[kdecoration2] Detect double clicks on the decoration title bar

No longer handled by the Decoration.

client.cpp

@@ -519,12 +519,6 @@ void Client::createDecoration(const QRect& oldgeom)
     if (m_decoration) {
         m_decoration->update();
         connect(m_decoration, &KDecoration2::Decoration::shadowChanged, this, &Toplevel::getShadow);
-        connect(m_decoration, &KDecoration2::Decoration::titleBarDoubleClicked, this,
-            [this]() {
-                Workspace::self()->performWindowOperation(this, options->operationTitlebarDblClick());
-                dontMoveResize();
-            }
-        );
         connect(m_decoration, &KDecoration2::Decoration::resizeOnlyBordersChanged, this, &Client::updateInputWindow);
         connect(m_decoration, &KDecoration2::Decoration::bordersChanged, this,
             [this]() {

client.h

@@ -29,6 +29,7 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #include "toplevel.h"
 #include "xcbutils.h"
 // Qt
+#include <QElapsedTimer>
 #include <QPixmap>
 #include <QWindow>
 // X
@@ -868,6 +869,7 @@ private:
     QScopedPointer<QWindow> m_frameWrapper;
     KDecoration2::Decoration *m_decoration;
     QPointer<Decoration::DecoratedClientImpl> m_decoratedClient;
+    QElapsedTimer m_decorationDoubleClickTimer;
     int desk;
     QStringList activityList;
     int m_activityUpdatesBlocked;

events.cpp

@@ -50,6 +50,7 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 #include <QApplication>
 #include <QDebug>
+#include <QStyleHints>
 #include <QWhatsThis>
 
 #include <kkeyserver.h>
@@ -1232,6 +1233,19 @@ bool Client::processDecorationButtonPress(int button, int /*state*/, int x, int
     if (!wantsInput())    // we cannot be active, use it anyway
         active = true;
 
+    // check whether it is a double click
+    if (button == XCB_BUTTON_INDEX_1) {
+        if (m_decorationDoubleClickTimer.isValid() &&
+                m_decoration->titleBar().contains(x, y) &&
+                !m_decorationDoubleClickTimer.hasExpired(QGuiApplication::styleHints()->mouseDoubleClickInterval())) {
+            Workspace::self()->performWindowOperation(this, options->operationTitlebarDblClick());
+            dontMoveResize();
+            m_decorationDoubleClickTimer.invalidate();
+            return false;
+        }
+        m_decorationDoubleClickTimer.invalidate();
+    }
+
     if (button == XCB_BUTTON_INDEX_1)
         com = active ? options->commandActiveTitlebar1() : options->commandInactiveTitlebar1();
     else if (button == XCB_BUTTON_INDEX_2)
@@ -1277,7 +1291,11 @@ bool Client::buttonReleaseEvent(xcb_window_t w, int button, int state, int x, in
                               x11ToQtMouseButton(button),
                               x11ToQtMouseButtons(state) & ~x11ToQtMouseButton(button),
                               x11ToQtKeyboardModifiers(state));
+            event.setAccepted(false);
             QCoreApplication::sendEvent(m_decoration, &event);
+            if (!event.isAccepted() && m_decoration->titleBar().contains(x, y) && button == XCB_BUTTON_INDEX_1) {
+                m_decorationDoubleClickTimer.start();
+            }
         }
     }
     if (w == wrapperId()) {

kcmkwin/kwindecoration/declarative-plugin/previewclient.cpp

@@ -113,16 +113,6 @@ PreviewClient::PreviewClient(DecoratedClient *c, Decoration *decoration)
             emit paletteChanged(m_palette);
         }
     );
-    connect(decoration, &Decoration::titleBarDoubleClicked, this,
-        [this]() {
-            if (!isMaximizeable()) {
-                return;
-            }
-            const bool maximize = !isMaximized();
-            setMaximizedHorizontally(maximize);
-            setMaximizedVertically(maximize);
-        }
-    );
     auto emitEdgesChanged = [this, c]() {
         c->adjacentScreenEdgesChanged(adjacentScreenEdges());
     };