My KWIN fork where I work on features like per-output virtual desktops
d2bbd2a124
Summary:
Any call made to a virtual method in constructor/destructor of a base
class won't go to a derived class because the base class may access
uninitialized or destroyed resources.
For example, let's consider the following two classes
class Base {
public:
Base() { foo()->bar(); }
virtual ~Base() { foo()->bar(); }
virtual Foo* foo() const { return nullptr; }
};
class Derived : public Base {
public:
Derived() : mFoo(new Foo) {}
~Derived() override { delete mFoo; }
Foo* foo() const override { return mFoo; }
private:
Foo* mFoo;
};
When an instance of Derived class is created, constructors will run in
the following order:
Base()
Derived()
It's not safe to dispatch foo() method call to Derived class because
constructor of Derived hasn't initialized yet mFoo.
Same story with destructors, they'll run in the following order:
~Derived()
~Base()
It's not safe to dispatch foo() method call in the destructor of Base
class to Derived class because mFoo was deleted.
So, what does that weird C++ behavior has something to do with KWin? Well,
recently Compositor class was split into two classes - WaylandCompositor,
and X11Compositor. Some functionality from X11 doesn't make sense on
Wayland. Therefore methods that implement that stuff were "purified," i.e.
they became pure virtual methods. Unfortunately, when Compositor tears
down it may call pure virtual methods on itself. Given that those calls
cannot be dispatched to X11Compositor or WaylandCompositor, the only
choice that C++ runtime has is to throw an exception.
The fix for this very delicate problem is very simple - do not call virtual
methods from constructors and the destructor. Avoid doing that if you can!
This change moves Compositor::updateClientCompositeBlocking to X11Compositor
so it longer has to be a virtual method. Also, it kind of doesn't make sense
to keep it in base Compositor class because compositing can be blocked only
on X11.
BUG: 411049
Test Plan: KWin no longer crashes when running kwin_x11 --replace command.
Reviewers: #kwin, romangg
Reviewed By: #kwin, romangg
Subscribers: anthonyfieroni, kwin
Tags: #kwin
Differential Revision: https://phabricator.kde.org/D23098
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|---|---|---|
| autotests | ||
| cmake/modules | ||
| colorcorrection | ||
| data | ||
| decorations | ||
| doc | ||
| effects | ||
| helpers | ||
| kcmkwin | ||
| kconf_update | ||
| libinput | ||
| libkwineffects | ||
| platformsupport | ||
| plugins | ||
| qml | ||
| scripting | ||
| scripts | ||
| tabbox | ||
| tests | ||
| xwl | ||
| .arcconfig | ||
| .arclint | ||
| abstract_client.cpp | ||
| abstract_client.h | ||
| abstract_opengl_context_attribute_builder.cpp | ||
| abstract_opengl_context_attribute_builder.h | ||
| abstract_output.cpp | ||
| abstract_output.h | ||
| abstract_wayland_output.cpp | ||
| abstract_wayland_output.h | ||
| activation.cpp | ||
| activities.cpp | ||
| activities.h | ||
| appmenu.cpp | ||
| appmenu.h | ||
| atoms.cpp | ||
| atoms.h | ||
| client.cpp | ||
| client.h | ||
| client_machine.cpp | ||
| client_machine.h | ||
| CMakeLists.txt | ||
| composite.cpp | ||
| composite.h | ||
| config-kwin.h.cmake | ||
| COPYING | ||
| cursor.cpp | ||
| cursor.h | ||
| dbusinterface.cpp | ||
| dbusinterface.h | ||
| debug_console.cpp | ||
| debug_console.h | ||
| debug_console.ui | ||
| deleted.cpp | ||
| deleted.h | ||
| effectloader.cpp | ||
| effectloader.h | ||
| effects.cpp | ||
| effects.h | ||
| egl_context_attribute_builder.cpp | ||
| egl_context_attribute_builder.h | ||
| events.cpp | ||
| fixqopengl.h | ||
| focuschain.cpp | ||
| focuschain.h | ||
| geometry.cpp | ||
| geometrytip.cpp | ||
| geometrytip.h | ||
| gestures.cpp | ||
| gestures.h | ||
| globalshortcuts.cpp | ||
| globalshortcuts.h | ||
| group.cpp | ||
| group.h | ||
| HACKING.md | ||
| idle_inhibition.cpp | ||
| idle_inhibition.h | ||
| input.cpp | ||
| input.h | ||
| input_event.cpp | ||
| input_event.h | ||
| input_event_spy.cpp | ||
| input_event_spy.h | ||
| internal_client.cpp | ||
| internal_client.h | ||
| keyboard_input.cpp | ||
| keyboard_input.h | ||
| keyboard_layout.cpp | ||
| keyboard_layout.h | ||
| keyboard_layout_switching.cpp | ||
| keyboard_layout_switching.h | ||
| keyboard_repeat.cpp | ||
| keyboard_repeat.h | ||
| killwindow.cpp | ||
| killwindow.h | ||
| kwin.kcfg | ||
| kwin.notifyrc | ||
| kwinbindings.cpp | ||
| KWinDBusInterfaceConfig.cmake.in | ||
| layers.cpp | ||
| logind.cpp | ||
| logind.h | ||
| main.cpp | ||
| main.h | ||
| main_wayland.cpp | ||
| main_wayland.h | ||
| main_x11.cpp | ||
| main_x11.h | ||
| Mainpage.dox | ||
| manage.cpp | ||
| Messages.sh | ||
| modifier_only_shortcuts.cpp | ||
| modifier_only_shortcuts.h | ||
| moving_client_x11_filter.cpp | ||
| moving_client_x11_filter.h | ||
| netinfo.cpp | ||
| netinfo.h | ||
| onscreennotification.cpp | ||
| onscreennotification.h | ||
| options.cpp | ||
| options.h | ||
| org.kde.kappmenu.xml | ||
