Add Desktops settings tab to control which virtual desktops Karousel operates on (#133)

* Add Desktops settings tab to control which virtual desktops Karousel operates on

* Fix cursor follow focus to only work on matched desktops

* Resolve review comments

- Implement a RegExp-based DesktopFilter.
- Add new config key tiledDesktops (String) with default ".*" (match all).
- Make DesktopManager return undefined for desktops that should not be tiled.
- Mark KWinDesktop.name as readonly.
- Replace multiline desktop editor in settings UI with a single-line QLineEdit (moved to top of Window Rules tab), shorten label to "Tiled desktops:" and add a tooltip with examples.

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>

package/contents/ui/config.ui

@@ -458,6 +458,30 @@
                             <string>Window Rules</string>
                         </attribute>
                         <layout class="QVBoxLayout">
+                            <item>
+                                <layout class="QHBoxLayout">
+                                    <item>
+                                        <widget class="QLabel" name="label_desktops">
+                                            <property name="text">
+                                                <string>Tiled desktops:</string>
+                                            </property>
+                                            <property name="wordWrap">
+                                                <bool>true</bool>
+                                            </property>
+                                        </widget>
+                                    </item>
+                                    <item>
+                                        <widget class="QLineEdit" name="kcfg_tiledDesktops">
+                                            <property name="font">
+                                                <font><family>Monospace</family></font>
+                                            </property>
+                                            <property name="toolTip">
+                                                <string>Regex string to match desktops. Default value is ".*". Example: "Desktop [1-3]"</string>
+                                            </property>
+                                        </widget>
+                                    </item>
+                                </layout>
+                            </item>
                             <item>
                                 <widget class="QPlainTextEdit" name="kcfg_windowRules">
                                     <property name="tabChangesFocus">

src/lib/config/config.ts

@@ -25,4 +25,5 @@ interface Config {
     tiledKeepBelow: boolean;
     floatingKeepAbove: boolean;
     windowRules: string;
+    tiledDesktops: string;
 }

src/lib/config/definition.ts

@@ -189,4 +189,9 @@ const configDef = [
         type: "String",
         default: defaultWindowRules,
     },
+    {
+        name: "tiledDesktops",
+        type: "String",
+        default: ".*",
+    },
 ];

src/lib/extern/kwin.ts

@@ -102,6 +102,7 @@ interface KwinDesktop {
     __brand: "KwinDesktop";
 
     readonly id: string;
+    readonly name: string;
 }
 
 interface ShortcutHandler extends QmlObject {

src/lib/keyBindings/Actions.ts

@@ -62,7 +62,11 @@ class Actions {
     };
 
     public readonly focusStart = (cm: ClientManager, dm: DesktopManager) => {
-        const grid = dm.getCurrentDesktop().grid;
+        const desktop = dm.getCurrentDesktop();
+        if (desktop === undefined) {
+            return;
+        }
+        const grid = desktop.grid;
         const firstColumn = grid.getFirstColumn();
         if (firstColumn === null) {
             return;
@@ -71,7 +75,11 @@ class Actions {
     };
 
     public readonly focusEnd = (cm: ClientManager, dm: DesktopManager) => {
-        const grid = dm.getCurrentDesktop().grid;
+        const desktop = dm.getCurrentDesktop();
+        if (desktop === undefined) {
+            return;
+        }
+        const grid = desktop.grid;
         const lastColumn = grid.getLastColumn();
         if (lastColumn === null) {
             return;
@@ -196,6 +204,9 @@ class Actions {
 
     public readonly columnsWidthEqualize = (cm: ClientManager, dm: DesktopManager) => {
         const desktop = dm.getCurrentDesktop();
+        if (desktop === undefined) {
+            return;
+        }
         const visibleRange = desktop.getCurrentVisibleRange();
         const visibleColumns = Array.from(desktop.grid.getVisibleColumns(visibleRange, true));
 
