The active keyboard grab can be spared then. This way the passive
key grabs allow other key combinations (eg. alt-tab) that are not
mandatory to grab here.
Always associate a drag context with a GdkDisplay and use that when
getting a cursor for a given action.
If we don't do this, dragging on a window that doesn't use the default
display will make us use cursors from the wrong display.
https://bugzilla.gnome.org/show_bug.cgi?id=765565
This allows us to decide when the R and B color channels should be
flipped with a much better granularity.
For instance, when using GLX_EXT_texture_from_pixmap to create a GL
texture from a surface we don't need to swap the R and B channels, as
the internal representation of the texture data will already have the
appropriate colors.
We also don't need to flip color channels when blitting from a texture.
Windows save in hardware_keycode an information which is not so low
level and some application require the hardware scancode.
As Windows provides this information save it in GdkEventPrivate
and provide a function to get this information.
For no Windows system the function return the hardware_keycode instead.
Signed-off-by: Frediano Ziglio <fziglio@redhat.com>
https://bugzilla.gnome.org/show_bug.cgi?id=765259
Because there are multiple different types of styluses that can be used with
tablets, we have to have some sort of identifier for them attached to the
GdkDeviceTool, especially since knowing the actual tool type for a GdkDeviceTool
is necessary for matching up a GdkDeviceTool with it's appropriate
GdkInputSource in Wayland (eg. matching up a GdkDeviceTool eraser with the
GDK_SOURCE_ERASER GdkInputSource of a wayland tablet).
Signed-off-by: Stephen Chandler Paul <thatslyude@gmail.com>
We were just relying on the drag context finalize() to destroy
the window. But with garbage-collected bindings, that might
not happen as soon as we like, so explicitly hide the window
when the drag ends successfully.
https://bugzilla.gnome.org/show_bug.cgi?id=763659
The virtual host assigns the name of the mouse device to
"VirtualBox USB Tablet" in VirtualBox and we'd use that device as mouse.
If not, GtkTooltip is not enabled.
https://bugzilla.gnome.org/show_bug.cgi?id=763017
Fixes bug 763023: in certain circumstances, XRRGetOutputInfo will return
a null pointer. This commit adds a check to detect and handle this
return value.
gdk_display_list_devices is deprecated and all the backends
implement the same fallback by delegating to the device manager
and caching the list (caching it is needed since the method does
not transfer ownership of the container).
The compat code can be shared among all backends and we can
initialize the list lazily only in the case someone calls the
deprecated method.
https://bugzilla.gnome.org/show_bug.cgi?id=762891
The g_print documentation explicitly says not to do this, since
g_print is meant to be redirected by applications. Instead use
g_message for logging that can be triggered via GTK_DEBUG.
Sigh.
Now that we've neutered the QEMU USB tablet, I'm finding that
spice is doing just the same nonsense. It has a fake "spice vdagent
tablet". Blacklist that as well.
The significant change here is a memory leak fix in init_xrandr15.
The rest of the changes makes init_xrandr13 and init_xrandr15 more
parallel, and simplifies init_multihead.
We should conform to a minimal set of reasons for the gtk side to emit
a better GtkDragResult than GTK_DRAG_RESULT_ERROR. This fixes the notebook
tab DnD feature, where we rely on GTK_DRAG_RESULT_NO_TARGET.
In the wayland side, unfortunately we can't honor either NO_TARGET nor
USER_CANCELLED, we don't know of the latter, so we could return false
positives on the former.
https://bugzilla.gnome.org/show_bug.cgi?id=761954
The fallback behaviour of get_work_area () divides the
screen width and height by the window scaling factor, but
those values are already scaled down.
https://bugzilla.gnome.org/show_bug.cgi?id=761474
Set _GTK_THEME_VARIANT to empty string when default theme variant
is used. This will allow to understand whether _GTK_THEME_VARIANT
is not supported or default variant is requested.
https://bugzilla.gnome.org/show_bug.cgi?id=761476
Presently, Gtk will only send a startup notification completion message
for the first window that is shown. This is not good for the case of
GtkApplication, where we are expected to participate in
startup-notification for all windows.
