Cover stroke commit face input binding helper

tests/paint_renderer/compositor_tests.cpp

@@ -1885,6 +1885,43 @@ void retained_stroke_commit_input_binder_uses_sequence_slots(pp::tests::Harness&
     PP_EXPECT(h, bound_samplers[4].second == 4);
 }
 
+void retained_stroke_commit_face_input_binder_forwards_sequence_slots(pp::tests::Harness& h)
+{
+    const auto sequence = plan_canvas_stroke_commit_sequence(
+        CanvasStrokeCommitRequest {
+            .erase_mode = false,
+            .alpha_locked = false,
+            .selection_mask_active = true,
+            .dual_stroke_enabled = true,
+            .pattern_enabled = true,
+        });
+
+    std::vector<int> active_slots;
+    std::vector<CanvasStrokeCommitTextureRole> bound_textures;
+    std::vector<std::pair<CanvasStrokeCommitTextureRole, int>> bound_samplers;
+
+    pp::panopainter::bind_legacy_canvas_stroke_commit_face_inputs(
+        sequence,
+        [&](int texture_slot) {
+            active_slots.push_back(texture_slot);
+        },
+        [&](CanvasStrokeCommitTextureRole role) {
+            bound_textures.push_back(role);
+        },
+        [&](CanvasStrokeCommitTextureRole role, int texture_slot) {
+            bound_samplers.emplace_back(role, texture_slot);
+        });
+
+    PP_EXPECT(h, active_slots.size() == 5U);
+    PP_EXPECT(h, bound_textures.size() == 5U);
+    PP_EXPECT(h, bound_samplers.size() == 5U);
+    PP_EXPECT(h, active_slots[0] == 0);
+    PP_EXPECT(h, active_slots[4] == 4);
+    PP_EXPECT(h, bound_textures[2] == CanvasStrokeCommitTextureRole::selection_mask);
+    PP_EXPECT(h, bound_samplers[3].first == CanvasStrokeCommitTextureRole::dual_stroke);
+    PP_EXPECT(h, bound_samplers[3].second == 3);
+}
+
 void retained_stroke_commit_dilate_copy_uses_layer_scratch_slot(pp::tests::Harness& h)
 {
     const auto sequence = plan_canvas_stroke_commit_sequence(