This is the relevant part of the code:
btn1 = gtk_button_new_with_label("one");
gtk_grid_attach (GTK_GRID (grid_ptr), btn1, 0, 1, 1, 1);
gtk_widget_set_name ( btn1, "btn1");
GtkCssProvider *prvdr = gtk_css_provider_new ();
GtkStyleContext *cntxt = gtk_widget_get_style_context ( btn1 );
gtk_css_provider_load_from_data (prvdr, "button#btn1 { text-decoration: underline white;}", -1);
gtk_style_context_add_provider (cntxt, GTK_STYLE_PROVIDER (prvdr), GTK_STYLE_PROVIDER_PRIORITY_APPLICATION);
It compiles without any issues, and runs without errors or warnings, but nothing gets underlined.
I have also tried these with the same result: "button#btn1 { text-decoration: underline;}" "button#btn1 { text-decoration-line: underline;}"
I have changed the text colour using "button#btn1 { color: #00ff00;}".
Can anyone explain why it does not work, or how to fix it?
text-decorationis not available on buttons in gtk4. A possible fix could be styling the label instead?