@@ -297,11 +308,18 @@ class Actions {
     };
 
     private readonly gridScroll = (desktopManager: DesktopManager, amount: number) => {
-        desktopManager.getCurrentDesktop().adjustScroll(amount, false);
+        const desktop = desktopManager.getCurrentDesktop();
+        if (desktop !== undefined) {
+            desktop.adjustScroll(amount, false);
+        }
     };
 
     public readonly gridScrollStart = (cm: ClientManager, dm: DesktopManager) => {
-        const grid = dm.getCurrentDesktop().grid;
+        const desktop = dm.getCurrentDesktop();
+        if (desktop === undefined) {
+            return;
+        }
+        const grid = desktop.grid;
         const firstColumn = grid.getFirstColumn();
         if (firstColumn === null) {
             return;
@@ -310,7 +328,11 @@ class Actions {
     };
 
     public readonly gridScrollEnd = (cm: ClientManager, dm: DesktopManager) => {
-        const grid = dm.getCurrentDesktop().grid;
+        const desktop = dm.getCurrentDesktop();
+        if (desktop === undefined) {
+            return;
+        }
+        const grid = desktop.grid;
         const lastColumn = grid.getLastColumn();
         if (lastColumn === null) {
             return;
@@ -328,7 +350,11 @@ class Actions {
     };
 
     public readonly gridScrollLeftColumn = (cm: ClientManager, dm: DesktopManager) => {
-        const grid = dm.getCurrentDesktop().grid;
+        const desktop = dm.getCurrentDesktop();
+        if (desktop === undefined) {
+            return;
+        }
+        const grid = desktop.grid;
         const column = grid.getLeftmostVisibleColumn(grid.desktop.getCurrentVisibleRange(), true);
         if (column === null) {
             return;
@@ -343,7 +369,11 @@ class Actions {
     };
 
     public readonly gridScrollRightColumn = (cm: ClientManager, dm: DesktopManager) => {
-        const grid = dm.getCurrentDesktop().grid;
+        const desktop = dm.getCurrentDesktop();
+        if (desktop === undefined) {
+            return;
+        }
+        const grid = desktop.grid;
         const column = grid.getRightmostVisibleColumn(grid.desktop.getCurrentVisibleRange(), true);
         if (column === null) {
             return;
@@ -362,7 +392,11 @@ class Actions {
     };
 
     public readonly focus = (columnIndex: number, cm: ClientManager, dm: DesktopManager) => {
-        const grid = dm.getCurrentDesktop().grid;
+        const desktop = dm.getCurrentDesktop();
+        if (desktop === undefined) {
+            return;
+        }
+        const grid = desktop.grid;
         const targetColumn = grid.getColumnAtIndex(columnIndex);
         if (targetColumn === null) {
             return;
@@ -396,7 +430,11 @@ class Actions {
         if (kwinDesktop === undefined) {
             return;
         }
-        const newGrid = dm.getDesktopInCurrentActivity(kwinDesktop).grid;
+        const newDesktop = dm.getDesktopInCurrentActivity(kwinDesktop);
+        if (newDesktop === undefined) {
+            return;
+        }
+        const newGrid = newDesktop.grid;
         if (newGrid === null || newGrid === oldGrid) {
             return;
         }
@@ -408,7 +446,11 @@ class Actions {
         if (kwinDesktop === undefined) {
             return;
         }
-        const newGrid = dm.getDesktopInCurrentActivity(kwinDesktop).grid;
+        const newDesktop = dm.getDesktopInCurrentActivity(kwinDesktop);
+        if (newDesktop === undefined) {
+            return;
+        }
+        const newGrid = newDesktop.grid;
         if (newGrid === null || newGrid === oldGrid) {
             return;
         }

