support kdecoration2 blurregion

--use kdecoration2 blurred regions to adjust blur effect appropriately when
needed

CCBUG:395725

Requires: https://invent.kde.org/plasma/kdecoration/-/merge_requests/17

autotests/test_window_paint_data.cpp

@@ -189,6 +189,9 @@ public:
     bool decorationHasAlpha() const override {
         return false;
     }
+    KDecoration2::Decoration *decoration() const override {
+        return nullptr;
+    }
     QString caption() const override {
         return QString();
     }

src/effects.cpp

@@ -52,6 +52,7 @@
 #include "wayland_server.h"
 
 #include "decorations/decorationbridge.h"
+#include <KDecoration2/Decoration>
 #include <KDecoration2/DecorationSettings>
 
 namespace KWin
@@ -355,6 +356,10 @@ void EffectsHandlerImpl::setupClientConnections(AbstractClient* c)
     connect(c, &AbstractClient::visibleGeometryChanged, this, [this, c]() {
         Q_EMIT windowExpandedGeometryChanged(c->effectWindow());
     });
+
+    connect(c, &AbstractClient::decorationChanged, this, [this, c]() {
+        Q_EMIT windowDecorationChanged(c->effectWindow());
+    });
 }
 
 void EffectsHandlerImpl::setupUnmanagedConnections(Unmanaged* u)
@@ -2078,6 +2083,16 @@ QRect EffectWindowImpl::decorationInnerRect() const
     return toplevel->rect() - toplevel->frameMargins();
 }
 
+KDecoration2::Decoration *EffectWindowImpl::decoration() const
+{
+    auto client = qobject_cast<AbstractClient *>(toplevel);
+    if (!client) {
+        return nullptr;
+    }
+
+    return client->decoration();
+}
+
 QByteArray EffectWindowImpl::readProperty(long atom, long type, int format) const
 {
     if (!kwinApp()->x11Connection()) {

src/effects.h

@@ -490,6 +490,7 @@ public:
     qlonglong windowId() const override;
 
     QRect decorationInnerRect() const override;
+    KDecoration2::Decoration *decoration() const override;
     QByteArray readProperty(long atom, long type, int format) const override;
     void deleteProperty(long atom) const override;
 

src/effects/CMakeLists.txt

@@ -55,6 +55,7 @@ set(kwin_effect_KDE_LIBS
     KF5::Plasma # screenedge effect
     KF5::WindowSystem
     KF5::Service # utils / screenshot effect
+    KDecoration2::KDecoration # blur effect
     Plasma::KWaylandServer
 )
 

src/effects/blur/blur.cpp

@@ -25,6 +25,8 @@
 #include <KSharedConfig>
 #include <KConfigGroup>
 
+#include <KDecoration2/Decoration>
+
 namespace KWin
 {
 
@@ -65,6 +67,7 @@ BlurEffect::BlurEffect()
 
     connect(effects, &EffectsHandler::windowAdded, this, &BlurEffect::slotWindowAdded);
     connect(effects, &EffectsHandler::windowDeleted, this, &BlurEffect::slotWindowDeleted);
+    connect(effects, &EffectsHandler::windowDecorationChanged, this, &BlurEffect::setupDecorationConnections);
     connect(effects, &EffectsHandler::propertyNotify, this, &BlurEffect::slotPropertyNotify);
     connect(effects, &EffectsHandler::virtualScreenGeometryChanged, this, &BlurEffect::slotScreenGeometryChanged);
     connect(effects, &EffectsHandler::xcbConnectionChanged, this,
@@ -334,6 +337,7 @@ void BlurEffect::slotWindowAdded(EffectWindow *w)
         internal->installEventFilter(this);
     }
 
+    setupDecorationConnections(w);
     updateBlurRegion(w);
 }
 
@@ -354,6 +358,17 @@ void BlurEffect::slotPropertyNotify(EffectWindow *w, long atom)
     }
 }
 
+void BlurEffect::setupDecorationConnections(EffectWindow *w)
+{
+    if (!w->decoration()) {
+        return;
+    }
+
+    connect(w->decoration(), &KDecoration2::Decoration::blurRegionChanged, this, [this, w] () {
+        updateBlurRegion(w);
+    });
+}
+
 bool BlurEffect::eventFilter(QObject *watched, QEvent *event)
 {
     auto internal = qobject_cast<QWindow*>(watched);
@@ -399,6 +414,23 @@ bool BlurEffect::supported()
     return supported;
 }
 
