add reflow command

book/src/generated/typable-cmd.md

@@ -58,6 +58,7 @@
 | `:set-option`, `:set` | Set a config option at runtime |
 | `:sort` | Sort ranges in selection. |
 | `:rsort` | Sort ranges in selection in reverse order. |
+| `:reflow` | Hard-wrap the current selection of lines to a given width. |
 | `:tree-sitter-subtree`, `:ts-subtree` | Display tree sitter subtree under cursor, primarily for debugging queries. |
 | `:config-reload` | Refreshes helix's config. |
 | `:config-open` | Open the helix config.toml file. |

helix-core/Cargo.toml

@@ -41,6 +41,7 @@ encoding_rs = "0.8"
 chrono = { version = "0.4", default-features = false, features = ["alloc", "std"] }
 
 etcetera = "0.3"
+textwrap = "0.15.0"
 
 [dev-dependencies]
 quickcheck = { version = "1", default-features = false }

helix-core/src/lib.rs

@@ -27,6 +27,7 @@ pub mod syntax;
 pub mod test;
 pub mod textobject;
 mod transaction;
+pub mod wrap;
 
 pub mod unicode {
     pub use unicode_general_category as category;

helix-core/src/wrap.rs

@@ -0,0 +1,7 @@
+use smartstring::{LazyCompact, SmartString};
+
+/// Given a slice of text, return the text re-wrapped to fit it
+/// within the given width.
+pub fn reflow_hard_wrap(text: &str, max_line_len: usize) -> SmartString<LazyCompact> {
+    textwrap::refill(text, max_line_len).into()
+}

helix-term/src/commands/typed.rs

@@ -1012,6 +1012,37 @@ fn sort_impl(
     Ok(())
 }
 
+fn reflow(
+    cx: &mut compositor::Context,
+    args: &[Cow<str>],
+    _event: PromptEvent,
+) -> anyhow::Result<()> {
+    // TODO: Can we instead take an Option<Cow<str>>, and then if the user
+    // doesn't pass in a selection, default to 79 characters per line?
+
+    const DEFAULT_MAX_LEN: Cow<'static, str> = Cow::Borrowed("79");
+    let max_line_len: usize = args.get(0).unwrap_or(&DEFAULT_MAX_LEN).parse()?;
+
+    let (view, doc) = current!(cx.editor);
+    let rope = doc.text();
+
+    // TODO: If only a single character is selected, we should expand the
+    // selection to whatever "object" (can we use treesitter for this? text query?)
+    // that single selection is part of.
+    let selection = doc.selection(view.id);
+    let transaction = Transaction::change_by_selection(rope, selection, |range| {
+        let fragment = range.fragment(rope.slice(..));
+        let reflowed_text = helix_core::wrap::reflow_hard_wrap(&fragment, max_line_len);
+
+        (range.from(), range.to(), Some(reflowed_text))
+    });
+
+    doc.apply(&transaction, view.id);
+    doc.append_changes_to_history(view.id);
+
+    Ok(())
+}
+
 fn tree_sitter_subtree(
     cx: &mut compositor::Context,
     _args: &[Cow<str>],
@@ -1474,6 +1505,13 @@ pub const TYPABLE_COMMAND_LIST: &[TypableCommand] = &[
             fun: sort_reverse,
             completer: None,
         },
+        TypableCommand {
+            name: "reflow",
+            aliases: &[],
+            doc: "Hard-wrap the current selection of lines to a given width.",
+            fun: reflow,
+            completer: None,
+        },
         TypableCommand {
             name: "tree-sitter-subtree",
             aliases: &["ts-subtree"],