Some of the flags got lost in the meson transition or were demoted from
error flags to warning flags.
This commit reintroduces them.
It also includes fixes for the code that had warnings with those flags.
The big one being -Wshadow.
Tools on the same physical item have the same serial number, so the eraser
and the pen part of a single pen share that serial number. With the current
lookup code, we'll always return whichever tool comes first into proximity.
Change the code to use the hw id in addition to the serial number, this way we
can differ between two tools.
Generic tools (Bamboo, built-in tablets) always have the same serial number
assigned by the wacom driver. This includes the touch tool when the wacom
driver handles the touch evdev node (common where users require the wacom
gestures to work).
When the first device is the touch device, a tool is created with that serial.
All future tools now return the touch tool on lookup since they all share the
same serial number. Worse, this happens *across* devices, so the pen
event node gets assigned the touch tool because they all have the same serial.
Since we don't actually care about the touch as a tool, let's skip any unknown
tool. This captures pads as well.
Any wacom device currently sets the tool type to UNKNOWN. The wacom driver has
a property that exports the tool type as one of stylus, eraser, cursor, pad or
touch. Only three of those are useful here but that's better than having all
of them as unknown.
As per the spec:
> The back buffer can
> either be reported as invalid (has an age of 0) or it may be
> reported to contain the contents from n frames prior to the
> current frame.
So a buffer age of 1 means that the buffer was used in the last frame.
We were handling buffer_age==1 the same as buffer_age==0, i.e. we
returned the full damage for the surface.
[1] https://www.khronos.org/registry/EGL/extensions/EXT/EGL_EXT_buffer_age.txt
GtkEntryCompletion can rapidly release and claim ownership of the
primary selection. This generates multiple XFixesSelectionNotify events,
first stating that no one owns the selection, then another stating that
we own the selection. The notification that no one owns the selection
causes GtkEntryCompletion to deselect the text, breaking inline
autocompletion.
This fixes it by ignoring any XFixesSelectionNotify with a timestamp
earlier than our clipboard timestamp.
Fixes#14
Change GdkDrag::action to GdkDrag::selected-action, which is
more clearly different from actions, and follows the existing
name of the struct field and getter.
This lets us drop the ::action-changed signal for the
property change notification. But, can just as well move
the signal class handers which just update the cursor
to the ::action setter. No need to do this in the backends.
Rename gdkdnd.h to gdkdrag.h, to go along with gdkdrop.h
This commit includes the necessary updates to the X11, Wayland
and Broadway backends. Other backends have to be updated separately.
This is to go along with the newly introduced GdkDrop.
This commit includes the necessary updates to the X11, Wayland
and Broadway backends. Other backends have to be updated separately.
This might be foreign Windows and we don't want to create surfaces for
those.
Also, stop using GdkDragContext.dest_surface, that variable is meant to
go away.
In particular, this patch removes:
gdk_surface_get_events()
gdk_surface_set_events()
gdk_surface_get_device_events()
gdk_surface_set_device_events()
Event masks so far still exist for grabs.
GdkDragContext => GdkDrop
This is all in preparation of separation of the drag and drop.
Also, don't check for GDK_DRAG_PROTO_XDND anymore - it's the only
possible value for the protocol on the target side.
Use the new method of connecting to the xevent signal instead.
Also, don't consume the xevent, there might be other code listening for
it. And we don't use PropertyNotify in the generic code path anymore, so
it'll just be ignored there.
Instead of looking at the list of contexts, just look at the current
drop context. There is only one, after all.
Then remove the is_source argument from gdk_drag_context_find().
The filters now return TRUE/FALSE and no longer a GdkFilterReturn. They
also don't conform to the GdkFilterFunc typedef anymore but instead take
the arguments that they need.
In 01455399e8 ("gdk: do not deactivate surface on keyboard grabs"), we
made gdk avoid deactivating surfaces when another application takes a
keyboard grab, by using has_focus_window instead of has_focus. That however
broke activating surfaces when the gdk application acquired a grab itself,
in which case has_focus_window is false but has_focus is true.
We thus actually need to use both: surfaces should be activated either
because we have normal keyboard focus, or because we grabbed the keyboard.
This also renames HAS_FOCUS to APPEARS_FOCUSED to better reflect its
role.
