I'm writing a GUI program using dlangui. It has some checkboxes.
I'm trying to figure out how to invoke a callback function when
the user clicks the box. What are the valid ways of doing that?
I can copy from dlangide's source, where a delegate is defined
in-line and assigned. That seems to work. But is that the only
way?
bool g_x = true;
bool checkbox_b_clicked(Widget source, bool checked)
{
g_x = checked;
if (checked) {
writeln(checked);
}
return true;
}
auto check_a = new CheckBox("wantalt", "Alternating"d);
auto check_b = new CheckBox("wantblinkb", "Blink(delg)"d);
auto check_c = new CheckBox("wantblinkc",
"Blink(direct)"d);
check_a.checkChange = delegate(Widget w, bool checked) {
g_x=checked;
return true;
};
check_b.checkChange = delegate(Widget w, bool checked) {
return checkbox_b_clicked(w,checked);
};
check_c.checkChange = checkbox_b_clicked;
check_c.checkChange = &checkbox_b_clicked;
The assignment to check_a is fine with the compiler.
For check_b, I try calling a function defined earlier. (Maybe in
real life it's too complex to try having inline.) It was giving
a compiler error until I realized I'm dumb, wasn't passing 'w'
and 'checked' to it. Fixed, works fine now. Okay!
But what I think I should be able to do: assign
checkbox_b_clicked directly to the .checkChange property of the
checkbox, as shown for check_c. It doesn't work. Oh, I see an
example where '&' is used - okay let's try that... nope!
The compiler errors I get are, for no '&' and with '&':
Error: function `app.checkbox_b_clicked(Widget source, bool
checked)` is not callable using argument types `()`
Error: none of the overloads of `opAssign` are callable using
argument types `(bool function(Widget source, bool checked))`
