icon: refactor Icon to be dyn

Same as for `CustomCursor`. However, the API uses `dyn` stuff only
because of `Windows` backend at the time of writing, generally, platforms
should just have a separate method that deals with all of that, and e.g.
top-level winit only guarantees `Rgba`.

src/platform_impl/linux/mod.rs

@@ -13,7 +13,6 @@ use crate::application::ApplicationHandler;
 use crate::dpi::Size;
 use crate::error::{EventLoopError, NotSupportedError};
 use crate::event_loop::ActiveEventLoop;
-pub(crate) use crate::icon::RgbaIcon as PlatformIcon;
 use crate::platform::pump_events::PumpStatus;
 #[cfg(x11_platform)]
 use crate::platform::x11::WindowType as XWindowType;

src/platform_impl/linux/x11/window.rs

@@ -28,15 +28,16 @@ use crate::dpi::{PhysicalInsets, PhysicalPosition, PhysicalSize, Position, Size}
 use crate::error::{NotSupportedError, RequestError};
 use crate::event::{SurfaceSizeWriter, WindowEvent};
 use crate::event_loop::AsyncRequestSerial;
+use crate::icon::RgbaIcon;
 use crate::monitor::{
     Fullscreen, MonitorHandle as CoreMonitorHandle, MonitorHandleProvider, VideoMode,
 };
 use crate::platform::x11::WindowType;
+use crate::platform_impl::common;
 use crate::platform_impl::x11::atoms::*;
 use crate::platform_impl::x11::{
     xinput_fp1616_to_float, MonitorHandle as X11MonitorHandle, WakeSender, X11Error,
 };
-use crate::platform_impl::{common, PlatformIcon};
 use crate::window::{
     CursorGrabMode, ImePurpose, ResizeDirection, Theme, UserAttentionType, Window as CoreWindow,
     WindowAttributes, WindowButtons, WindowId, WindowLevel,
@@ -203,7 +204,11 @@ impl CoreWindow for Window {
     }
 
     fn set_window_icon(&self, window_icon: Option<crate::window::Icon>) {
-        self.0.set_window_icon(window_icon.map(|inner| inner.inner))
+        let icon = match window_icon.as_ref() {
+            Some(icon) => icon.0.cast_ref::<RgbaIcon>(),
+            None => None,
+        };
+        self.0.set_window_icon(icon)
     }
 
     fn set_ime_cursor_area(&self, position: Position, size: Size) {
@@ -765,8 +770,10 @@ impl UnownedWindow {
             .check());
 
             // Set window icons
-            if let Some(icon) = window_attrs.window_icon {
-                leap!(window.set_icon_inner(icon.inner)).ignore_error();
+            if let Some(icon) =
+                window_attrs.window_icon.as_ref().and_then(|icon| icon.0.cast_ref::<RgbaIcon>())
+            {
+                leap!(window.set_icon_inner(icon)).ignore_error();
             }
 
             // Opt into handling window close and resize synchronization
@@ -1404,7 +1411,7 @@ impl UnownedWindow {
         self.xconn.flush_requests().expect("Failed to set window-level state");
     }
 
-    fn set_icon_inner(&self, icon: PlatformIcon) -> Result<VoidCookie<'_>, X11Error> {
+    fn set_icon_inner(&self, icon: &RgbaIcon) -> Result<VoidCookie<'_>, X11Error> {
         let atoms = self.xconn.atoms();
         let icon_atom = atoms[_NET_WM_ICON];
         let data = icon.to_cardinals();
@@ -1431,7 +1438,7 @@ impl UnownedWindow {
     }
 
     #[inline]
-    pub(crate) fn set_window_icon(&self, icon: Option<PlatformIcon>) {
+    pub(crate) fn set_window_icon(&self, icon: Option<&RgbaIcon>) {
         match icon {
             Some(icon) => self.set_icon_inner(icon),
             None => self.unset_icon_inner(),