| org.kde.kwin.ColorCorrect.xml | ||
| org.kde.kwin.Compositing.xml | ||
| org.kde.kwin.Effects.xml | ||
| org.kde.kwin.OrientationSensor.xml | ||
| org.kde.KWin.VirtualDesktopManager.xml | ||
| org.kde.KWin.xml | ||
| orientation_sensor.cpp | ||
| orientation_sensor.h | ||
| osd.cpp | ||
| osd.h | ||
| outline.cpp | ||
| outline.h | ||
| outputscreens.cpp | ||
| outputscreens.h | ||
| overlaywindow.cpp | ||
| overlaywindow.h | ||
| placement.cpp | ||
| placement.h | ||
| platform.cpp | ||
| platform.h | ||
| pointer_input.cpp | ||
| pointer_input.h | ||
| popup_input_filter.cpp | ||
| popup_input_filter.h | ||
| README.md | ||
| rootinfo_filter.cpp | ||
| rootinfo_filter.h | ||
| rules.cpp | ||
| rules.h | ||
| scene.cpp | ||
| scene.h | ||
| screenedge.cpp | ||
| screenedge.h | ||
| screenlockerwatcher.cpp | ||
| screenlockerwatcher.h | ||
| screens.cpp | ||
| screens.h | ||
| settings.kcfgc | ||
| shadow.cpp | ||
| shadow.h | ||
| shell_client.cpp | ||
| shell_client.h | ||
| shortcutdialog.ui | ||
| sm.cpp | ||
| sm.h | ||
| tabgroup.cpp | ||
| tabgroup.h | ||
| tabletmodemanager.cpp | ||
| tabletmodemanager.h | ||
| TESTING.md | ||
| thumbnailitem.cpp | ||
| thumbnailitem.h | ||
| toplevel.cpp | ||
| toplevel.h | ||
| touch_hide_cursor_spy.cpp | ||
| touch_hide_cursor_spy.h | ||
| touch_input.cpp | ||
| touch_input.h | ||
| udev.cpp | ||
| udev.h | ||
| unmanaged.cpp | ||
| unmanaged.h | ||
| useractions.cpp | ||
| useractions.h | ||
| utils.cpp | ||
| utils.h | ||
| virtual_terminal.cpp | ||
| virtual_terminal.h | ||
| virtualdesktops.cpp | ||
| virtualdesktops.h | ||
| virtualdesktopsdbustypes.cpp | ||
| virtualdesktopsdbustypes.h | ||
| virtualkeyboard.cpp | ||
| virtualkeyboard.h | ||
| virtualkeyboard_dbus.cpp | ||
| virtualkeyboard_dbus.h | ||
| was_user_interaction_x11_filter.cpp | ||
| was_user_interaction_x11_filter.h | ||
| wayland_cursor_theme.cpp | ||
| wayland_cursor_theme.h | ||
| wayland_server.cpp | ||
| wayland_server.h | ||
| window_property_notify_x11_filter.cpp | ||
| window_property_notify_x11_filter.h | ||
| workspace.cpp | ||
| workspace.h | ||
| x11eventfilter.cpp | ||
| x11eventfilter.h | ||
| xcbutils.cpp | ||
| xcbutils.h | ||
| xkb.cpp | ||
| xkb.h | ||
| xkb_qt_mapping.h | ||
KWin
KWin is an easy to use, but flexible, composited Window Manager for Xorg windowing systems (Wayland, X11) on Linux. Its primary usage is in conjunction with a Desktop Shell (e.g. KDE Plasma Desktop). KWin is designed to go out of the way; users should not notice that they use a window manager at all. Nevertheless KWin provides a steep learning curve for advanced features, which are available, if they do not conflict with the primary mission. KWin does not have a dedicated targeted user group, but follows the targeted user group of the Desktop Shell using KWin as it's window manager.
KWin is not...
- a standalone window manager (c.f. openbox, i3) and does not provide any functionality belonging to a Desktop Shell.
- a replacement for window managers designed for use with a specific Desktop Shell (e.g. GNOME Shell)
- a minimalistic window manager
- designed for use without compositing or for X11 network transparency, though both are possible.
Contacting KWin development team
- mailing list: kwin@kde.org
- IRC: #kwin on freenode
Support
Application Developer
If you are an application developer having questions regarding windowing systems (either X11 or Wayland) please do not hesitate to contact us. Preferable through our mailing list. Ideally subscribe to the mailing list, so that your mail doesn't get stuck in the moderation queue.
End user
Please contact the support channels of your Linux distribution for user support. The KWin development team does not provide end user support.
Reporting bugs
Please use KDE's bugtracker and report for product KWin.
Developing on KWin
Please refer to hacking documentation for how to build and start KWin. Further information about KWin's test suite can be found in TESTING.md.
Guidelines for new features
A new Feature can only be added to KWin if:
- it does not violate the primary missions as stated at the start of this document
- it does not introduce instabilities
- it is maintained, that is bugs are fixed in a timely manner (second next minor release) if it is not a corner case.
- it works together with all existing features
- it supports both single and multi screen (xrandr)
- it adds a significant advantage
- it is feature complete, that is supports at least all useful features from competitive implementations
- it is not a special case for a small user group
- it does not increase code complexity significantly
- it does not affect KWin's license (GPLv2+)
All new added features are under probation, that is if any of the non-functional requirements as listed above do not hold true in the next two feature releases, the added feature will be removed again.
The same non functional requirements hold true for any kind of plugins (effects, scripts, etc.). It is suggested to use scripted plugins and distribute them separately.