Add basic ico support (#40822)

Closes https://github.com/zed-industries/zed/discussions/40763

<img width="867" height="1088" alt="Screenshot 2025-10-21 at 23 14 47"
src="https://github.com/user-attachments/assets/d691fb2a-afc6-4445-a335-054ef164e0d3"
/>

Also improves error handling on image open failure:

<img width="864" height="1083" alt="Screenshot 2025-10-21 at 23 14 30"
src="https://github.com/user-attachments/assets/d5388b61-995f-441b-b375-ad5136d1533b"
/>


Release Notes:

- Added basic ico support, improved unsupported image handling

crates/gpui/src/platform/linux/x11/clipboard.rs

@@ -86,6 +86,7 @@ x11rb::atom_manager! {
         SVG__MIME: ImageFormat::mime_type(ImageFormat::Svg ).as_bytes(),
         BMP__MIME: ImageFormat::mime_type(ImageFormat::Bmp ).as_bytes(),
         TIFF_MIME: ImageFormat::mime_type(ImageFormat::Tiff).as_bytes(),
+        ICO__MIME: ImageFormat::mime_type(ImageFormat::Ico ).as_bytes(),
 
         // This is just some random name for the property on our window, into which
         // the clipboard owner writes the data we requested.
@@ -1003,6 +1004,7 @@ impl Clipboard {
             ImageFormat::Svg => self.inner.atoms.SVG__MIME,
             ImageFormat::Bmp => self.inner.atoms.BMP__MIME,
             ImageFormat::Tiff => self.inner.atoms.TIFF_MIME,
+            ImageFormat::Ico => self.inner.atoms.ICO__MIME,
         };
         let data = vec![ClipboardData {
             bytes: image.bytes,

crates/gpui/src/platform/mac/platform.rs

@@ -1607,6 +1607,7 @@ impl From<ImageFormat> for UTType {
             ImageFormat::Gif => Self::gif(),
             ImageFormat::Bmp => Self::bmp(),
             ImageFormat::Svg => Self::svg(),
+            ImageFormat::Ico => Self::ico(),
         }
     }
 }
@@ -1645,6 +1646,11 @@ impl UTType {
         Self(unsafe { ns_string("public.svg-image") })
     }
 
+    pub fn ico() -> Self {
+        // https://developer.apple.com/documentation/uniformtypeidentifiers/uttype-swift.struct/ico
+        Self(unsafe { ns_string("com.microsoft.ico") })
+    }
+
     pub fn tiff() -> Self {
         // https://developer.apple.com/documentation/uniformtypeidentifiers/uttype-swift.struct/tiff
         Self(unsafe { NSPasteboardTypeTIFF }) // This is a rare case where there's a built-in NSPasteboardType