• Martin Flöser's avatar
    Add windowsystem plugin for KWin's qpa · 02a05610
    Martin Flöser authored
    Summary:
    KWindowSystem provides a plugin interface to have platform specific
    implementations. So far KWin relied on the implementation in
    KWayland-integration repository.
    
    This is something I find unsuited, for the following reasons:
     * any test in KWin for functionality set through the plugin would fail
     * it's not clear what's going on where
     * in worst case some code could deadlock
     * KWin shouldn't use KWindowSystem and only a small subset is allowed
    to be used
    
    The last point needs some further explanation. KWin internally does not
    and cannot use KWindowSystem. KWindowSystem (especially KWindowInfo) is
    exposing information which KWin sets. It's more than weird if KWin asks
    KWindowSystem for the state of a window it set itself. On X11 it's just
    slow, on Wayland it can result in roundtrips to KWin itself which is
    dangerous.
    
    But due to using Plasma components we have a few areas where we use
    KWindowSystem. E.g. a Plasma::Dialog sets a window type, the slide in
    direction, blur and background contrast. This we want to support and
    need to support. Other API elements we do not want, like for examples
    the available windows. KWin internal windows either have direct access
    to KWin or a scripting interface exposed providing (limited) access -
    there is just no need to have this in KWindowSystem.
    
    To make it more clear what KWin supports as API of KWindowSystem for
    internal windows this change implements a stripped down version of the
    kwayland-integration plugin. The main difference is that it does not use
    KWayland at all, but a QWindow internal side channel.
    
    To support this EffectWindow provides an accessor for internalWindow and
    the three already mentioned effects are adjusted to read from the
    internal QWindow and it's dynamic properties.
    
    This change is a first step for a further refactoring. I plan to split
    the internal window out of ShellClient into a dedicated class. I think
    there are nowadays too many special cases. If it moves out there is the
    question whether we really want to use Wayland for the internal windows
    or whether this is just historic ballast (after all we used to use
    qwayland for that in the beginning).
    
    As the change could introduce regressions I'm targetting 5.16.
    
    Test Plan:
    new test case for window type, manual testing using Alt+Tab
    for the effects integration. Sliding popups, blur and contrast worked fine.
    
    Reviewers: #kwin
    
    Subscribers: kwin
    
    Tags: #kwin
    
    Differential Revision: https://phabricator.kde.org/D18228
    02a05610
slidingpopups.h 3.17 KB