markdown: Add support for right-click menu copy item (#45572)

Danilo Leal created 5 days ago

In https://github.com/zed-industries/zed/pull/45440, we're implementing
the ability to right-click in the agent panel and copy the rendered
markdown. However, that presented itself as not as straightforward as
just making the menu item fire the `CopyAsMarkdown` action because any
selection in markdown is cleared after a new mouse click, and for the
right-click copy menu item to work, we need to persist that selection
even after the menu itself is opened and the "Copy" menu item is
clicked.

This all demanded a bit of work in the markdown file itself, and given
we may want to use this functionality for other non-agent thread view
markdown use cases in the future, I felt like it'd be better breaking it
down into a separate PR that we can more easily track in the future.

The context menu still needs to be built in the place where the markdown
is created and rendered, though. This PR only adds the infrastructure
needed so that this menu can simply fire the `CopyAsMarkdown` and make
the copying work.

Release Notes:

- N/A

Change summary

crates/markdown/src/markdown.rs | 42 ++++++++++++++++++++++++++++++----
1 file changed, 37 insertions(+), 5 deletions(-)

Detailed changes

crates/markdown/src/markdown.rs

@@ -22,9 +22,9 @@ use collections::{HashMap, HashSet};
 use gpui::{
     AnyElement, App, BorderStyle, Bounds, ClipboardItem, CursorStyle, DispatchPhase, Edges, Entity,
     FocusHandle, Focusable, FontStyle, FontWeight, GlobalElementId, Hitbox, Hsla, Image,
-    ImageFormat, KeyContext, Length, MouseDownEvent, MouseEvent, MouseMoveEvent, MouseUpEvent,
-    Point, ScrollHandle, Stateful, StrikethroughStyle, StyleRefinement, StyledText, Task,
-    TextLayout, TextRun, TextStyle, TextStyleRefinement, actions, img, point, quad,
+    ImageFormat, KeyContext, Length, MouseButton, MouseDownEvent, MouseEvent, MouseMoveEvent,
+    MouseUpEvent, Point, ScrollHandle, Stateful, StrikethroughStyle, StyleRefinement, StyledText,
+    Task, TextLayout, TextRun, TextStyle, TextStyleRefinement, actions, img, point, quad,
 };
 use language::{Language, LanguageRegistry, Rope};
 use parser::CodeBlockMetadata;
@@ -112,6 +112,7 @@ pub struct Markdown {
     options: Options,
     copied_code_blocks: HashSet<ElementId>,
     code_block_scroll_handles: HashMap<usize, ScrollHandle>,
+    context_menu_selected_text: Option<String>,
 }
 
 struct Options {
@@ -181,6 +182,7 @@ impl Markdown {
             },
             copied_code_blocks: HashSet::default(),
             code_block_scroll_handles: HashMap::default(),
+            context_menu_selected_text: None,
         };
         this.parse(cx);
         this
@@ -205,6 +207,7 @@ impl Markdown {
             },
             copied_code_blocks: HashSet::default(),
             code_block_scroll_handles: HashMap::default(),
+            context_menu_selected_text: None,
         };
         this.parse(cx);
         this
@@ -289,6 +292,14 @@ impl Markdown {
         }
     }
 
+    pub fn selected_text(&self) -> Option<String> {
+        if self.selection.end <= self.selection.start {
+            None
+        } else {
+            Some(self.source[self.selection.start..self.selection.end].to_string())
+        }
+    }
+
     fn copy(&self, text: &RenderedText, _: &mut Window, cx: &mut Context<Self>) {
         if self.selection.end <= self.selection.start {
             return;
@@ -297,7 +308,11 @@ impl Markdown {
         cx.write_to_clipboard(ClipboardItem::new_string(text));
     }
 
-    fn copy_as_markdown(&self, _: &mut Window, cx: &mut Context<Self>) {
+    fn copy_as_markdown(&mut self, _: &mut Window, cx: &mut Context<Self>) {
+        if let Some(text) = self.context_menu_selected_text.take() {
+            cx.write_to_clipboard(ClipboardItem::new_string(text));
+            return;
+        }
         if self.selection.end <= self.selection.start {
             return;
         }
@@ -305,6 +320,10 @@ impl Markdown {
         cx.write_to_clipboard(ClipboardItem::new_string(text));
     }
 
+    fn capture_selection_for_context_menu(&mut self) {
+        self.context_menu_selected_text = self.selected_text();
+    }
+
     fn parse(&mut self, cx: &mut Context<Self>) {
         if self.source.is_empty() {
             return;
@@ -665,6 +684,19 @@ impl MarkdownElement {
 
         let on_open_url = self.on_url_click.take();
 
+        self.on_mouse_event(window, cx, {
+            let hitbox = hitbox.clone();
+            move |markdown, event: &MouseDownEvent, phase, window, _| {
+                if phase.capture()
+                    && event.button == MouseButton::Right
+                    && hitbox.is_hovered(window)
+                {
+                    // Capture selected text so it survives until menu item is clicked
+                    markdown.capture_selection_for_context_menu();
+                }
+            }
+        });
+
         self.on_mouse_event(window, cx, {
             let rendered_text = rendered_text.clone();
             let hitbox = hitbox.clone();
@@ -713,7 +745,7 @@ impl MarkdownElement {
                         window.prevent_default();
                         cx.notify();
                     }
-                } else if phase.capture() {
+                } else if phase.capture() && event.button == MouseButton::Left {
                     markdown.selection = Selection::default();
                     markdown.pressed_link = None;
                     cx.notify();