Block selection flickers when the cursor is above+right from the starting point #1991
Description
Repro:
- create a buffer which has more lines than the window height
- go to the last line, around the center of the line
- press Ctrl+V to enter block selection mode
- move up and right with the cursor
- notice that there is a "temporary" cursor flickering the the bottom right corner of the selection
- if you keep moving the cursor upwards so the bottom of the selection is no longer visible, then moving the cursor will make the whole buffer flicker (temporarily the bottom of the selection is visible)
- the visualization of the selection is also incorrect (only part of the selection is visualized. If you keep moving upwards, the selection is not visible at all)
- if I move the cursor to the left, so the block becomes defined by the bottom-right/top-left corner, the problem doesn't happen.
Here's a video showing the problem (it doesn't exactly show the full problem, I used gif-screencast, and apparently it doesn't save all the frames, so some of the flickering/temporary cursor flickering not visible):
