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`.

1 files changed, 47 insertions, 0 deletions

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,
+        }
+    }
+}