prevent off-screen transients (fixes #11)

src/layout/ScrollView.ts

@@ -127,6 +127,7 @@ class ScrollView {
         // TODO (optimization): only arrange visible windows
         this.updateArea();
         this.grid.arrange(this.tilingArea.x - this.scrollX);
+        this.world.ensureFocusedTransientsVisible(); // TODO: refactor - call from elsewhere
     }
 
     public onGridWidthChanged() {

src/world/ClientWrapper.ts

@@ -119,6 +119,25 @@ class ClientWrapper {
         this.transients.splice(i, 1);
     }
 
+    public ensureTransientsVisible(screenSize: QRect) {
+        for (const transient of this.transients) {
+            if (transient.stateManager.getState() instanceof ClientStateFloating) {
+                transient.ensureVisible(screenSize);
+                transient.ensureTransientsVisible(screenSize);
+
+            }
+        }
+    }
+
+    public ensureVisible(screenSize: QRect) {
+        const frame = this.kwinClient.frameGeometry;
+        if (frame.left < 0) {
+            frame.x = 0;
+        } else if (frame.right > screenSize.width) {
+            frame.x = screenSize.width - frame.width;
+        }
+    }
+
     destroy(passFocus: boolean) {
         this.stateManager.destroy(passFocus);
         this.signalManager.destroy();

src/world/World.ts

@@ -113,6 +113,12 @@ class World {
         return transientFor;
     }
 
+    public ensureFocusedTransientsVisible() {
+        this.doIfTiledFocused(true, (window, column, grid) => {
+            window.client.ensureTransientsVisible(grid.container.clientArea);
+        });
+    }
+
     minimizeClient(kwinClient: AbstractClient) {
         const client = this.clientMap.get(kwinClient);
         if (client === undefined) {