paint-round-corners: fix widget positions not updating on zoom/pan

Added a rAF loop (same pattern as paint-gradient-editor) that watches
paper.view.matrix while the tool is active. When zoom or pan changes
the matrix key, drawWidgets() is called to reposition all corner handles.
The loop exits immediately when isToolActive is false, so there is no
overhead once the tool is deactivated.

Author: griffpatch

addons/paint-round-corners/userscript.js

@@ -719,6 +719,21 @@ export default async function ({ addon, msg }) {
     isToolActive = true;
     if (isSelectedClass) rcBtn.classList.add(isSelectedClass);
 
+    // Reposition widgets when the user zooms or pans (paper.view.matrix changes).
+    // Mirrors the same rAF pattern used by paint-gradient-editor.
+    let lastViewKey = "";
+    const viewSyncLoop = () => {
+      if (!isToolActive) return;
+      const m = paper.view.matrix;
+      const key = `${m.a.toFixed(3)},${m.tx.toFixed(1)},${m.ty.toFixed(1)}`;
+      if (key !== lastViewKey) {
+        lastViewKey = key;
+        drawWidgets();
+      }
+      requestAnimationFrame(viewSyncLoop);
+    };
+    requestAnimationFrame(viewSyncLoop);
+
     // Watch for tool switches (CHANGE_MODE), tab navigation, and undo/redo events.
     modeChangeHandler = ({ detail }) => {
       if (!isToolActive) return;