desktop/window: go back to the previously focused window in a group (#12763)

hyprtester/src/tests/main/window.cpp

@@ -373,6 +373,41 @@ static void testMaximizeSize() {
     EXPECT(Tests::windowCount(), 0);
 }
 
+static void testGroupFallbackFocus() {
+    NLog::log("{}Testing group fallback focus", Colors::GREEN);
+
+    EXPECT(spawnKitty("kitty_A"), true);
+
+    OK(getFromSocket("/dispatch togglegroup"));
+
+    EXPECT(spawnKitty("kitty_B"), true);
+    EXPECT(spawnKitty("kitty_C"), true);
+    EXPECT(spawnKitty("kitty_D"), true);
+
+    {
+        auto str = getFromSocket("/activewindow");
+        EXPECT(str.contains("class: kitty_D"), true);
+    }
+
+    OK(getFromSocket("/dispatch focuswindow class:kitty_B"));
+    OK(getFromSocket("/dispatch focuswindow class:kitty_D"));
+    OK(getFromSocket("/dispatch killactive"));
+
+    Tests::waitUntilWindowsN(3);
+
+    // Focus must return to the last focus, in this case B.
+    {
+        auto str = getFromSocket("/activewindow");
+        EXPECT(str.contains("class: kitty_B"), true);
+    }
+
+    NLog::log("{}Killing all windows", Colors::YELLOW);
+    Tests::killAllWindows();
+
+    NLog::log("{}Expecting 0 windows", Colors::YELLOW);
+    EXPECT(Tests::windowCount(), 0);
+}
+
 static void testBringActiveToTopMouseMovement() {
     NLog::log("{}Testing bringactivetotop mouse movement", Colors::GREEN);
 
@@ -847,6 +882,8 @@ static bool test() {
 
     testBringActiveToTopMouseMovement();
 
+    testGroupFallbackFocus();
+
     NLog::log("{}Reloading config", Colors::YELLOW);
     OK(getFromSocket("/reload"));
 

src/desktop/view/Window.cpp

@@ -2437,7 +2437,24 @@ void CWindow::unmapWindow() {
     }
 
     bool      wasLastWindow = false;
-    PHLWINDOW nextInGroup   = m_groupData.pNextWindow ? m_groupData.pNextWindow.lock() : nullptr;
+    PHLWINDOW nextInGroup   = [this] -> PHLWINDOW {
+        if (!m_groupData.pNextWindow)
+            return nullptr;
+
+        // walk the history to find a suitable window
+        const auto HISTORY = Desktop::History::windowTracker()->fullHistory();
+        for (const auto& w : HISTORY | std::views::reverse) {
+            if (!w || !w->m_isMapped || w == m_self)
+                continue;
+
+            if (!hasInGroup(w.lock()))
+                continue;
+
+            return w.lock();
+        }
+
+        return nullptr;
+    }();
 
     if (m_self.lock() == Desktop::focusState()->window()) {
         wasLastWindow = true;