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`.

3 files changed, 52 insertions, 1 deletions

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,
+        }
+    }
+}