Add a video export quality choice: Small file, Standard or High

A Quality dropdown under Video on Setup, --video-quality on the command
line, and "quality" in a project's video settings (written only when it is
not Standard). One table, videoQualities(), holds the ffmpeg settings per
codec; Standard is what every video was written with before.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/core_tests.cpp

@@ -2082,6 +2082,16 @@ int main() {
         const std::string base = "{\"chain\": [{\"effect\": \"blur\"}], \"video\": {\"duration\": ";
         check(!effector::projectFromJson(base + "2, \"preset\": \"cinema\"}}").video.preset.size(),
               "an unknown preset reads as custom");
+        check(effector::projectToJson(project).find("\"quality\"") == std::string::npos,
+              "the standard quality is not written");
+        project.video.quality = "small";
+        check(effector::projectFromJson(effector::projectToJson(project)).video.quality == "small",
+              "another quality is kept");
+        check(effector::projectFromJson(base + "2, \"quality\": \"lossless\"}}").video.quality.empty(),
+              "an unknown quality reads as the standard one");
+        check(effector::videoQualityOrDefault("").key == effector::kDefaultVideoQuality &&
+                  effector::videoQualityByKey(effector::kDefaultVideoQuality) != nullptr,
+              "an empty quality is the standard one, which the table holds");
         bool rejected = false;
         try {
             effector::projectFromJson(base + "2, \"fps\": 500}}");
@@ -2106,6 +2116,9 @@ int main() {
         check(!parsedOptions({"--fps", "0"}) && !parsedOptions({"--duration", "abc"}) &&
                   !parsedOptions({"--duration", "400"}) && !parsedOptions({"--video-preset", "vhs"}),
               "a bad rate, length or preset is refused");
+        const auto quality = parsedOptions({"--duration", "2", "--video-quality", "high"});
+        check(quality && quality->video.quality == "high", "--video-quality picks the encoding");
+        check(!parsedOptions({"--video-quality", "best"}), "and refuses one it does not know");
         check(!parsedOptions({"-o", "x.png"})->video.enabled, "without them the output is a still");
 
         bool wrongName = false;
@@ -2128,6 +2141,18 @@ int main() {
             }
             check(std::filesystem::exists(file) && std::filesystem::file_size(file) > 0,
                   "ffmpeg writes an .mp4 of odd size");
+            // Every quality, through every codec.
+            bool everyQuality = true;
+            for (const auto& quality : effector::videoQualities()) {
+                for (const char* extension : {".mp4", ".webm", ".gif"}) {
+                    const auto encoded = (dir / (quality.key + extension)).string();
+                    effector::VideoWriter writer(encoded, 16, 16, 12, quality.key);
+                    for (int i = 0; i < 2; ++i) writer.write(gradient(16, 16, 60 * i));
+                    writer.finish();
+                    everyQuality = everyQuality && std::filesystem::file_size(encoded) > 0;
+                }
+            }
+            check(everyQuality, "every quality writes .mp4, .webm and .gif");
             const auto dropped = (dir / "dropped.webm").string();
             {
                 effector::VideoWriter writer(dropped, 16, 16, 12);

tests/gui_tests.cpp

@@ -553,6 +553,11 @@ void testVideo(Gtk::Window& window, const std::filesystem::path& dir) {
     stack->set_visible_child("setup");
     pump(100);
     check(preset->is_drawable() && duration->is_drawable(), "and its preset and length");
+    auto* quality = named<Gtk::DropDown>(window, "video-quality");
+    check(quality != nullptr && quality->is_drawable() &&
+              effector::videoQualities().at(quality->get_selected()).key ==
+                  effector::kDefaultVideoQuality,
+          "and its file quality, standard to begin with");
 
     preset->set_selected(1);  // Instagram story, the first preset
     pump(200);