Fix cargo test --all-features breaking rendering due to unity vertexes (#5542)

* Closes #5297 
* [x] I have followed the instructions in the PR template

It's not great but I wasn't able to come up with a better solution.

.github/workflows/rust.yml

@@ -238,12 +238,10 @@ jobs:
         uses: Swatinem/rust-cache@v2
 
       - name: Run tests
-        # TODO(lucasmerlin): Enable --all-features (currently this breaks the rendering in the tests because of the `unity` feature)
-        run: cargo test
+        run: cargo test --all-features
 
       - name: Run doc-tests
-        # TODO(lucasmerlin): Enable --all-features (currently this breaks the rendering in the tests because of the `unity` feature)
-        run: cargo test --doc
+        run: cargo test --all-features --doc
 
       - name: Upload artifacts
         uses: actions/upload-artifact@v4

CONTRIBUTING.md

@@ -32,7 +32,8 @@ For small things, just go ahead an open a PR. For bigger things, please file an
 Browse through [`ARCHITECTURE.md`](ARCHITECTURE.md) to get a sense of how all pieces connects.
 
 You can test your code locally by running `./scripts/check.sh`.
-There are snapshots test that might need to be updated. Run the tests with `UPDATE_SNAPSHOTS=true` to update them.
+There are snapshots test that might need to be updated. 
+Run the tests with `UPDATE_SNAPSHOTS=true cargo test --workspace --all-features` to update all of them.
 For more info about the tests see [egui_kittest](./crates/egui_kittest/README.md).
 
 We use [git-lfs](https://git-lfs.com/) to store big files in the repository.

crates/egui/Cargo.toml

@@ -74,6 +74,10 @@ serde = ["dep:serde", "epaint/serde", "accesskit?/serde"]
 ## Change Vertex layout to be compatible with unity
 unity = ["epaint/unity"]
 
+## Override and disable the unity feature
+## This exists, so that when testing with --all-features, snapshots render correctly.
+_override_unity = ["epaint/_override_unity"]
+
 
 [dependencies]
 emath = { workspace = true, default-features = false }

crates/egui_demo_lib/tests/snapshots/demos/Code Editor.png

@@ -1,3 +1,3 @@
 version https://git-lfs.github.com/spec/v1
-oid sha256:b8ca5a27491c0589a97e43a70bc10dc52778d25ca3f7e7c895dbbbb784adfcfa
-size 33245
+oid sha256:0a1099b85a1aaf20f3f1e091bc68259f811737feaefdfcc12acd067eca8f9117
+size 27083

crates/egui_demo_lib/tests/snapshots/demos/Code Example.png

@@ -1,3 +1,3 @@
 version https://git-lfs.github.com/spec/v1
-oid sha256:37ba383a2ba7f00f8064d21203c22f9de2f688ea4fbd45d400c979187686cf33
-size 80861
+oid sha256:6969c6da67ea6cc7ebbbd7a2cc1cb13d4720befe28126367cbf2b2679d037674
+size 82363

crates/epaint/Cargo.toml

@@ -66,6 +66,10 @@ serde = ["dep:serde", "ahash/serde", "emath/serde", "ecolor/serde"]
 ## Change Vertex layout to be compatible with unity
 unity = []
 
+## Override and disable the unity feature
+## This exists, so that when testing with --all-features, snapshots render correctly.
+_override_unity = []
+
 [dependencies]
 emath.workspace = true
 ecolor.workspace = true

crates/epaint/src/mesh.rs

@@ -6,7 +6,7 @@ use emath::{Pos2, Rect, Rot2, TSTransform, Vec2};
 /// Should be friendly to send to GPU as is.
 #[repr(C)]
 #[derive(Clone, Copy, Debug, Default, PartialEq, Eq)]
-#[cfg(not(feature = "unity"))]
+#[cfg(any(not(feature = "unity"), feature = "_override_unity"))]
 #[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
 #[cfg_attr(feature = "bytemuck", derive(bytemuck::Pod, bytemuck::Zeroable))]
 pub struct Vertex {
@@ -25,7 +25,7 @@ pub struct Vertex {
 
 #[repr(C)]
 #[derive(Clone, Copy, Debug, Default, PartialEq, Eq)]
-#[cfg(feature = "unity")]
+#[cfg(all(feature = "unity", not(feature = "_override_unity")))]
 #[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
 #[cfg_attr(feature = "bytemuck", derive(bytemuck::Pod, bytemuck::Zeroable))]
 pub struct Vertex {