Group glow config in a struct (#8108)

This is a breaking public API change, but is otherwise trivial due to it
not changing any actual runtime behaviour.

This renames eframe's NativeOptions `vsync` option to `glow_vsync` to
make clear without even looking at docs fully that this is specific to
the `glow` backend.

While I think a better option would actually be to change the wgpu
creation options to match the vsync option if not specified (either to
`AutoVsync` or `AutoNoVsync` depending on setting) this would require
this be made an `Option<PresentMode>`, which would be confusing - and
the `WgpuConfiguration` should probably take priority over other options
here, as there's more than 2 present modes that are relevant. So I think
this is a suitable way to go.

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* This does not close an issue - this was a trivial amount of code to
change, so I might as well just make it a PR on the spot.
* [x] I have followed the instructions in the PR template

---------

Co-authored-by: Emil Ernerfeldt <emil.ernerfeldt@gmail.com>

crates/egui_glow/src/lib.rs

@@ -95,3 +95,60 @@ pub fn check_for_gl_error_impl(gl: &glow::Context, file: &str, line: u32, contex
         }
     }
 }
+
+/// Selects the level of hardware graphics acceleration.
+#[cfg(not(target_arch = "wasm32"))]
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
+pub enum HardwareAcceleration {
+    /// Require graphics acceleration.
+    Required,
+
+    /// Prefer graphics acceleration, but fall back to software.
+    Preferred,
+
+    /// Do NOT use graphics acceleration.
+    ///
+    /// On some platforms (macOS) this is ignored and treated the same as [`Self::Preferred`].
+    Off,
+}
+
+/// Configuration for using glow with eframe or the egui-glow winit feature.
+#[derive(Clone)]
+pub struct GlowConfiguration {
+    /// Turn on vertical syncing, limiting the FPS to the display refresh rate.
+    ///
+    /// The default is `true`.
+    #[cfg(not(target_arch = "wasm32"))]
+    pub vsync: bool,
+
+    /// Specify whether or not hardware acceleration is preferred, required, or not.
+    ///
+    /// Default: [`HardwareAcceleration::Preferred`].
+    #[cfg(not(target_arch = "wasm32"))]
+    pub hardware_acceleration: HardwareAcceleration,
+
+    /// Needed for cross compiling for VirtualBox VMSVGA driver with OpenGL ES 2.0 and OpenGL 2.1 which doesn't support SRGB texture.
+    /// See <https://github.com/emilk/egui/pull/1993>.
+    ///
+    /// For OpenGL ES 2.0: set this to [`ShaderVersion::Es100`] to solve blank texture problem (by using the "fallback shader").
+    pub shader_version: Option<ShaderVersion>,
+}
+
+#[cfg_attr(target_arch = "wasm32", expect(clippy::derivable_impls))]
+impl Default for GlowConfiguration {
+    fn default() -> Self {
+        Self {
+            #[cfg(not(target_arch = "wasm32"))]
+            vsync: true,
+            #[cfg(not(target_arch = "wasm32"))]
+            hardware_acceleration: HardwareAcceleration::Preferred,
+            shader_version: None,
+        }
+    }
+}
+
+#[test]
+fn glow_config_impl_send_sync() {
+    fn assert_send_sync<T: Send + Sync>() {}
+    assert_send_sync::<GlowConfiguration>();
+}