
However, the theme loading code doesn't take into account that Xcursor
theme loading helpers may not return cursor sprites of size size * scale
if the theme has no such a size.
For example, if the cursor theme only provides 24, 36, and 48 sizes and
kwin attempts to load cursors of size 48 with a scale factor of 2, we
will get cursors of size 48 instead of 96. Unfortunately, this will
result in the issue where the cursor shrinks when hovering decorations
because kwin doesn't know that the effective scale factor (1) is
different from the requested scale factor (2).
In order to fix loading of HiDPI cursors, we need to approximate the
effective scale factor of every cursor sprite as we load it.
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.
