Fix selection while scrolling

Properly update an active selection while scrolling the main scrollback buffer.

This does not affect the alternate screen buffer, since no scrollback buffer is
available.

CHANGELOG.md

@@ -34,6 +34,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Selection memory leak and glitches in the alternate screen buffer
 - Invalid default configuration on macOS and Linux
 - Middle mouse pasting if mouse mode is enabled
+- Selections now properly update as you scroll the scrollback buffer while selecting
 
 ## Version 0.2.1
 

src/event.rs

@@ -58,6 +58,17 @@ impl<'a, N: Notify + 'a> input::ActionContext for ActionContext<'a, N> {
 
     fn scroll(&mut self, scroll: Scroll) {
         self.terminal.scroll_display(scroll);
+
+        if let ElementState::Pressed = self.mouse().left_button_state {
+            let (x, y) = (self.mouse().x, self.mouse().y);
+            let size_info = self.size_info();
+            let point = size_info.pixels_to_coords(x, y);
+            let cell_side = self.mouse().cell_side;
+            self.update_selection(Point {
+                line: point.line,
+                col: point.col
+            }, cell_side);
+        }
     }
 
     fn clear_history(&mut self) {