Support scrolling popup contents using mouse (helix-editor#10053)

* Extract popup scrolling code into named functions

* Scroll popup contents on mouse scroll event

* Ignore mouse events outside the popup

* Remove unneeded return statement

helix-term/src/ui/popup.rs

@@ -11,6 +11,7 @@ use tui::{
 use helix_core::Position;
 use helix_view::{
     graphics::{Margin, Rect},
+    input::{MouseEvent, MouseEventKind},
     Editor,
 };
 
@@ -23,6 +24,7 @@ pub struct Popup<T: Component> {
     margin: Margin,
     size: (u16, u16),
     child_size: (u16, u16),
+    area: Rect,
     position_bias: Open,
     scroll: usize,
     auto_close: bool,
@@ -40,6 +42,7 @@ impl<T: Component> Popup<T> {
             size: (0, 0),
             position_bias: Open::Below,
             child_size: (0, 0),
+            area: Rect::new(0, 0, 0, 0),
             scroll: 0,
             auto_close: false,
             ignore_escape_key: false,
@@ -146,6 +149,14 @@ impl<T: Component> Popup<T> {
         }
     }
 
+    pub fn scroll_half_page_down(&mut self) {
+        self.scroll(self.size.1 as usize / 2, true)
+    }
+
+    pub fn scroll_half_page_up(&mut self) {
+        self.scroll(self.size.1 as usize / 2, false)
+    }
+
     /// Toggles the Popup's scrollbar.
     /// Consider disabling the scrollbar in case the child
     /// already has its own.
@@ -171,12 +182,44 @@ impl<T: Component> Popup<T> {
         // clip to viewport
         viewport.intersection(Rect::new(rel_x, rel_y, self.size.0, self.size.1))
     }
+
+    fn handle_mouse_event(
+        &mut self,
+        &MouseEvent {
+            kind,
+            column: x,
+            row: y,
+            ..
+        }: &MouseEvent,
+    ) -> EventResult {
+        let mouse_is_within_popup = x >= self.area.left()
+            && x < self.area.right()
+            && y >= self.area.top()
+            && y < self.area.bottom();
+
+        if !mouse_is_within_popup {
+            return EventResult::Ignored(None);
+        }
+
+        match kind {
+            MouseEventKind::ScrollDown if self.has_scrollbar => {
+                self.scroll_half_page_down();
+                EventResult::Consumed(None)
+            }
+            MouseEventKind::ScrollUp if self.has_scrollbar => {
+                self.scroll_half_page_up();
+                EventResult::Consumed(None)
+            }
+            _ => EventResult::Ignored(None),
+        }
+    }
 }
 
 impl<T: Component> Component for Popup<T> {
     fn handle_event(&mut self, event: &Event, cx: &mut Context) -> EventResult {
         let key = match event {
             Event::Key(event) => *event,
+            Event::Mouse(event) => return self.handle_mouse_event(event),
             Event::Resize(_, _) => {
                 // TODO: calculate inner area, call component's handle_event with that area
                 return EventResult::Ignored(None);
@@ -200,11 +243,11 @@ impl<T: Component> Component for Popup<T> {
                 EventResult::Consumed(Some(close_fn))
             }
             ctrl!('d') => {
-                self.scroll(self.size.1 as usize / 2, true);
+                self.scroll_half_page_down();
                 EventResult::Consumed(None)
             }
             ctrl!('u') => {
-                self.scroll(self.size.1 as usize / 2, false);
+                self.scroll_half_page_up();
                 EventResult::Consumed(None)
             }
             _ => {
@@ -249,6 +292,7 @@ impl<T: Component> Component for Popup<T> {
 
     fn render(&mut self, viewport: Rect, surface: &mut Surface, cx: &mut Context) {
         let area = self.area(viewport, cx.editor);
+        self.area = area;
         cx.scroll = Some(self.scroll);
 
         // clear area