Mouse selection support (#509)

* Initial mouse selection support

Signed-off-by: Dmitry Sharshakov <d3dx12.xx@gmail.com>

* Disable mouse event capture if editor crashes

Signed-off-by: Dmitry Sharshakov <d3dx12.xx@gmail.com>

* Translate screen coordinates to view position

Signed-off-by: Dmitry Sharshakov <d3dx12.xx@gmail.com>

* Select full lines by dragging on line numbers

Signed-off-by: Dmitry Sharshakov <d3dx12.xx@gmail.com>

* editor: don't register dragging as a jump

Signed-off-by: Dmitry Sharshakov <d3dx12.xx@gmail.com>

* Count graphemes correctly

Signed-off-by: Dmitry Sharshakov <d3dx12.xx@gmail.com>

* Do not select lines when dragging on the line number bar

Signed-off-by: Dmitry Sharshakov <d3dx12.xx@gmail.com>

* Split out verify_screen_coords

Signed-off-by: Dmitry Sharshakov <d3dx12.xx@gmail.com>

* Do not iterate over the graphemes twice

Signed-off-by: Dmitry Sharshakov <d3dx12.xx@gmail.com>

* Switch view by clicking on it

Signed-off-by: Dmitry Sharshakov <d3dx12.xx@gmail.com>

* Add disable-mouse config option

Signed-off-by: Dmitry Sharshakov <d3dx12.xx@gmail.com>

* Support multiple selections with mouse

Signed-off-by: Dmitry Sharshakov <d3dx12.xx@gmail.com>

* Remove unnecessary check

Signed-off-by: Dmitry Sharshakov <d3dx12.xx@gmail.com>

* Refactor using match expression

Co-authored-by: Gokul Soumya <gokulps15@gmail.com>
Signed-off-by: Dmitry Sharshakov <d3dx12.xx@gmail.com>

* Rename local variable

Signed-off-by: Dmitry Sharshakov <d3dx12.xx@gmail.com>

* Rename mouse option

Signed-off-by: Dmitry Sharshakov <d3dx12.xx@gmail.com>

* Refactor code

Signed-off-by: Dmitry Sharshakov <d3dx12.xx@gmail.com>

* Fix dragging selection

Signed-off-by: Dmitry Sharshakov <d3dx12.xx@gmail.com>

* Fix crash when clicking past last line

Signed-off-by: Dmitry Sharshakov <d3dx12.xx@gmail.com>

* Count characters better

Signed-off-by: Dmitry Sharshakov <d3dx12.xx@gmail.com>

* Remove comparison not needed anymore

Signed-off-by: Dmitry Sharshakov <d3dx12.xx@gmail.com>

* Validate coordinates before resolving position

Signed-off-by: Dmitry Sharshakov <d3dx12.xx@gmail.com>

* Tidy up references to editor tree

Signed-off-by: Dmitry Sharshakov <d3dx12.xx@gmail.com>

* Better way to determine line end and avoid overflow

Signed-off-by: Dmitry Sharshakov <d3dx12.xx@gmail.com>

* Fix for last line

Signed-off-by: Dmitry Sharshakov <d3dx12.xx@gmail.com>

* Add unit tests for text_pos_at_screen_coords

Signed-off-by: Dmitry Sharshakov <d3dx12.xx@gmail.com>

Co-authored-by: Gokul Soumya <gokulps15@gmail.com>

3 files changed, 86 insertions, 3 deletions

diff --git a/helix-term/src/application.rs b/helix-term/src/application.rs
index c55d4c98..5f350671 100644
--- a/helix-term/src/application.rs
+++ b/helix-term/src/application.rs
@@ -15,7 +15,7 @@ use std::{
 use anyhow::Error;
 
 use crossterm::{
-    event::{Event, EventStream},
+    event::{DisableMouseCapture, EnableMouseCapture, Event, EventStream},
     execute, terminal,
 };
 
@@ -449,6 +449,9 @@ impl Application {
         let mut stdout = stdout();
 
         execute!(stdout, terminal::EnterAlternateScreen)?;
+        if self.config.terminal.mouse {
+            execute!(stdout, EnableMouseCapture)?;
+        }
 
         // Exit the alternate screen and disable raw mode before panicking
         let hook = std::panic::take_hook();
@@ -456,6 +459,7 @@ impl Application {
             // We can't handle errors properly inside this closure.  And it's
             // probably not a good idea to `unwrap()` inside a panic handler.
             // So we just ignore the `Result`s.
+            let _ = execute!(std::io::stdout(), DisableMouseCapture);
             let _ = execute!(std::io::stdout(), terminal::LeaveAlternateScreen);
             let _ = terminal::disable_raw_mode();
             hook(info);
@@ -468,6 +472,7 @@ impl Application {
         // reset cursor shape
         write!(stdout, "\x1B[2 q")?;
 
