Pick the text stage's font with a font chooser

A new Font param type (ParamSpec::makeFont) is a font family as the
machine names it. The interface shows it as a family-only
FontDialogButton; the command line and the project file treat it as a
plain string, as they did the Text param it replaces, so existing
projects and --font-family keep working. A family the machine lacks is
kept as written. Bumps the version to 0.8.1.

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

src/cli/options.cpp

@@ -182,6 +182,7 @@ Options parseOptions(int argc, char** argv) {
                 }
                 case ParamSpec::Type::Path:
                 case ParamSpec::Type::Text:
+                case ParamSpec::Type::Font:
                     options.params[spec->key] = requireValue(argc, argv, i, arg);
                     break;
                 case ParamSpec::Type::Color: {

src/core/params.cpp

@@ -100,6 +100,17 @@ ParamSpec ParamSpec::makeColor(std::string key, std::string label, std::string d
     return spec;
 }
 
+ParamSpec ParamSpec::makeFont(std::string key, std::string label, std::string defaultFamily,
+                              std::string help) {
+    ParamSpec spec;
+    spec.type = Type::Font;
+    spec.key = std::move(key);
+    spec.label = std::move(label);
+    spec.help = std::move(help);
+    spec.defaultChoice = std::move(defaultFamily);
+    return spec;
+}
+
 namespace {
 
 const ParamValue* find(const ParamValues& values, const std::string& key) {
@@ -121,6 +132,7 @@ ParamValue paramDefault(const ParamSpec& spec) {
         case ParamSpec::Type::Path:
         case ParamSpec::Type::Text:
         case ParamSpec::Type::Color:
+        case ParamSpec::Type::Font:
             break;
     }
     return spec.defaultChoice;

src/core/params.hpp

@@ -11,7 +11,7 @@ namespace effector {
 // Declarative description of one effect knob. The GUI turns these into widgets
 // and the CLI turns them into flags, so neither knows about any effect.
 struct ParamSpec {
-    enum class Type { Int, Double, Bool, Choice, Path, Text, Color };
+    enum class Type { Int, Double, Bool, Choice, Path, Text, Color, Font };
 
     Type type = Type::Int;
     std::string key;
@@ -56,6 +56,11 @@ struct ParamSpec {
     // spelling as a flag value.
     static ParamSpec makeColor(std::string key, std::string label, std::string defaultColor,
                                std::string help = {});
+    // A font family as it is named on this machine ("Sans", "DejaVu Serif"):
+    // a font chooser in the interface, a flag taking any string on the
+    // command line. A family the machine lacks is kept as written.
+    static ParamSpec makeFont(std::string key, std::string label, std::string defaultFamily,
+                              std::string help = {});
 };
 
 using ParamValue = std::variant<long, double, bool, std::string>;

src/core/project.cpp

@@ -366,6 +366,7 @@ void writeParams(std::ostream& out, const std::vector<ParamSpec>& specs, const P
                 break;
             case ParamSpec::Type::Choice:
             case ParamSpec::Type::Text:
+            case ParamSpec::Type::Font:
                 out << quote(paramText(values, spec.key, spec.defaultChoice));
                 break;
             case ParamSpec::Type::Color: {
@@ -412,6 +413,7 @@ void readParams(const std::vector<ParamSpec>& specs, const Json& params,
                 }
                 break;
             case ParamSpec::Type::Text:
+            case ParamSpec::Type::Font:
                 if (value->kind == Json::Kind::String) values[spec.key] = value->text;
                 break;
             case ParamSpec::Type::Color: {

src/effects/text.cpp

@@ -16,7 +16,7 @@ const std::vector<ParamSpec>& TextEffect::params() const {
     static const std::vector<ParamSpec> specs = {
         ParamSpec::makeText("text", "Text", "Effector",
                             "What to write; a line break starts a new line."),
-        ParamSpec::makeText("font_family", "Font", "Sans",
+        ParamSpec::makeFont("font_family", "Font", "Sans",
                             "Font family, as it is named on this machine: Sans, Serif, Monospace, "
                             "\"DejaVu Serif\", ...")
             .styled(),

src/gui/window.cpp

@@ -995,6 +995,21 @@ void EffectorWindow::buildParamWidgets() {
                 widget = std::move(button);
                 break;
             }
+            case ParamSpec::Type::Font: {
+                // Only the family is chosen here: weight, slant and size are
+                // params of their own.
+                auto button = std::make_unique<Gtk::FontDialogButton>(Gtk::FontDialog::create());
+                button->set_halign(Gtk::Align::START);
+                button->set_level(Gtk::FontLevel::FAMILY);
+                button->set_use_font(true);
+                Pango::FontDescription font;
+                font.set_family(paramText(values, spec.key, spec.defaultChoice));
+                button->set_font_desc(font);
+                button->property_font_desc().signal_changed().connect(
+                    sigc::mem_fun(*this, &EffectorWindow::onParamChanged));
+                widget = std::move(button);
+                break;
+            }
             case ParamSpec::Type::Choice: {
                 std::vector<Glib::ustring> choices(spec.choices.begin(), spec.choices.end());
                 auto dropdown = std::make_unique<Gtk::DropDown>();
@@ -1051,6 +1066,14 @@ ParamValues EffectorWindow::paramValues() const {
                 values[entry.spec.key] = formatColor(rgb);
                 break;
             }
+            case ParamSpec::Type::Font: {
+                // A family the machine lacks keeps its name, so a project
+                // from elsewhere still says which font it wanted.
+                const auto family =
+                    static_cast<Gtk::FontDialogButton*>(entry.widget)->get_font_desc().get_family();
+                if (!family.empty()) values[entry.spec.key] = std::string(family);
+                break;
+            }
             case ParamSpec::Type::Choice: {
                 const auto index = static_cast<Gtk::DropDown*>(entry.widget)->get_selected();
                 if (index < entry.spec.choices.size()) values[entry.spec.key] = entry.spec.choices[index];