1265105 - Windows widget does not receive an eMouseUp at the end of a drag session

Status: NEW

(Core :: Widget: Win32, defect, P3)

Description

[Botond Ballo [:botond]]

STR:
  Drag a link or a piece of selected text in the browser window.
  A test page can be found in bug 1260018.

Expected results:
  Widget receives an eMouseDown event at the start of the drag,
  eMouseMove events during the drag, an an eMouseUp event at
  the end of the drag.

Actual results:
  Widget receives the eMouseDown and eMouseMove events, but
  does not receive an eMouseUp event.

The proximate reason for this is that the widget window's WindowProc does not receive the native WM_LBUTTONUP event that usually generates the Gecko eMouseUp event. I don't know why that happens in turn. Some discussion on this topic can be found in bug 1260018 comment 19 through bug 1260018 comment 22. I'd rather not block bug 1260018 on this issue though, so I'm splitting it out here.

Note that on Linux, the widget does receive an eMouseUp event at the end of the drag.