fix(super-editor): prevent cursor jump when changing font from toolbar (#2468)

When the user selects a font from the toolbar dropdown, the hidden
ProseMirror editor loses focus. On re-focus, the browser places the DOM
selection at an arbitrary position inside the off-screen contenteditable
(left: -9999px). ProseMirror's DOMObserver reads this stale position via
a selectionchange event and overwrites PM state, causing the cursor to
jump to position 2 (near the top of the document).

The wrapped focus in PresentationEditor only called view.dom.focus()
without calling selectionToDOM(), unlike ProseMirror's original focus()
which stops the observer, focuses, syncs the selection, then restarts.

Fix: call view.domObserver.suppressSelectionUpdates() after focusing when
the editor was not previously focused. This tells PM to re-apply its own
selection to the DOM instead of reading the stale browser position.

Author: tupizz

packages/super-editor/src/core/presentation-editor/PresentationEditor.ts

@@ -753,6 +753,7 @@ export class PresentationEditor extends EventEmitter {
 
       const beforeX = win.scrollX;
       const beforeY = win.scrollY;
+      const alreadyFocused = view.hasFocus();
       let focused = false;
 
       // Strategy 1: Try focus with preventScroll option (modern browsers)
@@ -791,6 +792,16 @@ export class PresentationEditor extends EventEmitter {
         }
       }
 
+      // When the editor was not focused before, the browser places the DOM selection
+      // at an arbitrary position inside the off-screen contenteditable. ProseMirror's
+      // DOMObserver would read this stale position via a selectionchange event and
+      // overwrite PM state, causing the cursor to jump. Suppress selection updates
+      // for the next 50ms so PM re-applies its own selection to the DOM instead.
+      if (!alreadyFocused) {
+        // eslint-disable-next-line @typescript-eslint/no-explicit-any
+        (view as any).domObserver.suppressSelectionUpdates();
+      }
+
       // Restore scroll position if any focus attempt changed it
       if (win.scrollX !== beforeX || win.scrollY !== beforeY) {
         win.scrollTo(beforeX, beforeY);

packages/super-editor/src/core/presentation-editor/tests/PresentationEditor.draggableFocus.test.ts

@@ -118,6 +118,12 @@ vi.mock('../../Editor.js', () => {
           focus: function () {
             // Plain function that can be wrapped
           },
+          hasFocus: function () {
+            return domElement === domElement.ownerDocument.activeElement;
+          },
+          domObserver: {
+            suppressSelectionUpdates: vi.fn(),
+          },
           dispatch: vi.fn(),
         },
         options: {

packages/super-editor/src/core/presentation-editor/tests/PresentationEditor.focusWrapping.test.ts

@@ -133,6 +133,12 @@ vi.mock('../../Editor.js', () => {
           focus: function () {
             // Plain function that can be wrapped
           },
+          hasFocus: function () {
+            return domElement === domElement.ownerDocument.activeElement;
+          },
+          domObserver: {
+            suppressSelectionUpdates: vi.fn(),
+          },
           dispatch: vi.fn(),
         },
         options: {