Add `egui_kittest::Harness::set_options` (#7638)

Makes it easier to set the same options for many tests

---------

Co-authored-by: Lucas Meurer <hi@lucasmerlin.me>

crates/egui_kittest/src/builder.rs

@@ -14,6 +14,9 @@ pub struct HarnessBuilder<State = ()> {
     pub(crate) state: PhantomData<State>,
     pub(crate) renderer: Box<dyn TestRenderer>,
     pub(crate) wait_for_pending_images: bool,
+
+    #[cfg(feature = "snapshot")]
+    pub(crate) default_snapshot_options: crate::SnapshotOptions,
 }
 
 impl<State> Default for HarnessBuilder<State> {
@@ -28,6 +31,9 @@ impl<State> Default for HarnessBuilder<State> {
             step_dt: 1.0 / 4.0,
             wait_for_pending_images: true,
             os: egui::os::OperatingSystem::Nix,
+
+            #[cfg(feature = "snapshot")]
+            default_snapshot_options: crate::SnapshotOptions::default(),
         }
     }
 }
@@ -56,6 +62,12 @@ impl<State> HarnessBuilder<State> {
         self
     }
 
+    /// Set the default options used for snapshot tests on this harness.
+    #[cfg(feature = "snapshot")]
+    pub fn with_options(&mut self, options: crate::SnapshotOptions) {
+        self.default_snapshot_options = options;
+    }
+
     /// Override the [`egui::os::OperatingSystem`] reported to egui.
     ///
     /// This affects e.g. the way shortcuts are displayed. So for snapshot tests,

crates/egui_kittest/src/lib.rs

@@ -75,6 +75,9 @@ pub struct Harness<'a, State = ()> {
     step_dt: f32,
     wait_for_pending_images: bool,
     queued_events: EventQueue,
+
+    #[cfg(feature = "snapshot")]
+    default_snapshot_options: SnapshotOptions,
 }
 
 impl<State> Debug for Harness<'_, State> {
@@ -100,6 +103,9 @@ impl<'a, State> Harness<'a, State> {
             state: _,
             mut renderer,
             wait_for_pending_images,
+
+            #[cfg(feature = "snapshot")]
+            default_snapshot_options,
         } = builder;
         let ctx = ctx.unwrap_or_default();
         ctx.set_theme(theme);
@@ -147,6 +153,9 @@ impl<'a, State> Harness<'a, State> {
             step_dt,
             wait_for_pending_images,
             queued_events: Default::default(),
+
+            #[cfg(feature = "snapshot")]
+            default_snapshot_options,
         };
         // Run the harness until it is stable, ensuring that all Areas are shown and animations are done
         harness.run_ok();

crates/egui_kittest/src/snapshot.rs

@@ -7,6 +7,7 @@ use std::path::PathBuf;
 pub type SnapshotResult = Result<(), SnapshotError>;
 
 #[non_exhaustive]
+#[derive(Clone, Debug)]
 pub struct SnapshotOptions {
     /// The threshold for the image comparison.
     /// The default is `0.6` (which is enough for most egui tests to pass across different
@@ -556,9 +557,17 @@ pub fn image_snapshot(current: &image::RgbaImage, name: impl Into<String>) {
 
 #[cfg(any(feature = "wgpu", feature = "snapshot"))]
 impl<State> Harness<'_, State> {
+    /// The default options used for snapshot tests.
+    /// set by [`crate::HarnessBuilder::with_options`].
+    pub fn options(&self) -> &SnapshotOptions {
+        &self.default_snapshot_options
+    }
+
     /// Render an image using the setup [`crate::TestRenderer`] and compare it to the snapshot
     /// with custom options.
     ///
+    /// These options will override the ones set by [`crate::HarnessBuilder::with_options`].
+    ///
     /// If you want to change the default options for your whole project, you could create an
     /// [extension trait](http://xion.io/post/code/rust-extension-traits.html) to create a
     /// new `my_image_snapshot` function on the Harness that calls this function with the desired options.
@@ -586,6 +595,9 @@ impl<State> Harness<'_, State> {
     }
 
     /// Render an image using the setup [`crate::TestRenderer`] and compare it to the snapshot.
+    ///
+    /// This is like [`Self::try_snapshot_options`] but will use the options set by [`crate::HarnessBuilder::with_options`].
+    ///
     /// The snapshot will be saved under `tests/snapshots/{name}.png`.
     /// The new image from the last test run will be saved under `tests/snapshots/{name}.new.png`.
     /// If the new image didn't match the snapshot, a diff image will be saved under `tests/snapshots/{name}.diff.png`.
@@ -597,12 +609,14 @@ impl<State> Harness<'_, State> {
         let image = self
             .render()
             .map_err(|err| SnapshotError::RenderError { err })?;
-        try_image_snapshot(&image, name)
+        try_image_snapshot_options(&image, name.into(), &self.default_snapshot_options)
     }
 
     /// Render an image using the setup [`crate::TestRenderer`] and compare it to the snapshot
     /// with custom options.
     ///
+    /// These options will override the ones set by [`crate::HarnessBuilder::with_options`].
+    ///
     /// If you want to change the default options for your whole project, you could create an
     /// [extension trait](http://xion.io/post/code/rust-extension-traits.html) to create a
     /// new `my_image_snapshot` function on the Harness that calls this function with the desired options.
@@ -629,6 +643,9 @@ impl<State> Harness<'_, State> {
     }
 
     /// Render an image using the setup [`crate::TestRenderer`] and compare it to the snapshot.
+    ///
+    /// This is like [`Self::snapshot_options`] but will use the options set by [`crate::HarnessBuilder::with_options`].
+    ///
     /// The snapshot will be saved under `tests/snapshots/{name}.png`.
     /// The new image from the last test run will be saved under `tests/snapshots/{name}.new.png`.
     /// If the new image didn't match the snapshot, a diff image will be saved under `tests/snapshots/{name}.diff.png`.