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java.awt.Robot taking screenshots
Proposed solution isSolution: Use xdg-desktop-portal, a cross-platform stable D-Bus API which works on GNOME, KDE and wlroots-based compostiros. Specifically, it provides org.freedesktop.portal.Screenshot
. It is still a DBUS API, but at least it seems to be a public one.which can be used to create a screenshot.
Earlier discussion:
It is doable as of now, but not in a standard and convenient way. It can be done using some shell specific APIs, e.g. org.gnome.Shell.Screenshot DBUS API (which will not work for KDE, it has it's has another API)
It has several drawbacks:
- There is no direct access to the screenshot data. Screenshot is saved to
png
file, after that you have to read it, decode it. - Filesystem footprint. You need to save it to some file(its filesystem can be slow). It can be workarounded by using shared memory object though.
- Using DBUS API in this case is really slow. For instance, just a sync DBUS call to take a 1000x1000 screenshot and save it to the shared memory object file is ~14 time slower(it is just saving, without decoding and extracting data) comparing to full X11 implementation.
So, it would be great to get some standard API to get screenshot data in memory. I see that there is an open bug against this issue.
java.awt.Robot emulating keyboard/mouse events
Looks like the solution for native Wayland client willSolution: This will probably be implemented be libEI. Its shipping time(even estimated) is not yet known.
Earlier discussion:
It mostly works for X11 compatibility mode (except when trying to reach outside XWayland and windows are not restacked on emulated mouse click).
Looks like the solution for native Wayland client will be libEI
X11 compatibility: HiDPI.
No solution yet.Solution: None for XWayland (yet). Wayland-native applications support HiDPI
Earlier discussion:
Quote from Maxim Kartashev's e-mail:
There's
a
quality-of-service
problem
with
running
via
the
compatibility
layer
as
under
certain
circumstances
native
X
windows
look
blurry.
Users
with
small(ish)
HiDPI
displays
tend
to
enable
fractional
scaling
and
with
that
enabled
(regardless
of
the
actual
scale),
XWayland
pretends
that
the
screen
size
is
smaller
and
then
pixel-stretches
the
resulting
window
according
to
the
global
scale.
This
works
as
a
temporary
solution,
but
people
get
quickly
tired
of
looking
at
text
that
is
blurry.
See
https://gitlab.gnome.org/GNOME/mutter/-/issues/402
and
https://github.com/swaywm/sway/issues/5917
for
some
more
details.
X11 compatibility: Popup menu dismiss in X11 compatibility mode.
Can be not perfectly workarounded by dismissing menu on focus lost event
We are using XGrabPointer
to get mouse input and dismiss popup menus on mouse click.
Obviously, it does not work outside of XWayland server.
E.g. if we have shown some popup menu, it will be closed upon clicking on any of XWayland's windows.
But it will not be closed if we click on some other window from Wayland.
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For a first look this workaround seems to work reliably except only one case:
clicking on window's title containing origin component does not lead to focus change, thus we don't hiding a popup.
I see a behavior similar to this workaround in some other third party application running on XWayland.
X11 compatibility: fake configure event for XRandR emulation
Should be resolved with this MR.
We are not getting updates from the system after "changing" screen resolution via XRRSetScreenConfigAndRate
.
Excerpt from Olivier's mail:
Also worth noting that the XRandR emulation is per window/X11 client, whereas the root window is shared between all X11 clients, but maybe we could send a fake ConfigureNotify event to the given client, I would need to check if that's doable.
This notification would be helpful.
X11 compatibility: Wayland crash on huge window
Resolved by 1 and 2. Waiting for its propagation to Linux distros.
// gcc hugeFrame.c -o hugeFrame -lX11 && ./hugeFrame #include <X11/Xlib.h> #include <unistd.h> static Display* display; int main(void) { int width = 22000; int height = 25000; display = XOpenDisplay(NULL); Window win = XCreateSimpleWindow(display, DefaultRootWindow(display), 0, 0, width, height, 0, 0L, 0L); XMapWindow(display, win); XFlush(display); sleep(1); }
/var/log/syslog
shows:
gnome-shell[1248]: WL: error in client communication (pid 1248)
gnome-shell[1298]: (EE)
gnome-shell[1298]: Fatal server error:
gnome-shell[1298]: (EE) wl_shm@5: error 1: invalid size (-2094967296)
gnome-shell[1298]: (EE)
where -2094967296 looks like an integer overflow of 4 * 22000 * 25000
So it fails to create a pool, but doesn't handle it gracefully.
X11 compatibility: crash when mapping a lot of windows
No solution yet
GUI are crashing if you are trying to map a lot( > ~260) of windows at once.
Filed as xorg/xserver/-/issues/1222.
// gcc windowSpawnDoS.c -o windowSpawnDoS -lX11 && ./windowSpawnDoS
#include <X11/Xlib.h>
#include <unistd.h>
int main(void) {
XInitThreads();
Display* dpy = XOpenDisplay(NULL);
Window root = DefaultRootWindow(dpy);
for (int i = 0; i < 500; ++i) {
Window ww = XCreateSimpleWindow(dpy, root, 50, 50, 50, 50, 0, 0, 0);
XMapWindow(dpy, ww);
}
for(;;) {
XEvent e;
XNextEvent(dpy, &e);
}
}
It may be faced when running some tests which are trying to map a lot of windows, e.g. one for every GraphicsConfiguration.
If you have 210 GraphicsConfigurations per display on Xwayland, then running such test in 2 display configuration will lead to crash.
X11 compatibility: Robot.mouseMove does not visually move mouse cursor
Javadoc for java.awt.Robot#moseMove
says:
/**
* Moves mouse pointer to given screen coordinates.
* @param x X position
* @param y Y position
*/
public synchronized void mouseMove(int x, int y) {
Despite the fact that this mouse movement is successfully emulated within the XWayland server(following mouse press emulation will be in a right place), the mouse cursor does not visually move.
With current specification of java.awt.Robot#moseMove
it may be a conformance issue.
X11 compatibility: Drag and Drop java → Wayland does not work
Solution: Might be solved by updating to the latest versions of Wayland, Xwayland
Drag and drop from java to wayland apps does not work with current JDK implementation.
Showing a splash screen
Solution: This will need a Wayland protocol extension, which is already tracked upstream (https://gitlab.freedesktop.org/wayland/wayland-protocols/-/issues/67)
Apparently splash screens display in top lefe (the window positioning problem)
A splash screen (output only) surface role could probably be proposed upstream.
it'd just need a fallback implementation for compositors that doesn't support it, e.g. a dialog
Maybe similar to this PiP request : https://gitlab.freedesktop.org/wayland/wayland-protocols/-/merge_requests/132
For more info on roles: https://wayland-book.com/surfaces/roles.html
Add input to this existing issue : https://gitlab.freedesktop.org/wayland/wayland-protocols/-/issues/67