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

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: {