Fixes#85
Includes implementation for Wayland and X11, which are the only backends
implementing the Startup Notification Protocol, returns NULL otherwise.
https://gitlab.gnome.org/GNOME/gtk/issues/1084
Similar to what has been done recently for DESKTOP_AUTOSTART_ID [1],
we need to get rid of this call to g_unsetenv() in the displays'
backends for X11 and Wayland, so that it's guarantee to happen any
thread is created, while still being accessible when needed.
Let's stash the value of this environment variable when loading the
GDK library, and provide a private method so that it can be retrieved
from the displays' backend when implementing gdk_display_make_default().
[1] https://gitlab.gnome.org/GNOME/gtk/commit/22269902
Closes: https://gitlab.gnome.org/GNOME/gtk/issues/979
The check survived from GTK2 when that function could still return
GdkPixmap and GdkFont objects and was accompanied by this comment:
/* We may receive events such as NoExpose/GraphicsExpose
* and ShmCompletion for pixmaps
*/
When pressing e.g. a window manager shortcut, which acquires keyboard grab,
Xorg would send FocusOut NotifyGrab then FocusIn NotifyUngrab. Currently
gdk would then deactivate the current surface, which makes accessibility
screen readers think that we have switched to a non-accessible application
and came back again, and thus reannounce the application frame etc. which we
don't want when e.g. just raising volume.
And actually, receiving FocusOut NotifyGrab does not mean losing the
X focus, it only means an application aqcuired a grab, i.e. it is
temporarily stealing keyboard events. On Wayland, this isn't even
notified actually.
This commit makes gdk only deactivate surfaces when there was an actual
focus switch to another window, as determined by has_focus_window (instead
of just has_focus), which happens either normally through FocusOut with
NotifyNormal, or during grabs through FocusOut with NotifyWhileGrabbed.
Fixes#85
Now that all Cairo contexts are ported to managing cairo surfaces
themselves, the old fallback code that didi the managing is no longer
needed.
Also clarify the behavior of gdk_cairo_context_cairo_create() wrt the
vfunc by doing the early exit and the clipping outside of it.
We used to pass 2 regions to GdkDrawCotnext.end_frame() but code was
confusing what they meant. So we now don't do that anymore and only pass
the region that matters: The frame region.
This makes the previous gdk_draw_context_is_drawing() function public
under a new name.
I decided against the old name because we use the term "frame" for a
drawing operation, so I wanted to have this boolean flag reuse the term.
Also, don't implement SurfaceClass.ref_cairo_surface() anymore. This
means calls to it will crash now. But as they only happen in the generic
GdkCairoContext implementation, we shouldn't be affected by that.
Plus, once all backends have been ported, that call is going away
anyway.
And make the GdkCairoContext as abstract.
The idea of this and thje following commits is to get rid of all
Cairo code in gdksurface.c (and $backend/gdksurface-$backend.c)
by moving that code into the Cairo context files.
In particular, the GdkSurfaceClass.begin_frame/end_frame()
functions (which are currently exclusively used by the Cairo code
should end up being moved to GdkDrawContextClass.begin/end_frame().
This has multiple benefits:
1. It unifies code between the different drawing contexts.
GL lives in GLContext, Vulkan in VulkanContext and Cairo in
CairoContext. In turn, this makes it way easier to reason about
what's going on in surface-specific code. Currently pretty much
all backends do things wrong when they want to sync to drawing
or to the frame clock.
2. It makes the API of GdkSurface smaller. No drawing code (apart
from creating the contexts) needs to remain.
3. It confines Cairo to the Drawcontext, thereby making it way
more obvious when backends are still using it in situations
where it may now conflict with OpenGL (like when doing the dnd
failed animation or in the APIs that I'm removing in this
branch).
4. We have 2 very different types of Cairo contexts: The X/win32
model, where we have a natively supported Cairo backend but do
double buffering ourselves and use similar surfaces and the
Wayland/Broadway model where we use image surfaces without any
Cairo backend support and have to submit the buffers manually.
By not sharing code between those 2 versions, we can make the
actual code way smaller. We also get around the need to create
1x1 image surfaces in the Wayland backend where we pretend
there's a native Cairo surface.
When asked for a nonexistent (positive) monitor number,
gdk_x11_display_get_monitor would (at best) return an uninitialized pointer,
instead of returning NULL.
That way, we can store the right region there: The actual painted area
instead of the exposed area (which is way too small).
Also, the GL context is the only user of this data, so storing it there
seems way smarter.
This ensures that the frame clock gets updated with correct presentation
times even if nothing was drawn.
