Summary of the Pull Request

This is a pair of related fixes to conpty. For both of these bugs, the root cause was that the cursor was getting set to Off in conpty. Without the CursorBlinkerTimer, the cursor would remain off, and frames that only had cursor movements would not update the cursor position in the terminal.

References

PR Checklist

• Closes Curses programming: cursor handled incorrectly #4102
• Closes Emacs cursor displayed incorrectly #2642
• Closes MSYS2 bash: Cursor display doesn't follow arrow keys after running Emacs #2697
• I work here
• Tests added/passed
• [n/a] Requires documentation to be updated

Detailed Description of the Pull Request / Additional comments

Recall that there's a bunch of cursor state that's hard to parse without looking up:

• Visibility This controls whether the cursor is visible at all, regardless if it's been blinked on or off
• Blinking controls whether the blinker timer should do something, or leave the cursor alone.
• IsOn: When the cursor is blinking, this alternates between true and false.

The trick here is that we only TriggerCursorMoved when the cursor is On, and there are some scenarios where the cursor is manually set to off.

Fundamentally, these two bugs are similar cases, but they are triggered by different things:

• Emacs cursor displayed incorrectly #2642 was caused by DoSrvPrivateAllowCursorBlinking(false) (^[[?12l) also manually turning the cursor off.
• Curses programming: cursor handled incorrectly #4102 was caused by the client calling SetConsoleScreenBuffer to change the active buffer. win-curses actually uses that API instead of the alt buffer.