Add sanity checks before updating pointer position and on screen changes

We don't want the cursor to leave the visible area, so better check that
the cursor doesn't leave it. And when the screens changes better check
that the cursor is still on a visible screen. If not: put it back to the
center of the closest screen.

input.cpp

@@ -226,10 +226,13 @@ void InputRedirection::setupLibInput()
                 processPointerMotion(screen, time);
             }
         );
+        connect(screens(), &Screens::changed, this, &InputRedirection::updatePointerAfterScreenChange);
         // set pos to center of all screens
         if (screens()) {
             m_globalPointer = screens()->geometry().center();
             emit globalPointerChanged(m_globalPointer);
+            // sanitize
+            updatePointerAfterScreenChange();
         }
     }
 #endif
@@ -259,8 +262,7 @@ void InputRedirection::processPointerMotion(const QPointF &pos, uint32_t time)
     Q_UNUSED(time)
     // first update to new mouse position
 //     const QPointF oldPos = m_globalPointer;
-    m_globalPointer = pos;
-    emit globalPointerChanged(m_globalPointer);
+    updatePointerPosition(pos);
 
     // TODO: check which part of KWin would like to intercept the event
     QMouseEvent event(QEvent::MouseMove, m_globalPointer.toPoint(), m_globalPointer.toPoint(),
@@ -558,4 +560,35 @@ void InputRedirection::registerAxisShortcut(Qt::KeyboardModifiers modifiers, Poi
     m_shortcuts->registerAxisShortcut(action, modifiers, axis);
 }
 
+static bool screenContainsPos(const QPointF &pos)
+{
+    for (int i = 0; i < screens()->count(); ++i) {
+        if (screens()->geometry(i).contains(pos.toPoint())) {
+            return true;
+        }
+    }
+    return false;
+}
+
+void InputRedirection::updatePointerPosition(const QPointF &pos)
+{
+    // verify that at least one screen contains the pointer position
+    if (!screenContainsPos(pos)) {
+        return;
+    }
+    m_globalPointer = pos;
+    emit globalPointerChanged(m_globalPointer);
+}
+
+void InputRedirection::updatePointerAfterScreenChange()
+{
+    if (screenContainsPos(m_globalPointer)) {
+        // pointer still on a screen
+        return;
+    }
+    // pointer no longer on a screen, reposition to closes screen
+    m_globalPointer = screens()->geometry(screens()->number(m_globalPointer.toPoint())).center();
+    emit globalPointerChanged(m_globalPointer);
+}
+
 } // namespace

input.h

@@ -156,6 +156,8 @@ private:
     static Qt::MouseButton buttonToQtMouseButton(uint32_t button);
     Toplevel *findToplevel(const QPoint &pos);
     void setupLibInput();
+    void updatePointerPosition(const QPointF &pos);
+    void updatePointerAfterScreenChange();
     QPointF m_globalPointer;
     QHash<uint32_t, PointerButtonState> m_pointerButtons;
 #if HAVE_XKB