Port 'CSS Gradients' demo to Vala (#155)

Author: BharatAtbrat

src/CSS Gradients/main.vala

@@ -0,0 +1,121 @@
+#! /usr/bin/env -S vala workbench.vala --pkg libadwaita-1 --pkg gtksourceview-5
+
+private GtkSource.Buffer gtksource_buffer;
+private Adw.ComboRow combo_row_gradient_type;
+private Adw.SpinRow spin_row_angle;
+private Gtk.ColorDialogButton button_color_1;
+private Gtk.ColorDialogButton button_color_2;
+private Gtk.ColorDialogButton button_color_3;
+private Adw.StyleManager style_manager;
+private GtkSource.StyleSchemeManager scheme_manager;
+private Gtk.CssProvider css_provider;
+private string css;
+
+void update () {
+    spin_row_angle.sensitive = combo_row_gradient_type.selected != 1;
+    css = generate_css ();
+    gtksource_buffer.set_text (css, -1);
+    update_css_provider (css);
+}
+
+void update_css_provider (string css) {
+    var display = Gdk.Display.get_default ();
+    if (css_provider == null) {
+        css_provider = new Gtk.CssProvider ();
+    } else {
+        Gtk.StyleContext.remove_provider_for_display (display, css_provider);
+    }
+
+    css_provider.load_from_string (css);
+    Gtk.StyleContext.add_provider_for_display (display, css_provider, Gtk.STYLE_PROVIDER_PRIORITY_APPLICATION);
+}
+
+string generate_css () {
+    double angle = spin_row_angle.get_value ();
+    string angle_string = angle.to_string ();
+    string first_color_string = button_color_1.get_rgba ().to_string ();
+    string second_color_string = button_color_2.get_rgba ().to_string ();
+    string third_color_string = button_color_3.get_rgba ().to_string ();
+
+    uint selected = combo_row_gradient_type.selected;
+    switch (selected) {
+    case 0:
+        css = @".background-gradient {
+    background-image: linear-gradient(
+        $(angle_string)deg,
+        $(first_color_string),
+        $(second_color_string),
+        $(third_color_string)
+    );
+}";
+        break;
+    case 1:
+        css = @".background-gradient {
+    background-image: radial-gradient(
+        $(first_color_string),
+        $(second_color_string),
+        $(third_color_string)
+    );
+}";
+        break;
+    case 2:
+        css = @".background-gradient {
+    background-image: conic-gradient(
+        from $(angle_string)deg,
+        $(first_color_string),
+        $(second_color_string),
+        $(third_color_string)
+    );
+}";
+        break;
+    }
+    return css;
+}
+
+void update_color_scheme () {
+    string scheme_name = style_manager.dark ? "Adwaita-dark" : "Adwaita";
+    GtkSource.StyleScheme scheme = scheme_manager.get_scheme (scheme_name);
+
+    if (scheme != null) {
+        gtksource_buffer.style_scheme = scheme;
+    }
+}
+
+public void main () {
+    combo_row_gradient_type = (Adw.ComboRow) workbench.builder.get_object ("combo_row_gradient_type");
+    spin_row_angle = (Adw.SpinRow) workbench.builder.get_object ("spin_row_angle");
+    button_color_1 = (Gtk.ColorDialogButton) workbench.builder.get_object ("button_color_1");
+    button_color_2 = (Gtk.ColorDialogButton) workbench.builder.get_object ("button_color_2");
+    button_color_3 = (Gtk.ColorDialogButton) workbench.builder.get_object ("button_color_3");
+    gtksource_buffer = (GtkSource.Buffer) workbench.builder.get_object ("gtksource_buffer");
+    var button_copy_css = (Gtk.Button) workbench.builder.get_object ("button_copy_css");
+
+    combo_row_gradient_type.notify["selected"].connect (update);
+    spin_row_angle.notify["value"].connect (update);
+    button_color_1.notify["rgba"].connect (update);
+    button_color_2.notify["rgba"].connect (update);
+    button_color_3.notify["rgba"].connect (update);
+    /*
+     * code view
+     */
+    Gdk.Clipboard clipboard = Gdk.Display.get_default ().get_clipboard ();
+
+    button_copy_css.clicked.connect (() => {
+        Gtk.TextIter start, end;
+        gtksource_buffer.get_start_iter (out start);
+        gtksource_buffer.get_end_iter (out end);
+        string text = gtksource_buffer.get_text (start, end, false);
+        clipboard.set_text (text);
+    });
+
+    scheme_manager = GtkSource.StyleSchemeManager.get_default ();
+    style_manager = Adw.StyleManager.get_default ();
+    style_manager.notify["dark"].connect (() => update_color_scheme ());
+
+    var language_manager = GtkSource.LanguageManager.get_default ();
+    GtkSource.Language css_language = language_manager.get_language ("css");
+    gtksource_buffer.language = css_language;
+
+    update ();
+    update_color_scheme ();
+}