class Command;
class Toggle;
+ui::ToolButton toolbar_append_button( ui::Toolbar toolbar, const char* description, const char* icon );
ui::ToolButton toolbar_append_button( ui::Toolbar toolbar, const char* description, const char* icon, const Callback<void()>& callback );
ui::ToolButton toolbar_append_button( ui::Toolbar toolbar, const char* description, const char* icon, const Command& command );
ui::ToggleToolButton toolbar_append_toggle_button( ui::Toolbar toolbar, const char* description, const char* icon, const Callback<void()>& callback );