Apply screencopy transform to subsurfaces

Fixes https://github.com/pop-os/cosmic-workspaces-epoch/issues/17.

src/backend/mock.rs

@@ -60,6 +60,7 @@ fn create_solid_capture_image(r: u8, g: u8, b: u8) -> CaptureImage {
             .into(),
         ))
         .0,
+        transform: wl_output::Transform::Normal,
         #[cfg(feature = "no-subsurfaces")]
         image: cosmic::widget::image::Handle::from_rgba(512, 512, [r, g, b, 255].repeat(512 * 512)),
     }

src/backend/mod.rs

@@ -47,6 +47,7 @@ pub struct CaptureImage {
     pub width: u32,
     pub height: u32,
     pub wl_buffer: SubsurfaceBuffer,
+    pub transform: wl_output::Transform,
     #[cfg(feature = "no-subsurfaces")]
     pub image: cosmic::widget::image::Handle,
 }

src/backend/wayland/screencopy.rs

@@ -162,7 +162,7 @@ impl ScreencopyHandler for AppData {
         conn: &Connection,
         qh: &QueueHandle<Self>,
         screencopy_frame: &zcosmic_screencopy_frame_v2::ZcosmicScreencopyFrameV2,
-        _frame: Frame,
+        frame: Frame,
     ) {
         let session = &screencopy_frame.data::<FrameData>().unwrap().session;
         let Some(capture) = Capture::for_session(session) else {
@@ -207,6 +207,10 @@ impl ScreencopyHandler for AppData {
             wl_buffer: buffer,
             width: front.size.0,
             height: front.size.1,
+            transform: match frame.transform {
+                WEnum::Value(value) => value,
+                WEnum::Unknown(value) => panic!("invalid capture transform: {}", value),
+            },
             #[cfg(feature = "no-subsurfaces")]
             image: cosmic::widget::image::Handle::from_rgba(
                 front.size.0,