Allow software rendering OpenGL by default (#1693)

Follow-up to https://github.com/emilk/egui/pull/1681

CHANGELOG.md

@@ -6,7 +6,6 @@ NOTE: [`epaint`](epaint/CHANGELOG.md), [`eframe`](eframe/CHANGELOG.md), [`egui-w
 
 ## Unreleased
 ### Added ⭐
-* Added `NativeOptions::hardware_acceleration` to allow opting out of hardware acceleration for less power consumption ([#1681](https://github.com/emilk/egui/pull/1681)).
 * Added `*_released` & `*_clicked` methods for `PointerState` ([#1582](https://github.com/emilk/egui/pull/1582)).
 * Added `egui::hex_color!` to create `Color32`'s from hex strings under the `color-hex` feature ([#1596](https://github.com/emilk/egui/pull/1596)).
 * Optimized painting of filled circles (e.g. for scatter plots) by 10x or more ([#1616](https://github.com/emilk/egui/pull/1616)).

eframe/CHANGELOG.md

@@ -10,7 +10,7 @@ NOTE: [`egui-winit`](../egui-winit/CHANGELOG.md), [`egui_glium`](../egui_glium/C
   * Add features "wgpu" and "glow"
   * Add `NativeOptions::renderer` to switch between the rendering backends
 * Fix clipboard on Wayland ([#1613](https://github.com/emilk/egui/pull/1613)).
-
+* Allow running on native without hardware accelerated rendering. Change with `NativeOptions::hardware_acceleration` ([#1681]([#1693](https://github.com/emilk/egui/pull/1693)).
 
 ## 0.18.0 - 2022-04-30
 * MSRV (Minimum Supported Rust Version) is now `1.60.0` ([#1467](https://github.com/emilk/egui/pull/1467)).

eframe/src/epi.rs

@@ -148,6 +148,21 @@ pub trait App {
     fn post_rendering(&mut self, _window_size_px: [u32; 2], _frame: &Frame) {}
 }
 
+/// Selects the level of hardware graphics acceleration.
+#[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,
+}
+
 /// Options controlling the behavior of a native window.
 ///
 /// Only a single native window is currently supported.
@@ -221,10 +236,10 @@ pub struct NativeOptions {
     /// `egui` doesn't need the stencil buffer, so the default value is 0.
     pub stencil_buffer: u8,
 
-    /// Use hardware acceleration if available. On macOS, this will possibly
+    /// Specify wether or not hardware acceleration is preferred, required, or not.
-    /// use a dedicated GPU which will lead to higher power consumption.
+    ///
-    /// The default value is `Some(true)`
+    /// Default: [`HardwareAcceleration::Preferred`].
-    pub hardware_acceleration: Option<bool>,
+    pub hardware_acceleration: HardwareAcceleration,
 
     /// What rendering backend to use.
     pub renderer: Renderer,
@@ -248,7 +263,7 @@ impl Default for NativeOptions {
             multisampling: 0,
             depth_buffer: 0,
             stencil_buffer: 0,
-            hardware_acceleration: Some(true),
+            hardware_acceleration: HardwareAcceleration::Preferred,
             renderer: Renderer::default(),
         }
     }

eframe/src/native/run.rs

@@ -15,9 +15,18 @@ fn create_display(
     glow::Context,
 ) {
     crate::profile_function!();
+
+    use crate::HardwareAcceleration;
+
+    let hardware_acceleration = match native_options.hardware_acceleration {
+        HardwareAcceleration::Required => Some(true),
+        HardwareAcceleration::Preferred => None,
+        HardwareAcceleration::Off => Some(false),
+    };
+
     let gl_window = unsafe {
         glutin::ContextBuilder::new()
-            .with_hardware_acceleration(native_options.hardware_acceleration)
+            .with_hardware_acceleration(hardware_acceleration)
             .with_depth_buffer(native_options.depth_buffer)
             .with_multisampling(native_options.multisampling)
             .with_srgb(true)