Setting dark mode color scheme initial state in official adwaita tutorial

Platform
1

Hi,

I tried to follow the official tutorial to learn Gnome application development with modern Adwaita widgets. I managed to get to the last step without any problem, but my app fails to compile when I try to run adw_style_manager_get_default in the text_viewer_application_init function.

Did I get something wrong or is the tutorial to blame?

The problematic code is in this page, in the second to last code snippet : Forcing The Dark Color Scheme - GNOME Developer Documentation

More specifically, here:

static void
text_viewer_application_init (TextViewerApplication *self)
{
  self->settings = g_settings_new ("com.example.TextViewer");

  gboolean dark_mode = g_settings_get_boolean (self->settings, "dark-mode");
  AdwStyleManager *style_manager = adw_style_manager_get_default ();
  […]

I get this error:

(process:2): Gdk-ERROR **: 00:31:06.667: gdk_display_manager_get() was called before gtk_init()

I managed to get the application to compile by adding a gtk_init(); at the beginning of the function, but I somehow know that’s not the right way to solve this problem.

Thanks in advance to those who can help me understand the issue at hand.

2

You called the fn too early, this has to happen after adw_init which is called during an AdwApplication’s startup phase. Init goes before that.

3

Thanks @Maximiliano for your answer.

I did understand that this function was called too early, but I followed the tutorial very strictly.

I am but a very beginner developer, but I guess the tutorial is wrong. Could someone check it to confirm my guess, and correct it ?

I’ll try to implement a _startup function in which I’ll call the problematic function, but I might still be wrong.

4

This is a change in GTK/libadwaita that was introduced after the tutorial was written.

The appropriate place to set up the style manager is the GApplicationClass.startup virtual function, where adw_init() is called, e.g.

static void
text_viewer_application_startup (GApplication *application)
{
  // chain up, to let GTK and libadwaita initialize themselves
  G_APPLICATION_CLASS (text_viewer_application_parent_class)->startup (application);

  TextViewerApplication *self = TEXT_VIEWER_APPLICATION (application);

  gboolean dark_mode = g_settings_get_boolean (self->settings, "dark-mode");
  AdwStyleManager *style_manager = adw_style_manager_get_default ();

  // ...
}
1 Like
5

Thanks a lot @ebassi for your answer. I did manage to find, by myself, the exact same solution to this problem by replicating what I previously learned in Gtk’s official tutorials. You confirmed I made the correct technical choice (and I have to admit I’m quite proud of myself…)

Who could I contact to help update Gnome’s tutorial ? There are several other minor differences between what is taught and Gnome Builder’s default application code.

6

You should file an issue on the developer docs website’s issue tracker.