This is necessary for benchmarking but would also be relevant for videos
that want to sync to the frame clock but draw frames a lot less.
... and its implementation in the X11 backend.
GDK does lots of work trying to reduce the region in expose events
so that when the server sends multiple expose events, touching the
same area we can make sure to only redraw stuff once. However:
(1) this is only relevant of there's tons of delay and multiple
expose events get sent
(2) we coalesce multiple events into a single expose event anyway
(3) we do this on the frame clock
But most importantly:
(4) Since the invention of compositing, servers caches all contents
anyway
This is an automatic rename of various things related
to the window->surface rename.
Public symbols changed by this is:
GDK_MODE_WINDOW
gdk_device_get_window_at_position
gdk_device_get_window_at_position_double
gdk_device_get_last_event_window
gdk_display_get_monitor_at_window
gdk_drag_context_get_source_window
gdk_drag_context_get_dest_window
gdk_drag_context_get_drag_window
gdk_draw_context_get_window
gdk_drawing_context_get_window
gdk_gl_context_get_window
gdk_synthesize_window_state
gdk_surface_get_window_type
gdk_x11_display_set_window_scale
gsk_renderer_new_for_window
gsk_renderer_get_window
gtk_text_view_buffer_to_window_coords
gtk_tree_view_convert_widget_to_bin_window_coords
gtk_tree_view_convert_tree_to_bin_window_coords
The commands that generated this are:
git sed -f g "GDK window" "GDK surface"
git sed -f g window_impl surface_impl
(cd gdk; git sed -f g impl_window impl_surface)
git sed -f g WINDOW_IMPL SURFACE_IMPL
git sed -f g GDK_MODE_WINDOW GDK_MODE_SURFACE
git sed -f g gdk_draw_context_get_window gdk_draw_context_get_surface
git sed -f g gdk_drawing_context_get_window gdk_drawing_context_get_surface
git sed -f g gdk_gl_context_get_window gdk_gl_context_get_surface
git sed -f g gsk_renderer_get_window gsk_renderer_get_surface
git sed -f g gsk_renderer_new_for_window gsk_renderer_new_for_surface
(cd gdk; git sed -f g window_type surface_type)
git sed -f g gdk_surface_get_window_type gdk_surface_get_surface_type
git sed -f g window_at_position surface_at_position
git sed -f g event_window event_surface
git sed -f g window_coord surface_coord
git sed -f g window_state surface_state
git sed -f g window_cursor surface_cursor
git sed -f g window_scale surface_scale
git sed -f g window_events surface_events
git sed -f g monitor_at_window monitor_at_surface
git sed -f g window_under_pointer surface_under_pointer
(cd gdk; git sed -f g for_window for_surface)
git sed -f g window_anchor surface_anchor
git sed -f g WINDOW_IS_TOPLEVEL SURFACE_IS_TOPLEVEL
git sed -f g native_window native_surface
git sed -f g source_window source_surface
git sed -f g dest_window dest_surface
git sed -f g drag_window drag_surface
git sed -f g input_window input_surface
git checkout NEWS* po-properties po docs/reference/gtk/migrating-3to4.xml
Rename all *window.[ch] source files.
This is an automatic operation, done by the following commands:
for i in $(git ls-files gdk | grep window); do
git mv $i $(echo $i | sed s/window/surface/);
git sed -f g $(basename $i) $(basename $i | sed s/window/surface/) ;
done
git checkout NEWS* po-properties po
This renames the GdkWindow class and related classes (impl, backend
subclasses) to surface. Additionally it renames related types:
GdkWindowAttr, GdkWindowPaint, GdkWindowWindowClass, GdkWindowType,
GdkWindowTypeHint, GdkWindowHints, GdkWindowState, GdkWindowEdge
This is an automatic conversion using the below commands:
git sed -f g GdkWindowWindowClass GdkSurfaceSurfaceClass
git sed -f g GdkWindow GdkSurface
git sed -f g "gdk_window\([ _\(\),;]\|$\)" "gdk_surface\1" # Avoid hitting gdk_windowing
git sed -f g "GDK_WINDOW\([ _\(]\|$\)" "GDK_SURFACE\1" # Avoid hitting GDK_WINDOWING
git sed "GDK_\([A-Z]*\)IS_WINDOW\([_ (]\|$\)" "GDK_\1IS_SURFACE\2"
git sed GDK_TYPE_WINDOW GDK_TYPE_SURFACE
git sed -f g GdkPointerWindowInfo GdkPointerSurfaceInfo
git sed -f g "BROADWAY_WINDOW" "BROADWAY_SURFACE"
git sed -f g "broadway_window" "broadway_surface"
git sed -f g "BroadwayWindow" "BroadwaySurface"
git sed -f g "WAYLAND_WINDOW" "WAYLAND_SURFACE"
git sed -f g "wayland_window" "wayland_surface"
git sed -f g "WaylandWindow" "WaylandSurface"
git sed -f g "X11_WINDOW" "X11_SURFACE"
git sed -f g "x11_window" "x11_surface"
git sed -f g "X11Window" "X11Surface"
git sed -f g "WIN32_WINDOW" "WIN32_SURFACE"
git sed -f g "win32_window" "win32_surface"
git sed -f g "Win32Window" "Win32Surface"
git sed -f g "QUARTZ_WINDOW" "QUARTZ_SURFACE"
git sed -f g "quartz_window" "quartz_surface"
git sed -f g "QuartzWindow" "QuartzSurface"
git checkout NEWS* po-properties
is_touchpad_device() for XI2 was hardcoded to look for libinput only.
