Add configurable seamless animated panel gradient

tests/config_test.cpp

@@ -49,6 +49,9 @@ int main(int argc, char** argv) {
     assert(!load_config(path).clock_24h);
     assert(load_config(path).date_format == DateFormat::MonthDayYear);
     assert(load_config(path).wrist.width == .30f);
+    assert(load_config(path).gradient.enabled);
+    assert(load_config(path).gradient.period_seconds == 30.f);
+    assert(load_config(path).gradient.strength == .12f);
     auto example = load_config(std::filesystem::path(argv[1]) / "config.example.json");
     assert(example.buttons.at("ptt") == "/user/hand/right/input/x");
     assert(example.buttons.at("quick_chat") == "/user/hand/right/input/y");
@@ -62,6 +65,7 @@ int main(int argc, char** argv) {
     assert(!example.lock_layout);
     assert(!example.clock_24h && example.date_format == DateFormat::MonthDayYear);
     assert(example.wrist.y == .18f && example.wrist.z == .089f);
+    assert(example.gradient.enabled && example.gradient.period_seconds == 30.f && example.gradient.strength == .12f);
     std::filesystem::create_directories(path.parent_path());
     assert(save_backend(path, "fixture_cpu"));
     assert(load_config(path).backend == "fixture_cpu");
@@ -203,6 +207,26 @@ int main(int argc, char** argv) {
                                R"({"wrist":{"x":1e999}})"}) {
         put(path, invalid); fails([&] { load_config(path); });
     }
+    put(path, R"({"gradient":{"enabled":false,"period_seconds":45.5,"strength":0.2}})");
+    auto gradient = load_config(path).gradient;
+    assert(!gradient.enabled && gradient.period_seconds == 45.5f && gradient.strength == .2f);
+    assert(save_auto_insert(path, true)); // unrelated settings retain the effect
+    assert(load_config(path).gradient.period_seconds == 45.5f);
+    put(path, R"({"gradient":{"strength":0}})");
+    assert(load_config(path).gradient.enabled && load_config(path).gradient.period_seconds == 30.f);
+    assert(load_config(path).gradient.strength == 0.f);
+    put(path, R"({"gradient":{"period_seconds":5,"strength":0.3}})");
+    assert(load_config(path).gradient.period_seconds == 5.f && load_config(path).gradient.strength == .3f);
+    put(path, R"({"gradient":{"period_seconds":300}})");
+    assert(load_config(path).gradient.period_seconds == 300.f);
+    for (auto invalid : {R"({"gradient":true})", R"({"gradient":{"enabled":1}})",
+                         R"({"gradient":{"enabled":"false"}})", R"({"gradient":{"period_seconds":0}})",
+                         R"({"gradient":{"period_seconds":301}})", R"({"gradient":{"period_seconds":1e99}})",
+                         R"({"gradient":{"period_seconds":true}})", R"({"gradient":{"strength":-0.1}})",
+                         R"({"gradient":{"strength":0.31}})", R"({"gradient":{"strength":1e99}})",
+                         R"({"gradient":{"strength":"0.1"}})", R"({"gradient":{"unknown":1}})"}) {
+        put(path, invalid); fails([&] { load_config(path); });
+    }
     put(path, R"({"theme":{"background":"#123ABC","accent":"#abcdef","frame_end":"#010203"},"font":"/nonexistent/face.ttf","buttons":{"ptt":"/user/hand/left/input/y","cancel":"/user/hand/right/input/b","right_grip":""}})");
     auto config = load_config(path);
     assert((config.theme.background == Rgba{0x12, 0x3a, 0xbc, 255}));