We have avoided this problem by manually emitting the startup complete
message from after_emit in GtkApplication.
Unfortunately, this causes problems for windows that are shown with a
delay. It is also a dirty hack.
The reason for the original behaviour is simple: there is a static
boolean in gtkwindow.c which controls it. We remove this.
Instead, clear the startup notification ID stored in GDK when sending
the completion message. GtkApplication will re-set this the next time
an event comes in which needs startup-notification handling. In the
non-GtkApplication case, newly shown windows will still not send the
message, since the cookie will have been cleared.
Finally, we remove the hack from GtkApplication's after_emit.
This will probably cause some regressions in terms of lingering startup
notification messages. The correct solution here is to always use
gtk_window_present(), including when merely opening a new document (with
a new tab, for example).
https://bugzilla.gnome.org/show_bug.cgi?id=690791
This includes managing input events and source-side DND events,
as well as setting the appropriate cursor and emitting the signals
that are expected in this mode of operation.
We are getting the mime data destroy notify called when we
destroy the surface in finalize. Trying to set the XSync counters
at this time is a) pointless and b) yielding an X error because
the counters have already been destroyed.
To avoid this, unhook the damage tracking before destroying
the surface.
https://bugzilla.gnome.org/show_bug.cgi?id=760188
We are setting mime data with a destroy notify on the cairo
surface to get notified when cairo registers damage for the
surface (in that case, it clears the mime data, calling the
destroy notify). Unfortunately, the destroy notify is also
called when we remove the mime data ourselves, which was
not intentional.
Use a flag in the window impl struct to ignore the callback
when we are clearing the hook.
Instead of creating an intermediate pixbuf, just render
the window surface onto the new surface. Doing things this
way lets us avoid the cairo_surface_mark_dirty() call in
gdk_pixbuf_get_from_window(), which is not generally safe
to call on 'random' surfaces - it asserts that the surface
has no mime data attached, and the X11 backend uses mime
data for damage tracking purposes...
We destroy the widget that is wrapped around the drag window
when the object data on the drag context gets cleared. Destroying
the window before that happens leads to unpleasantries. E.g. we may
try to access the frame clock, which doesn't exist anymore, and
things go downhill from there. So, keep the window alive for
a little longer.
Always returning a left_ptr if we can't find anything better
broke firefox application-specific fallback for missing cursors.
Keep that working by only doing the fallback for the CSS cursor
names, not for things like hashes.
https://bugzilla.gnome.org/show_bug.cgi?id=760141
Showing the drag cancel animation can be done in the X11
drag context implementation now that we hold the drag
window there, and have the start coordinates.
Since we can't control if and when the application destroys
the drag widget, we take a snapshot of the window contents
and display that during the animation. This should be good
enough for all practical purposes.
Add a variant of gdk_drag_begin that takes the start position
in addition to the device. All backend implementation have been
updated to accept (and ignore) the new arguments.
Subsequent commits will make use of the data in some backends.
Commit 1266d15c4 also broke Xwayland, as it does the same trick
than VMWare pointers. Let's extend the heuristic to check for "pointer"
in the device name, what can possibly go wrong...
https://bugzilla.gnome.org/show_bug.cgi?id=757358
We currently just look for a master device with input source MOUSE.
After recent changes to the way input devices are classified, xwayland
on my system comes up with a virtual core pointer that has input
source TOUCHSCREEN. This was causing assertion failures. Be a little
more careful and accept a touchscreen as core pointer, if there is
no mouse.