+        execute!(stdout, DisableMouseCapture)?;
         execute!(stdout, terminal::LeaveAlternateScreen)?;
 
         terminal::disable_raw_mode()?;
diff --git a/helix-term/src/config.rs b/helix-term/src/config.rs
index f3f0ba53..38cd3bfb 100644
--- a/helix-term/src/config.rs
+++ b/helix-term/src/config.rs
@@ -9,6 +9,8 @@ pub struct Config {
     pub lsp: LspConfig,
     #[serde(default)]
     pub keys: Keymaps,
+    #[serde(default)]
+    pub terminal: TerminalConfig,
 }
 
 #[derive(Debug, Default, Clone, PartialEq, Deserialize)]
@@ -17,6 +19,18 @@ pub struct LspConfig {
     pub display_messages: bool,
 }
 
+#[derive(Debug, Clone, PartialEq, Deserialize)]
+#[serde(rename_all = "kebab-case")]
+pub struct TerminalConfig {
+    pub mouse: bool,
+}
+
+impl Default for TerminalConfig {
+    fn default() -> Self {
+        Self { mouse: true }
+    }
+}
+
 #[test]
 fn parsing_keymaps_config_file() {
     use crate::keymap;
diff --git a/helix-term/src/ui/editor.rs b/helix-term/src/ui/editor.rs
index d5c907b8..ec5687bd 100644
--- a/helix-term/src/ui/editor.rs
+++ b/helix-term/src/ui/editor.rs
@@ -12,7 +12,7 @@ use helix_core::{
     syntax::{self, HighlightEvent},
     unicode::segmentation::UnicodeSegmentation,
     unicode::width::UnicodeWidthStr,
-    LineEnding, Position, Range,
+    LineEnding, Position, Range, Selection,
 };
 use helix_view::{
     document::Mode,
@@ -24,7 +24,7 @@ use helix_view::{
 };
 use std::borrow::Cow;
 
-use crossterm::event::Event;
+use crossterm::event::{Event, MouseButton, MouseEvent, MouseEventKind};
 use tui::buffer::Buffer as Surface;
 
 pub struct EditorView {
@@ -805,6 +805,70 @@ impl Component for EditorView {
 
                 EventResult::Consumed(callback)
             }
+            Event::Mouse(MouseEvent {
+                kind: MouseEventKind::Down(MouseButton::Left),
+                row,
+                column,
+                modifiers,
+                ..
+            }) => {
+                let editor = &mut cx.editor;
+
+                let result = editor.tree.views().find_map(|(view, _focus)| {
+                    view.pos_at_screen_coords(
+                        &editor.documents[view.doc],
+                        row as usize,
+                        column as usize,
+                    )
+                    .map(|pos| (pos, view.id))
+                });
+
+                if let Some((pos, id)) = result {
+                    let doc = &mut editor.documents[editor.tree.get(id).doc];
+                    let jump = (doc.id(), doc.selection(id).clone());
+                    editor.tree.get_mut(id).jumps.push(jump);
+
+                    if modifiers == crossterm::event::KeyModifiers::ALT {
+                        let selection = doc.selection(id).clone();
+                        doc.set_selection(id, selection.push(Range::point(pos)));
+                    } else {
+                        doc.set_selection(id, Selection::point(pos));
+                    }
+
+                    editor.tree.focus = id;
+
+                    return EventResult::Consumed(None);
+                }
+
+                EventResult::Ignored
+            }
+
+            Event::Mouse(MouseEvent {
+                kind: MouseEventKind::Drag(MouseButton::Left),
+                row,
+                column,
+                ..
+            }) => {
+                let (view, doc) = current!(cx.editor);
+
+                let pos = view.pos_at_screen_coords(doc, row as usize, column as usize);
+
+                if pos == None {
+                    return EventResult::Ignored;
+                }
+
+                let selection = doc.selection(view.id).clone();
+                let primary_anchor = selection.primary().anchor;
+                let new_selection = selection.transform(|range| -> Range {
+                    if range.anchor == primary_anchor {
+                        return Range::new(primary_anchor, pos.unwrap());
+                    }
+                    range
+                });
+
+                doc.set_selection(view.id, new_selection);
+                EventResult::Consumed(None)
+            }
             Event::Mouse(_) => EventResult::Ignored,
         }
     }