As in commit d45996c, the x and y coordinates passed into begin_drag and
begin_move are no longer root coordinates but are now surface
coordinates.
Use the x and y surface coordinates to acquire the root x and y
coordinates so that resizing and moving can work as expected.
ImmIsIME() doesn't work (always returns TRUE) since Vista.
Use ITfActiveLanguageProfileNotifySink to detect TSF changes,
which are equal to IME changes for us.
Also make sure that IMMultiContext re-loads the IM when keyboard layout
changes, otherwise there's a subtle bug that could happen:
* Run GTK application with non-IME layout (US, for example)
* Focus on an editable widget (GtkEntry, for example)
* IM Context is initialized to use the simple IM
* Switch to an IME layout (such as Korean)
* Start typing
* Since IME module is not loaded yet, keypresses are handled
by a default MS IME handler
* Once IME commits a character, GDK will get a WM_KEYDOWN,
which will trigger a GdkKeyEvent, which will be handled by
an event filter in IM Context, which will finally re-evaluate
its status and load IME, and only after that GTK will get
to handle IME by itself - but by that point input would
already be broken.
To avoid this we can emit a dummy event (with Void keyval),
which will cause IM Context to load the appropriate module
immediately.
This makes apps use "Segoe UI 9" by default instead of whatever matches "Sans 10".
It also cleans up the code and uses some new pango API while at it.
This was previously disabled in 9e686d1fb5 because it led to a poor glyph coverage
on certain versions of Windows which don't default to "Segoe UI 9" (Chinese, Korean, ..)
because the font fallback list was missing in pango.
This is about to get fixed in https://gitlab.gnome.org/GNOME/pango/merge_requests/34
so enable it again when we detect a new enough pango version.
(See !436 for the original MR)
GTK widgets expect the scroll deltas to be 1 or -1 and calculate a scroll value from that.
Multiplying the delta by the Windows scroll line setting (which defaults to 3) results
in a much larger delta and vastly different behaviour for running a GTK app on Windows
vs on Linux. For example text view and tree view scroll by 9 lines per scroll wheel tick
per default this way while on Linux it is around 3.
Remove the multiplication for now.
See !426 for the gtk3 MR
Enables hinting, antialiasing and set the subpixel orientation according to the
active clear type setting. This ensures that font rendering with the fontconfig backend
looks similar to the win32 backend, at least with the default system font.
See !437
Do not lie to W32 about the formats that we provide or accept.
Originally the logic behind such lies was that GdkPixbuf allows us to
convert any supported image to BMP or PNG, and therefore we should
announce that we always provide/accept BMP and PNG along with other
formats.
But that's not how it works. GDK has built-in serializers and
deserializers for all pixbuf formats (where it just invokes GdkPixbuf
API) and will use them automatically to read or write GdkTexture
objects (internally wrapping GdkPixbuf objects where necessary). The
encoding and decoding of images is handled
by GdkContent(De)Serializers, backend has nothing to do with it.
Therefore W32 GDK backend should only offer formats that it can
actually do conversion for by itself (such as image/bmp <-> CF_DIB,
or text/uri-list <-> CFSTR_SHELLIDLIST).
This leverages the normal input context switching mechanism in GTK
by making it think that the gtk-im-module setting changed.
The backend returns gtk-im-module value as "ime" if W32
IME API says that an IME is in use. Otherwise it returns
and empty string - this still triggers an input context
switching code, which, not being able to create the desired context
(which is and empty string), falls back to looking at current
keyboard layout (currently that code is still a FIXME).
Paired with the code that signals gtk-im-module change on keyboard layout
switches, this is sufficient to make GTK capable of switching to
the appropriate IM context at runtime. At least, the kinds of context
that specify languages for which they are used automatically by default
(once locale matching is implemented), and the IME context.
Loading other kinds of IM context might still work via specifying
the gtk-im-module setting in gtk ini file, but doing so will likely
make GTK incapable of using the IME context that is used
for Korean, Chinese and Japanese (and some other languages).
Until someone figures out a way to actually change gtk-im-module
setting on Windows at runtime with meaningful values, the behaviour
introduced by this commit seems like a sufficient workaround.
Commit 359df028be changed the
code to send GDK_SCROLL_SMOOTH with deltas instead of
GDK_SCROLL_(UP|DOWN|LEFT|RIGHT).
