fix(tiling): Windows launching onto window that isn't focused

Author: LinuxHeki

src/auto_tiler.ts

@@ -656,7 +656,7 @@ export class AutoTiler {
             return Err('ignoring focus');
         }
 
-        const prev = ext.prev_focused[1]
+        const prev = ext.previously_focused(win)
 
         if (!prev) {
             return Err('no window has been previously focused');

src/extension.ts

@@ -152,7 +152,7 @@ export class Ext extends Ecs.System<ExtEvent> {
     injections: Array<Injection> = new Array();
 
     /** The window that was focused before the last window */
-    prev_focused: [null | Entity, null | Entity] = [null, null];
+    private prev_focused: [null | Entity, null | Entity] = [null, null];
 
     tween_signals: Map<string, [SignalID, any]> = new Map();
 
@@ -789,8 +789,11 @@ export class Ext extends Ecs.System<ExtEvent> {
             this.exception_add(win)
         }
 
-        this.prev_focused[0] = this.prev_focused[1];
-        this.prev_focused[1] = win.entity;
+                // Track history of focused windows, but do not permit duplicates.
+        if (this.prev_focused[1] !== win.entity) {
+            this.prev_focused[0] = this.prev_focused[1];
+            this.prev_focused[1] = win.entity;
+        }
 
         // Update the active tab in the stack.
         if (null !== this.auto_tiler && null !== win.stack) {
@@ -1063,6 +1066,17 @@ export class Ext extends Ecs.System<ExtEvent> {
             this.tiler.snap(this, win);
         }
     }
+    
+    previously_focused(active: Window.ShellWindow): null | Ecs.Entity {
+        for (const id of [1, 0]) {
+            const prev = this.prev_focused[id]
+            if (prev && ! Ecs.entity_eq(active.entity, prev)) {
+                return prev;
+            }
+        }
+
+        return null
+    }
 
     movement_is_valid(win: Window.ShellWindow, movement: movement.Movement) {
         if ((movement & Movement.SHRINK) !== 0) {