Theme preview doesn't return theme to normal when navigating command history

[Omnikar]

Summary

The theme preview when using :theme will keep the previewed theme if you switch away from the command using history navigation.

Reproduction Steps

1. Enter any (not necessarily valid) command, that is not a :theme command, such as :abc<ret>.
2. Type :theme and hover the completion over a theme other than the currently selected one, thus previewing it.
3. Press the up arrow key, causing the command to switch to the one entered in step 1.
4. Press <esc>, exiting the command prompt.

The previewed theme will persist after the command is switched away from using the up arrow key.

Helix log

Nothing relevant

Platform

MacOS

Terminal Emulator

iTerm2 v3.4.16

Helix Version

Helix 22.08

[jharrilim]

I can make the following changes in a PR, but the gist of it is we need to:

1. Ensure that history navigation aborts the previous command. This can be done by changing

helix/helix-term/src/ui/prompt.rs

Lines 564 to 575 in ec28b2b

	ctrl!('p') | key!(Up) => {
	if let Some(register) = self.history_register {
	self.change_history(cx, register, CompletionDirection::Backward);
	(self.callback_fn)(cx, &self.line, PromptEvent::Update);
	}
	}
	ctrl!('n') | key!(Down) => {
	if let Some(register) = self.history_register {
	self.change_history(cx, register, CompletionDirection::Forward);
	(self.callback_fn)(cx, &self.line, PromptEvent::Update);
	}
	}

to:

            ctrl!('p') | key!(Up) => {
                if let Some(register) = self.history_register {
                    (self.callback_fn)(cx, &self.line, PromptEvent::Abort);
                    let register = cx.editor.registers.get_mut(register);
                    self.change_history(register.read(), CompletionDirection::Backward);
                    (self.callback_fn)(cx, &self.line, PromptEvent::Update);
                }
            }
            ctrl!('n') | key!(Down) => {
                if let Some(register) = self.history_register {
                    (self.callback_fn)(cx, &self.line, PromptEvent::Abort);
                    let register = cx.editor.registers.get_mut(register);
                    self.change_history(register.read(), CompletionDirection::Forward);
                    (self.callback_fn)(cx, &self.line, PromptEvent::Update);
                }
            }

2. We need to ensure the completion items are updated too. This can be done by using the following code in the above functions after change_history:

helix/helix-term/src/ui/prompt.rs

Lines 590 to 615 in ec28b2b

	self.completion = cx
	.editor
	.registers
	.inner()
	.iter()
	.map(|(ch, reg)| {
	let content = reg
	.read()
	.get(0)
	.and_then(|s| s.lines().next().to_owned())
	.unwrap_or_default();
	(0.., format!("{} {}", ch, &content).into())
	})
	.collect();
	self.next_char_handler = Some(Box::new(|prompt, c, context| {
	prompt.insert_str(
	context
	.editor
	.registers
	.read(c)
	.and_then(|r| r.first())
	.map_or("", |r| r.as_str()),
	context.editor,
	);
	}));
	(self.callback_fn)(cx, &self.line, PromptEvent::Update);

---

Unrelated to the issue above but discovered along the way: The preview isn't rolled back if you hold backspace and then enter a new command.

eg.

1. type :theme acme
2. hold backspace until it's just :
3. type :open README.md and press enter

This requires a change in this part:

helix/helix-term/src/commands/typed.rs

Lines 717 to 726 in ec28b2b

	PromptEvent::Update => {
	if let Some(theme_name) = args.first() {
	if let Ok(theme) = cx.editor.theme_loader.load(theme_name) {
	if !(true_color || theme.is_16_color()) {
	bail!("Unsupported theme: theme requires true color support");
	}
	cx.editor.set_theme_preview(theme);
	};
	};
	}

to:

        PromptEvent::Update => {
            if args.is_empty() {
                cx.editor.unset_theme_preview();
            } else if let Some(theme_name) = args.first() {
                if let Ok(theme) = cx.editor.theme_loader.load(theme_name) {
                    if !(true_color || theme.is_16_color()) {
                        bail!("Unsupported theme: theme requires true color support");
                    }
                    cx.editor.set_theme_preview(theme);
                };
            };
        }