Windows defines deltas inversed for vertical direction
(positive values mean the wheel was turned forward)
but not for horizontal direction
(positive values mean the wheel was turned towards the right).
This commit fixes behavior as both axes were inverted previously.
Commit d64467b334 changed the
code to send GDK_SCROLL_SMOOTH with deltas instead of
GDK_SCROLL_(UP|DOWN|LEFT|RIGHT). Change it again, to send
both the GDK_SCROLL_SMOOTH and the GDK_SCROLL_(UP|DOWN|LEFT|RIGHT)
event separately (with the discrete event marked as emulated),
as this is what other backends (such as wayland) do.
Set delta_x or delta_y for GdkScrollEvent.
HIWORD (wParam) in WM_MOUSE(H)WHEEL is the scroll delta.
A delta value of WHEEL_DELTA (which is 120) means scrolling
one full unit of something (for example, a line).
The delta should also be multiplied by the value that the
SystemParametersInfo (SPI_GETWHEELSCROLL(LINES|CHARS), 0, &value, 0)
call gives back, unless it gives back 0xffffffff, in which case
it indicates that scrolling is page- or screen-based, not line-based
(GDK doesn't support that at the moment).
Also, all deltas should be inverted, since MS sends negative deltas
when scrolling down (rotating the wheel back, in the direction of
the user).
With deltas set the mode should be set to GDK_SCROLL_SMOOTH.
Fixes issue 1263.
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.
* There's no GdkDragContext->dest_surface anymore.
Add dest_window field to GdkWin32DragContext,
and use that instead.
* Remove unused function prototypes
* Add more comments
* Rename variables and fields from 'window' to 'surface'
where appropriate
* Fix header indentation a bit
* Try to ensure that uninitialized/unknown handle variables
and fields are set to INVALID_HANDLE_VALUE instead of NULL,
as there may be cases where NULL is a valid handle value.
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.
* Remove clipdrop->dnd_target_state, it's not used anymore
* Remove non-functioning _gdk_dropfiles_store(), store dropfiles
list in GdkWin32Drop instead
* Fix multiple comment typos
* Fix _gdk_win32_get_clipboard_format_name_as_interned_mimetype() to
leave names that look like mime/types alone
* Refactor _gdk_win32_add_w32format_to_pairs() to populate
GdkContentFormatsBuilder directly, instead of making a GList
* Rename context -> drag (still using GdkDragContext type,
but [almost?] all variables and comments say "drag" now)
* Rename GdkDropContext -> GdkDrop
* Rename some parameter names for clarity
* Rewrite local protocol to look more like OLE2 protocol
instead of mirroring the structure of the X11 API.
* Add handle_events field to GdkWin32DragContext,
to shut off event handling (temporary fix until GTK is patched up)
* Remove _gdk_win32_drag_context_find() - the drag object is stored
in GdkDrop instead. Use _gdk_win32_find_drag_for_dest_surface()
to get it initially.
* Remove target_ctx_for_window, droptarget context is stored
in the surface instead.
* Call gdk_drag_context_set_cursor() just like wayland backend does
(slightly broken for now)
* Clean up the action choosing code (filter source actions by using
keyboard state, pass that to GTK, get all actions supported by GTK in
response, match them up with filtered source actions, return the
result, falling back to COPY in case of multiple actions)
* Check drag_win32->protocol instead of the use_ole2_dnd variable where
possible
* Remove protocol checks from functions that are only used by the local
protocol
* Use event state to manufacture the keyboard state for WM_MOUSEMOVE
* Change function names printed by GDK_NOTE to name the actual
functions, not their theoretical generic GDK stack ancestors
* Consistently use drag_win32 and drop_win32 variables instead of a mix
of that and win32_drag/win32_drop
* Return FALSE from button handler to ensure that GTK gets the button
event to break implicit grab
* Emit leave event on failed idroptarget_drop() calls
There is no reason why we shouldn't pass this flag every time
Z-order changes. We have separate routines that are used to
maintain relative Z-order, so it should be completely OK to
pass SWP_NOOWNERZORDER to let the OS know that it shouldn't try
to maintain relative Z-order of the windows when raising them.
Pass SWP_NOOWNERZORDER when rising TEMP surfaces to the top. This ensures that
they don't drag anything else to the top with them. The use-case for this is
a tooltip appearing for a non-foreground surface, causing said surface to rise
above other surfaces, some of which maybe foreground at the moment.
https://bugzilla.gnome.org/show_bug.cgi?id=784766
According to the old new thing[0], we should use the instance handle
of the GDK/GTK DLL when registering GDK-specific types in the system.
