agent: Copy text as Markdown (#28272)

Release Notes:

- agent: Copying text in the Agent Panel will now copy it as Markdown.

Co-authored-by: Antonio Scandurra <me@as-cii.com>

crates/markdown/src/markdown.rs

@@ -90,7 +90,7 @@ struct Options {
     copy_code_block_buttons: bool,
 }
 
-actions!(markdown, [Copy]);
+actions!(markdown, [Copy, CopyAsMarkdown]);
 
 impl Markdown {
     pub fn new(
@@ -178,6 +178,14 @@ impl Markdown {
         cx.write_to_clipboard(ClipboardItem::new_string(text));
     }
 
+    fn copy_as_markdown(&self, _: &mut Window, cx: &mut Context<Self>) {
+        if self.selection.end <= self.selection.start {
+            return;
+        }
+        let text = self.source[self.selection.start..self.selection.end].to_string();
+        cx.write_to_clipboard(ClipboardItem::new_string(text));
+    }
+
     fn parse(&mut self, cx: &mut Context<Self>) {
         if self.source.is_empty() {
             return;
@@ -1040,8 +1048,8 @@ impl Element for MarkdownElement {
         let mut context = KeyContext::default();
         context.add("Markdown");
         window.set_key_context(context);
-        let entity = self.markdown.clone();
         window.on_action(std::any::TypeId::of::<crate::Copy>(), {
+            let entity = self.markdown.clone();
             let text = rendered_markdown.text.clone();
             move |_, phase, window, cx| {
                 let text = text.clone();
@@ -1050,6 +1058,14 @@ impl Element for MarkdownElement {
                 }
             }
         });
+        window.on_action(std::any::TypeId::of::<crate::CopyAsMarkdown>(), {
+            let entity = self.markdown.clone();
+            move |_, phase, window, cx| {
+                if phase == DispatchPhase::Bubble {
+                    entity.update(cx, move |this, cx| this.copy_as_markdown(window, cx))
+                }
+            }
+        });
 
         self.paint_mouse_listeners(hitbox, &rendered_markdown.text, window, cx);
         rendered_markdown.element.paint(window, cx);