Add Context::copy_image (#5533)

* Closes https://github.com/emilk/egui/issues/5424

This adds support for copying images to the system clipboard on native
and on web using `Context::copy_image`.

crates/egui-winit/Cargo.toml

@@ -36,11 +36,11 @@ android-game-activity = ["winit/android-game-activity"]
 android-native-activity = ["winit/android-native-activity"]
 
 ## [`bytemuck`](https://docs.rs/bytemuck) enables you to cast [`egui::epaint::Vertex`], [`egui::Vec2`] etc to `&[u8]`.
-bytemuck = ["egui/bytemuck"]
+bytemuck = ["egui/bytemuck", "dep:bytemuck"]
 
 ## Enable cut/copy/paste to OS clipboard.
 ## If disabled a clipboard will be simulated so you can still copy/paste within the egui app.
-clipboard = ["arboard", "smithay-clipboard"]
+clipboard = ["arboard", "bytemuck", "smithay-clipboard"]
 
 ## Enable opening links in a browser when an egui hyperlink is clicked.
 links = ["webbrowser"]
@@ -69,6 +69,8 @@ winit = { workspace = true, default-features = false }
 # feature accesskit
 accesskit_winit = { version = "0.23", optional = true }
 
+bytemuck = { workspace = true, optional = true }
+
 ## Enable this when generating docs.
 document-features = { workspace = true, optional = true }
 
@@ -84,4 +86,6 @@ smithay-clipboard = { version = "0.7.2", optional = true }
 wayland-cursor = { version = "0.31.1", default-features = false, optional = true }
 
 [target.'cfg(not(target_os = "android"))'.dependencies]
-arboard = { version = "3.3", optional = true, default-features = false }
+arboard = { version = "3.3", optional = true, default-features = false, features = [
+    "image-data",
+] }

crates/egui-winit/src/clipboard.rs

@@ -82,7 +82,7 @@ impl Clipboard {
         Some(self.clipboard.clone())
     }
 
-    pub fn set(&mut self, text: String) {
+    pub fn set_text(&mut self, text: String) {
         #[cfg(all(
             any(
                 target_os = "linux",
@@ -108,6 +108,24 @@ impl Clipboard {
 
         self.clipboard = text;
     }
+
+    pub fn set_image(&mut self, image: &egui::ColorImage) {
+        #[cfg(all(feature = "arboard", not(target_os = "android")))]
+        if let Some(clipboard) = &mut self.arboard {
+            if let Err(err) = clipboard.set_image(arboard::ImageData {
+                width: image.width(),
+                height: image.height(),
+                bytes: std::borrow::Cow::Borrowed(bytemuck::cast_slice(&image.pixels)),
+            }) {
+                log::error!("arboard copy/cut error: {err}");
+            }
+            log::debug!("Copied image to clipboard");
+            return;
+        }
+
+        log::error!("Copying images is not supported. Enable the 'clipboard' feature of `egui-winit` to enable it.");
+        _ = image;
+    }
 }
 
 #[cfg(all(feature = "arboard", not(target_os = "android")))]

crates/egui-winit/src/lib.rs

@@ -190,7 +190,7 @@ impl State {
 
     /// Places the text onto the clipboard.
     pub fn set_clipboard_text(&mut self, text: String) {
-        self.clipboard.set(text);
+        self.clipboard.set_text(text);
     }
 
     /// Returns [`false`] or the last value that [`Window::set_ime_allowed()`] was called with, used for debouncing.
@@ -840,7 +840,10 @@ impl State {
         for command in commands {
             match command {
                 egui::OutputCommand::CopyText(text) => {
-                    self.clipboard.set(text);
+                    self.clipboard.set_text(text);
+                }
+                egui::OutputCommand::CopyImage(image) => {
+                    self.clipboard.set_image(&image);
                 }
                 egui::OutputCommand::OpenUrl(open_url) => {
                     open_url_in_browser(&open_url.url);
@@ -855,7 +858,7 @@ impl State {
         }
 
         if !copied_text.is_empty() {
-            self.clipboard.set(copied_text);
+            self.clipboard.set_text(copied_text);
         }
 
         let allow_ime = ime.is_some();