Using the instance handle for the whole application in these circumstances
is not an error, but can potentially clash with the types registered
by the application itself.
Also, extract window class icons from the GDK/GTK DLL, not from the
application executable.
[0]: https://blogs.msdn.microsoft.com/oldnewthing/20050418-59/?p=35873
It's quite old, but mostly harmless (both "message == WM_KEYUP"
and "message = WM_KEYUP" evaluate to not-FALSE, and message
value is not used after that line).
* Remove DC refcounting (we trust GDK to always do
begin_frame/end_frame calls in pairs)
* Now that there's no GDK-provided double-buffer up the stack,
double-buffering is implemented here
(though it's disabled by default - in my tests it didn't provide
any visual improvements, but did decrease performance).
* For some reason delaying window resizes until the point where
we need to blit the double-buffer into the window leads
to visual glitches, so doulbe-buffered windows are resized
in begin_frame, same as non-double-buffered ones.
* New code to clear the paint region, for all drawing modes.
Hopefully, it isn't duplicated anywhere up the stack.
* GL has its own context now, so remove any GL-related comments.
* Layered windows are still used (because cairo actually works
better with them)
* A bit more code re-use for layered windows
* Some functions that were local to gdksurface-win32.c are made
usable for the whole backend
* Drag-indicator drawing is temporarily commented out to match
a similar change in X11 backend
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.
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.
* Previous commit had misleading info. The code was
added to begin_paint() instead of end_paint(). Though
that did not affect its performance in any visible way.
* Company advised to move the code to an "after_paint" signal
handler, so that it works on all renderers, not just Cairo.
This change caused high fluctuation in FPS values in fishbowl
when it is put in a situation where it cannot achieve 60fps
(such as using Cairo renderer at ultra-high resolution).
This seems to be deliberate and not a bug.
There is no easily apparent way of being notified when frame updates
happene exactly, so we just query frame info at the end of each paint.
If we query too often (faster than DWM refresh rate), we just get
the same values twice in a row, but that is, hopefully, highly unlikely.
This commit ensures that each GdkSurface impl remembers the
cursor that GDK sets for it, and that this cursor is set
each time WM_SETCURSOR is called for that sufrace's HWND.
This is needed because W32, unlike X, has no per-window cursors -
the cursor on W32 is a global resource, and we need to keep track
of which cursor should be set when pointer is over which surface
ourselves (WM_SETCURSOR exists exactly for this reason).
This commit also makes GDK remember the surface that has an implicit
grab (since implicit grabs are gone from the upper levels of the toolkit),
and ensures that crossing events are correctly synthesized and the grab
is broken when surface focus changes. This fixes a bug where opening
a new window (by clicking something in some other, pre-existing window)
will make that new window not get any mouse input due to the fact
that the mouse-button-down event from that click caused an implicit
grab on the pre-existing window, and that grab was not released afterward.
Instead of now-unused GdkWin32Cursor class (a subclass of GdkCursor),
add a stand-alone GdkWin32HCursor class that is a wrapper around
HCURSOR handle.
On creation it's given a display instance, a HCURSOR handle and a boolean
that indicates whether the HCURSOR handle can or cannot be destroyed
(this depends on how the handle was obtained).
That information is stored in a hash table inside the GdkWin32Display
singleton, each entry of that table has reference count.
When the GdkWin32HCursor object is finalized, it reduces the reference
count on the table entry in the GdkWin32Display. When it's created,
it either adds such an entry or refs an existing one.
This way two pieces of code (or the same piece of code called
multiple times) that independently obtain the same HCURSOR from the OS
will get to different GdkWin32HCursor instances, but GdkWin32Display
will know that both use the same handle.
Once the reference count reaches 0 on the table entry, it is freed
and the handle (if destroyable) is put on the destruction list,
and an idle destruction function is queued.
If the same handle is once again registered for use before the
idle destructior is invoked (this happens, for example, when
an old cursor is destroyed and then replaced with a new one),
the handle gets removed from the destruction list.
The destructor just calls DestroyCursor() on each handle, calling
SetCursor(NULL) before doing that when the handle is in use.
This ensures that SetCursor(NULL) (which will cause cursor to disappear,
which is bad by itself, and which will also cause flickering if the
cursor is set to a non-NULL again shortly afterward)
is almost never called, unless GTK messes up and keeps using a cursor
beyond its lifetime.
