From: Anders da Silva Rytter Hansen <andersrh@users.noreply.github.com>
Date: Thu, 02 Jul 2026 13:00:00 +0000
Subject: [PATCH] Reduce per-frame compositor work during panel floating animation

PanelView::updateMask() is called once per animation frame while the
panel transitions between docked and floating. It calls
KWindowEffects::enableBlurBehind() and enableBackgroundContrast() which
update the compositor's effect region via X11/D-Bus. Doing this for
every frame causes visible stutter when other animations are running.

Additionally, the animation's valueChanged handler was calling
positionAndResizePanel() every frame, which calls setGeometry(),
emits availableScreenRegionChanged() and calls slideWindow() every
frame even though the panel's X window geometry is constant during the
animation.

Coalesce the blur/contrast updates with a 50 ms single-shot timer and
replace the per-frame positionAndResizePanel() call with a lightweight
updateMask() call. Finalize geometry and effects once when the
animation finishes. This keeps the QML geometry/opacity animation
smooth while drastically reducing synchronous work sent to the
compositor.
---
 shell/panelview.cpp | 19 +++++++++++++++++++
 shell/panelview.h   | 5 +++++
 2 files changed, 24 insertions(+)

--- a/shell/panelview.h	2026-04-08 06:33:10.000000000 -0300
+++ b/shell/panelview.h	2026-07-02 13:09:59.011179892 -0300
@@ -8,6 +8,7 @@
 
 #include <Plasma/Theme>
 #include <QPointer>
+#include <QAbstractAnimation>
 #include <QPropertyAnimation>
 #include <QTimer>
 #include <QWindow> // For WId
@@ -306,6 +307,7 @@
     void adaptToScreen();
     void handleQmlStatusChange(QQmlComponent::Status status);
     void updateMask();
+    void applyPendingMaskUpdate();
     void updateEnabledBorders();
     void updatePadding();
     void updateFloating();
@@ -363,6 +365,9 @@
     LengthMode m_lengthMode;
     Plasma::Theme m_theme;
     QTimer m_unhideTimer;
+    QTimer m_maskThrottleTimer;
+    bool m_pendingMaskUpdate = false;
+    bool m_forceMaskUpdate = false;
     Plasma::Types::BackgroundHints m_backgroundHints;
     KSvg::FrameSvg::EnabledBorders m_enabledBorders = KSvg::FrameSvg::AllBorders;
     QPointer<QScreen> m_lastScreen;
--- a/shell/panelview.cpp	2026-04-08 06:33:10.000000000 -0300
+++ b/shell/panelview.cpp	2026-07-02 13:39:01.337688294 -0300
@@ -111,6 +111,10 @@
     m_strutsTimer.setSingleShot(true);
     connect(&m_strutsTimer, &QTimer::timeout, this, &PanelView::updateExclusiveZone);
 
+    m_maskThrottleTimer.setSingleShot(true);
+    m_maskThrottleTimer.setInterval(50ms);
+    connect(&m_maskThrottleTimer, &QTimer::timeout, this, &PanelView::applyPendingMaskUpdate);
+
     connect(m_corona, &Plasma::Corona::editModeChanged, this, &PanelView::updateEditModeLabel);
 
     // Register enums
@@ -1304,6 +1308,17 @@
         return;
     }
 
+    if (m_floatingnessAnimation.state() == QAbstractAnimation::Running && !m_forceMaskUpdate) {
+        m_pendingMaskUpdate = true;
+        if (!m_maskThrottleTimer.isActive()) {
+            m_maskThrottleTimer.start();
+        }
+        return;
+    }
+
+    m_forceMaskUpdate = false;
+    m_pendingMaskUpdate = false;
+
     // Popups now align to the mask, without it they appear in the wrong position
     // always create it and show blur and contrast when needed
     QRegion mask;
@@ -1364,6 +1379,14 @@
     }
 }
 
+void PanelView::applyPendingMaskUpdate()
+{
+    if (m_pendingMaskUpdate) {
+        m_forceMaskUpdate = true;
+        updateMask();
+    }
+}
+
 bool PanelView::canSetStrut() const
 {
     // read the wm name, need to do this every time which means a roundtrip unfortunately
@@ -1587,10 +1610,10 @@
                     return;
                 }
                 m_floatingness = get<double>(value);
-                positionAndResizePanel();
+                updateMask();
             });
             connect(&m_floatingnessAnimation, &QPropertyAnimation::finished, rootObject, [this]() {
-                updateMask();
+                positionAndResizePanel();
             });
             connect(rootObject, SIGNAL(minPanelHeightChanged()), this, SLOT(updatePadding()));
             connect(rootObject, SIGNAL(minPanelWidthChanged()), this, SLOT(updatePadding()));