VMWare seems to create mouse devices with abs axes which confuses
our detection of single-touch touchscreens. Those have though a
name we can match on ("VirtualPS/2 VMware VMMouse"), it should
be pretty safe to assume that no real touchscreens have "mouse"
in their name...
https://bugzilla.gnome.org/show_bug.cgi?id=757358
Those won't have ABS_MT_* axes, so won't be reported has having
XITouchClassInfo. Fallback on these to checking whether abs x/y axes are
available. After the Wacom checks, any remaining device with absolute axes
should be touchscreens, and GDK_SOURCE_MOUSE does indeed just make sense on
devices with relative axes.
https://bugzilla.gnome.org/show_bug.cgi?id=757358
Using a NULL GAppInfo with g_app_launch_context_get_display() will
generate a critical warning in gio.
Use the display name instead as we don't have any valid GAppInfo to pass
to g_app_launch_context_get_display().
bugzilla: https://bugzilla.gnome.org/show_bug.cgi?id=756439
If GLX has support for the GLX_ARB_create_context_profile extension,
then we use the GLX_CONTEXT_COMPATIBILITY_PROFILE_BIT_ARB; if it does
not, we fall back to the old glXCreateNewContext() API.
We use the shared GdkGLContext to decide whether the GLX context should
use the legacy bit or not.
https://bugzilla.gnome.org/show_bug.cgi?id=756142
Otherwise the outer loop control variable is messed up, and we end
up with uninitialized axes if there were any more valuators after
the XIKeyClass one.
This bug was sneakily introduced by fdb9a8e14, many thanks to
Carlos Soriano for helping spot the source of this bug.
https://bugzilla.gnome.org/show_bug.cgi?id=753431
When dealing with selection events, we might see windows from
other screens in the requestor field. The current x11 backend
code fails to wrap these in a foreign GdkWindow, since we
don't have the corresponding GdkScreen anymore. Work around
this by creating such 'foreign screens' on demand. We still
maintain the 1:1 relation between the display and the screen
returned by gdk_display_get_default_screen().
https://bugzilla.gnome.org/show_bug.cgi?id=721398
When using frame times from _NET_WM_FRAME_DRAWN and _NET_WM_FRAME_TIMINGS, we
were treating them as local monotonic times, but they are actually extended-precision
versions of the server time, and need to be translated to monotonic times in the
case where the X server and client aren't running on the same system.
This fixes rendering stalls when using X over a remote ssh connection.
https://bugzilla.gnome.org/show_bug.cgi?id=741800
Avoid using a stale timestamp (from the last user interaction with the
application) when a message arrives from D-Bus requesting that a new
window be created.
In this case the most-correct thing that we can do is to use no
timestamp at all.
We modify gdk_x11_display_set_startup_notification_id() to allow a NULL
value to mean "reset everything" and then call this function
unconditionally on receipt of D-Bus activation requests. The result
will be that a missing desktop-startup-id in the platform-data struct
will reset the timestamp.
Under their default configuration metacity and mutter will both map
windows presented with no timestamp in the foreground. This could
result in false-positive, but there is very little we can do about that
without the original timestamp from the user event.
https://bugzilla.gnome.org/show_bug.cgi?id=752000
If we don't find Xft values in the X resource db, simply fall
back to the values that are hardcoded in /etc/X11/Xresources
anyway. Extra trickery with likely-made-up screen dimensions
is not going to yield better results, and only makes for a
deeper rabbit hole when debugging.
We used to "invalidate" scroll valuators, so the next scroll event could
be used as the base for the next scroll deltas. This has the inconvenience
that it invariably consumes the first event received after enter and,
due to interactions with WM overeager passive button grabs, there's a
possibility we don't scroll at all if we receive interleaved "smooth
scroll" XI_Motion events and XI_Enter events (Normally triggered by regular
scroll wheels in mice).
