[Feature Request] Custom Widget#measure virtual method

[BigBoyBarney]

Hi!

This is either:

• a bug
• unimplemented
• me being incompetent :D

I would like to create a custom widget and implement its #measure virtual method, according to https://docs.gtk.org/gtk4/class.Widget.html

in Vala, it would look something like (snippet from Highscore

protected override void measure (
    Gtk.Orientation orientation,
    int for_size,
    out int minimum,
    out int natural,
    out int minimum_baseline,
    out int natural_baseline
) {
    stack.measure (orientation, for_size, out minimum, null, null, null);

    minimum = int.max (minimum, 64);

    if ((orientation == HORIZONTAL) == width_for_height)
        natural = for_size >= 0 ? for_size : 64;
    else
        natural = int.min (minimum, 64);

    minimum_baseline = natural_baseline = -1;
}

---

In a similar case for a custom Paintable's snapshot vfunc, what I did was:

@[GObject::Virtual]
def snapshot(snapshot : Gdk::Snapshot, width : Float64, height : Float64) : Nil
end

so I tried the same here

@[GObject::Virtual]
def measure(orientation : Gtk::Orientation, for_size : Int32, minimum : Int32, natural : Int32, minimum_baseline : Int32, natural_baseline : Int32) : Nil
end

But it still resulted in the following error:

Error: undefined local variable or method 'minimum' for MyWidget.class

Thanks in advance!

---

EDIT:
It appears to be the macro method in src/auto/gtk-4.0/widget.cr#L3818

[BigBoyBarney]

This is the currently generated macro def:

      private def self._vfunc_measure(%this : Pointer(Void), lib_orientation :  UInt32, lib_for_size :  Int32, lib_minimum :  Int32, lib_natural :  Int32, lib_minimum_baseline :  Int32, lib_natural_baseline :  Int32, ) : Void
        # @orientation: 
# @for_size: 
# @minimum: (out) (transfer full) (optional) 
# @natural: (out) (transfer full) (optional) 
# @minimum_baseline: (out) (transfer full) (optional) 
# @natural_baseline: (out) (transfer full) (optional) 

# Generator::BuiltInTypeArgPlan
orientation=Gtk::Orientation.new(lib_orientation)
for_size=lib_for_size
# Generator::OutArgUsedInReturnPlan
# Generator::OutArgUsedInReturnPlan
# Generator::OutArgUsedInReturnPlan
# Generator::OutArgUsedInReturnPlan


        %instance = LibGObject.g_object_get_qdata(%this, GICrystal::INSTANCE_QDATA_KEY)
        raise GICrystal::ObjectCollectedError.new if %instance.null?

        %retval = %instance.as(self).{{ impl_method_name.id }}(orientation, for_size, minimum, natural, minimum_baseline, natural_baseline)

        puts %retval
        
        %retval
      end

Adding the following lets it run, but it still behaves incorrectly. I'm not sure what the puts is doing in there either, so something is probably off here.

minimum = lib_minimum
natural = lib_natural
minimum_baseline = lib_minimum_baseline
natural_baseline = lib_natural_baseline

%retval evaluates to nil, and the values for minimum, natural, minimum_baseline, natural_baseline all seem to be random numbers. That part doesn't seem to be doing anything at all?

I am out of my depth, however, and don't know much else. If / when your time permits it, could you take a look?

Thanks in advance! ❤️

[BigBoyBarney]

I am quite literally just attempting implementations of semi-reasonable guesses.

The following finally worked, after changing the parameters to pointers.

private def self._vfunc_measure(
  %this : Pointer(Void), 
  lib_orientation : UInt32, 
  lib_for_size : Int32, 
  lib_minimum : Pointer(Int32), 
  lib_natural : Pointer(Int32), 
  lib_minimum_baseline : Pointer(Int32), 
  lib_natural_baseline : Pointer(Int32)
) : Void
  orientation = Gtk::Orientation.new(lib_orientation)
      
  %instance = LibGObject.g_object_get_qdata(%this, GICrystal::INSTANCE_QDATA_KEY)
  raise GICrystal::ObjectCollectedError.new if %instance.null?
      
  %instance.as(self).measure(
    orientation, 
    lib_for_size, 
    lib_minimum, 
    lib_natural, 
    lib_minimum_baseline, 
    lib_natural_baseline
  )
end

def self._class_init(type_struct : Pointer(LibGObject::TypeClass), user_data : Pointer(Void)) : Nil
  vfunc_ptr = (type_struct.as(Pointer(Void)) + 232).as(Pointer(Pointer(Void)))
  vfunc_ptr.value = (->_vfunc_measure(Pointer(Void), UInt32, Int32, Pointer(Int32), Pointer(Int32), Pointer(Int32), Pointer(Int32))).pointer
  previous_def
end

and then defining the vfunc in my custom widget as

@[GObject::Virtual]
def measure(
  orientation : Gtk::Orientation,
  for_size : Int32,
  minimum : Int32*,
  natural : Int32*,
  minimum_baseline : Int32*,
  natural_baseline : Int32*
) : Nil
  natural.value = 64
  minimum_baseline.value = -1
  natural_baseline.value = -1
  minimum.value = 50
end

This isn't ideal as I'm forced to manipulate the pointers, but at least it does something 🤣

---

EDIT: I just noticed that this is a duplicate of #32, so feel free to close this.