Implement register selection

User can select register to yank into with the " command.
A new state is added to `Editor` and `commands::Context` structs.
This state is managed by leveraging a new struct `RegisterSelection`.

7 files changed, 96 insertions, 25 deletions

diff --git a/helix-core/src/register.rs b/helix-core/src/register.rs
index 0be0ce89..0176d23e 100644
--- a/helix-core/src/register.rs
+++ b/helix-core/src/register.rs
@@ -6,16 +6,15 @@ use std::{collections::HashMap, sync::RwLock};
 static REGISTRY: Lazy<RwLock<HashMap<char, Vec<String>>>> =
     Lazy::new(|| RwLock::new(HashMap::new()));
 
-pub fn get(register: char) -> Option<Vec<String>> {
+/// Read register values.
+pub fn get(register_name: char) -> Option<Vec<String>> {
     let registry = REGISTRY.read().unwrap();
-
-    // TODO: no cloning
-    registry.get(&register).cloned()
+    registry.get(&register_name).cloned() // TODO: no cloning
 }
 
+/// Read register values.
 // restoring: bool
-pub fn set(register: char, values: Vec<String>) {
+pub fn set(register_name: char, values: Vec<String>) {
     let mut registry = REGISTRY.write().unwrap();
-
-    registry.insert(register, values);
+    registry.insert(register_name, values);
 }
diff --git a/helix-term/src/commands.rs b/helix-term/src/commands.rs
index 15fac7ad..94175006 100644
--- a/helix-term/src/commands.rs
+++ b/helix-term/src/commands.rs
@@ -35,6 +35,7 @@ use crossterm::event::{KeyCode, KeyEvent};
 use once_cell::sync::Lazy;
 
 pub struct Context<'a> {
+    pub register: helix_view::RegisterSelection,
     pub count: usize,
     pub editor: &'a mut Editor,
 
@@ -777,7 +778,7 @@ pub fn extend_line(cx: &mut Context) {
 
 // heuristic: append changes to history after each command, unless we're in insert mode
 
-fn _delete_selection(doc: &mut Document, view_id: ViewId) {
+fn _delete_selection(reg: char, doc: &mut Document, view_id: ViewId) {
     // first yank the selection
     let values: Vec<String> = doc
         .selection(view_id)
@@ -785,8 +786,6 @@ fn _delete_selection(doc: &mut Document, view_id: ViewId) {
         .map(Cow::into_owned)
         .collect();
 
-    // TODO: allow specifying reg
-    let reg = '"';
     register::set(reg, values);
 
     // then delete
@@ -800,8 +799,9 @@ fn _delete_selection(doc: &mut Document, view_id: ViewId) {
 }
 
 pub fn delete_selection(cx: &mut Context) {
+    let reg = cx.register.name();
     let (view, doc) = cx.current();
-    _delete_selection(doc, view.id);
+    _delete_selection(reg, doc, view.id);
 
     doc.append_changes_to_history(view.id);
 
@@ -810,8 +810,9 @@ pub fn delete_selection(cx: &mut Context) {
 }
 
 pub fn change_selection(cx: &mut Context) {
+    let reg = cx.register.name();
     let (view, doc) = cx.current();
-    _delete_selection(doc, view.id);
+    _delete_selection(reg, doc, view.id);
     enter_insert_mode(doc);
 }
 
@@ -1893,11 +1894,13 @@ pub fn yank(cx: &mut Context) {
         .map(Cow::into_owned)
         .collect();
 
-    // TODO: allow specifying reg
-    let reg = '"';
-    let msg = format!("yanked {} selection(s) to register {}", values.len(), reg);
+    let msg = format!(
+        "yanked {} selection(s) to register {}",
+        values.len(),
+        cx.register.name()
+    );
 
-    register::set(reg, values);
+    register::set(cx.register.name(), values);
 
     cx.editor.set_status(msg)
 }
@@ -1908,9 +1911,7 @@ enum Paste {
     After,
 }
 
-fn _paste(doc: &mut Document, view: &View, action: Paste) -> Option<Transaction> {
-    // TODO: allow specifying reg
-    let reg = '"';
+fn _paste(reg: char, doc: &mut Document, view: &View, action: Paste) -> Option<Transaction> {
     if let Some(values) = register::get(reg) {
         let repeat = std::iter::repeat(
             values
@@ -1956,18 +1957,20 @@ fn _paste(doc: &mut Document, view: &View, action: Paste) -> Option<Transaction>
 // default insert
 
 pub fn paste_after(cx: &mut Context) {
+    let reg = cx.register.name();
     let (view, doc) = cx.current();
 
-    if let Some(transaction) = _paste(doc, view, Paste::After) {
+    if let Some(transaction) = _paste(reg, doc, view, Paste::After) {
         doc.apply(&transaction, view.id);
         doc.append_changes_to_history(view.id);
     }
 }
 
 pub fn paste_before(cx: &mut Context) {
+    let reg = cx.register.name();
     let (view, doc) = cx.current();
 
-    if let Some(transaction) = _paste(doc, view, Paste::Before) {
+    if let Some(transaction) = _paste(reg, doc, view, Paste::Before) {
         doc.apply(&transaction, view.id);
         doc.append_changes_to_history(view.id);
     }
@@ -2426,6 +2429,18 @@ pub fn wclose(cx: &mut Context) {
     cx.editor.close(view_id, /* close_buffer */ false);
 }
 
