This is probably due to a run loop being used for drag. We should probably disable dragging if asyncify is off as drag hogs the main thread.

Reproduction steps:

• build the dialogs manual test for WASM (without asyncify):
  • qtbase/tests/manual/dialogs/
• run it
• select the text in the Name filters text area
• drag the selected text

Result:

Apparent hang

Proposed solution:

Disable drag when asyncify is off since we cannot use the run loop then.