QWaylandWindow: Support Qt::WindowTransparentForInput

This is achieved by setting an explicitly empty input
region (as opposed to a "null" region) on the window.

Unlike set_opaque_region, where a null region means an
empty region, in set_input_region it means an
infinite region.

Change-Id: I018d53196bc816b5eaea7dd3b24626a9738c9f47
Reviewed-by: David Edmundson <davidedmundson@kde.org>
(cherry picked from commit 604db6b5499f5de1d700f19c03bc43fe2f59380d)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

2 files changed, 39 insertions, 9 deletions

diff --git a/src/client/qwaylandwindow.cpp b/src/client/qwaylandwindow.cpp
index acc698f07..aea2cfff9 100644
--- a/src/client/qwaylandwindow.cpp
+++ b/src/client/qwaylandwindow.cpp
@@ -451,6 +451,32 @@ void QWaylandWindow::setGeometry(const QRect &r)
         setOpaqueArea(QRect(QPoint(0, 0), rect.size()));
 }
 
+void QWaylandWindow::updateInputRegion()
+{
+    if (!mSurface)
+        return;
+
+    const bool transparentInputRegion = mFlags.testFlag(Qt::WindowTransparentForInput);
+
+    QRegion inputRegion;
+    if (!transparentInputRegion)
+        inputRegion = mMask;
+
+    if (mInputRegion == inputRegion && mTransparentInputRegion == transparentInputRegion)
+        return;
+
+    mInputRegion = inputRegion;
+    mTransparentInputRegion = transparentInputRegion;
+
+    if (mInputRegion.isEmpty() && !mTransparentInputRegion) {
+        mSurface->set_input_region(nullptr);
+    } else {
+        struct ::wl_region *region = mDisplay->createRegion(mInputRegion);
+        mSurface->set_input_region(region);
+        wl_region_destroy(region);
+    }
+}
+
 void QWaylandWindow::updateViewport()
 {
     if (!surfaceSize().isEmpty())
@@ -561,17 +587,12 @@ void QWaylandWindow::setMask(const QRegion &mask)
 
     mMask = mask;
 
-    if (mMask.isEmpty()) {
-        mSurface->set_input_region(nullptr);
+    updateInputRegion();
 
-        if (isOpaque())
+    if (isOpaque()) {
+        if (mMask.isEmpty())
             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())
+        } else {
             setOpaqueArea(mMask);
     }
 
@@ -986,6 +1007,9 @@ void QWaylandWindow::setWindowFlags(Qt::WindowFlags flags)
 
     mFlags = flags;
     createDecoration();
+
+    QReadLocker locker(&mSurfaceLock);
+    updateInputRegion();
 }
 
 bool QWaylandWindow::createDecoration()
diff --git a/src/client/qwaylandwindow_p.h b/src/client/qwaylandwindow_p.h
index 17140c52e..fbf629066 100644
--- a/src/client/qwaylandwindow_p.h
+++ b/src/client/qwaylandwindow_p.h
@@ -312,6 +312,11 @@ protected:
 
     Qt::WindowFlags mFlags;
     QRegion mMask;
+
+    // Empty QRegion maps to "infinite" input region, needs a dedicated "deliberately empty" state.
+    QRegion mInputRegion;
+    bool mTransparentInputRegion = false;
+
     QRegion mOpaqueArea;
     Qt::WindowStates mLastReportedWindowStates = Qt::WindowNoState;
     ToplevelWindowTilingStates mLastReportedToplevelWindowTilingStates = WindowNoState;
@@ -337,6 +342,7 @@ private:
     QPlatformScreen *calculateScreenFromSurfaceEvents() const;
     void setOpaqueArea(const QRegion &opaqueArea);
     bool isOpaque() const;
+    void updateInputRegion();
     void updateViewport();
 
     void handleMouseEventWithDecoration(QWaylandInputDevice *inputDevice, const QWaylandPointerEvent &e);