eframe: Set app icon on Mac and Windows (#2940)

* eframe: Set app icon on Mac and Windows

Also: correctly set window title on Mac when launching from
another process, e.g. python.

Co-authored-by: Wumpf <[email protected]>

* lint fixes

* Fix web build

* fix typo

* Try fix windows build

---------

Co-authored-by: Wumpf <[email protected]>

crates/eframe/Cargo.toml

@@ -58,7 +58,7 @@ web_screen_reader = ["tts"]
 
 ## If set, eframe will look for the env-var `EFRAME_SCREENSHOT_TO` and write a screenshot to that location, and then quit.
 ## This is used to generate images for the examples.
-__screenshot = ["dep:image"]
+__screenshot = []
 
 ## Use [`wgpu`](https://docs.rs/wgpu) for painting (via [`egui-wgpu`](https://github.com/emilk/egui/tree/master/crates/egui-wgpu)).
 ## This overrides the `glow` feature.
@@ -98,6 +98,9 @@ egui-winit = { version = "0.21.1", path = "../egui-winit", default-features = fa
   "clipboard",
   "links",
 ] }
+image = { version = "0.24", default-features = false, features = [
+  "png",
+] } # Needed for app icon
 raw-window-handle = { version = "0.5.0" }
 winit = "0.28.1"
 
@@ -112,12 +115,18 @@ pollster = { version = "0.3", optional = true } # needed for wgpu
 # this can be done at the same time we expose x11/wayland features of winit crate.
 glutin = { version = "0.30", optional = true }
 glutin-winit = { version = "0.3.0", optional = true }
-image = { version = "0.24", optional = true, default-features = false, features = [
-  "png",
-] }
 puffin = { version = "0.14", optional = true }
 wgpu = { version = "0.15.0", optional = true }
 
+# mac:
+[target.'cfg(any(target_os = "macos"))'.dependencies]
+cocoa = "0.24.1"
+objc = "0.2.7"
+
+# windows:
+[target.'cfg(any(target_os = "windows"))'.dependencies]
+winapi = "0.3.9"
+
 # -------------------------------------------
 # web:
 [target.'cfg(target_arch = "wasm32")'.dependencies]

crates/eframe/src/epi/icon_data.rs

@@ -0,0 +1,64 @@
+/// Image data for an application icon.
+///
+/// Use a square image, e.g. 256x256 pixels.
+/// You can use a transparent background.
+#[derive(Clone)]
+pub struct IconData {
+    /// RGBA pixels, with separate/unmultiplied alpha.
+    pub rgba: Vec<u8>,
+
+    /// Image width. This should be a multiple of 4.
+    pub width: u32,
+
+    /// Image height. This should be a multiple of 4.
+    pub height: u32,
+}
+
+impl IconData {
+    /// Convert into [`image::RgbaImage`]
+    ///
+    /// # Errors
+    /// If this is not a valid png.
+    pub fn try_from_png_bytes(png_bytes: &[u8]) -> Result<Self, image::ImageError> {
+        let image = image::load_from_memory(png_bytes)?;
+        Ok(Self::from_image(image))
+    }
+
+    fn from_image(image: image::DynamicImage) -> Self {
+        let image = image.into_rgba8();
+        Self {
+            width: image.width(),
+            height: image.height(),
+            rgba: image.into_raw(),
+        }
+    }
+
+    /// Convert into [`image::RgbaImage`]
+    ///
+    /// # Errors
+    /// If `width*height != 4 * rgba.len()`, or if the image is too big.
+    pub fn to_image(&self) -> Result<image::RgbaImage, String> {
+        let Self {
+            rgba,
+            width,
+            height,
+        } = self.clone();
+        image::RgbaImage::from_raw(width, height, rgba).ok_or_else(|| "Invalid IconData".to_owned())
+    }
+
+    /// Encode as PNG.
+    ///
+    /// # Errors
+    /// The image is invalid, or the PNG encoder failed.
+    pub fn to_png_bytes(&self) -> Result<Vec<u8>, String> {
+        let image = self.to_image()?;
+        let mut png_bytes: Vec<u8> = Vec::new();
+        image
+            .write_to(
+                &mut std::io::Cursor::new(&mut png_bytes),
+                image::ImageOutputFormat::Png,
+            )
+            .map_err(|err| err.to_string())?;
+        Ok(png_bytes)
+    }
+}

crates/eframe/src/epi.rs → crates/eframe/src/epi/mod.rs

@@ -6,6 +6,12 @@
 
 #![warn(missing_docs)] // Let's keep `epi` well-documented.
 
+#[cfg(not(target_arch = "wasm32"))]
+mod icon_data;
+
+#[cfg(not(target_arch = "wasm32"))]
+pub use icon_data::IconData;
+
 #[cfg(target_arch = "wasm32")]
 use std::any::Any;
 
@@ -621,19 +627,6 @@ impl std::str::FromStr for Renderer {
 
 // ----------------------------------------------------------------------------
 
-/// Image data for an application icon.
-#[derive(Clone)]
-pub struct IconData {
-    /// RGBA pixels, unmultiplied.
-    pub rgba: Vec<u8>,
-
-    /// Image width. This should be a multiple of 4.
-    pub width: u32,
-
-    /// Image height. This should be a multiple of 4.
-    pub height: u32,
-}
-
 /// Represents the surroundings of your app.
 ///
 /// It provides methods to inspect the surroundings (are we on the web?),