nvda

c7509267 - Fix enable/disable of highlighter locking up the system (PR #10520)

Fix enable/disable of highlighter locking up the system (PR #10520) When disabling the highlighter, NVDA would sometimes locked up. This was because the thread is joined before it was told to terminate. Calling HighlightWindow.updateLocationForDisplays blocked the main thread when calling SetWindowPos. The cause of this was that the highlighter window had the NVDA main frame as its parent. - The highlighter no longer has the NVDA main window as its parent. To ensure we're never blocked by wx. - CustomWindow classes may now only have one instance. This is because the window class is created with the window and destroyed with it. Debugging this issue revealed that sometimes, multiple instances were created when reinitializing too quickly, but that should never happen. - The highlighter now fails to initialize if something goes wrong in the highlighter thread