Add ExpandSelection mouse binding action

Fixes #4132.

6 files changed, 91 insertions, 47 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 796d1c3c..9e2ec6b7 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,10 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
 ## 0.10.0-dev
 
+### Changed
+
+- `ExpandSelection` is now a configurable mouse binding action
+
 ## 0.9.0
 
 ### Packaging
diff --git a/alacritty.yml b/alacritty.yml
index a7628203..e93f3f74 100644
--- a/alacritty.yml
+++ b/alacritty.yml
@@ -507,13 +507,19 @@
 #   - Right
 #   - Numeric identifier such as `5`
 #
-# - `action` (see key bindings)
+# - `action` (see key bindings for actions not exclusive to mouse mode)
+#
+# - Mouse exclusive actions:
+#
+#   - ExpandSelection
+#       Expand the selection to the current mouse cursor location.
 #
 # And optionally:
 #
 # - `mods` (see key bindings)
 #mouse_bindings:
-#  - { mouse: Middle, action: PasteSelection }
+#  - { mouse: Right,             action: ExpandSelection }
+#  - { mouse: Middle, mode: ~Vi, action: PasteSelection  }
 
 # Key bindings
 #
diff --git a/alacritty/src/config/bindings.rs b/alacritty/src/config/bindings.rs
index 57237ad3..a4271430 100644
--- a/alacritty/src/config/bindings.rs
+++ b/alacritty/src/config/bindings.rs
@@ -109,6 +109,10 @@ pub enum Action {
     #[config(skip)]
     Search(SearchAction),
 
+    /// Perform mouse binding exclusive action.
+    #[config(skip)]
+    Mouse(MouseAction),
+
     /// Paste contents of system clipboard.
     Paste,
 
@@ -227,12 +231,19 @@ impl From<SearchAction> for Action {
     }
 }
 
+impl From<MouseAction> for Action {
+    fn from(action: MouseAction) -> Self {
+        Self::Mouse(action)
+    }
+}
+
 /// Display trait used for error logging.
 impl Display for Action {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match self {
             Action::ViMotion(motion) => motion.fmt(f),
             Action::Vi(action) => action.fmt(f),
+            Action::Mouse(action) => action.fmt(f),
             _ => write!(f, "{:?}", self),
         }
     }
@@ -283,6 +294,13 @@ pub enum SearchAction {
     SearchHistoryNext,
 }
 
+/// Mouse binding specific actions.
+#[derive(ConfigDeserialize, Debug, Copy, Clone, PartialEq, Eq)]
+pub enum MouseAction {
+    /// Expand the selection to the current mouse cursor position.
+    ExpandSelection,
+}
+
 macro_rules! bindings {
     (
         KeyBinding;
@@ -343,6 +361,7 @@ macro_rules! bindings {
 pub fn default_mouse_bindings() -> Vec<MouseBinding> {
     bindings!(
         MouseBinding;
+        MouseButton::Right;                    MouseAction::ExpandSelection;
         MouseButton::Middle, ~BindingMode::VI; Action::PasteSelection;
     )
 }
@@ -1027,6 +1046,9 @@ impl<'a> Deserialize<'a> for RawBinding {
                                 SearchAction::deserialize(value.clone())
                             {
                                 Some(search_action.into())
+                            } else if let Ok(mouse_action) = MouseAction::deserialize(value.clone())
+                            {
+                                Some(mouse_action.into())
                             } else {
                                 match Action::deserialize(value.clone()).map_err(V::Error::custom) {
                                     Ok(action) => Some(action),
@@ -1102,6 +1124,15 @@ impl<'a> Deserialize<'a> for RawBinding {
                         }
                         action
                     },
+                    (Some(action @ Action::Mouse(_)), None, None) => {
+                        if mouse.is_none() {
+                            return Err(V::Error::custom(format!(
+                                "action `{}` is only available for mouse bindings",
+                                action,
+                            )));
+                        }
+                        action
+                    },
                     (Some(action), None, None) => action,
                     (None, Some(chars), None) => Action::Esc(chars),
                     (None, None, Some(cmd)) => Action::Command(cmd),
diff --git a/alacritty/src/config/mod.rs b/alacritty/src/config/mod.rs
index 840a4b68..43cade6d 100644
--- a/alacritty/src/config/mod.rs
+++ b/alacritty/src/config/mod.rs
@@ -22,7 +22,9 @@ mod bindings;
 mod mouse;
 
 use crate::cli::Options;
-pub use crate::config::bindings::{Action, Binding, BindingMode, Key, SearchAction, ViAction};
+pub use crate::config::bindings::{
+    Action, Binding, BindingMode, Key, MouseAction, SearchAction, ViAction,
+};
 #[cfg(test)]
 pub use crate::config::mouse::{ClickHandler, Mouse};
 use crate::config::ui_config::UiConfig;
diff --git a/alacritty/src/event.rs b/alacritty/src/event.rs
index 37d28bb9..bc9c305a 100644
--- a/alacritty/src/event.rs
+++ b/alacritty/src/event.rs
@@ -671,6 +671,42 @@ impl<'a, N: Notify + 'a, T: EventListener> input::ActionContext<T> for ActionCon
         }
     }
 
