Wayland taskbar support v2

[gfgit]

Depends on #2041 (WM abstraction)
Replaces #2031

This is an experimental implementation on taskbar, desktopswitch and showdesktop functionality for KWin Wayland compositor.
It uses following protocols:

• org-kde-plasma-virtual-desktop
• plasma-window-management

(Taken from plasma-wayland-protocols repository)

Code is inspired by libtaskmanager/waylandtasksmodel.cpp

Ideally the Wayland backend should have sub-backends targeting specific compositors when no standard protocol is available.

It also uses layer shell protocol to place panel on screen edge.

NOTE: panel auto-hide is not working yet

[stefonarch]

Nice! Taskbar under kwin_wayland works again I see.

NOTE: panel auto-hide is not working yet

It does here :) (had always worked on this branch).

[stefonarch]

Something has gone wrong I think, I recompiled the changes this afternoon and taskbar is gone again.

[stefonarch]

Taskbar is back here now I see, and crash on clicking showdesktop is avoided too.

[stefonarch]

Just noticed a different behavior here compared to wlroots and X11 (any WM): the taskbar buttons only activates windows, but don't toggle minimize/restore.

[stefonarch]

I get always 2 panels now after login as there is also the lxqt-panel.desktop from regular installation in autostart - in some way it ends up also in /etc/xdg/autostart/ with the _wayland name, didn't have time to investigate.

[stefonarch]

It's here, it installs any *.desktop file:

lxqt-panel/autostart/CMakeLists.txt

Line 1 in 2ad883e

file(GLOB DESKTOP_FILES_IN *.desktop.in)

[stefonarch]

IMO panel_wayland.conf.in could be panel_kwin.conf.in and be inside the plasma backend folder, as it's not generic for wayland but compositor-specific.

[gfgit]

I think it's better to install a single .desktop file (plus another or symlink inside autostart folder)
This is because KWin might get confused about which file the panel belongs and it needs to check the one with absolute path and KDE specific entries.
In the meantime we discuss this issue, I will solve the double install problem

[stefonarch]

It has the /usr/local/bin path again now:

Because it's not named lxqt-panel.wayland.desktop.in it doesn't get configured I guess.

[stefonarch]

From my tests it looks that export XDG_SESSION_DESKTOP="KDE in the startscript is not needed (anymore).

Another remaining issue is the "Maximize" item in menu which is always greyed out.

[marcusbritanicus]

NOTE: panel auto-hide is not working yet

Is this not implemented yet, or, the implementation gives some problems?

Edit:

   // Emulate auto-hide on Wayland
   // NOTE: we cannot move window out of screen so we make it smaller

   // NOTE: a cleaner approach would be to use screen edge protocol
   // but it's specific to KWin

From the code it seems to me that you have problems about how. With layer-shell, we can set the margin to a negative value. For a bottom panel, setting the bottom margin to -PANEL_HEIGHT would mean that the panel is effectively hidden.

However, the issue of how to show the panel becomes a problem. With wayfire, we can use wayfire-shell or wayfire-desktop-shell, both of which provide an equivalent of screen-edge protocol.

But in general, we can partially hide the panel, instead of resizing the panel. For example, set the bottom margin to -PANEL_HEIGHT + PANEL_HIDE_SIZE. This would leave a few pixels sticking out. If the mouse pointer enters the panel, then it can be revealed completely. In place of QPropertyAnimation, you can apply QVariantAnimation and change the bottom margin value from -PANEL_HEIGHT + PANEL_HIDE_SIZE to 0 and other way around.

[gfgit]

Are negative margin value allowed by layer shell?
Didn't know about it!
Current implementation sort of works but on my setup it triggers auto-show even if cursor is not yet at screen edge.
This makes it impossible to click for example statusbar of applications or other UI elements near screen edge because panel shows first and you end up click the panel instead.
It may be a bug in kwin mouse logic

[marcusbritanicus]

Well... It's not specifically, disallowed. On wayfire, we simply use negative margins. I've not tested on other compositors, though.

[Consolatis]

Negative layershell margins may end up on other outputs or don't receive frame / configure events anymore because the surface is not actually visible (which revealed a bug in the GTK layershell wrapper in the past), depending on the compositor. (Although I'd actually categorize the shows-up-on-other-output as a compositor bug). AFAIR a discussion in the ext-layershell protocol MR concluded to not allow negative margins at all (but memory is a bit fuzzy there).

Another option that should always work is hiding the panel and replacing it with a transparent hitbox without exclusive zone. On mouse movement on the hitbox that one is hidden and the panel is shown again.

This implements it in Python with GTK but something similar should be possible with Qt as well.

