Add HarnessBuilder::with_render_options() (closes #7630) (#8060)

Allows to override the default `PREDICTABLE` render options, e.g. if
it's desired to create snapshots with the exact texture options used by
the app.

See #7630 for details / examples.

crates/egui_kittest/src/builder.rs

@@ -18,6 +18,9 @@ pub struct HarnessBuilder<State = ()> {
 
     #[cfg(feature = "snapshot")]
     pub(crate) default_snapshot_options: crate::SnapshotOptions,
+
+    #[cfg(feature = "wgpu")]
+    pub(crate) render_options: egui_wgpu::RendererOptions,
 }
 
 impl<State> Default for HarnessBuilder<State> {
@@ -35,6 +38,9 @@ impl<State> Default for HarnessBuilder<State> {
 
             #[cfg(feature = "snapshot")]
             default_snapshot_options: crate::SnapshotOptions::default(),
+
+            #[cfg(feature = "wgpu")]
+            render_options: egui_wgpu::RendererOptions::PREDICTABLE,
         }
     }
 }
@@ -119,6 +125,16 @@ impl<State> HarnessBuilder<State> {
         self
     }
 
+    /// Configures the [`egui_wgpu::RendererOptions`] used by this harness.
+    ///
+    /// The default is [`egui_wgpu::RendererOptions::PREDICTABLE`].
+    #[cfg(feature = "wgpu")]
+    #[inline]
+    pub fn with_render_options(mut self, options: egui_wgpu::RendererOptions) -> Self {
+        self.render_options = options;
+        self
+    }
+
     /// Set the [`TestRenderer`] to use for rendering.
     ///
     /// By default, a [`LazyRenderer`] is used.
@@ -133,7 +149,8 @@ impl<State> HarnessBuilder<State> {
     /// This sets up a [`crate::wgpu::WgpuTestRenderer`] with the default setup.
     #[cfg(feature = "wgpu")]
     pub fn wgpu(self) -> Self {
-        self.renderer(crate::wgpu::WgpuTestRenderer::default())
+        let test_renderer = crate::wgpu::WgpuTestRenderer::with_render_options(self.render_options);
+        self.renderer(test_renderer)
     }
 
     /// Enable wgpu rendering with the given setup.

crates/egui_kittest/src/lib.rs

@@ -116,6 +116,11 @@ impl<'a, State> Harness<'a, State> {
 
             #[cfg(feature = "snapshot")]
             default_snapshot_options,
+
+            // rustfmt adds this weird indentation below.
+            // See: https://github.com/rust-lang/rustfmt/issues/5920
+            #[cfg(feature = "wgpu")]
+                render_options: _,
         } = builder;
         let ctx = ctx.unwrap_or_default();
         ctx.set_theme(theme);

crates/egui_kittest/src/wgpu.rs

@@ -58,7 +58,10 @@ pub fn default_wgpu_setup() -> egui_wgpu::WgpuSetup {
     egui_wgpu::WgpuSetup::CreateNew(setup)
 }
 
-pub fn create_render_state(setup: WgpuSetup) -> egui_wgpu::RenderState {
+pub fn create_render_state(
+    setup: WgpuSetup,
+    options: egui_wgpu::RendererOptions,
+) -> egui_wgpu::RenderState {
     // No display handle needed for headless testing — we don't present to a window.
     let instance = pollster::block_on(setup.new_instance());
 
@@ -69,7 +72,7 @@ pub fn create_render_state(setup: WgpuSetup) -> egui_wgpu::RenderState {
         },
         &instance,
         None,
-        egui_wgpu::RendererOptions::PREDICTABLE,
+        options,
     ))
     .expect("Failed to create render state")
 }
@@ -89,14 +92,17 @@ impl WgpuTestRenderer {
     /// Create a new [`WgpuTestRenderer`] with the default setup.
     pub fn new() -> Self {
         Self {
-            render_state: create_render_state(default_wgpu_setup()),
+            render_state: create_render_state(
+                default_wgpu_setup(),
+                egui_wgpu::RendererOptions::PREDICTABLE,
+            ),
         }
     }
 
     /// Create a new [`WgpuTestRenderer`] with the given setup.
     pub fn from_setup(setup: WgpuSetup) -> Self {
         Self {
-            render_state: create_render_state(setup),
+            render_state: create_render_state(setup, egui_wgpu::RendererOptions::PREDICTABLE),
         }
     }
 
@@ -115,6 +121,13 @@ impl WgpuTestRenderer {
         );
         Self { render_state }
     }
+
+    /// Create a new [`WgpuTestRenderer`] with custom render options.
+    pub fn with_render_options(options: egui_wgpu::RendererOptions) -> Self {
+        Self {
+            render_state: create_render_state(default_wgpu_setup(), options),
+        }
+    }
 }
 
 impl crate::TestRenderer for WgpuTestRenderer {