Extend it slightly to correctly identify other Xorg touchpad drivers.
https://gitlab.gnome.org/GNOME/gtk/issues/97
The Wayland backend was already not supporting this setting
since it is an XSetting that is not backed by a GSetting.
Drop this setting altogether, since we will stop supporting
general-purpose modules.
Drop the public filtering API. The x11 backend already has
the ::xevent signal as replacement. The win32 backend needs
a similar signal to replace filtering.
Reshuffle header inclusions in the x11 backend a little bit
to avoid a cyclic inclusion between gdkprivate-x11.h and
gdkdisplay-x11.h that is otherwise causing problems.
Remove all the old 2.x and 3.x version annotations.
GTK+ 4 is a new start, and from the perspective of a
GTK+ 4 developer all these APIs have been around since
the beginning.
The GDK_POINTER_MOTION_HINT_MASK enumeration value is gone, but we're
still keeping around the "is_hint" field in GdkEventMotion, even though
every backend sets it to `false` — except for the core X11 device
manager.
GdkContentFormatsBuilder is currently not introspectable, as it does not
have a GType. We can turn it into a boxed type, but we need to implement
memory management for it.
The current gdk_content_formats_builder_free() function returns a newly
constructed value, so we cannot use it as a GBoxedFreeFunc; additionally
copying a GdkContentFormatsBuilder contents would make it a bit odd, as
you could get multiple identical GdkContentFormats out of the copies.
A simple approach is to model the GdkContentFormatsBuilder API to follow
the GBytes one: use reference counting for memory management, and have
a function to release a reference, return a GdkContentFormats, and reset
the GdkContentFormatsBuilder state.
For language bindings, we can provide a get_formats() function that
returns the GdkContentFormats instance and resets the builder instance,
leaving the reference count untouched.
For C convenience we can keep gdk_content_formats_builder_free(), and
make it a wrapper around gdk_content_formats_builder_get_formats(), with
the guarantee that it'll free the builder instance regardless of its
current reference count.
https://bugzilla.gnome.org/show_bug.cgi?id=793097https://blogs.gnome.org/otte/2018/02/03/builders/
GDK has a lock to mark critical sections inside the backends.
Additionally, code that would re-enter into the GTK main loop was
supposed to hold the lock.
Back in the Good Old Days™ this was guaranteed to kind of work only on
the X11 backend, and would cause a neat explosion on any other GDK
backend.
During GTK+ 3.x we deprecated the API to enter and leave the critical
sections, and now we can remove all the internal uses of the lock, since
external API that uses GTK+ 4.x won't be able to hold the GDK lock.
https://bugzilla.gnome.org/show_bug.cgi?id=793124
The main GDK thread lock is not portable and deprecated.
The only reason why gdk_threads_add_timeout() and
gdk_threads_add_timeout_full() exist is to allow invoking a callback
with the GDK lock held, in case 3rd party libraries still use the
deprecated gdk_threads_enter()/gdk_threads_leave() API.
Since we're removing the GDK lock, and we're releasing a new major API,
such code cannot exist any more; this means we can use the GLib API for
installing timeout callbacks.
https://bugzilla.gnome.org/show_bug.cgi?id=793124
The main GDK thread lock is not portable and deprecated.