#!/usr/bin/env python3

from functools import partial

import gi
gi.require_version("GLib", "2.0")
gi.require_version("Gdk", "3.0")
gi.require_version("Gtk", "3.0")
gi.require_version('GtkLayerShell', '0.1')
from gi.repository import GLib, Gdk, Gtk, GtkLayerShell


class Context:
	def __init__(self):
		self.panel = Panel(self, auto_hide_seconds=5)
		self.dummy = HitBox(self)
		self.show_panel()

	def log(self, msg):
		print(f"[{self.__class__.__name__}] {msg}")

	def hide_panel(self):
		self.log("Hiding panel")
		self.dummy.show()
		self.panel.hide()

	def show_panel(self):
		self.log("Showing panel")
		self.dummy.hide()
		self.panel.show()


class Base(Gtk.Window):
	def __init__(self, context):
		super().__init__()
		self.context = context
		self.connect('motion-notify-event', self.on_mouse_move)
		self.set_events(Gdk.EventMask.POINTER_MOTION_MASK)
		self.set_size_request(-1, 30)
		GtkLayerShell.init_for_window(self)
		GtkLayerShell.set_anchor(self, GtkLayerShell.Edge.BOTTOM, True)
		GtkLayerShell.set_anchor(self, GtkLayerShell.Edge.LEFT, True)
		GtkLayerShell.set_anchor(self, GtkLayerShell.Edge.RIGHT, True)
		self.log = partial(context.__class__.log, self)
		self.log("init done")

	def on_mouse_move(self, src, event):
		pass

	def add_style(self, css):
		if isinstance(css, str):
			css = css.encode('utf-8')
		css_provider = Gtk.CssProvider()
		css_provider.load_from_data(css)
		style_context = Gtk.StyleContext()
		style_context.add_provider_for_screen(
			Gdk.Screen.get_default(),
			css_provider,
			Gtk.STYLE_PROVIDER_PRIORITY_APPLICATION
		)


class Panel(Base):
	def __init__(self, *args, auto_hide_seconds=3, **kwargs):
		super().__init__(*args, **kwargs)
		GtkLayerShell.set_layer(self, GtkLayerShell.Layer.BOTTOM)
		GtkLayerShell.auto_exclusive_zone_enable(self)
		self.auto_hide_seconds = auto_hide_seconds
		self.timer = None

	def timer_rearm(self):
		if self.timer:
			GLib.source_remove(self.timer)
		self.timer = GLib.timeout_add_seconds(
			self.auto_hide_seconds, self.on_timer,
			priority=GLib.PRIORITY_LOW
		)

	def on_timer(self):
		self.log("Timer hit")
		self.context.hide_panel()
		self.timer = None
		return False

	def show(self):
		super().show()
		self.timer_rearm()

	def on_mouse_move(self, src, event):
		self.timer_rearm()


class HitBox(Base):
	def __init__(self, *args, **kwargs):
		super().__init__(*args, **kwargs)
		#self.set_size_request(-1, 2)
		GtkLayerShell.set_layer(self, GtkLayerShell.Layer.TOP)
		self.set_name('hitbox')
		#self.add_style('#hitbox { background-color: transparent; }')
		self.add_style('#hitbox { background-color: rgba(255, 128, 128, 0.5); }')

	def on_mouse_move(self, src, event):
		self.context.show_panel()


if __name__ == '__main__':
	context = Context()
	Gtk.main()

The variant also has the benefit that rather than just having a transparent non-exclusive hitbox, one could also anchor the replacement surface to e.g. the bottom-left edge and show a small button instead which - when triggered - hides the replacement surface and restores the panel one. That replacement surface would then be non-exclusive, only be the width of the button and using the top layer so its always visible on top of usual windows.

[stefonarch]

Current implementation sort of works but on my setup it triggers auto-show even if cursor is not yet at screen edge.
This makes it impossible to click for example statusbar of applications or other UI elements near screen edge because panel shows first and you end up click the panel instead.
It may be a bug in kwin mouse logic

I didn't notice that as I don't really use it, but it's on all compositors the same, getting triggered at panel height and not screen border.

[Consolatis]

Current implementation sort of works but on my setup it triggers auto-show even if cursor is not yet at screen edge.
This makes it impossible to click for example statusbar of applications or other UI elements near screen edge because panel shows first and you end up click the panel instead.
It may be a bug in kwin mouse logic

I didn't notice that as I don't really use it, but it's on all compositors the same, getting triggered at panel height and not screen border.

That could also be solved by using the transparent replacement surface, either via the button-only variant or by defining a 1px or 2px height of the surface (added a commented out call to the GTK example above).

[tsujan]

Under X11, the panel is moved out of the screen appropriately, such that only 4 pixels (PANEL_HIDE_SIZE) of its height or width remain visible, depending on whether it's horizontal or vertical. Then its opacity is made zero. Those invisible 4 pixels serve to show the panel on mouse-over.

Since the panel is never positioned between screens, this method works fine. Of course, there are other details/options, like animation and auto-hiding on overlapping windows.

[stefonarch]

Btw what about lxqt/lxqt#2531 (comment) ?

[gfgit]

Btw what about lxqt/lxqt#2531 (comment) ?

I'm ok for extracting layer shell code and make a new PR

[Sodivad]

Code is inspired by libtaskmanager/waylandtasksmodel.cpp

Awesome that the code works for you but in this case the inspiration seems was rather strong and seems to include copied code from Plasma in multiple files as the commented out lines still references the original class and the general structure of the code (for example org_kde_plasma_window_icon_changed). We do not mind this as it's free software after all but would appreciate it if the original license headers could be preserved, thanks!

The original license headers are the two SPDX- lines at the top of the file, e.g. SPDX-License-Identifier: LGPL-2.1-only. Since lxqt is LGPL v2.1, you can specifically choose to re-use the code from KDE under the LGPL v2.1.

[tsujan]

seems to include copied code from Plasma in multiple files

In that case, the original codes should be referenced by comments like "Adapted from...".

[gfgit]

@Sodivad Hi, I've updated the license headers. Is it ok like that?