Introduce Workspace::stackAbove()

The main purpose is to simplify X11 Above stack mode implementation.

src/focuschain.cpp

@@ -151,6 +151,26 @@ void FocusChain::moveAfterWindow(Window *window, Window *reference)
     moveAfterWindowInChain(window, reference, m_mostRecentlyUsed);
 }
 
+void FocusChain::moveBeforeWindow(Window *window, Window *reference)
+{
+    if (window->isDeleted()) {
+        return;
+    }
+    if (!window->wantsTabFocus()) {
+        return;
+    }
+
+    for (auto it = m_desktopFocusChains.begin();
+         it != m_desktopFocusChains.end();
+         ++it) {
+        if (!window->isOnDesktop(it.key())) {
+            continue;
+        }
+        moveBeforeWindowInChain(window, reference, it.value());
+    }
+    moveBeforeWindowInChain(window, reference, m_mostRecentlyUsed);
+}
+
 void FocusChain::moveAfterWindowInChain(Window *window, Window *reference, Chain &chain)
 {
     if (window->isDeleted()) {
@@ -173,6 +193,28 @@ void FocusChain::moveAfterWindowInChain(Window *window, Window *reference, Chain
     }
 }
 
+void FocusChain::moveBeforeWindowInChain(Window *window, Window *reference, Chain &chain)
+{
+    if (window->isDeleted()) {
+        return;
+    }
+    if (!chain.contains(reference)) {
+        return;
+    }
+    if (Window::belongToSameApplication(reference, window)) {
+        chain.removeAll(window);
+        chain.insert(chain.indexOf(reference) + 1, window);
+    } else {
+        chain.removeAll(window);
+        for (int i = chain.size() - 1; i >= 0; --i) {
+            if (Window::belongToSameApplication(reference, chain.at(i))) {
+                chain.insert(i + 1, window);
+                break;
+            }
+        }
+    }
+}
+
 Window *FocusChain::firstMostRecentlyUsed() const
 {
     if (m_mostRecentlyUsed.isEmpty()) {

src/focuschain.h

@@ -79,6 +79,14 @@ public:
      * @return void
      */
     void moveAfterWindow(Window *window, Window *reference);
+    /**
+     * @brief Moves @p window in front of the @p reference Window in all focus chains.
+     *
+     * @param window The Window to move in the chains
+     * @param reference The Window in front of which the @p window should be moved
+     * @return void
+     */
+    void moveBeforeWindow(Window *window, Window *reference);
     /**
      * @brief Finds the best Window to become the new active Window in the focus chain for the given
      * virtual @p desktop.
@@ -197,6 +205,7 @@ private:
      */
     void makeLastInChain(Window *window, Chain &chain);
     void moveAfterWindowInChain(Window *window, Window *reference, Chain &chain);
+    void moveBeforeWindowInChain(Window *window, Window *reference, Chain &chain);
     void updateWindowInChain(Window *window, Change change, Chain &chain);
     void insertWindowIntoChain(Window *window, Chain &chain);
     Chain m_mostRecentlyUsed;

src/layers.cpp

@@ -464,6 +464,25 @@ void Workspace::stackBelow(Window *window, Window *reference)
     updateStackingOrder();
 }
 
+void Workspace::stackAbove(Window *window, Window *reference)
+{
+    if (window->isDeleted()) {
+        qCWarning(KWIN_CORE) << "Workspace::stackAbove: closed window" << window << "cannot be restacked";
+        return;
+    }
+
+    Q_ASSERT(unconstrained_stacking_order.contains(reference));
+    if (reference == window) {
+        return;
+    }
+
+    unconstrained_stacking_order.removeAll(window);
+    unconstrained_stacking_order.insert(unconstrained_stacking_order.indexOf(reference) + 1, window);
+
+    m_focusChain->moveBeforeWindow(window, reference);
+    updateStackingOrder();
+}
+
 void Workspace::restackWindowUnderActive(Window *window)
 {
     if (!m_activeWindow || m_activeWindow == window || m_activeWindow->layer() != window->layer()) {

src/workspace.h

@@ -236,6 +236,7 @@ public:
     void lowerWindowRequest(Window *window);
     void restackWindowUnderActive(Window *window);
     void stackBelow(Window *window, Window *reference);
+    void stackAbove(Window *window, Window *reference);
     void raiseOrLowerWindow(Window *window);
     void updateStackingOrder(bool propagate_new_windows = false);
     void forceRestacking();