On 2020-07-25 17:35, Carlo Wood wrote:
Why would this core dump??
LinuxChessboardWidget is defined as:
class LinuxChessboardWidget : public cwmm::ChessPositionWidget, public
Gio::ActionMap
{
...
I have to derive from Gio::ActionMap because its constructor is protected.
The call to `add_action` above is to that class.
Can someone tell me what I'm doing wrong?
Carlo
Gio::ActionMap is an interface. That's why its constructor is protected.
An interface can't be instantiated by itself. It must be implemented by
a class which can be instantiated. If you really must implement
Gio::ActionMap in your class (which I doubt), there is one or (probably)
two errors.
First, interfaces must come before the widget class in the list of base
classes.
class LinuxChessboardWidget : public Gio::ActionMap, public
cwmm::ChessPositionWidget
This is opposite to what's done in gtkmm's classes that wrap gtk classes.
Second, your constructor must call a special Glib::ObjectBase constructor that
registers your class with its own GType in glib's GType system. For instance
LinuxChessboardWidget(......) : Glib::ObjectBase("myWidgetClass") ..... // Or
whatever you want to call it.
This is an unusual way of using Gio::ActionMap. I don't know if these are the
only necessary changes. Much more common is to use one of the classes that
already implement Gio::ActionMap: Gio::SimpleActionGroup, Gtk::Application (via
Gio::Application) or Gtk::ApplicationWindow.
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