Getting objects out of a GValue

Question

Because gtk_style_context_get_background_color is deprected since version gtk v3.16 I want to read out the following style-property: GTK_STYLE_PROPERTY_BACKGROUND_COLOR

Currrently my code looks like that:

  GdkRGBA         *color;

  ...
  GValue value = G_VALUE_INIT;
  gtk_style_context_get_property (context,GTK_STYLE_PROPERTY_BACKGROUND_COLOR, state, &value);
  color = g_value_get_object (&value);

However it seems like I am doing it wrong. During runtime I only get the following GLib-GObject-CRITICAL:

(thunar:6564): GLib-GObject-CRITICAL **: g_value_get_object: assertion 'G_VALUE_HOLDS_OBJECT (value)' failed

So how I can make use of gtk properties which are holding more complex datatypes ?

EDIT: Here the complete solution which now works for me:

  GtkStateFlags    state;
  GdkRGBA          *color;
  GtkStyleContext *context = gtk_widget_get_style_context (widget);

  // get the color
  gtk_style_context_get (context, GTK_STATE_FLAG_SELECTED, GTK_STYLE_PROPERTY_BACKGROUND_COLOR, &color, NULL);

  // do something with the color
  gdk_cairo_set_source_rgba (cr, color);

  // dont forget to free it afterwards !! (Otherwise segfaults may occur)
  gdk_rgba_free (color);

GdkRgba it's not an object. It's a simple struct with color components. — José Fonte

ptomato ptomato · Accepted Answer · 2017-11-19T02:41:01

You can skip going through GValue entirely:

GdkRGBA *c;
gtk_style_context_get (context,
                       GTK_STYLE_PROPERTY_BACKGROUND_COLOR, &c,
                       NULL);
// ...
gdk_rgba_free (c);

Getting objects out of a GValue

1 Answers