GTKmm application: Gdk key press signals not firing - gtkmm

Question

I have (sort of) copied (but with some modifications) the example in the GTKmm tutorials on keyboard events. (link)
https://developer.gnome.org/gtkmm-tutorial/stable/sec-keyboardevents-overview.html.en#keyboardevents-simple-example
Here is my code:
#include <gtkmm/application.h>
#include <gtkmm/window.h>
#include <gtkmm/textview.h>
#include <iostream>
class MainWindow
{
public:
MainWindow()
{
_window_.set_default_size(600, 400);
_window_.add(_textview_);
Glib::RefPtr<Gtk::TextBuffer> textbuffer_rp{_textview_.get_buffer()};
textbuffer_rp->set_text("some text here");
_textview_.set_monospace();
_window_.add_events(Gdk::KEY_PRESS_MASK);
_window_.show_all_children();
}
Gtk::Window &get_window()
{
return _window_;
}
protected:
bool on_key_press_event(GdkEventKey* event)
{
std::cout << "some keypress event" << std::endl;
if
(
(event->keyval == GDK_KEY_H) &&
((event->state & (GDK_SHIFT_MASK | GDK_CONTROL_MASK | GDK_MOD1_MASK) == GDK_CONTROL_MASK))
)
{
std::cout << "Hello world!" << std::endl;
}
if
(
(event->keyval == GDK_KEY_C) &&
((event->state & (GDK_SHIFT_MASK | GDK_CONTROL_MASK | GDK_MOD1_MASK) == GDK_CONTROL_MASK))
)
{
signal_textview_CTRL_C();
}
else if
(
(event->keyval == GDK_KEY_V) &&
((event->state & (GDK_SHIFT_MASK | GDK_CONTROL_MASK | GDK_MOD1_MASK) == GDK_CONTROL_MASK))
)
{
signal_textview_CTRL_V();
}
else
{
std::cout << "unhandled key" << std::endl;
}
return true;
}
void signal_textview_CTRL_C()
{
_text_register_0_ = "some text gets put here";
}
void signal_textview_CTRL_V()
{
Glib::RefPtr<Gtk::TextBuffer> textbuffer_rp{_textview_.get_buffer()};
textbuffer_rp->set_text(_text_register_0_);
}
private:
Gtk::Window _window_;
Gtk::TextView _textview_;
Glib::ustring _text_register_0_;
};
int main(int argc, char *argv[])
{
auto app = Gtk::Application::create(argc, argv, "org.gtkmm.examples.base");
MainWindow mainwindow;
return app->run(mainwindow.get_window());
}
However it is not working - none of the signal events appear to fire when I press the key sequences CTRL-C, CTRL-V, CTRL-H.
I think I have stripped all the irrelevant stuff from the code so this should be a working MWE.

Answer 1

Connect your handler as first.
_window_.signal_key_press_event().connect(sigc::mem_fun(*this, &MainWindow::on_key_press_event), false);
Return false to let _textview_ get the key.
Your conditions are contradictory.
GDK_KEY_H is keysym for shift+h. Then you check (event->state & (GDK_SHIFT_MASK | GDK_CONTROL_MASK | GDK_MOD1_MASK) == GDK_CONTROL_MASK). You are asking if state (which we know is with GDK_SHIFT_MASK) is ONLY GDK_CONTROL_MASK.
Code:
#include <gtkmm/application.h>
#include <gtkmm/window.h>
#include <gtkmm/textview.h>
#include <iostream>
class MainWindow
{
public:
MainWindow()
{
_window_.set_default_size(600, 400);
_window_.add(_textview_);
Glib::RefPtr<Gtk::TextBuffer> textbuffer_rp{_textview_.get_buffer()};
textbuffer_rp->set_text("some text here");
_textview_.set_monospace();
_window_.add_events(Gdk::KEY_PRESS_MASK);
_window_.signal_key_press_event().connect(sigc::mem_fun(*this, &MainWindow::on_key_press_event), false);
_window_.show_all_children();
}
Gtk::Window &get_window()
{
return _window_;
}
protected:
bool on_key_press_event(GdkEventKey* event)
{
std::cout << "some keypress event " << std::hex<<event->keyval<<" "<<std::hex<<event->state<<std::endl;
if
(
(event->keyval == GDK_KEY_h) &&
(event->state & GDK_CONTROL_MASK)
)
{
std::cout << "Hello world!" << std::endl;
return true;
}
if
(
(event->keyval == GDK_KEY_c) &&
(event->state & GDK_CONTROL_MASK)
)
{
std::cout<<"ctrl c"<<std::endl;
signal_textview_CTRL_C();
return true;
}
else if
(
(event->keyval == GDK_KEY_v) &&
(event->state & GDK_CONTROL_MASK)
)
{
std::cout<<"ctrl v"<<std::endl;
signal_textview_CTRL_V();
return true;
}
else
{
std::cout << "unhandled key" << std::endl;
}
return false;
}
void signal_textview_CTRL_C()
{
_text_register_0_ = "some text gets put here";
}
void signal_textview_CTRL_V()
{
Glib::RefPtr<Gtk::TextBuffer> textbuffer_rp{_textview_.get_buffer()};
textbuffer_rp->set_text(_text_register_0_);
}
private:
Gtk::Window _window_;
Gtk::TextView _textview_;
Glib::ustring _text_register_0_;
};
int main(int argc, char *argv[])
{
auto app = Gtk::Application::create(argc, argv, "org.gtkmm.examples.base");
MainWindow mainwindow;
return app->run(mainwindow.get_window());
}