set-anchor

Turns anchoring on or off. This method can be overridden to affect or detect changes in the anchor state.

• (send a-wx:media-edit set-anchor on?) -> void
      on? : boolean

  If on? is not #f, then the selection will be automatically extended when cursor keys are used, otherwise anchoring is turned off. Anchoring is automatically turned off if the user does anything besides cursor movements.