From ba8bf45dbcf53c6076aacd91072673cf75223071 Mon Sep 17 00:00:00 2001
From: Emil <65846814+emil28092005@users.noreply.github.com>
Date: Thu, 24 Sep 2026 02:30:41 +0300
Subject: [PATCH] Add repeatable synthetic Editor input latency probe

---
 cmake/EditorUI.cmake        |  3 ++
 tests/editor_ui_latency.cpp | 70 +++++++++++++++++++++++++++++++++++++
 2 files changed, 73 insertions(+)
 create mode 100644 tests/editor_ui_latency.cpp

diff --git a/cmake/EditorUI.cmake b/cmake/EditorUI.cmake
index 63556c3..d53698c 100644
--- a/cmake/EditorUI.cmake
+++ b/cmake/EditorUI.cmake
@@ -47,5 +47,8 @@ if(TARGET faset_ui AND TARGET faset_editor_session AND TARGET faset_scene_view)
         set_tests_properties(editor_ui_gizmos PROPERTIES LABELS "gpu")
         add_test(NAME editor_ui_authoring COMMAND faset_editor_ui_tests)
         set_tests_properties(editor_ui_authoring PROPERTIES LABELS "gpu")
+        add_executable(faset_editor_ui_latency ${PROJECT_SOURCE_DIR}/tests/editor_ui_latency.cpp)
+        target_link_libraries(faset_editor_ui_latency PRIVATE faset_editor_ui)
+        target_compile_definitions(faset_editor_ui_latency PRIVATE FASET_TEST_ENGINE="${PROJECT_SOURCE_DIR}")
     endif()
 endif()
diff --git a/tests/editor_ui_latency.cpp b/tests/editor_ui_latency.cpp
new file mode 100644
index 0000000..2c4196c
--- /dev/null
+++ b/tests/editor_ui_latency.cpp
@@ -0,0 +1,70 @@
+#include <chrono>
+#include <cmath>
+#include <faset/core/io.hpp>
+#include <faset/editor/editor_ui.hpp>
+#include <iostream>
+#include <stdexcept>
+
+int main(int argc, char** argv) {
+    using namespace faset;
+    using Clock = std::chrono::steady_clock;
+    if (argc != 2) {
+        std::cerr << "Usage: faset_editor_ui_latency OUTPUT.json\n";
+        return 2;
+    }
+    const auto root = std::filesystem::temp_directory_path() /
+                      path_from_utf8("faset-ui-latency-" + new_id());
+    try {
+        std::filesystem::create_directories(root);
+        atomic_write_json(root / "project.faset.json",
+                          {{"format", "faset.project"},
+                           {"version", 1},
+                           {"name", "UI latency fixture"},
+                           {"dimension", 3}});
+        editor::Session session({root, path_from_utf8(FASET_TEST_ENGINE), root});
+        render::Renderer renderer({1280, 800, "Editor input latency", true, true});
+        editor::EditorUI ui(session, renderer,
+                            path_from_utf8(FASET_TEST_ENGINE) / "assets/fonts/NotoSans.ttf",
+                            path_from_utf8(FASET_TEST_ENGINE) / "assets/ui/dark.json");
+        ui.frame({});
+        Json samples = Json::array();
+        constexpr int warmup = 10, measured = 100;
+        for (int index = 0; index < warmup + measured; ++index) {
+            render::Event event;
+            event.type = render::Event::Type::KeyDown;
+            event.key = index % 2 == 0 ? "E" : "W";
+            const auto started = Clock::now();
+            ui.frame({event});
+            renderer.render(ui.snapshot());
+            const auto elapsed = std::chrono::duration<double, std::milli>(Clock::now() - started)
+                                     .count();
+            const auto target = index % 2 == 0 ? "gizmo-Rotate" : "gizmo-Move";
+            if (!ui.widgets().find(target)->selected ||
+                renderer.stats().validation_errors != 0 || !std::isfinite(elapsed) ||
+                elapsed <= 0)
+                throw std::runtime_error("Synthetic input was not visible in a valid frame");
+            if (index >= warmup)
+                samples.push_back({{"iteration", index - warmup + 1},
+                                   {"milliseconds", elapsed},
+                                   {"gizmo", event.key == "E" ? "Rotate" : "Move"}});
+        }
+        atomic_write_json(path_from_utf8(argv[1]),
+                          {{"format", "faset.editor-ui-latency"},
+                           {"version", 1},
+                           {"warmup_frames", warmup},
+                           {"measured_frames", measured},
+                           {"presentation_mode", "offscreen"},
+                           {"method", "KeyDown gizmo toggle through EditorUI::frame and "
+                                      "offscreen Vulkan render completion; no window present"},
+                           {"device", renderer.stats().device},
+                           {"validation_enabled", renderer.stats().validation_enabled},
+                           {"validation_errors", renderer.stats().validation_errors},
+                           {"samples", samples}});
+        std::filesystem::remove_all(root);
+        std::cout << "Measured " << measured << " synthetic Editor input frames\n";
+        return 0;
+    } catch (const std::exception& error) {
+        std::cerr << error.what() << "\nFixture: " << path_to_utf8(root) << '\n';
+        return 1;
+    }
+}