+pub fn select_register(cx: &mut Context) {
+    cx.on_next_key(move |cx, event| {
+        if let KeyEvent {
+            code: KeyCode::Char(ch),
+            ..
+        } = event
+        {
+            cx.editor.register.select(ch);
+        }
+    })
+}
+
 pub fn space_mode(cx: &mut Context) {
     cx.on_next_key(move |cx, event| {
         if let KeyEvent {
@@ -2439,7 +2454,7 @@ pub fn space_mode(cx: &mut Context) {
                 'b' => buffer_picker(cx),
                 'w' => window_mode(cx),
                 // ' ' => toggle_alternate_buffer(cx),
-                // TODO: temporary since space mode took it's old key
+                // TODO: temporary since space mode took its old key
                 ' ' => keep_primary_selection(cx),
                 _ => (),
             }
diff --git a/helix-term/src/keymap.rs b/helix-term/src/keymap.rs
index 27ef9b9e..d2fa46c7 100644
--- a/helix-term/src/keymap.rs
+++ b/helix-term/src/keymap.rs
@@ -284,6 +284,8 @@ pub fn default() -> Keymaps {
 
         key!(' ') => commands::space_mode,
         key!('z') => commands::view_mode,
+
+        key!('"') => commands::select_register,
     );
     // TODO: decide whether we want normal mode to also be select mode (kakoune-like), or whether
     // we keep this separate select mode. More keys can fit into normal mode then, but it's weird
diff --git a/helix-term/src/ui/editor.rs b/helix-term/src/ui/editor.rs
index cd66b703..4f485ed2 100644
--- a/helix-term/src/ui/editor.rs
+++ b/helix-term/src/ui/editor.rs
@@ -537,6 +537,9 @@ impl EditorView {
                 // if this fails, count was Some(0)
                 // debug_assert!(cxt.count != 0);
 
+                // set the register
+                cxt.register = cxt.editor.register.take();
+
                 if let Some(command) = self.keymap[&mode].get(&event) {
                     command(cxt);
                 }
@@ -575,11 +578,12 @@ impl Component for EditorView {
                 let mode = doc.mode();
 
                 let mut cxt = commands::Context {
-                    editor: &mut cx.editor,
+                    register: helix_view::RegisterSelection::default(),
                     count: 1,
+                    editor: &mut cx.editor,
                     callback: None,
-                    callbacks: cx.callbacks,
                     on_next_key_callback: None,
+                    callbacks: cx.callbacks,
                 };
 
                 if let Some(on_next_key) = self.on_next_key.take() {
diff --git a/helix-view/src/editor.rs b/helix-view/src/editor.rs
index fa8dea2f..b69ae22f 100644
--- a/helix-view/src/editor.rs
+++ b/helix-view/src/editor.rs
@@ -1,4 +1,4 @@
-use crate::{theme::Theme, tree::Tree, Document, DocumentId, View, ViewId};
+use crate::{theme::Theme, tree::Tree, Document, DocumentId, RegisterSelection, View, ViewId};
 use tui::layout::Rect;
 
 use std::path::PathBuf;
@@ -13,6 +13,7 @@ pub struct Editor {
     pub tree: Tree,
     pub documents: SlotMap<DocumentId, Document>,
     pub count: Option<usize>,
+    pub register: RegisterSelection,
     pub theme: Theme,
     pub language_servers: helix_lsp::Registry,
 
@@ -57,6 +58,7 @@ impl Editor {
             tree: Tree::new(area),
             documents: SlotMap::with_key(),
             count: None,
+            register: RegisterSelection::default(),
             theme,
             language_servers,
             status_msg: None,
diff --git a/helix-view/src/lib.rs b/helix-view/src/lib.rs
index 00bddad6..7e253320 100644
--- a/helix-view/src/lib.rs
+++ b/helix-view/src/lib.rs
@@ -1,5 +1,6 @@
 pub mod document;
 pub mod editor;
+pub mod register_selection;
 pub mod theme;
 pub mod tree;
 pub mod view;
@@ -10,5 +11,6 @@ new_key_type! { pub struct ViewId; }
 
 pub use document::Document;
 pub use editor::Editor;
+pub use register_selection::RegisterSelection;
 pub use theme::Theme;
 pub use view::View;
diff --git a/helix-view/src/register_selection.rs b/helix-view/src/register_selection.rs
new file mode 100644
index 00000000..d7f073b6
--- /dev/null
+++ b/helix-view/src/register_selection.rs
@@ -0,0 +1,47 @@
+/// Register selection and configuration
+///
+/// This is a kind a of specialized `Option<char>` for register selection.
+/// Point is to keep whether the register selection has been explicitely
+/// set or not while being convenient by knowing the default register name.
+pub struct RegisterSelection {
+    selected: char,
+    default_name: char,
+}
+
+impl RegisterSelection {
+    pub fn new(default_name: char) -> Self {
+        Self {
+            selected: default_name,
+            default_name,
+        }
+    }
+
+    pub fn select(&mut self, name: char) {
+        self.selected = name;
+    }
+
+    pub fn take(&mut self) -> Self {
+        Self {
+            selected: std::mem::replace(&mut self.selected, self.default_name),
+            default_name: self.default_name,
+        }
+    }
+
+    pub fn is_default(&self) -> bool {
+        self.selected == self.default_name
+    }
+
+    pub fn name(&self) -> char {
+        self.selected
+    }
+}
+
+impl Default for RegisterSelection {
+    fn default() -> Self {
+        let default_name = '"';
+        Self {
+            selected: default_name,
+            default_name,
+        }
+    }
+}