Example: changing header bar colors depending on WebKitWebView:theme-color

webkitgtk-themecolor-example.c

/*
 * Compile with:
 * gcc $(pkg-config webkitgtk-6.0 --cflags --libs) webkitgtk-themecolor-example.c
 *
 * SPDX-License-Identifier: MIT
 */

#include <gio/gio.h>
#include <webkit/webkit.h>

static void
handle_web_view_theme_color_notify(WebKitWebView *web_view, GParamSpec *pspec, GtkWindow *window)
{
    GdkRGBA rgba;
    g_autofree char *css_class = g_strdup_printf("tinted_%" PRIu64, (uint64_t) window);

    if (webkit_web_view_get_theme_color(web_view, &rgba)) {
        const unsigned r = MAX(0, MIN(255, (unsigned) nearbyint(rgba.red   * 255)));
        const unsigned g = MAX(0, MIN(255, (unsigned) nearbyint(rgba.green * 255)));
        const unsigned b = MAX(0, MIN(255, (unsigned) nearbyint(rgba.red   * 255)));
        const gboolean w = ((r * 299 + g * 587 + b * 114) / 1000) <= 128;

        gtk_widget_add_css_class(GTK_WIDGET(window), css_class);
        g_autofree char *css_snippet = g_strdup_printf(
               "window.%s > headerbar { color: %s; background: rgb(%u, %u, %u); }",
               css_class, w ? "white" : "black", r, g, b);
        gtk_css_provider_load_from_string(
               g_object_get_data(G_OBJECT(window), "tint-css-provider"),
               css_snippet);
    } else {
        gtk_widget_remove_css_class(GTK_WIDGET(window), css_class);
    } 
}

static GtkWidget* handle_web_view_create(WebKitWebView*, WebKitNavigationAction*, GtkApplication*);

static GtkWidget*
add_window(GtkApplication *app, WebKitWebView *related_view, const char *uri)
{
    WebKitWebView *web_view = g_object_new(WEBKIT_TYPE_WEB_VIEW,
                                           "related-view", related_view,
                                           NULL);

    GtkWidget *header = gtk_header_bar_new();
    gtk_header_bar_set_show_title_buttons(GTK_HEADER_BAR(header), TRUE);

    GtkWidget *window = gtk_application_window_new(app);
    gtk_window_set_titlebar(GTK_WINDOW(window), header);
    gtk_window_set_child(GTK_WINDOW(window), GTK_WIDGET(web_view));
    gtk_window_set_default_size(GTK_WINDOW(window), 1200, 900);
    gtk_window_set_default_widget(GTK_WINDOW(window), GTK_WIDGET(web_view));

    GtkCssProvider *tint_css_provider = gtk_css_provider_new();
    gtk_style_context_add_provider_for_display(gdk_display_get_default(),
                                               GTK_STYLE_PROVIDER(tint_css_provider),
                                               GTK_STYLE_PROVIDER_PRIORITY_APPLICATION);
    g_object_set_data_full(G_OBJECT(window), "tint-css-provider", tint_css_provider, g_object_unref);

    g_object_bind_property(web_view, "title", window, "title", G_BINDING_SYNC_CREATE);
    g_signal_connect(web_view, "notify::theme-color", G_CALLBACK(handle_web_view_theme_color_notify), window);
    g_signal_connect(web_view, "create", G_CALLBACK(handle_web_view_create), app);
    if (uri) webkit_web_view_load_uri(web_view, uri);

    gtk_window_present(GTK_WINDOW(window));
    return GTK_WIDGET(web_view);
}

static void
handle_app_activate(GtkApplication *app)
{
    add_window(app, NULL, "https://duckduckgo.com");
}

static void
handle_app_open(GtkApplication *app, GFile *files[], int n_files, char *hint)
{
    for (int i = 0; i < n_files; i++) {
        g_autofree char *uri = g_file_get_uri(files[i]);
        add_window(app, NULL, uri);
    }
}

static GtkWidget*
handle_web_view_create(WebKitWebView *web_view, WebKitNavigationAction *action, GtkApplication *app)
{
    return add_window(app, web_view, NULL);
}

int
main(int argc, char *argv[])
{
    gtk_init();

    g_autoptr(GtkApplication) app = gtk_application_new(NULL, G_APPLICATION_HANDLES_OPEN);
    g_signal_connect(app, "activate", G_CALLBACK(handle_app_activate), NULL);
    g_signal_connect(app, "open", G_CALLBACK(handle_app_open), NULL);

    return g_application_run(G_APPLICATION(app), argc, argv);
}