In order to fix this, and at the expense of some sync-call overhead on
XI_Enter events (one XIQueryDevice call per slave device), query the
current scroll valuator state for all the slaves of the entered pointer,
so we do know beforehand the right base values. If new devices are plugged
while the pointer is on top of the client, the initialized scroll values
will match the valuators'.
https://bugzilla.gnome.org/show_bug.cgi?id=750994https://bugzilla.gnome.org/show_bug.cgi?id=750870
gdk_x11_device_xi2_window_at_position() may attempt to push/pop
a few error trap pairs while traversing the window tree. Move it
outside the server grab, and around the multiple XIQueryPointer
calls we may do here.
https://bugzilla.gnome.org/show_bug.cgi?id=751739
This patch introduces support for using the newly introduced
monitor objects in the XRandR protocol. These objects are meant
to be used to denote a set of rectangles representing a logical
monitor, and are used to hide details like monitor tiling and
virtual gpu outputs.
This uses the new objects instead of crtc/outputs objects when
they are available to create the monitor lists. X server 1.18
is required on the server side for randr 1.5.
https://bugzilla.gnome.org/show_bug.cgi?id=749561
We interpret buttons 4-7 as old-school scroll events, so it does
not make sense to add these to the mask. Also fix an off-by-one
in the loop here, buttons_mask is 1-based.
GdkKeymap already has support for _get_num_lock_state() and
_get_caps_lock_state(). Adding _get_scroll_lock_state() would be good
for completness and some backends (Windows?) could take advantage of
this.
XSetWindowBackgroundPixmap() will throw BadMatch only in the case of a
different parent window depth. Different visuals are fine and actually
expected in Gtk+ 3.16 (since we don't stick to the system default visual
but try to pick a better one).
https://bugzilla.gnome.org/show_bug.cgi?id=747524
If the GLX_EXT_texture_from_pixmap extension is not available when we
did the extensions check, then there's no point in using the backend
specific code paths that rely on it.
When configuring Gtk+ with --disable-xkb, the build fails because of an
undefined reference to get_xkb().
This patch fixes this issue.
Signed-off-by: Eric Le Bihan <eric.le.bihan.dev@free.fr>
https://bugzilla.gnome.org/show_bug.cgi?id=739070
And use these for the missing axes if the valuator mask is incomplete.
This used to work fine on tablets because the Wacom driver ensures all
valuators are sent, which is not true if using the evdev driver.
https://bugzilla.gnome.org/show_bug.cgi?id=703610
The existence of OpenGL implementations that do not provide the full
core profile compatibility because of reasons beyond the technical, like
llvmpipe not implementing floating point buffers, makes the existence of
GdkGLProfile and documenting the fact that we use core profiles a bit
harder.
Since we do not have any existing profile except the default, we can
remove the GdkGLProfile and its related API from GDK and GTK+, and sweep
the whole thing under the carpet, while we wait for an extension that
lets us ask for the most compatible profile possible.
https://bugzilla.gnome.org/show_bug.cgi?id=744407
Now that we have a two-stages GL context creation sequence, we can move
the profile to a pre-realize option, like the debug and forward
compatibility bits, or the GL version to use.
We simply don't want to care about legacy OpenGL.
All supported platforms also have support for OpenGL ≥ 3.2; it would
complicate the internal code; and would force us to use legacy GL
contexts internally if the first context created by the user is a legacy
GL context, and disable creation of core-3.2 contexts after that.
We will need to fix all our code examples to use the Core 3.2 profile.
https://bugzilla.gnome.org/show_bug.cgi?id=741946
One of the major requests by OpenGL users has been the ability to
specify settings when creating a GL context, like the version to use
or whether the debug support should be enabled.
We have a couple of requirements in terms of API:
• avoid, if at all possible, the "C arrays of integers with
attribute, value pairs", which are hard to write and hard
to bind in non-C languages.
• allow failing in a recoverable way.
• do not make the GL context creation API a mess of arguments.
Looking at prior art, it seems that a common pattern is to split the
construction phase in two:
• a first phase that creates a GL context wrapper object and
does preliminary checks on the environment.
