Show infobox to hint textobjects with mi and ma (#1686)

* Show infobox to hint textobjects with `mi` and `ma`

* Add note to infobox than any pair of characters will work too

The wording could probably be a little more clear, but I wanted to
keep it short but still accurate.

* Don't allocate a vec for the static help text

* Fix bug where `mi<esc>` would swallow next input and persist infobox

* Better help text for arbitrary pair matching in textobject selection

* Add way to add fake pending key data below status, use with `mi`/`ma`

This is a bit hacky as it makes use of global state which will end
up managed in multiple places, but has precedent in the way autoinfo
works. There should probably be a bigger refactor to handle this
kind of state better.

* Return early on anything other than `mi` and `ma` for autoinfo

* Remove "ascii" from help text with `mi` and `ma`

* Update helix-term/src/ui/editor.rs

Co-authored-by: Blaž Hrastnik <blaz@mxxn.io>

helix-term/src/commands.rs

@@ -5353,7 +5353,10 @@ fn select_textobject_inner(cx: &mut Context) {
 
 fn select_textobject(cx: &mut Context, objtype: textobject::TextObject) {
     let count = cx.count();
+
     cx.on_next_key(move |cx, event| {
+        cx.editor.autoinfo = None;
+        cx.editor.pseudo_pending = None;
         if let Some(ch) = event.char() {
             let textobject = move |editor: &mut Editor| {
                 let (view, doc) = current!(editor);
@@ -5402,7 +5405,32 @@ fn select_textobject(cx: &mut Context, objtype: textobject::TextObject) {
             textobject(cx.editor);
             cx.editor.last_motion = Some(Motion(Box::new(textobject)));
         }
-    })
+    });
+
+    if let Some((title, abbrev)) = match objtype {
+        textobject::TextObject::Inside => Some(("Match inside", "mi")),
+        textobject::TextObject::Around => Some(("Match around", "ma")),
+        _ => return,
+    } {
+        let help_text = [
+            ("w", "Word"),
+            ("W", "WORD"),
+            ("c", "Class (tree-sitter)"),
+            ("f", "Function (tree-sitter)"),
+            ("p", "Parameter (tree-sitter)"),
+            ("m", "Matching delimiter under cursor"),
+            (" ", "... or any character acting as a pair"),
+        ];
+
+        cx.editor.autoinfo = Some(Info::new(
+            title,
+            help_text
+                .into_iter()
+                .map(|(col1, col2)| (col1.to_string(), col2.to_string()))
+                .collect(),
+        ));
+        cx.editor.pseudo_pending = Some(abbrev.to_string());
+    };
 }
 
 fn surround_add(cx: &mut Context) {

helix-term/src/ui/editor.rs

@@ -1211,6 +1211,9 @@ impl Component for EditorView {
                     disp.push_str(&s);
                 }
             }
+            if let Some(pseudo_pending) = &cx.editor.pseudo_pending {
+                disp.push_str(pseudo_pending.as_str())
+            }
             let style = cx.editor.theme.get("ui.text");
             let macro_width = if cx.editor.macro_recording.is_some() {
                 3

helix-view/src/editor.rs

@@ -299,6 +299,7 @@ pub struct Editor {
 
     pub idle_timer: Pin<Box<Sleep>>,
     pub last_motion: Option<Motion>,
+    pub pseudo_pending: Option<String>,
 
     pub exit_code: i32,
 }
@@ -346,6 +347,7 @@ impl Editor {
             autoinfo: None,
             idle_timer: Box::pin(sleep(config.idle_timeout)),
             last_motion: None,
+            pseudo_pending: None,
             config,
             auto_pairs,
             exit_code: 0,