Refactor viewport ids in eframe (#3607)

Simplifies some things

crates/egui_glow/src/winit.rs

@@ -1,7 +1,7 @@
 pub use egui_winit;
 pub use egui_winit::EventResponse;
 
-use egui::{ViewportId, ViewportIdPair, ViewportOutput};
+use egui::{ViewportId, ViewportOutput};
 use egui_winit::winit;
 
 use crate::shader_version::ShaderVersion;
@@ -35,6 +35,7 @@ impl EguiGlow {
             .unwrap();
 
         let egui_winit = egui_winit::State::new(
+            ViewportId::ROOT,
             event_loop,
             native_pixels_per_point,
             Some(painter.max_texture_side()),
@@ -58,9 +59,7 @@ impl EguiGlow {
 
     /// Call [`Self::paint`] later to paint.
     pub fn run(&mut self, window: &winit::window::Window, run_ui: impl FnMut(&egui::Context)) {
-        let raw_input = self
-            .egui_winit
-            .take_egui_input(window, ViewportIdPair::ROOT);
+        let raw_input = self.egui_winit.take_egui_input(window);
 
         let egui::FullOutput {
             platform_output,
@@ -87,12 +86,8 @@ impl EguiGlow {
             }
         }
 
-        self.egui_winit.handle_platform_output(
-            window,
-            ViewportId::ROOT,
-            &self.egui_ctx,
-            platform_output,
-        );
+        self.egui_winit
+            .handle_platform_output(window, &self.egui_ctx, platform_output);
 
         self.shapes = shapes;
         self.pixels_per_point = pixels_per_point;