• a second phase that creates the backend-specific GL object.
We adopted a similar pattern:
• gdk_window_create_gl_context() creates a GdkGLContext
• gdk_gl_context_realize() creates the underlying resources
Calling gdk_gl_context_make_current() also realizes the context, so
simple GL users do not need to care. Advanced users will want to
call gdk_window_create_gl_context(), set up the optional requirements,
and then call gdk_gl_context_realize(). If either of these two steps
fails, it's possible to recover by changing the requirements, or simply
creating a new GdkGLContext instance.
https://bugzilla.gnome.org/show_bug.cgi?id=741946
- Specifically request GL version when creating context. Just specifying core
profile bit results in the requested version defaulting to 1.0 which causes
the core profile bit to be ignored and an arbitrary compatability context to be
returned.
- Fix GL painting by removing GL calls that have been depricated by the 3.2 core
profile.
- Additionally remove glInvalidateFramebuffer() call, it is not supported by 3.2
core.
https://bugzilla.gnome.org/show_bug.cgi?id=742953
The ICCCM says:
If the specified property is None, the requestor is an obsolete client.
Owners are encouraged to support these clients by using the specified
target atom as the property name to be used for the reply.
Lets do that, instead of crashing.
https://bugzilla.gnome.org/show_bug.cgi?id=740613
The previous fix for this issue in 732af31424 was incomplete.
If we use GDK_GL_PROFILE_3_2_CORE we are asking for a core profile
according to the GLX_ARB_create_context_profile extension. For that,
we pass the GLX_CONTEXT_CORE_PROFILE_BIT_ARB value for the
GLX_CONTEXT_PROFILE_MASK_ARB attribute.
The specification for the extension says that:
If the requested OpenGL version is less than 3.2,
GLX_CONTEXT_PROFILE_MASK_ARB is ignored and the functionality
of the context is determined solely by the requested version.
Since we're asking for a core profile, we assume a GL version greater
than or equal to 3.2; thus, we don't need to specify the
GLX_CONTEXT_MAJOR_VERSION_ARB or the GLX_CONTEXT_MINOR_VERSION_ARB
attributes, and instead just rely on whatever version GLX gives us.
This seems to work around a strange issue in Mesa; if we ask for a core
profile and any version > 3.0, we get broken rendering on any shared
context we create.
We've observed hangs of mutter when it initializes GTK+, which
are caused by initializing GL, which in turn makes xwayland
call back into mutter. With this change, mutter should just
disable GL support in GDK, and things will work.
The ICCCM says:
If the specified property is None , the requestor is an obsolete client.
Owners are encouraged to support these clients by using the specified
target atom as the property name to be used for the reply.
Lets do that, instead of crashing.
https://bugzilla.gnome.org/show_bug.cgi?id=740613
This is required for the X backend GL integration. If the
window has a height that is not a multiple of the window scale
we can't properly do the y coordinate flipping that GL needs.
Other backends can ignore this and use the default implementation.
https://bugzilla.gnome.org/show_bug.cgi?id=739750
Rather than just rounding down the position *and* the size separately
we correctly calculate a rectangle in scaled window coords that fully
covers the real window size. This really only makes a difference
when the window size/position isn't a multiple of the window scale.
https://bugzilla.gnome.org/show_bug.cgi?id=739750
Keep track of the exact size of X windows in underlying pixels; we
generally use the scaled size instead, but to properly handle the GL
viewport for windows that aren't a multiple of window_scale,
we need to know the real size.
https://bugzilla.gnome.org/show_bug.cgi?id=739750
Although we specify a resize increment to try and get a size that is
a multiple of the window scale, maximization typically wins
over the resize increment, so the window might be odd sized.
Round *up* in this case, rather than down, since it's better to
truncate a line or two at the bottom and right of the window rather
than have a line or two that we don't know what to do with.
https://bugzilla.gnome.org/show_bug.cgi?id=739750
If buffer age is undefined and the updated area is not the whole
window then we use bit-blits instead of swap-buffers to end the
frame.