src/lib/rules/DesktopFilter.ts

@@ -0,0 +1,29 @@
+class DesktopFilter {
+    private readonly desktopRegex: RegExp | null; // null means all desktops
+
+    constructor(desktopsConfig: string) {
+        this.desktopRegex = DesktopFilter.parseDesktopConfig(desktopsConfig);
+    }
+
+    public shouldWorkOnDesktop(kwinDesktop: KwinDesktop): boolean {
+        if (this.desktopRegex === null) {
+            return true; // Work on all desktops
+        }
+        return this.desktopRegex.test(kwinDesktop.name);
+    }
+
+    private static parseDesktopConfig(config: string): RegExp | null {
+        const trimmed = config.trim();
+
+        if (trimmed.length === 0) {
+            return null; // Empty config means work on all desktops
+        }
+
+        try {
+            return new RegExp(`^${trimmed}$`);
+        } catch (e) {
+            log(`Invalid regex pattern in tiledDesktops config: ${trimmed}. Working on all desktops.`);
+            return null; // Invalid regex means work on all desktops as fallback
+        }
+    }
+}

src/lib/world/ClientManager.ts

@@ -31,16 +31,16 @@ class ClientManager {
         console.assert(!this.hasClient(kwinClient));
 
         let constructState: (client: ClientWrapper) => ClientState.State;
+        let desktop: Desktop | undefined;
         if (kwinClient.dock) {
             constructState = () => new ClientState.Docked(this.world, kwinClient);
         } else if (
             Clients.canTileEver(kwinClient) &&
-            this.windowRuleEnforcer.shouldTile(kwinClient)
+            this.windowRuleEnforcer.shouldTile(kwinClient) &&
+            (desktop = this.desktopManager.getDesktopForClient(kwinClient)) !== undefined
         ) {
             Clients.makeTileable(kwinClient);
             console.assert(Clients.canTileNow(kwinClient));
-            const desktop = this.desktopManager.getDesktopForClient(kwinClient);
-            console.assert(desktop !== undefined);
             constructState = (client: ClientWrapper) => new ClientState.Tiled(this.world, client, desktop!.grid);
         } else {
             constructState = (client: ClientWrapper) => new ClientState.Floating(this.world, client, this.config, false);

src/lib/world/DesktopManager.ts

@@ -9,6 +9,7 @@ class DesktopManager {
         private readonly config: Desktop.Config,
         private readonly layoutConfig: LayoutConfig,
         private readonly focusPasser: FocusPassing.Passer,
+        private readonly desktopFilter: DesktopFilter,
         currentActivity: string,
         currentDesktop: KwinDesktop,
     ) {
@@ -19,10 +20,15 @@ class DesktopManager {
         this.selectedScreen = Workspace.activeScreen;
         this.kwinActivities = new Set(Workspace.activities);
         this.kwinDesktops = new Set(Workspace.desktops);
-        this.addDesktop(currentActivity, currentDesktop);
+        if (this.desktopFilter.shouldWorkOnDesktop(currentDesktop)) {
+            this.addDesktop(currentActivity, currentDesktop);
+        }
     }
 
     public getDesktop(activity: string, kwinDesktop: KwinDesktop) {
+        if (!this.desktopFilter.shouldWorkOnDesktop(kwinDesktop)) {
+            return undefined;
+        }
         const desktopKey = DesktopManager.getDesktopKey(activity, kwinDesktop);
         const desktop = this.desktops.get(desktopKey);
         if (desktop !== undefined) {

src/lib/world/World.ts

@@ -5,12 +5,10 @@ class World {
     private readonly workspaceSignalManager: SignalManager;
     private readonly shortcutActions: ShortcutAction[];
     private readonly screenResizedDelayer: Delayer;
-    private readonly cursorFollowsFocus: boolean;
 
     constructor(config: Config) {
         const focusPasser = new FocusPassing.Passer();
         this.workspaceSignalManager = initWorkspaceSignalHandlers(this, focusPasser);
-        this.cursorFollowsFocus = config.cursorFollowsFocus;
 
         let presetWidths = {
             next: (currentWidth: number, minWidth: number, maxWidth: number) => currentWidth,
@@ -70,6 +68,7 @@ class World {
             },
             layoutConfig,
             focusPasser,
+            new DesktopFilter(config.tiledDesktops),
             Workspace.currentActivity,
             Workspace.currentDesktop,
         );
@@ -98,12 +97,20 @@ class World {
     }
 
