diff --git a/src/decorationitem.cpp b/src/decorationitem.cpp
index e38919eb20..473a32322b 100644
--- a/src/decorationitem.cpp
+++ b/src/decorationitem.cpp
@@ -148,16 +148,21 @@ DecorationItem::DecorationItem(KDecoration2::Decoration *decoration, Window *win
     handleOutputChanged();
 }
 
-QRegion DecorationItem::shape() const
+QVector<QRectF> DecorationItem::shape() const
 {
     QRectF left, top, right, bottom;
     m_window->layoutDecorationRects(left, top, right, bottom);
-    return QRegion(left.toRect()).united(top.toRect()).united(right.toRect()).united(bottom.toRect());
+    return {left, top, right, bottom};
 }
 
 QRegion DecorationItem::opaque() const
 {
-    return m_window->decorationHasAlpha() ? QRegion() : shape();
+    if (m_window->decorationHasAlpha()) {
+        return QRegion();
+    }
+    QRectF left, top, right, bottom;
+    m_window->layoutDecorationRects(left, top, right, bottom);
+    return QRegion(left.toRect()).united(top.toRect()).united(right.toRect()).united(bottom.toRect());
 }
 
 void DecorationItem::preprocess()
diff --git a/src/decorationitem.h b/src/decorationitem.h
index 4e3f380202..86a42969fd 100644
--- a/src/decorationitem.h
+++ b/src/decorationitem.h
@@ -83,7 +83,7 @@ public:
     DecorationRenderer *renderer() const;
     Window *window() const;
 
-    QRegion shape() const override final;
+    QVector<QRectF> shape() const override final;
     QRegion opaque() const override final;
 
 private Q_SLOTS:
diff --git a/src/item.cpp b/src/item.cpp
index fc11a7da2e..1254f2e4aa 100644
--- a/src/item.cpp
+++ b/src/item.cpp
@@ -169,9 +169,9 @@ void Item::updateBoundingRect()
     }
 }
 
-QRegion Item::shape() const
+QVector<QRectF> Item::shape() const
 {
-    return rect().toAlignedRect();
+    return QVector<QRectF>();
 }
 
 QRegion Item::opaque() const
diff --git a/src/item.h b/src/item.h
index 80393b57ee..b3db8c9319 100644
--- a/src/item.h
+++ b/src/item.h
@@ -11,6 +11,7 @@
 
 #include <QMatrix4x4>
 #include <QObject>
+#include <QVector>
 
 #include <optional>
 
@@ -51,7 +52,7 @@ public:
      */
     QRectF boundingRect() const;
 
-    virtual QRegion shape() const;
+    virtual QVector<QRectF> shape() const;
     virtual QRegion opaque() const;
 
     /**
diff --git a/src/scenes/opengl/scene_opengl.cpp b/src/scenes/opengl/scene_opengl.cpp
index 4883471b05..8141c8e2b4 100644
--- a/src/scenes/opengl/scene_opengl.cpp
+++ b/src/scenes/opengl/scene_opengl.cpp
@@ -386,8 +386,18 @@ void SceneOpenGL::createRenderNode(Item *item, RenderContext *context)
         SurfacePixmap *pixmap = surfaceItem->pixmap();
         if (pixmap) {
             if (!geometry.isEmpty()) {
+                bool hasAlpha = pixmap->hasAlphaChannel();
+                bool isCompletelyOpaque = true;
                 // Don't bother with blending if the entire surface is opaque
-                bool hasAlpha = pixmap->hasAlphaChannel() && !surfaceItem->shape().subtracted(surfaceItem->opaque()).isEmpty();
+                const QVector<QRectF> shape = surfaceItem->shape();
+                for (const QRectF &shapePart : shape) {
+                    if (!item->opaque().contains(shapePart.toRect())) {
+                        isCompletelyOpaque = false;
+                        break;
+                    }
+                }
+                hasAlpha &= !isCompletelyOpaque;
+
                 context->renderNodes.append(RenderNode{
                     .texture = bindSurfaceTexture(surfaceItem),
                     .geometry = geometry,
diff --git a/src/scenes/qpainter/scene_qpainter.cpp b/src/scenes/qpainter/scene_qpainter.cpp
index 282ab880d8..76e31eb9e8 100644
--- a/src/scenes/qpainter/scene_qpainter.cpp
+++ b/src/scenes/qpainter/scene_qpainter.cpp
@@ -167,7 +167,7 @@ void SceneQPainter::renderSurfaceItem(QPainter *painter, SurfaceItem *surfaceIte
     }
     surfaceItem->resetDamage();
 
