[linux] Wrong accent color on Manjaro GNOME

[ReadOnlyMAIN]

I tried to build and run a flutter project using system_theme on the latest version of Linux Manjaro GNOME. (GNOME 48 | Linux 6.14.6-2-MANJARO)
In the OS appearance settings UI, I've set the accent color to orange. System_theme gets an accent color from the OS but it seems to get the wrong one: the default bluish green (Color(alpha: 1.0000, red: 0.0863, green: 0.6275, blue: 0.5216, colorSpace: ColorSpace.sRGB))

When I run the following command, it returns 'orange':
gsettings get org.gnome.desktop.interface accent-color

This problem seems to stem more from the OS. The Settings UI also uses the bluish green accent color (see the green outline in "Style" setting).

But as the command above returns the color selected by the user, maybe system_theme can find a workaround or simply wait the OS to expose the accent color in a better way, you see.

Thanks for considering this feedback.

[bdlukaa]

This is the function we use to get the system theme color on Linux:

system_theme/system_theme/linux/system_theme_plugin.cc

Lines 21 to 34 in 4d8f115

	static FlValue *get_accent_color(GtkWidget *widget) {
	GdkRGBA accentColor;
	GtkStyleContext *context = gtk_widget_get_style_context(widget);
	gtk_style_context_lookup_color(context, "theme_selected_bg_color", &accentColor);
	FlValue *map = fl_value_new_map();
	fl_value_set_string_take(map, "R", fl_value_new_int((int) (accentColor.red * 255)));
	fl_value_set_string_take(map, "G", fl_value_new_int((int) (accentColor.green * 255)));
	fl_value_set_string_take(map, "B", fl_value_new_int((int) (accentColor.blue * 255)));
	fl_value_set_string_take(map, "A", fl_value_new_int((int) (accentColor.alpha * 255)));
	return map;
	}

Maybe changing theme_selected_bg_color to accent-color would fix this issue, but there are many distros to be aware of. Another option is exposing this property.

[bdlukaa]

To support GNOME 47/48+ and other modern environments reliably, the plugin needs to move away from inferring colors from GTK widgets and instead query the XDG Desktop Portal (org.freedesktop.portal.Settings). This is the modern, cross-distribution standard (supported by GNOME, KDE, Hyprland, etc.) for retrieving the true system accent color.

A proper fix involves updating system_theme_plugin.cc to:

1. Attempt to read the accent-color key from the org.freedesktop.appearance namespace via DBus.
2. Fall back to the current gtk_style_context_lookup_color method only if the portal is unavailable.

Since gsettings returns the correct value on your machine, a portal-based implementation would correctly return 'orange' regardless of what the GTK theme is displaying.