     private update() {
-        this.desktopManager.getCurrentDesktop().arrange();
-        this.moveCursorToFocus();
+        const currentDesktop = this.desktopManager.getCurrentDesktop();
+        if (currentDesktop !== undefined) {
+            currentDesktop.arrange();
+            this.moveCursorToFocus();
+        }
     }
 
     private moveCursorToFocus() {
-        if (this.cursorFollowsFocus && Workspace.activeWindow !== null) {
+        if (Workspace.activeWindow !== null) {
+            // Only move cursor for tiled windows
+            const tiledWindow = this.clientManager.findTiledWindow(Workspace.activeWindow);
+            if (tiledWindow === null) {
+                return;
+            }
             const cursorAlreadyInFocus = rectContainsPoint(Workspace.activeWindow.frameGeometry, Workspace.cursorPos);
             if (cursorAlreadyInFocus) {
                 return;
@@ -141,11 +148,21 @@ class World {
     }
 
     public gestureScroll(amount: number) {
-        this.do((clientManager, desktopManager) => desktopManager.getCurrentDesktop().gestureScroll(amount));
+        this.do((clientManager, desktopManager) => {
+            const currentDesktop = desktopManager.getCurrentDesktop();
+            if (currentDesktop !== undefined) {
+                currentDesktop.gestureScroll(amount);
+            }
+        });
     }
 
     public gestureScrollFinish() {
-        this.do((clientManager, desktopManager) => desktopManager.getCurrentDesktop().gestureScrollFinish());
+        this.do((clientManager, desktopManager) => {
+            const currentDesktop = desktopManager.getCurrentDesktop();
+            if (currentDesktop !== undefined) {
+                currentDesktop.gestureScrollFinish();
+            }
+        });
     }
 
     public destroy() {

src/tests/flows/cursorFollowsFocus.ts

@@ -34,3 +34,49 @@ tests.register("Drag tiled window, untile", 10, () => {
     Workspace.activeWindow = null;
     Assert.assert(pointEquals(Workspace.cursorPos, lastCursorPos), { message: "Cursor should not have been moved" });
 });
+
+tests.register("Cursor follows focus only on matched desktops", 1, () => {
+    // Test that cursor follow focus only works for windows on matched desktops (tiled windows)
+    const config = getDefaultConfig();
+    config.cursorFollowsFocus = true;
+    config.tiledDesktops = "^Desktop 1$"; // Only work on Desktop 1
+    const { workspaceMock, world } = init(config);
+
+    // Create a client on Desktop 1 (matched desktop) - should be tiled
+    const client1 = new MockKwinClient();
+    client1.desktops = [workspaceMock.desktops[0]]; // Desktop 1
+    workspaceMock.createWindows(client1);
+    
+    // Create a client on Desktop 2 (non-matched desktop) - should be floating
+    const client2 = new MockKwinClient();
+    client2.desktops = [workspaceMock.desktops[1]]; // Desktop 2
+    workspaceMock.createWindows(client2);
+
+    // Set initial cursor position outside both windows
+    const initialCursorPos = new MockQmlPoint(10, 10);
+    workspaceMock.cursorPos = initialCursorPos.clone();
+
+    // Test 1: Focus client1 on matched desktop (Desktop 1) - cursor should move
+    workspaceMock.currentDesktop = workspaceMock.desktops[0]; // Switch to Desktop 1
+    Workspace.activeWindow = client1;
+    world.do(() => {});
+    Assert.assert(rectContainsPoint(client1.frameGeometry, Workspace.cursorPos), 
+        { message: "Cursor should have moved to tiled window on matched desktop" });
+
+    // Test 2: Switch to non-matched desktop (Desktop 2) and focus client2 - cursor should NOT move
+    workspaceMock.cursorPos = initialCursorPos.clone();
+    workspaceMock.currentDesktop = workspaceMock.desktops[1]; // Switch to Desktop 2
+    Workspace.activeWindow = client2;
+    world.do(() => {});
+    Assert.assert(pointEquals(Workspace.cursorPos, initialCursorPos), 
+        { message: "Cursor should NOT move on non-matched desktop" });
+
+    // Test 3: Even if we focus client1 (tiled) while on Desktop 2, cursor should NOT move
+    // because the current desktop is not matched
+    workspaceMock.cursorPos = initialCursorPos.clone();
+    workspaceMock.currentDesktop = workspaceMock.desktops[1]; // Stay on Desktop 2
+    Workspace.activeWindow = client1;
+    world.do(() => {});
+    Assert.assert(pointEquals(Workspace.cursorPos, initialCursorPos), 
+        { message: "Cursor should NOT move even for tiled window when current desktop is not matched" });
+});