-    const QRegion shape = surfaceItem->shape();
+    const QVector<QRectF> shape = surfaceItem->shape();
     for (const QRectF rect : shape) {
         const QMatrix4x4 matrix = surfaceItem->surfaceToBufferMatrix();
         const QPointF bufferTopLeft = matrix.map(rect.topLeft());
diff --git a/src/surfaceitem.cpp b/src/surfaceitem.cpp
index fa6eaaecc8..43c4ad349f 100644
--- a/src/surfaceitem.cpp
+++ b/src/surfaceitem.cpp
@@ -130,11 +130,11 @@ WindowQuadList SurfaceItem::buildQuads() const
         return {};
     }
 
-    const QRegion region = shape();
+    const QVector<QRectF> region = shape();
     const auto size = pixmap()->size();
 
     WindowQuadList quads;
-    quads.reserve(region.rectCount());
+    quads.reserve(region.count());
 
     for (const QRectF rect : region) {
         WindowQuad quad;
diff --git a/src/surfaceitem_internal.cpp b/src/surfaceitem_internal.cpp
index 29bb9a7a70..16141ea8d7 100644
--- a/src/surfaceitem_internal.cpp
+++ b/src/surfaceitem_internal.cpp
@@ -28,9 +28,9 @@ SurfaceItemInternal::SurfaceItemInternal(InternalWindow *window, Item *parent)
     setSurfaceToBufferMatrix(surfaceToBufferMatrix);
 }
 
-QRegion SurfaceItemInternal::shape() const
+QVector<QRectF> SurfaceItemInternal::shape() const
 {
-    return QRegion(rect().toAlignedRect());
+    return {rect()};
 }
 
 std::unique_ptr<SurfacePixmap> SurfaceItemInternal::createPixmap()
diff --git a/src/surfaceitem_internal.h b/src/surfaceitem_internal.h
index 58349338a5..9a49fb35e6 100644
--- a/src/surfaceitem_internal.h
+++ b/src/surfaceitem_internal.h
@@ -25,7 +25,7 @@ class KWIN_EXPORT SurfaceItemInternal : public SurfaceItem
 public:
     explicit SurfaceItemInternal(InternalWindow *window, Item *parent = nullptr);
 
-    QRegion shape() const override;
+    QVector<QRectF> shape() const override;
 
 private Q_SLOTS:
     void handleBufferGeometryChanged(Window *window, const QRectF &old);
diff --git a/src/surfaceitem_wayland.cpp b/src/surfaceitem_wayland.cpp
index e8853953cd..b2375de6a2 100644
--- a/src/surfaceitem_wayland.cpp
+++ b/src/surfaceitem_wayland.cpp
@@ -53,9 +53,9 @@ SurfaceItemWayland::SurfaceItemWayland(KWaylandServer::SurfaceInterface *surface
     setSurfaceToBufferMatrix(surface->surfaceToBufferMatrix());
 }
 
-QRegion SurfaceItemWayland::shape() const
+QVector<QRectF> SurfaceItemWayland::shape() const
 {
-    return QRegion(rect().toAlignedRect());
+    return {rect()};
 }
 
