fix: select last used window when moving focus up or to the left

When bismuth finds two windows are equally distanced from the current
window, the last used window will be chosen when focus is moved via
keyboard shortcuts.

Before, the closest windows were always determined based on the top-left
corner of each window. This is fine when focusing a window below or to
the right, since adjacent edge aligned windows will have the top-left
corner on the same line either horizontally or vertically.

When moving the focus up or to the left, however, this is no longer
guaranteed. Even though the bottom of two candidate windows might be
edge to edge with the current window, the top-left corners might be on
different levels since the candidate windows don't have to have the same
height. To correctly select the last used adjacent edge aligned window
to the top or to the left, the bottom-right corner will be used to find
the closest windows.

src/kwinscript/engine/index.ts

@@ -630,22 +630,27 @@ export class EngineImpl implements Engine {
     dir: Direction
   ): EngineWindow | null {
     let vertical: boolean;
+    let downOrRight: boolean;
     let sign: -1 | 1;
     switch (dir) {
       case "up":
         vertical = true;
+        downOrRight = false;
         sign = -1;
         break;
       case "down":
         vertical = true;
+        downOrRight = true;
         sign = 1;
         break;
       case "left":
         vertical = false;
+        downOrRight = false;
         sign = -1;
         break;
       case "right":
         vertical = false;
+        downOrRight = true;
         sign = 1;
         break;
       default:
@@ -680,21 +685,34 @@ export class EngineImpl implements Engine {
       return null;
     }
 
+    // When moving downOrRight, check the top-left corner for closest window
+    // When moving not downOrRight, check the bottom-right corner for closest window
     const min =
       sign *
-      candidates.reduce(
-        vertical
-          ? (prevMin, tile): number => Math.min(tile.geometry.y * sign, prevMin)
-          : (prevMin, tile): number =>
-              Math.min(tile.geometry.x * sign, prevMin),
-        Infinity
-      );
-
-    const closest = candidates.filter(
-      vertical
-        ? (tile): boolean => tile.geometry.y === min
-        : (tile): boolean => tile.geometry.x === min
-    );
+      candidates.reduce((prevMin, tile): number => {
+        if (vertical) {
+          return downOrRight
+            ? Math.min(tile.geometry.y * sign, prevMin)
+            : Math.min(tile.geometry.maxY * sign, prevMin);
+        } else {
+          return downOrRight
+            ? Math.min(tile.geometry.x * sign, prevMin)
+            : Math.min(tile.geometry.maxX * sign, prevMin);
+        }
+      }, Infinity);
+
+    const closest = candidates.filter((tile): boolean => {
+      // adjust min for potential pixel wide misalignment of tiles
+      if (vertical) {
+        return downOrRight
+          ? tile.geometry.y < min + 5
+          : tile.geometry.maxY > min - 5;
+      } else {
+        return downOrRight
+          ? tile.geometry.x < min + 5
+          : tile.geometry.maxX > min - 5;
+      }
+    });
 
     return closest.sort((a, b) => b.timestamp - a.timestamp)[0];
   }