+    /// Expand the selection to the current mouse cursor position.
+    #[inline]
+    fn expand_selection(&mut self) {
+        let selection_type = match self.mouse().click_state {
+            ClickState::Click => {
+                if self.modifiers().ctrl() {
+                    SelectionType::Block
+                } else {
+                    SelectionType::Simple
+                }
+            },
+            ClickState::DoubleClick => SelectionType::Semantic,
+            ClickState::TripleClick => SelectionType::Lines,
+            ClickState::None => return,
+        };
+
+        // Load mouse point, treating message bar and padding as the closest cell.
+        let display_offset = self.terminal().grid().display_offset();
+        let point = self.mouse().point(&self.size_info(), display_offset);
+
+        let cell_side = self.mouse().cell_side;
+
+        let selection = match &mut self.terminal_mut().selection {
+            Some(selection) => selection,
+            None => return,
+        };
+
+        selection.ty = selection_type;
+        self.update_selection(point, cell_side);
+
+        // Move vi mode cursor to mouse click position.
+        if self.terminal().mode().contains(TermMode::VI) && !self.search_active() {
+            self.terminal_mut().vi_mode_cursor.point = point;
+        }
+    }
+
     /// Paste a text into the terminal.
     fn paste(&mut self, text: &str) {
         if self.search_active() {
diff --git a/alacritty/src/input.rs b/alacritty/src/input.rs
index 3258137c..98a1b723 100644
--- a/alacritty/src/input.rs
+++ b/alacritty/src/input.rs
@@ -29,7 +29,7 @@ use alacritty_terminal::term::{ClipboardType, SizeInfo, Term, TermMode};
 use alacritty_terminal::vi_mode::ViMotion;
 
 use crate::clipboard::Clipboard;
-use crate::config::{Action, BindingMode, Config, Key, SearchAction, ViAction};
+use crate::config::{Action, BindingMode, Config, Key, MouseAction, SearchAction, ViAction};
 use crate::daemon::start_daemon;
 use crate::display::hint::HintMatch;
 use crate::display::window::Window;
@@ -104,6 +104,7 @@ pub trait ActionContext<T: EventListener> {
     fn toggle_vi_mode(&mut self) {}
     fn hint_input(&mut self, _character: char) {}
     fn trigger_hint(&mut self, _hint: &HintMatch) {}
+    fn expand_selection(&mut self) {}
     fn paste(&mut self, _text: &str) {}
 }
 
@@ -231,6 +232,7 @@ impl<T: EventListener> Execute<T> for Action {
             Action::Search(SearchAction::SearchDeleteWord) => ctx.search_pop_word(),
             Action::Search(SearchAction::SearchHistoryPrevious) => ctx.search_history_previous(),
             Action::Search(SearchAction::SearchHistoryNext) => ctx.search_history_next(),
+            Action::Mouse(MouseAction::ExpandSelection) => ctx.expand_selection(),
             Action::SearchForward => ctx.start_search(Direction::Right),
             Action::SearchBackward => ctx.start_search(Direction::Left),
             Action::Copy => ctx.copy_selection(ClipboardType::Clipboard),
@@ -531,51 +533,12 @@ impl<T: EventListener, A: ActionContext<T>> Processor<T, A> {
             let display_offset = self.ctx.terminal().grid().display_offset();
             let point = self.ctx.mouse().point(&self.ctx.size_info(), display_offset);
 
-            match button {
-                MouseButton::Left => self.on_left_click(point),
-                MouseButton::Right => self.on_right_click(point),
-                // Do nothing when using buttons other than LMB.
-                _ => self.ctx.mouse_mut().click_state = ClickState::None,
+            if let MouseButton::Left = button {
+                self.on_left_click(point)
             }
         }
     }
 
-    /// Handle selection expansion on right click.
-    fn on_right_click(&mut self, point: Point) {
-        match self.ctx.mouse().click_state {
-            ClickState::Click => {
-                let selection_type = if self.ctx.modifiers().ctrl() {
-                    SelectionType::Block
-                } else {
-                    SelectionType::Simple
-                };
-
-                self.expand_selection(point, selection_type);
-            },
-            ClickState::DoubleClick => self.expand_selection(point, SelectionType::Semantic),
-            ClickState::TripleClick => self.expand_selection(point, SelectionType::Lines),
-            ClickState::None => (),
-        }
-    }
-
-    /// Expand existing selection.
-    fn expand_selection(&mut self, point: Point, selection_type: SelectionType) {
-        let cell_side = self.ctx.mouse().cell_side;
-
-        let selection = match &mut self.ctx.terminal_mut().selection {
-            Some(selection) => selection,
-            None => return,
-        };
-
-        selection.ty = selection_type;
-        self.ctx.update_selection(point, cell_side);
-
-        // Move vi mode cursor to mouse click position.
-        if self.ctx.terminal().mode().contains(TermMode::VI) && !self.ctx.search_active() {
-            self.ctx.terminal_mut().vi_mode_cursor.point = point;
-        }
-    }
-
     /// Handle left click selection and vi mode cursor movement.
     fn on_left_click(&mut self, point: Point) {
         let side = self.ctx.mouse().cell_side;
@@ -749,8 +712,9 @@ impl<T: EventListener, A: ActionContext<T>> Processor<T, A> {
         } else {
             match state {
                 ElementState::Pressed => {
-                    self.process_mouse_bindings(button);
+                    // Process mouse press before bindings to update the `click_state`.
                     self.on_mouse_press(button);
+                    self.process_mouse_bindings(button);
                 },
                 ElementState::Released => self.on_mouse_release(button),
             }
@@ -1138,6 +1102,7 @@ mod tests {
 
                 let mut mouse = Mouse {
                     click_state: $initial_state,
+                    last_click_button: $initial_button,
                     ..Mouse::default()
                 };
 
@@ -1239,7 +1204,7 @@ mod tests {
             },
             window_id: unsafe { std::mem::transmute_copy(&0) },
         },
-        end_state: ClickState::None,
+        end_state: ClickState::Click,
     }
 
     test_clickstate! {