set-anchor

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

• (send a-text:info-mixin 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.

  Calls the anchor-status-changed method of the frame that is viewing this object. It uses get-canvas to get the canvas for this frame, and uses that canvas's top-level-window<%> as the frame.