src/tests/flows/desktopFiltering.ts

@@ -0,0 +1,73 @@
+tests.register("Desktop filtering", 1, () => {
+    // Test 1: Default config should work on all desktops
+    const config1 = getDefaultConfig();
+    const { workspaceMock: wm1, world: world1 } = init(config1);
+    
+    const client1 = new MockKwinClient();
+    client1.desktops = [wm1.desktops[0]];
+    wm1.createWindows(client1);
+    
+    world1.do((clientManager) => {
+        Assert.tiledClient(clientManager, client1, { message: "Client should be tiled on desktop1 with default config (*)" });
+    });
+});
+
+tests.register("Desktop filtering - specific desktop", 1, () => {
+    // Test 2: Specific desktop name - should work only on matching desktop
+    const config2 = getDefaultConfig();
+    config2.tiledDesktops = "^Desktop 1$";
+    const { workspaceMock: wm2, world: world2 } = init(config2);
+    
+    const client1 = new MockKwinClient();
+    client1.desktops = [wm2.desktops[0]]; // Desktop 1
+    wm2.createWindows(client1);
+    world2.do((clientManager) => {
+        Assert.tiledClient(clientManager, client1, { message: "Client should be tiled on Desktop 1" });
+    });
+    
+    wm2.removeWindow(client1);
+    
+    const client2 = new MockKwinClient();
+    client2.desktops = [wm2.desktops[1]]; // Desktop 2
+    wm2.createWindows(client2);
+    world2.do((clientManager) => {
+        Assert.notTiledClient(clientManager, client2, { message: "Client should NOT be tiled on Desktop 2" });
+    });
+});
+
+tests.register("Desktop filtering - multiple desktops", 1, () => {
+    // Test 3: Multiple desktop names using regex alternation
+    const config3 = getDefaultConfig();
+    config3.tiledDesktops = "^Desktop [12]$";
+    const { workspaceMock: wm3, world: world3 } = init(config3);
+    
+    const client1 = new MockKwinClient();
+    client1.desktops = [wm3.desktops[0]]; // Desktop 1
+    wm3.createWindows(client1);
+    world3.do((clientManager) => {
+        Assert.tiledClient(clientManager, client1, { message: "Client should be tiled on Desktop 1" });
+    });
+    
+    wm3.removeWindow(client1);
+    
+    const client2 = new MockKwinClient();
+    client2.desktops = [wm3.desktops[1]]; // Desktop 2
+    wm3.createWindows(client2);
+    world3.do((clientManager) => {
+        Assert.tiledClient(clientManager, client2, { message: "Client should be tiled on Desktop 2" });
+    });
+});
+
+tests.register("Desktop filtering - windows on multiple desktops", 1, () => {
+    // Test 4: Windows on multiple desktops should not be tiled (fallback to floating)
+    const config4 = getDefaultConfig();
+    config4.tiledDesktops = ".*";
+    const { workspaceMock: wm4, world: world4 } = init(config4);
+    
+    const client1 = new MockKwinClient();
+    client1.desktops = [wm4.desktops[0], wm4.desktops[1]]; // Multiple desktops
+    wm4.createWindows(client1);
+    world4.do((clientManager) => {
+        Assert.notTiledClient(clientManager, client1, { message: "Client on multiple desktops should not be tiled" });
+    });
+});

