collab: Add screen selector (#31506)

Instead of selecting a screen to share arbitrarily, we'll now allow user
to select the screen to share. Note that sharing multiple screens at the
time is still not supported (though prolly not too far-fetched).

Related to #4666

![image](https://github.com/user-attachments/assets/1afb664f-3cdb-4e0a-bb29-9d7093d87fa5)

Release Notes:

- Added screen selector dropdown to screen share button

---------

Co-authored-by: Kirill Bulatov <kirill@zed.dev>
Co-authored-by: Cole Miller <cole@zed.dev>

crates/gpui/src/platform/test/platform.rs

@@ -2,7 +2,7 @@ use crate::{
     AnyWindowHandle, BackgroundExecutor, ClipboardItem, CursorStyle, DevicePixels,
     ForegroundExecutor, Keymap, NoopTextSystem, Platform, PlatformDisplay, PlatformKeyboardLayout,
     PlatformTextSystem, PromptButton, ScreenCaptureFrame, ScreenCaptureSource, ScreenCaptureStream,
-    Size, Task, TestDisplay, TestWindow, WindowAppearance, WindowParams, size,
+    SourceMetadata, Task, TestDisplay, TestWindow, WindowAppearance, WindowParams, size,
 };
 use anyhow::Result;
 use collections::VecDeque;
@@ -44,11 +44,17 @@ pub(crate) struct TestPlatform {
 /// A fake screen capture source, used for testing.
 pub struct TestScreenCaptureSource {}
 
+/// A fake screen capture stream, used for testing.
 pub struct TestScreenCaptureStream {}
 
 impl ScreenCaptureSource for TestScreenCaptureSource {
-    fn resolution(&self) -> Result<Size<DevicePixels>> {
-        Ok(size(DevicePixels(1), DevicePixels(1)))
+    fn metadata(&self) -> Result<SourceMetadata> {
+        Ok(SourceMetadata {
+            id: 0,
+            is_main: None,
+            label: None,
+            resolution: size(DevicePixels(1), DevicePixels(1)),
+        })
     }
 
     fn stream(
@@ -64,7 +70,11 @@ impl ScreenCaptureSource for TestScreenCaptureSource {
     }
 }
 
-impl ScreenCaptureStream for TestScreenCaptureStream {}
+impl ScreenCaptureStream for TestScreenCaptureStream {
+    fn metadata(&self) -> Result<SourceMetadata> {
+        TestScreenCaptureSource {}.metadata()
+    }
+}
 
 struct TestPrompt {
     msg: String,
@@ -271,13 +281,13 @@ impl Platform for TestPlatform {
     #[cfg(feature = "screen-capture")]
     fn screen_capture_sources(
         &self,
-    ) -> oneshot::Receiver<Result<Vec<Box<dyn ScreenCaptureSource>>>> {
+    ) -> oneshot::Receiver<Result<Vec<Rc<dyn ScreenCaptureSource>>>> {
         let (mut tx, rx) = oneshot::channel();
         tx.send(Ok(self
             .screen_capture_sources
             .borrow()
             .iter()
-            .map(|source| Box::new(source.clone()) as Box<dyn ScreenCaptureSource>)
+            .map(|source| Rc::new(source.clone()) as Rc<dyn ScreenCaptureSource>)
             .collect()))
             .ok();
         rx