 QRegion SurfaceItemWayland::opaque() const
@@ -208,12 +208,16 @@ SurfaceItemXwayland::SurfaceItemXwayland(Window *window, Item *parent)
     connect(window, &Window::geometryShapeChanged, this, &SurfaceItemXwayland::discardQuads);
 }
 
-QRegion SurfaceItemXwayland::shape() const
+QVector<QRectF> SurfaceItemXwayland::shape() const
 {
     const QRectF clipRect = rect() & window()->clientGeometry().translated(-window()->bufferGeometry().topLeft());
-    const QRegion shape = window()->shapeRegion();
+    QVector<QRectF> shape = window()->shapeRegion();
 
-    return shape & clipRect.toRect();
+    // bounded to clipRect
+    for (QRectF &shapePart : shape) {
+        shapePart = shapePart.intersected(clipRect);
+    }
+    return shape;
 }
 
 } // namespace KWin
diff --git a/src/surfaceitem_wayland.h b/src/surfaceitem_wayland.h
index 53e5da76e3..4483fdee55 100644
--- a/src/surfaceitem_wayland.h
+++ b/src/surfaceitem_wayland.h
@@ -29,7 +29,7 @@ public:
     explicit SurfaceItemWayland(KWaylandServer::SurfaceInterface *surface,
                                 Window *window, Item *parent = nullptr);
 
-    QRegion shape() const override;
+    QVector<QRectF> shape() const override;
     QRegion opaque() const override;
     ContentType contentType() const override;
 
@@ -88,7 +88,7 @@ class KWIN_EXPORT SurfaceItemXwayland : public SurfaceItemWayland
 public:
     explicit SurfaceItemXwayland(Window *window, Item *parent = nullptr);
 
-    QRegion shape() const override;
+    QVector<QRectF> shape() const override;
 };
 
 } // namespace KWin
diff --git a/src/surfaceitem_x11.cpp b/src/surfaceitem_x11.cpp
index f68f9b0765..ddd12282ab 100644
--- a/src/surfaceitem_x11.cpp
+++ b/src/surfaceitem_x11.cpp
@@ -138,21 +138,29 @@ void SurfaceItemX11::handleGeometryShapeChanged()
     discardQuads();
 }
 
-QRegion SurfaceItemX11::shape() const
+QVector<QRectF> SurfaceItemX11::shape() const
 {
     const QRectF clipRect = window()->clientGeometry().translated(-window()->bufferGeometry().topLeft());
-    const QRegion shape = window()->shapeRegion();
-
-    return shape & clipRect.toAlignedRect();
+    QVector<QRectF> shape = window()->shapeRegion();
+    // bounded to clipRect
+    for (QRectF &shapePart : shape) {
+        shapePart = shapePart.intersected(clipRect);
+    }
+    return shape;
 }
 
 QRegion SurfaceItemX11::opaque() const
 {
-    if (!window()->hasAlpha()) {
-        return shape();
-    } else {
-        return window()->opaqueRegion() & shape();
+    QRegion shapeRegion;
+    for (const QRectF &shapePart : shape()) {
+        shapeRegion |= shapePart.toRect();
     }
+    if (!window()->hasAlpha()) {
+        return shapeRegion;
+    } else {
+        return window()->opaqueRegion() & shapeRegion;
+    }
+    return QRegion();
 }
 
 std::unique_ptr<SurfacePixmap> SurfaceItemX11::createPixmap()
diff --git a/src/surfaceitem_x11.h b/src/surfaceitem_x11.h
index 343c82dbbb..71e04d0aca 100644
--- a/src/surfaceitem_x11.h
+++ b/src/surfaceitem_x11.h
@@ -32,7 +32,7 @@ public:
     void waitForDamage();
     void destroyDamage();
 