src/tests/units/rules/DesktopFilter.ts

@@ -0,0 +1,41 @@
+tests.register("DesktopFilter", 1, () => {
+    const desktop1 = { __brand: "KwinDesktop" as const, id: "1", name: "Desktop 1" };
+    const desktop2 = { __brand: "KwinDesktop" as const, id: "2", name: "Work" };
+    const desktop3 = { __brand: "KwinDesktop" as const, id: "3", name: "Desktop 2" };
+
+    // Test 1: Empty config means all desktops
+    let filter = new DesktopFilter("");
+    Assert.assert(filter.shouldWorkOnDesktop(desktop1), { message: "Empty config should work on desktop1" });
+    Assert.assert(filter.shouldWorkOnDesktop(desktop2), { message: "Empty config should work on desktop2" });
+
+    // Test 2: Whitespace only means all desktops
+    filter = new DesktopFilter("  \n  \n  ");
+    Assert.assert(filter.shouldWorkOnDesktop(desktop1), { message: "Whitespace only should work on desktop1" });
+    Assert.assert(filter.shouldWorkOnDesktop(desktop2), { message: "Whitespace only should work on desktop2" });
+
+    // Test 3: Match all regex pattern
+    filter = new DesktopFilter(".*");
+    Assert.assert(filter.shouldWorkOnDesktop(desktop1), { message: "Regex '.*' should work on desktop1" });
+    Assert.assert(filter.shouldWorkOnDesktop(desktop2), { message: "Regex '.*' should work on desktop2" });
+
+    // Test 4: Partial match without anchors
+    filter = new DesktopFilter("Work");
+    Assert.assert(!filter.shouldWorkOnDesktop(desktop1), { message: "Should not work on desktop1" });
+    Assert.assert(filter.shouldWorkOnDesktop(desktop2), { message: "Should work on desktop2 containing 'Work'" });
+
+    // Test 5: Regex alternation for multiple desktops
+    filter = new DesktopFilter("Desktop 1|Work");
+    Assert.assert(filter.shouldWorkOnDesktop(desktop1), { message: "Should work on desktop1" });
+    Assert.assert(filter.shouldWorkOnDesktop(desktop2), { message: "Should work on desktop2" });
+    Assert.assert(!filter.shouldWorkOnDesktop(desktop3), { message: "Should not work on desktop3" });
+
+    // Test 6: Regex pattern with character class
+    filter = new DesktopFilter("Desktop [12]");
+    Assert.assert(filter.shouldWorkOnDesktop(desktop1), { message: "Should work on desktop1" });
+    Assert.assert(!filter.shouldWorkOnDesktop(desktop2), { message: "Should not work on desktop2" });
+    Assert.assert(filter.shouldWorkOnDesktop(desktop3), { message: "Should work on desktop3" });
+
+    // Test 7: Case-sensitive matching
+    filter = new DesktopFilter("work");
+    Assert.assert(!filter.shouldWorkOnDesktop(desktop2), { message: "Should not work on desktop2 (case mismatch)" });
+});

src/tests/utils/mocks/MockKwinClient.ts

@@ -52,6 +52,7 @@ class MockKwinClient {
         this.windowedFrameGeometry = _frameGeometry.clone();
         this.transient = transientFor !== null;
         this._desktops = [Workspace.currentDesktop];
+        this.activities = [Workspace.currentActivity];
     }
 
     setMaximize(vertically: boolean, horizontally: boolean) {

src/tests/utils/mocks/MockWorkspace.ts

@@ -3,8 +3,8 @@ class MockWorkspace {
 
     public activities = ["test-activity"];
     public desktops: KwinDesktop[] = [
-        { __brand: "KwinDesktop", id: "desktop1" },
-        { __brand: "KwinDesktop", id: "desktop2" },
+        { __brand: "KwinDesktop", id: "desktop1", name: "Desktop 1" },
+        { __brand: "KwinDesktop", id: "desktop2", name: "Desktop 2" },
     ];
     public currentActivity = this.activities[0];
     public activeScreen: Output = { __brand: "Output" };