Extract stroke commit request assembly

tests/paint_renderer/compositor_tests.cpp

@@ -1922,6 +1922,56 @@ void retained_stroke_commit_face_input_binder_forwards_sequence_slots(pp::tests:
     PP_EXPECT(h, bound_samplers[3].second == 3);
 }
 
+void retained_stroke_commit_request_builder_preserves_dirty_face_order(pp::tests::Harness& h)
+{
+    const pp::panopainter::LegacyCanvasStrokeCommitCallbacks callbacks {
+        .mark_commit_started = []() {},
+        .capture_render_state = []() {},
+        .prepare_render_state = []() {},
+        .restore_render_state = []() {},
+        .publish_history = []() {},
+        .capture_timelapse_frame = []() {},
+        .bind_layer_framebuffer = [](int) {},
+        .capture_history_region = [](int) {},
+        .apply_layer_dirty_region = [](int) {},
+        .copy_layer_to_commit_destination = [](int) {},
+        .bind_commit_inputs = [](int) {},
+        .execute_erase_composite = [](int) {},
+        .execute_paint_composite = [](int) {},
+        .copy_committed_to_dilate_source = [](int) {},
+        .execute_commit_dilate = [](int) {},
+        .unbind_layer_framebuffer = [](int) {},
+    };
+    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,
+        });
+    const std::array<pp::panopainter::LegacyCanvasStrokeCommitFace, 6> faces {
+        pp::panopainter::LegacyCanvasStrokeCommitFace { .index = 0, .dirty = false },
+        pp::panopainter::LegacyCanvasStrokeCommitFace { .index = 1, .dirty = true },
+        pp::panopainter::LegacyCanvasStrokeCommitFace { .index = 2, .dirty = false },
+        pp::panopainter::LegacyCanvasStrokeCommitFace { .index = 3, .dirty = true },
+        pp::panopainter::LegacyCanvasStrokeCommitFace { .index = 4, .dirty = false },
+        pp::panopainter::LegacyCanvasStrokeCommitFace { .index = 5, .dirty = true },
+    };
+
+    const auto request = pp::panopainter::LegacyCanvasStrokeCommitRequest {
+        .context = "test",
+        .faces = faces,
+        .sequence = sequence,
+        .callbacks = callbacks,
+    };
+
+    PP_EXPECT(h, request.faces[0].index == 0);
+    PP_EXPECT(h, request.faces[1].index == 1);
+    PP_EXPECT(h, request.faces[3].dirty);
+    PP_EXPECT(h, request.faces[5].index == 5);
+}
+
 void retained_stroke_commit_dilate_copy_uses_layer_scratch_slot(pp::tests::Harness& h)
 {
     const auto sequence = plan_canvas_stroke_commit_sequence(