The only reason why gdk_threads_add_idle() and
gdk_threads_add_idle_full() exist is to allow invoking a callback with
the GDK lock held, in case 3rd party libraries still use the deprecated
gdk_threads_enter()/gdk_threads_leave() API.
Since we're removing the GDK lock, and we're releasing a new major API,
such code cannot exist any more; this means we can use the GLib API for
installing idle callbacks.
https://bugzilla.gnome.org/show_bug.cgi?id=793124
This state flag is used in several places in GTK+, for example to
ignore RESIZE_INC hints if tiled. Setting it is also necessary for
backwards compatibility with applications that changed their behaviour
when tiled, such as GNOME Terminal and its MATE fork.
Signed-off-by: Simon McVittie <smcv@debian.org>
https://bugzilla.gnome.org/show_bug.cgi?id=789357
Commit c415bef5de introduced support for the new _GTK_EDGE_CONSTRAINTS
atom. If the compositor supports that atom, however, we were always
setting the tiled state, even if no actual tiling information is
available, where the correct action is to completely remove any traces
of the tiled state.
Fix that by correctly removing the tiled state when compositor supports
_GTK_EDGE_CONSTRAINTS Xatom.
https://bugzilla.gnome.org/show_bug.cgi?id=788516
The query function for cursor sizes and capabilities
are not very interesting. At least, they are not used
in GTK+, and all backends but X11 just hardcode
made-up values anyway. So, lets drop them.
As far as possible, use per-display debug flags.
This will minimize the debug spew that we get from
the inspector if it is running on a separate display.
Without selections, drags can't have them either.
Also included is removing the selection from GtkSelectionData.
Includes a bunch of crude cleanups to Wayland code that no longer has to
care about selection atoms.
Now all events structs are private, it doesn't make as much sense
having GdkEventPrivate wrapping allocating events. This is a first
step towards removing it.
It won't stand true anymore that the GdkEventType argument is the
first field of the GdkEvent* structs. All callers have been updated
to use event->any.type instead.
Instead of just passing the GdkContentFormats, we are now passing the
GdkContentProvider to gdk_drag_begin().
This means that GDK itself can now query the data from the provider
directly instead of having to send selection events.
Use this to provide the private API gdk_drag_context_write() that allows
backends to pass an output stream that this data will be written to.
Implement this as the mechanism for providing drag data on Wayland.
And to make this all work, implement a content provider named
GtkDragContent that is implemented by reverting to the old DND
drag-data-get machinery inside GTK, so for widgets everything works just
like before.
We now have a GdkX11Display::xevent signal that gets emitted for every
XEvent and allows you to interrupt processing via TRUE/FALSE return
values.
These return values to correspond to GDK_FILTER_REMOVE and
GDK_FILTER_CONTINUE respectively.
The GDK_FILTER_TRANSLATE case from gdk_window_add_filter() is now meant
to be handled via gdk_display_put_event().
This is in preparation for DND.
It moves a lot of code from gdkclipboard-x11.c to
gdkselectionoutputstream-x11.c to untangle it from GdkX11Clipboard
usage.
Instead, pass the actions as part of gdk_drag_begin() and insist DND is
always managed.
A new side effect is that gdk_drag_begin() can now return %NULL.
This is the replacement for selection usage.
Backend implementations for X11 (missing support for backwards compat
formats like COMPOUND_TEXT) and Wayland are included.
GTK code should be adapted to use gdk_drop_read_*() functions instead
of gtk_drag_get_data().
When the reply to a TARGETS request comes in, the clipboard may already
be reclaimed by the local app. Deal with that case (in an ugly way,
strictly speaking we should use a cancellable here).
This happens for example at startup when the initial TARGETS requests
have not been answered until after the main widow popped up. And if such
a window immediately claims the primary clipboard (like when the initial
focus is inside an entry), this race will happen.
This object tracks the SelectionNotifyEvent that has to be sent in
response to a SelectionRequest.
Currently it just looks like code reshuffling, but it's a prerequisite
for handling MULTIPLE, which requires to only send the notify after
every stream has writtten at least once.
But anyway, code is cleaner now, so it's a win!
(1) Try all passed in formats in order if one of them fails.
(2) Don't blindly accept all formats, make sure they are mime types
(3) Add a bunch of special non-mime types that plug converters to
get to mime types
This allows us not just to pass any mime type to the read function, but
it also makes it possible to pass multiple mime types and the clipboard
can then try them in order until it finds a supported one.