+QRegion BlurEffect::decorationBlurRegion(const EffectWindow *w) const
+{
+    if (!w || !effects->decorationSupportsBlurBehind() || !w->decoration()) {
+        return QRegion();
+    }
+
+    QRegion decorationRegion = QRegion(w->decoration()->rect()) - w->decorationInnerRect();
+
+    if (!w->decoration()->blurRegion().isNull()) {
+        //! we return only blurred regions that belong to decoration region
+        return decorationRegion.intersected(w->decoration()->blurRegion());
+    }
+
+    //! when decoration requests blur but does not provide any blur region we can assume it prefers entire decoration region
+    return decorationRegion;
+}
+
 QRect BlurEffect::expand(const QRect &rect) const
 {
     return rect.adjusted(-m_expandSize, -m_expandSize, m_expandSize, m_expandSize);
@@ -424,7 +456,7 @@ QRegion BlurEffect::blurRegion(const EffectWindow *w) const
         const QRegion appRegion = qvariant_cast<QRegion>(value);
         if (!appRegion.isEmpty()) {
             if (w->decorationHasAlpha() && effects->decorationSupportsBlurBehind()) {
-                region = QRegion(w->rect()) - w->decorationInnerRect();
+                region = decorationBlurRegion(w);
             }
             region |= appRegion.translated(w->contentsRect().topLeft()) &
                       w->decorationInnerRect();
@@ -436,7 +468,7 @@ QRegion BlurEffect::blurRegion(const EffectWindow *w) const
     } else if (w->decorationHasAlpha() && effects->decorationSupportsBlurBehind()) {
         // If the client hasn't specified a blur region, we'll only enable
         // the effect behind the decoration.
-        region = QRegion(w->rect()) - w->decorationInnerRect();
+        region = decorationBlurRegion(w);
     }
 
     return region;

src/effects/blur/blur.h

@@ -58,6 +58,7 @@ public Q_SLOTS:
     void slotWindowDeleted(KWin::EffectWindow *w);
     void slotPropertyNotify(KWin::EffectWindow *w, long atom);
     void slotScreenGeometryChanged();
+    void setupDecorationConnections(EffectWindow *w);
 
 private:
     QRect expand(const QRect &rect) const;
@@ -67,6 +68,7 @@ private:
     void initBlurStrengthValues();
     void updateTexture();
     QRegion blurRegion(const EffectWindow *w) const;
+    QRegion decorationBlurRegion(const EffectWindow *w) const;
     bool shouldBlur(const EffectWindow *w, int mask, const WindowPaintData &data) const;
     void updateBlurRegion(EffectWindow *w) const;
     void doBlur(const QRegion &shape, const QRect &screen, const float opacity, const QMatrix4x4 &screenProjection, bool isDock, QRect windowRect);

src/libkwineffects/kwineffects.h

@@ -54,6 +54,10 @@ class QTabletEvent;
  */
 Q_DECLARE_LOGGING_CATEGORY(KWINEFFECTS)
 
+namespace KDecoration2 {
+class Decoration;
+}
+
 namespace KWaylandServer {
     class SurfaceInterface;
     class Display;
@@ -1865,6 +1869,14 @@ Q_SIGNALS:
      */
     void sessionStateChanged();
 
+    /**
+     * This signal is emitted when decoration of @p was changed.
+     *
+     * @param w The window for which decoration changed
+     * @since 5.25
+     */
+    void windowDecorationChanged(KWin::EffectWindow *window);
+
     /**
      * This signal is emitted when the visible geometry of a window changed.
      */
@@ -2377,6 +2389,11 @@ public:
     virtual QRect decorationInnerRect() const = 0;
     bool hasDecoration() const;
     virtual bool decorationHasAlpha() const = 0;
+    /**
+     * Returns the decoration
+     * @since 5.25
+     */
+    virtual KDecoration2::Decoration *decoration() const = 0;
     virtual QByteArray readProperty(long atom, long type, int format) const = 0;
     virtual void deleteProperty(long atom) const = 0;