This scheme also ensures that non-destructable cursors are not destroyed.
It's also possible to call _gdk_win32_display_hcursor_ref()
and _gdk_win32_display_hcursor_unref() manually instead of creating
GdkWin32HCursor objects, but that is not recommended.
Add a new W32 backend-specific message filtering mechanism.
Works roughly the same way old event filtering did, but without
events (events are GDK/X11 concept that never really made sense
on W32), so there's no functionality for 'altering' events being
emitted. If an event needs to be emitted in response to a message
do it yourself.
Implemented like this, it should give better performance than
if we were to use GLib signals for this, since W32 sends a LOT
of messages (unlike X11, which doesn't send events as often)
all the time, and invoking the signal machinery on *each* message
would probably be bad.
https://bugzilla.gnome.org/show_bug.cgi?id=773299
Rename GdkWin32Selection to GdkWin32Clipdrop, since GdkSelection
is mostly gone, and the word "selection" does not reflect the
functionality of this object too well.
Clipboard is now handled by a separate thread, most of the code for
it now lives in gdkclipdrop-win32.c, gdkclipboard-win32.c just uses
clipdrop as a backend.
The DnD source part is also put into a thread.
The DnD target part does not spin the main loop, it just
emits a GDK event and returns a default value if it doesn't get a reply
by the time the event is processed.
Both clipboard and DnD use a new GOutputStream subclass to get data
from GTK and put it into a HGLOBAL.
GdkWin32DragContext is split into GdkWin32DragContext and GdkWin32DropContext,
anticipating a similar change that slated to happen to GdkDragContext.
OLE2 DnD protocol is now used by default, set GDK_WIN32_OLE2_DND envvar to 0
to make GDK use the old LOCAL and DROPFILES protocols.
https://bugzilla.gnome.org/show_bug.cgi?id=773299
Set the display for each event that we put.
Also reorganize the dnd_event_put() function a bit, giving it a surface
directly instead of setting it by implication.
https://bugzilla.gnome.org/show_bug.cgi?id=773299
dest_surface is going to always be NULL for source contexts.
Previously we used to put the root window there to pass this check,
but root windows are gone (and root surfaces never existed to begin
with), so we have to adapt.
https://bugzilla.gnome.org/show_bug.cgi?id=773299
This affects gdk_device_query_state() for the virtual device. It has
no window, and is forced to query the display itself, and display
defaults its scale to 1 even for HiDPI desktops. Use the same
"query scale of a NULL monitor" trick that we use in other places
to get the global desktop scale.
https://bugzilla.gnome.org/show_bug.cgi?id=773299
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
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
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.
No idea why it's here, the hash table can store any kind of data,
there's no reason why it wouldn't be able to store an old X string type.
Might be a holdout from the old days, when strings were handled in
a special way (stored directly in the clipboard?).
https://bugzilla.gnome.org/show_bug.cgi?id=786509
This prevents GTK from throwing a bunch of warnings when it tries
to get drag source window -> screen of that window -> ipc widget for that screen,
and then tries to attach a signal handler to that widget.
Specifically, this happens when we get a DnD move from another
application.
https://bugzilla.gnome.org/show_bug.cgi?id=786509
1) Ensure that any DELETE requests from the target are sent to GDK, even if
both the source and the target are in the same process and it
is therefore possible to use a shortcut and call the handler directly
in GTK layer
2) Ensure that target GDK doesn't do anything when GTK asks it to send
a DELETE request, just report back immediately (the code up the stack
does not check for successfullness when request is DELETE, so not giving
it any data is OK).
The source code already synthesizes a DELETE request, so that side is
also taken care of.
https://bugzilla.gnome.org/show_bug.cgi?id=786509
We need to know the target atom value to know when we need to
do something with side-effects (since side-effects are expressed via
special target values). Previously, the code side-stepped that by looking
at the data type (which was rather unique for the one side-effect
target that we supported, signalled by the TARGETS target),
but for the DELETE target that seems to be no longer an option, hence the new
field to carry this information past the convert_selection() routine.
This prevents GDK from throwing a warning when trying to convert
a DELETE target, which has no format or data objects set.
The side-effects for the DELETE target happen earlier, in GTK layer.
By the point it gets to change_property(), it's a no-op.
https://bugzilla.gnome.org/show_bug.cgi?id=786509
