Since MetaStackTracker is the code that knows about the current X stacking order
and the relationship between X windows and Wayland windows, it's cleaner to
encapsulate stack manipulation in MetaStackTracker rather than have the calling
code make the X calls and only call into MetaStackTracker to inform it about
the changes.
https://bugzilla.gnome.org/show_bug.cgi?id=736559
Putting X windows and pointers to MetaWindows into a union had a number of
problems:
- It caused awkward initialization and conditionalization
- There was no way to refer to Wayland windows (represented by
MetaWindow *) in the past, which is necessary for the MetaStackTracker
algorithms
- We never even cleaned up old MetaStackWindow so there could be
records in MetaStackWindow pointing to freed MetaWindow.
Replace MetaStackWindow with a 64-bit "stack ID" which is:
- The XID for X Windows
- a "window stamp" for Wayland windows - window stamps are assigned
for all MetaWindow and are unique across the life of the process.
https://bugzilla.gnome.org/show_bug.cgi?id=736559
This breaks down the assumptions in stack-tracker.c and stack.c that
Mutter is only stacking X windows.
The stack tracker now tracks windows using a MetaStackWindow structure
which is a union with a type member so that X windows can be
distinguished from Wayland windows.
Some notable changes are:
Queued stack tracker operations that affect Wayland windows will not be
associated with an X serial number.
If an operation only affects a Wayland window and there are no queued
stack tracker operations ("unvalidated predictions") then the operation
is applied immediately since there is no server involved with changing
the stacking for Wayland windows.
The stack tracker can no longer respond to X events by turning them into
stack operations and discarding the predicted operations made prior to
that event because operations based on X events don't know anything
about the stacking of Wayland windows.
Instead of discarding old predictions the new approach is to trust the
predictions but whenever we receive an event from the server that
affects stacking we cross-reference with the predicted stack and check
for consistency. So e.g. if we have an event that says ADD window A then
we apply the predictions (up to the serial for that event) and verify
the predicted state includes a window A. Similarly if an event says
RAISE_ABOVE(B, C) we can apply the predictions (up to the serial for
that event) and verify that window B is above C.
If we ever receive spurious stacking events (with a serial older than we
would expect) or find an inconsistency (some things aren't possible to
predict from the compositor) then we hit a re-synchronization code-path
that will query the X server for the full stacking order and then use
that stack to walk through our combined stack and force the X windows to
match the just queried stack but avoiding disrupting the relative
stacking of Wayland windows. This will be relatively expensive but
shouldn't be hit for compositor initiated restacking operations where
our predictions should be accurate.
The code in core/stack.c that deals with synchronizing the window stack
with the X server had to be updated quite heavily. In general the patch
avoids changing the fundamental approach being used but most of the code
did need some amount of re-factoring to consider what re-stacking
operations actually involve X or not and when we need to restack X
windows we sometimes need to search for a suitable X sibling to restack
relative too since the closest siblings may be Wayland windows.
If mutter is going to be a "real" library, then it should install its
includes so that users can do
#include <meta/display.h>
rather than
#include <display.h>
So rename the includedir accordingly, move src/include to src/meta,
and fix up all internal references.
There were a handful of header files in src/include that were not
installed; this appears to have been part of a plan to keep core/,
ui/, and compositor/ from looking at each others' private includes,
but that wasn't really working anyway. So move all non-installed
headers back into core/ or ui/.
https://bugzilla.gnome.org/show_bug.cgi?id=643959
In order to properly track the stacking order for override-redirect
windows, move meta_compositor_sync_stack() call into MetaStackTracker.
In the new location, we sync the stack as a before-redraw idle function,
rather then using the freeze-thaw facilities of MetaStack. This is
simpler, and also properly compresses multiple stack changes on
notifications received from the X server.
http://bugzilla.gnome.org/show_bug.cgi?id=585984
Wedging override-redirect windows into the constraint code in stack.c
results in Mutter getting confused about the stacking order of
these windows with respect to other windows, and may also in some
cases cause Mutter to restack override-redirect windows.
core/stack-tracker.c core/stack-tracker.h: MetaStackTracker - combine
events received from the X server with local changes we have made
to come up with the best possible idea of what the stacking order
is at any one point in time.
core/screen.c core/screen-private.h: Create a MetaStackTracker for
the screen.
core/display.c: Feed relevant events to MetaStackTracker
core/frame.c core/screen.c core/stack.c: When we make changes to the
stacking order or add windows, record those changes immediatley
in MetaStackTracker so we have the information without waiting
for a round-trip.
include/ui.h ui/ui.c: meta_ui_create_frame_window add a return value
for the X request serial used to create the window.
http://bugzilla.gnome.org/show_bug.cgi?id=585984
