The interplay between Backspace and CtrlH is complex (on Windows) and not documented

[vovcacik]

When user needs to distinguish between physically hitting backspace key and ctrl+h combo, the key events coming from tcell are hard to reason about. It is complex enough to make test cases for all combinations.

// redacted tests for brevity
type giveKey struct {
	Type tcell.Key
	Char rune
	Mods tcell.ModMask
}
giveKey{tcell.KeyCtrlH, rune(tcell.KeyCtrlH), tcell.ModNone},                    // actual "Backspace" keystroke
giveKey{tcell.KeyCtrlH, rune(tcell.KeyCtrlH), tcell.ModAlt},                     // actual "Alt+Backspace" keystroke
giveKey{tcell.KeyDEL,   rune(tcell.KeyDEL),   tcell.ModCtrl},                    // actual "Ctrl+Backspace" keystroke
giveKey{tcell.KeyCtrlH, rune(tcell.KeyCtrlH), tcell.ModShift},                   // actual "Shift+Backspace" keystroke
giveKey{tcell.KeyCtrlH, 0,                    tcell.ModCtrl | tcell.ModAlt},     // actual "Ctrl+Alt+Backspace" keystroke
giveKey{tcell.KeyCtrlH, 0,                    tcell.ModCtrl | tcell.ModShift},   // actual "Ctrl+Shift+Backspace" keystroke
giveKey{tcell.KeyCtrlH, rune(tcell.KeyCtrlH), tcell.ModShift | tcell.ModAlt},    // actual "Shift+Alt+Backspace" keystroke
                                                                                 // actual "Ctrl+Shift+Alt+Backspace" keystroke
giveKey{tcell.KeyCtrlH, 0,                    tcell.ModCtrl | tcell.ModAlt | tcell.ModShift},
giveKey{tcell.KeyCtrlH, rune(tcell.KeyCtrlH), tcell.ModCtrl},                    // actual "Ctrl+H" keystroke
giveKey{tcell.KeyCtrlH, rune(tcell.KeyCtrlH), tcell.ModCtrl | tcell.ModShift},   // actual "Ctrl+Shift+H" keystroke

https://github.com/junegunn/fzf/blob/5fc78e4584eface9f2055ee7c31c2ae8c5cedc87/src/tui/tcell_test.go#L113-L123

[gdamore]

So it turn out that there is a reason this is hard to reason about -- generally the underlying terminals (outside of Windows which is a special case) send CTRL-H as Backspace (or Delete, which is another confusing thing).

On Windows we get to know precisely which keys you pressed, but we also want the code to portable to other platforms. However, because with Windows we get the modifier keys we do actually send the modifiers we get.

[vovcacik]

Especially seeing tcell.KeyDEL on windows was strange, I think the OS itself doesn't use the 0x7F.

I noticed few other issues related to mysteries of backspace, so I wanted to file this issues as a memo. Feel free to close it.

[gdamore]

Ok. Will do so. There is not a lot we can with some of this.