wayland: Add windows when readyForPainting changes

A window is added to the workspace when it's mapped. It's assumed that
the first Window::windowShown signal indicates that. But it's not
entirely true. For example, if setHidden(false); setHidden(true); are
called in succession, the window will be marked as ready for painting
even though it isn't.

The Window::readyForPaintingChanged() signal fixes that. It's emitted
when the window is actually mapped.

autotests/integration/effects/wobbly_shade_test.cpp

@@ -119,8 +119,8 @@ void WobblyWindowsShadeTest::testShadeMove()
     QVERIFY(!window->isShade());
     QVERIFY(window->isActive());
 
-    QSignalSpy windowShownSpy(window, &Window::windowShown);
-    QVERIFY(windowShownSpy.wait());
+    QSignalSpy readyForPaintingChangedSpy(window, &Window::readyForPaintingChanged);
+    QVERIFY(readyForPaintingChangedSpy.wait());
 
     // now shade the window
     workspace()->slotWindowShade();

src/scene/windowitem.cpp

@@ -39,6 +39,9 @@ WindowItem::WindowItem(Window *window, Scene *scene, Item *parent)
     if (waylandServer()) {
         connect(waylandServer(), &WaylandServer::lockStateChanged, this, &WindowItem::updateVisibility);
     }
+    if (!window->readyForPainting()) {
+        connect(window, &Window::readyForPaintingChanged, this, &WindowItem::updateVisibility);
+    }
     connect(window, &Window::lockScreenOverlayChanged, this, &WindowItem::updateVisibility);
     connect(window, &Window::minimizedChanged, this, &WindowItem::updateVisibility);
     connect(window, &Window::hiddenChanged, this, &WindowItem::updateVisibility);

src/wayland_server.cpp

@@ -209,7 +209,9 @@ void WaylandServer::registerWindow(Window *window)
     if (window->readyForPainting()) {
         Q_EMIT windowAdded(window);
     } else {
-        connect(window, &Window::windowShown, this, &WaylandServer::windowAdded, Qt::SingleShotConnection);
+        connect(window, &Window::readyForPaintingChanged, this, [this, window]() {
+            Q_EMIT windowAdded(window);
+        });
     }
     m_windows << window;
 }

src/window.cpp

@@ -229,7 +229,7 @@ void Window::setReadyForPainting()
 {
     if (!ready_for_painting) {
         ready_for_painting = true;
-        Q_EMIT windowShown(this);
+        Q_EMIT readyForPaintingChanged();
     }
 }
 

src/window.h

@@ -1434,6 +1434,7 @@ Q_SIGNALS:
     void hiddenChanged();
     void hiddenByShowDesktopChanged();
     void lockScreenOverlayChanged();
+    void readyForPaintingChanged();
 
 protected:
     Window();