This allows us to not repaint the entire window unnecessarily if
buffer_age is not supported, like e.g. with DRI2.
Commit afd9709aff made us keep impl window
cairo surfaces around across changes of window scale. But the
window scale setter forgot to update the size and scale of the
surface. The effect of this was that toggling the window scale
from 1 to 2 in the inspector was not causing the window to draw
at twice the size, although the X window was made twice as big,
and input was scaled too. Fix this by updating the surface when
the window scale changes.
We need to use this in the code path where we make the context
non-current during destroy, because at that point the window
could be destroyed and gdk_window_get_display() would return
NULL.
This moves the code related to the frame sync code into
the is_attached check, which means we don't have to ever
run this when making non-window-paint contexts current.
This is a minior speed thing, but the main advantage
is that it makes making a non-paint context current
threadsafe.
This is not really needed. The gl context is totally tied to the
window it is created from by virtue of sharing the context with the
paint context of that window and that context always has the visual
of the window (which we already can get).
Also, all user visible contexts are essentially offscreen contexts, so
a visual doesn't make sense for them. They only use FBOs which have
whatever format that the users sets up.
To properly support multithreaded use we use a global GPrivate
to track the current context. Since we also don't need to track
the current context on the display we move gdk_display_destroy_gl_context
to GdkGLContext::discard.
We used to have a weak ref to the cairo surface and it was keep
alive by the references in the normal windows, but that reference
was removed by d48adf9cee, causing
us to constantly create and destroy the surface.
https://bugzilla.gnome.org/show_bug.cgi?id=738648
We want to create windows with the default visuals such that we then
have the right visual for GLX when we want to create the paint GL
context for the window.
For instance, (in bug 738670) the default rgba visual we picked for the
NVidia driver had an alpha size of 0 which gave us a BadMatch when later
trying to initialize a gl context on it with a alpha FBConfig.
Instead of just picking what the Xserver likes for the default, and just
picking the first rgba visual we now actually call into GLX to pick
an appropriate visual.
The visuals are typically sorted by some sort of "most useful first"
order. And picking the last one is likely to give us the weirdest
matching glx visual.
Commits 314b6abbe8 and eb9223c008 were ignoring
the fact that the code where found is set to 1 was modifying
col - which was an ok thing to do when that part of the code
was still breaking out of the loop, but it is no longer doing
that (since 2003 !). Fix things up by storing the final col
value in a separate variable and using that after the loop.
https://bugzilla.gnome.org/show_bug.cgi?id=738886
Its not really reasonable to handle failures to make_current, it
basically only happens if you pass invalid arguments to it, and
thats not something we trap on similar things on the X drawing side.
If GL is not supported that should be handled by the context creation
failing, and anything going wrong after that is essentially a critical
(or an async X error).
We make user facing gl contexts not attached to a surface if possible,
or attached to dummy surfaces. This means nothing can accidentally
read/write to the toplevel back buffer.
This adds the new type GdkGLContext that wraps an OpenGL context for a
particular native window. It also adds support for the gdk paint
machinery to use OpenGL to draw everything. As soon as anyone creates
a GL context for a native window we create a "paint context" for that
GdkWindow and switch to using GL for painting it.
This commit contains only an implementation for X11 (using GLX).
The way painting works is that all client gl contexts draw into
offscreen buffers rather than directly to the back buffer, and the
way something gets onto the window is by using gdk_cairo_draw_from_gl()
to draw part of that buffer onto the draw cairo context.
As a fallback (if we're doing redirected drawing or some effect like a
cairo_push_group()) we read back the gl buffer into memory and composite
using cairo. This means that GL rendering works in all cases, including
rendering to a PDF. However, this is not particularly fast.