This is so far not implemented though.
Turns out, way too many async operations are implemented by running the
sync operation in a thread. The easiest solution is to support that is
to use a GAsyncQueue for the buffers and deadlock if called from the
main thread.
(1) Turn X11 clipboard event handling into a regular filter function
(2) Maintain a timestamp in the clipboard, so we can pass it when
querying selections.
Make sure the API reflects the idea that GdkContentFormats is a set
containing mime types. In particular, treat the object itself as a
plural - it's named content format`S' after all - and therefor use
the correct verb form.
Also make GdkContentFormats keep an array instead of a list, now that
it's immutable.
Instead, turn the functions into backend API:
gdk_broadway_display_add_selection_targets()
gdk_broadway_display_clear_selection_targets()
Remove the old per-backend functions, too.
Instead of creating a GdkX11Cursor, create GdkCursors. Cache the XCursor
in a hash table instead.
Also, make use of the new fallback mechanism for fallback code: Make
sure to provide cursors for the names that are guaranteed to exist, but
do not do bad attempts at displaying texture surfaces.
Black/White/transparent is not a replacement for those.
Stop wrapping the xsettings manager window in a foreign
window. This means that we cannot use the gdk window filter
APIs anymore, so just do the filtering in a non-generic
way.
The preferred api to create cursors is by name, and the
GdkCursorType enumeration can directly trace its ancestry
to the horrible X cursor font. So lets stop using it.
gdk_display_get_default_screen is gone, but we still
have x11-specific screen apis that GTK+ is using, so
we need an alterative way to get the screen object.
GTK+ now uses the gtk-xft-dpi setting directly.
Note: this commit only fixes the backends that
currently provide this setting. The win32 and
Quartz backends still need to be fixed.
Drop the screen argument from gdk_dnd_find_window_for_screen
and rename the function to gdk_dnd_find_window. The screen
argument does not add anything here since the drag context
is already tied to the display. Update all backends, and
update all callers.
We are not emitting these events anymore, so lets remove them
from the api. The GdkSettingAction enum is moved to xsettings-client.c
where its only use remains.
Epoxy 1.4 has new ad hoc API that we can use to check whether GLX is
available on the current system.
If we didn't use this API, we'd have to manually dlopen libGL (or its
equivalent on different OSes) and check if it had GLX symbols; since
Epoxy already does all of this internally, we can simply ask it instead.
https://bugzilla.gnome.org/show_bug.cgi?id=775279
This patch makes that work using 1 of 2 options:
1. Add all missing enums to the switch statement
or
2. Cast the switch argument to a uint to avoid having to do that (mostly
for GdkEventType).
I even found a bug while doing that: clearing a GtkImage with a surface
did not notify thae surface property.
The reason for enabling this flag even though it is tedious at times is
that it is very useful when adding values to an enum, because it makes
GTK immediately warn about all the switch statements where this enum is
relevant.
And I expect changes to enums to be frequent during the GTK4 development
cycle.
-Wint-conversion is important because it checks casts from ints to
pointers.
-Wdiscarded-qualifiers is important to catch cases where we don't
strings when we should.
The behavior where a touchpoint takes over the pointer position is
really backend dependent. Since this went away from the generic code,
implement it here.
Instead of relying on special values of edge constraints, this
patch adds an internal-only gdk_window_supports_edge_constraints()
function that by default returns FALSE, and is implemented by
GdkWindowWayland and GdkWindowX11.
This way, we can properly detect server-side support for this
feature and adapt accordingly.
https://bugzilla.gnome.org/show_bug.cgi?id=783669
Following the previous patch, where edge constraints support
was added to the Wayland backend, this patch introduces the
necessary code to handle the _GTK_EDGE_CONSTRAINTS atom from
X11 backend.
https://bugzilla.gnome.org/show_bug.cgi?id=783669
Under X, we were not setting the right drag cursor initially,
because at current_action == action == 0, initially. Fix this
by explicitly using the right cursor when grabbing.
This property contains 5 integers, of which the last 2 respectively
contain the tool serial number and tool ID. We were only extracting the
first so far, but GdkDeviceTool also has API getters for the latter,
which remained 0.
https://bugzilla.gnome.org/show_bug.cgi?id=786400
Interpret NULL as "root window" here - we only have one
screen nowadays, so there is no choice involved, and this
will let us avoid dealing with the root window in the
fontend code.