-    QRegion shape() const override;
+    QVector<QRectF> shape() const override;
     QRegion opaque() const override;
 
 private Q_SLOTS:
diff --git a/src/window.cpp b/src/window.cpp
index 692f80b3b1..981b08b2a5 100644
--- a/src/window.cpp
+++ b/src/window.cpp
@@ -483,13 +483,12 @@ void Window::getWmOpaqueRegion()
     const auto rects = info->opaqueRegion();
     QRegion new_opaque_region;
     for (const auto &r : rects) {
-        new_opaque_region += Xcb::fromXNative(QRect(r.pos.x, r.pos.y, r.size.width, r.size.height)).toAlignedRect();
+        new_opaque_region |= Xcb::fromXNative(QRect(r.pos.x, r.pos.y, r.size.width, r.size.height)).toRect();
     }
-
     opaque_region = new_opaque_region;
 }
 
-QRegion Window::shapeRegion() const
+QVector<QRectF> Window::shapeRegion() const
 {
     if (m_shapeRegionIsValid) {
         return m_shapeRegion;
@@ -501,19 +500,21 @@ QRegion Window::shapeRegion() const
         auto cookie = xcb_shape_get_rectangles_unchecked(kwinApp()->x11Connection(), frameId(), XCB_SHAPE_SK_BOUNDING);
         UniqueCPtr<xcb_shape_get_rectangles_reply_t> reply(xcb_shape_get_rectangles_reply(kwinApp()->x11Connection(), cookie, nullptr));
         if (reply) {
-            m_shapeRegion = QRegion();
+            m_shapeRegion.clear();
             const xcb_rectangle_t *rects = xcb_shape_get_rectangles_rectangles(reply.get());
             const int rectCount = xcb_shape_get_rectangles_rectangles_length(reply.get());
             for (int i = 0; i < rectCount; ++i) {
-                m_shapeRegion += Xcb::fromXNative(QRect(rects[i].x, rects[i].y, rects[i].width, rects[i].height)).toAlignedRect();
+                QRectF region = Xcb::fromXNative(QRect(rects[i].x, rects[i].y, rects[i].width, rects[i].height)).toAlignedRect();
+                // make sure the shape is sane (X is async, maybe even XShape is broken)
+                region = region.intersected(QRectF(QPointF(0, 0), bufferGeometry.size()));
+
+                m_shapeRegion += region;
             }
-            // make sure the shape is sane (X is async, maybe even XShape is broken)
-            m_shapeRegion &= QRegion(0, 0, bufferGeometry.width(), bufferGeometry.height());
         } else {
-            m_shapeRegion = QRegion();
+            m_shapeRegion.clear();
         }
     } else {
-        m_shapeRegion = QRegion(0, 0, bufferGeometry.width(), bufferGeometry.height());
+        m_shapeRegion = {QRectF(0, 0, bufferGeometry.width(), bufferGeometry.height())};
     }
 
     m_shapeRegionIsValid = true;
@@ -523,7 +524,7 @@ QRegion Window::shapeRegion() const
 void Window::discardShapeRegion()
 {
     m_shapeRegionIsValid = false;
-    m_shapeRegion = QRegion();
+    m_shapeRegion.clear();
 }
 
 bool Window::isClient() const
diff --git a/src/window.h b/src/window.h
index fcda80c00b..1e05572f5e 100644
--- a/src/window.h
+++ b/src/window.h
@@ -773,7 +773,7 @@ public:
      * @see hasAlpha
      */
     const QRegion &opaqueRegion() const;
-    QRegion shapeRegion() const;
+    QVector<QRectF> shapeRegion() const;
 
     bool skipsCloseAnimation() const;
     void setSkipCloseAnimation(bool set);
@@ -1925,7 +1925,7 @@ private:
     ClientMachine *m_clientMachine;
     xcb_window_t m_wmClientLeader;
     QRegion opaque_region;
-    mutable QRegion m_shapeRegion;
+    mutable QVector<QRectF> m_shapeRegion;
     mutable bool m_shapeRegionIsValid = false;
     bool m_skipCloseAnimation;
     quint32 m_pendingSurfaceId = 0;