In the *typical* case, where we're drawing directly to the window in
the regular paint loop we hit the fast path. The fast path uses opengl
to draw the buffer to the window back buffer, either by blitting or
texturing. Then we track the region that was drawn, and when the draw
ends we paint the normal cairo surface to the window (using
texture-from-pixmap in the X11 case, or texture from cairo image
otherwise) in the regions where there is no gl painted.
There are some complexities wrt layering of gl and cairo areas though:
* We track via gdk_window_mark_paint_from_clip() whenever gtk is
painting over a region we previously rendered with opengl
(flushed_region). This area (needs_blend_region) is blended
rather than copied at the end of the frame.
* If we're drawing a gl texture with alpha we first copy the current
cairo_surface inside the target region to the back buffer before
we blend over it.
These two operations allow us full stacking of transparent gl and cairo
regions.
Before 5e325c4, the default BitGravity was NorthWestGravity.
When static gravities were removed in 5e325c4, the BitGravity regressed
to the X11 default, Forget. Forget causes giant graphical glitches and
black flashes when resizing, especially in some environments that aren't
synchronized to a paint clock yet, like XWayland.
I'm assuming that the author assumed that the default of BitGravity was
NorthWestGravity, which is the default of WinGravity. Just go ahead and
fix this regression to make resizing look smooth again.
Remove checks for NULL before g_free() and g_clear_object().
Merge check for NULL, freeing of pointer and its setting
to NULL by g_clear_pointer().
https://bugzilla.gnome.org/show_bug.cgi?id=733157
The warning may have had some value at some point, but if
people uninstall large icons just to make the warning go
away, it does more harm than good. So just remove it.
If we have a fullscreen window that covers a monitor, desktop
chrome is not relevant for placing of menus and other popups.
Therefore, return the full monitor geometry instead of the
workarea in this case.
https://bugzilla.gnome.org/show_bug.cgi?id=737251
gdk_x11_display_set_window_scale() affects the interpretation of the
Xft/DPI XSETTING - it is substituted inside GDK with the value of
Gdk/UnscaledDPI xsetting. However, this change is not propagated to
GTK+ and from GTK+ back to gdk_screen_set_resolution() until the
main loop is run.
Fix this by handling the screen resolution directly in gdk/x11.
This requires duplication of code between GDK and GTK+ since we still
have to handle DPI in GTK+ in the case that GdkSettings:gtk-xft-dpi
is set by the application.
https://bugzilla.gnome.org/show_bug.cgi?id=733076
Traditionally, the way painting was done in GTK+ was with the
"expose-event" handler, where you'd use GDK methods to do drawing on
your surface. In GTK+ 2.24, we added cairo support with gdk_cairo_create,
so you could paint your graphics with cairo.
Since then, we've added client-side windows, double buffering, the paint
clock, and various other enhancements, and the modern way to do drawing
is to connect to the "draw" signal on GtkWidget, which hands you a
cairo_t. To do double-buffering, the cairo_t we hand you is actually on
a secret surface, not the actual backing store of the window, and when
the draw handler completes we blit it into the main backing store
atomically.
The code to do this is with the APIs gdk_window_begin_paint_region,
which creates the temporary surface, and gdk_window_end_paint which
blits it back into the backing store. GTK+'s implementation of the
"draw" signal uses these APIs.
We've always sort-of supported people calling gdk_cairo_create
"outside" of a begin_paint / end_paint like old times, but then you're
not getting the benefit of double-buffering, and it's harder for GDK to
optimize.
Additionally, newer backends like Mir and Wayland can't actually support
this model, since they're based on double-buffering and swapping buffers
at various points in time. If we hand you a random cairo_t, we have no
idea when is a good time to swap.
Remove support for this.
This is technically a GDK API break: a warning is added in cases where
gdk_cairo_create is called outside of a paint cycle, and the returned
surface is a dummy that won't ever be composited back onto the main
surface. Testing with complex applications like Ardour didn't produce
any warnings.
