From cc779e0ed47ec4759dc3c23953dd02cfacc6885c Mon Sep 17 00:00:00 2001
From: Aleix Pol <aleixpol@kde.org>
Date: Wed, 30 Sep 2020 13:37:12 +0200
Subject: Issue set_opaque_region on opaque surfaces

The application will tell Qt whether the background is transparent
through either Qt::WA_TranslucentBackground or QQuickWindow::setColor.
These will set a QSurfaceFormat.
This change checks the QSurfaceFormat and issues the opacity information
so we can properly implement culling optimizations in the compositor.

Change-Id: I4f7562467449eac7931f3011d4b835934212adad
Reviewed-by: David Edmundson <davidedmundson@kde.org>
(cherry picked from commit 0db685834f8377e41b147d3367b8ec514841eff5)
---
 src/client/qwaylandwindow.cpp | 26 ++++++++++++++++++++++++++
 src/client/qwaylandwindow_p.h |  3 +++
 2 files changed, 29 insertions(+)

diff --git a/src/client/qwaylandwindow.cpp b/src/client/qwaylandwindow.cpp
index 1e26ee91e..bc031ed5a 100644
--- a/src/client/qwaylandwindow.cpp
+++ b/src/client/qwaylandwindow.cpp
@@ -364,6 +364,9 @@ void QWaylandWindow::setGeometry(const QRect &rect)
 
     if (mShellSurface)
         mShellSurface->setWindowGeometry(windowContentGeometry());
+
+    if (isOpaque() && mMask.isEmpty())
+        setOpaqueArea(rect);
 }
 
 void QWaylandWindow::resizeFromApplyConfigure(const QSize &sizeWithMargins, const QPoint &offset)
@@ -463,10 +466,16 @@ void QWaylandWindow::setMask(const QRegion &mask)
 
     if (mMask.isEmpty()) {
         mSurface->set_input_region(nullptr);
+
+        if (isOpaque())
+            setOpaqueArea(QRect(QPoint(0, 0), geometry().size()));
     } else {
         struct ::wl_region *region = mDisplay->createRegion(mMask);
         mSurface->set_input_region(region);
         wl_region_destroy(region);
+
+        if (isOpaque())
+            setOpaqueArea(mMask);
     }
 
     mSurface->commit();
@@ -1215,6 +1224,23 @@ bool QtWaylandClient::QWaylandWindow::startSystemMove()
     return false;
 }
 
+bool QWaylandWindow::isOpaque() const
+{
+    return window()->requestedFormat().alphaBufferSize() <= 0;
+}
+
+void QWaylandWindow::setOpaqueArea(const QRegion &opaqueArea)
+{
+    if (opaqueArea == mOpaqueArea || !mSurface)
+        return;
+
+    mOpaqueArea = opaqueArea;
+
+    struct ::wl_region *region = mDisplay->createRegion(opaqueArea);
+    mSurface->set_opaque_region(region);
+    wl_region_destroy(region);
+}
+
 }
 
 QT_END_NAMESPACE
diff --git a/src/client/qwaylandwindow_p.h b/src/client/qwaylandwindow_p.h
index 35a2c0321..6cc1664b7 100644
--- a/src/client/qwaylandwindow_p.h
+++ b/src/client/qwaylandwindow_p.h
@@ -254,6 +254,7 @@ protected:
 
     Qt::WindowFlags mFlags;
     QRegion mMask;
+    QRegion mOpaqueArea;
     Qt::WindowStates mLastReportedWindowStates = Qt::WindowNoState;
 
     QWaylandShmBackingStore *mBackingStore = nullptr;
@@ -270,6 +271,8 @@ private:
     void sendExposeEvent(const QRect &rect);
     static void closePopups(QWaylandWindow *parent);
     QPlatformScreen *calculateScreenFromSurfaceEvents() const;
+    void setOpaqueArea(const QRegion &opaqueArea);
+    bool isOpaque() const;
 
     void handleMouseEventWithDecoration(QWaylandInputDevice *inputDevice, const QWaylandPointerEvent &e);
     void handleScreensChanged();
-- 
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