Fix iOS build, and add iOS step to CI (#4898)

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This PR
- adds a pipeline to check the ios build
- removes the iOS WaitUntil workaround, which doesn't seem to be
necessary anymore after the winit update (and caused the build for iOS
to fail again because of a missing self
- ~removes a iOS workaround for window size which doesn't seem necessary
anymore~
Turns out it was still needed (but you need to actually restart the app
for the issue to show up, so I didn't catch it first)
- fixes some cargo check errors in run.rs

I've done all these changes in a single PR because otherwise the
pipeline doesn't run but I can also split them in separate PRs if that
makes it easier to review

.github/workflows/rust.yml

@@ -1,4 +1,4 @@
-on: [push, pull_request]
+on: [ push, pull_request ]
 
 name: Rust
 
@@ -167,6 +167,26 @@ jobs:
 
   # ---------------------------------------------------------------------------
 
+  ios:
+    name: ios
+    runs-on: ubuntu-22.04
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: dtolnay/rust-toolchain@master
+        with:
+          toolchain: 1.76.0
+          targets: aarch64-apple-ios
+
+      - name: Set up cargo cache
+        uses: Swatinem/rust-cache@v2
+
+        # Default features are disabled because glutin doesn't compile for ios.
+      - run: cargo check --features wgpu --target aarch64-apple-ios --no-default-features
+        working-directory: crates/eframe
+
+  # ---------------------------------------------------------------------------
+
   windows:
     name: Check Windows
     runs-on: windows-latest

crates/eframe/src/native/epi_integration.rs

@@ -7,11 +7,12 @@ use winit::event_loop::ActiveEventLoop;
 
 use raw_window_handle::{HasDisplayHandle as _, HasWindowHandle as _};
 
-use egui::{DeferredViewportUiCallback, NumExt as _, ViewportBuilder, ViewportId};
+use egui::{DeferredViewportUiCallback, ViewportBuilder, ViewportId};
 use egui_winit::{EventResponse, WindowSettings};
 
 use crate::epi;
 
+#[cfg_attr(target_os = "ios", allow(dead_code, unused_variables, unused_mut))]
 pub fn viewport_builder(
     egui_zoom_factor: f32,
     event_loop: &ActiveEventLoop,
@@ -53,8 +54,10 @@ pub fn viewport_builder(
 
         if clamp_size_to_monitor_size {
             if let Some(initial_window_size) = viewport_builder.inner_size {
-                let initial_window_size = initial_window_size
-                    .at_most(largest_monitor_point_size(egui_zoom_factor, event_loop));
+                let initial_window_size = egui::NumExt::at_most(
+                    initial_window_size,
+                    largest_monitor_point_size(egui_zoom_factor, event_loop),
+                );
                 viewport_builder = viewport_builder.with_inner_size(initial_window_size);
             }
         }
@@ -95,6 +98,7 @@ pub fn apply_window_settings(
     }
 }
 
+#[cfg(not(target_os = "ios"))]
 fn largest_monitor_point_size(egui_zoom_factor: f32, event_loop: &ActiveEventLoop) -> egui::Vec2 {
     crate::profile_function!();
 

crates/eframe/src/native/run.rs

@@ -1,4 +1,4 @@
-use std::{cell::RefCell, time::Instant};
+use std::time::Instant;
 
 use winit::{
     application::ApplicationHandler,
@@ -32,11 +32,12 @@ fn create_event_loop(native_options: &mut epi::NativeOptions) -> Result<EventLoo
 ///
 /// We reuse the event-loop so we can support closing and opening an eframe window
 /// multiple times. This is just a limitation of winit.
+#[cfg(not(target_os = "ios"))]
 fn with_event_loop<R>(
     mut native_options: epi::NativeOptions,
     f: impl FnOnce(&mut EventLoop<UserEvent>, epi::NativeOptions) -> R,
 ) -> Result<R> {
-    thread_local!(static EVENT_LOOP: RefCell<Option<EventLoop<UserEvent>>> = RefCell::new(None));
+    thread_local!(static EVENT_LOOP: std::cell::RefCell<Option<EventLoop<UserEvent>>> = std::cell::RefCell::new(None));
 
     EVENT_LOOP.with(|event_loop| {
         // Since we want to reference NativeOptions when creating the EventLoop we can't
@@ -174,16 +175,6 @@ impl<T: WinitApp> WinitAppWrapper<T> {
             });
 
         if let Some(next_repaint_time) = next_repaint_time {
-            // WaitUntil seems to not work on iOS
-            #[cfg(target_os = "ios")]
-            winit_app
-                .window_id_from_viewport_id(egui::ViewportId::ROOT)
-                .map(|window_id| {
-                    winit_app
-                        .window(window_id)
-                        .map(|window| window.request_redraw())
-                });
-
             event_loop.set_control_flow(ControlFlow::WaitUntil(next_repaint_time));
         };
     }