A good portion of geometry handling code was written during the X11
times. The main difference between X11 and Wayland is that kwin doesn't
know where a window will exactly be after resize() or moveResize().
In order to handle Wayland specifics, every window has a bounding
geometry that is being manipulated by move(), resize(), and moveResize().
The frameGeometry(), the clientGeometry(), and the bufferGeometry() are
not manipulated by move(), resize(), and moveResize() directly. Almost
everything that manipulates geometry should use moveResizeGeometry().
This creates a problem though, since the clientGeometry() will be
updated only after the client provides a new buffer, kwin has absolutely
no idea what the client geometry for a given move resize geometry will
be.
Another side of the coin is that decoration updates are performed
asynchronously on wayland, meaning that you cannot use border properties
for anything related to geometry handling and you should avoid using
borderLeft(), borderTop(), borderRight(), and borderBottom() in general.
clientGeometry(), bufferGeometry(), and border*() are good only if you
want to forward an event or render something. They can't be used for
manipulating the geometry.
Unfortunately, AbstractClient::checkWorkspacePosition() needs both,
which is a bit of a problem. To add more oil to the fire, contents
of a decorated window can be snapped to a screen edge. This goes against
the nature of geometry updates on wayland, where we try to indicate
the bounds of the frame geometry and avoid using client and buffer
geometries.
In order to make geometry handling more correct on wayland, this change
removes the ability to snap the contents of a decorated window to a
screen edge. This allows to avoid using the client geometry in
checkWorkspacePosition(), which is a very important function that ensures
the window is inside the workspace.
There is nothing wrong with snapping the frame rather than its contents
and that's what kwin used to do. It was changed with the removal of
"Display borders on maximized windows" option, the relevant commit
didn't provide any reasoning behind the change.
The English word "pack" is not really the correct word for these
actions, and does not succeed in communicating what they will do. Since
the actions simply move the active window as far as it will go in the
specified direction, the actions can be renamed to say that instead.
Also rename the action names in the code to match their new UI text for
clarity.
The new overloads take the client (as context) and the desired screen id
or a point and return the client area.
The main motivation behind this change is to make the transition to the
new virtual desktop model where a window can be on several desktops less
painful.
toplevel.h is included in many places. Changing virtualdesktops.h may
trigger rebuild of all kwin.
With this change, only cpp files that use virtualdesktops.h will need to
be recompiled.
Window management features were written with synchronous geometry
updates in mind. Currently, this poses a big problem on Wayland because
geometry updates are done in asynchronous fashion there.
At the moment, geometry is updated in a so called pseudo-asynchronous
fashion, meaning that the frame geometry will be reset to the old value
once geometry updates are unblocked. The main drawback of this approach
is that it is too error prone, the data flow is hard to comprehend, etc.
It is worth noting that there is already a machinery to perform async
geometry which is used during interactive move/resize operations.
This change extends the move/resize geometry usage beyond interactive
move/resize to make asynchronous geometry updates less error prone and
easier to comprehend.
With the proposed solution, all geometry updates must be done on the
move/resize geometry first. After that, the new geometry is passed on to
the Client-specific implementation of moveResizeInternal().
To be more specific, the frameGeometry() returns the current frame
geometry, it is primarily useful only to the scene. If you want to move
or resize a window, you need to use moveResizeGeometry() because it
corresponds to the last requested frame geometry.
It is worth noting that the moveResizeGeometry() returns the desired
bounding geometry. The client may commit the xdg_toplevel surface with a
slightly smaller window geometry, for example to enforce a specific
aspect ratio. The client is not allowed to resize beyond the size as
indicated in moveResizeGeometry().
The data flow is very simple: moveResize() updates the move/resize
geometry and calls the client-specific implementation of the
moveResizeInternal() method. Based on whether a configure event is
needed, moveResizeInternal() will update the frameGeometry() either
immediately or after the client commits a new buffer.
Unfortunately, both the compositor and xdg-shell clients try to update
the window geometry. It means that it's possible to have conflicts
between the two. With this change, the compositor's move resize geometry
will be synced only if there are no pending configure events, meaning
that the user doesn't try to resize the window.
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.
