(Feature) Custom PropertyDrawer for Unity Editor

[luaye]

Would you consider adding a custom property drawer for unity editor inspector?
Something like this works:

[CustomPropertyDrawer(typeof(fp))]
    public class FpPropertyDrawer : PropertyDrawer
    {
        public override void OnGUI(Rect position, SerializedProperty property, GUIContent label)
        {
            var rawProperty = property.FindPropertyRelative("m_rawValue");
            var fixedValue = fp.FromRaw(rawProperty.longValue);
            var floatValue = EditorGUI.FloatField(position, label, (float)fixedValue);
            fixedValue = (fp) floatValue;
            rawProperty.longValue = fixedValue.RawValue;
        }
    }

[orreborre2k]

Hello!
I, too, thought this would be a good idea. Turns out it was not :)
The float value that is saved in the inspector becomes slightly different each time entering play mode, so my simulations were off as soon as the fp value was used (I'm making a replay system).
We need to come up with a way to display and save the real value in the editor if this is supposed to work; it would be great being able to expose variables in the inspector. Maybe it is possible to extend SerializedProperty and add the correct value somehow? I might look into it later.

[aroman]

@orreborre2k I don't quite understand the issue you ran into. The float value should not change when entering play mode. It should only change when you modify the field.

Here is what I do to solve this problem, and it has been working deterministically in production for almost a year now. I use OdinValueDrawer from OdinInspector which makes custom property drawers easy.

public class FpValueDrawer : OdinValueDrawer<fp>
{
    private float displayedValue;

    protected override void DrawPropertyLayout(GUIContent label)
    {
        displayedValue = (float) ValueEntry.SmartValue;
        // Handles null check
        displayedValue = SirenixEditorFields.FloatField(label, displayedValue);

        ValueEntry.SmartValue = (fp) displayedValue;
    }
}

[aroman]

Oh, I see guess that OP's snippet probably works differently. Not too familiar with that API, but it seems like it's casting from float to fp on every OnGUI() call, which I can imagine will happen a lot, even if you're just looking at the property in the inspector and not intending to modify it. In my solution, I think Odin only re-serializes the field if it's actually modified.

[vex-ll]

@luaye thanks for the snippet, I started writing my own drawer and was having trouble creating a new instance of fp from the raw value (I didn't know about .FromRaw().

To your problem (if this is still a problem 3 years later), I had solved it with change checks:

    [CustomPropertyDrawer(typeof(fp))]
    public class FpPropertyDrawer : PropertyDrawer
    {
        public override void OnGUI(Rect position, SerializedProperty property, GUIContent label)
        {
            var rawProperty = property.FindPropertyRelative("m_rawValue");
            var fixedValue = fp.FromRaw(rawProperty.longValue);
            
            EditorGUI.BeginChangeCheck();
            var floatValue = EditorGUI.FloatField(position, label, (float) fixedValue);
            if (EditorGUI.EndChangeCheck())
            {
                fixedValue = (fp) floatValue;
                rawProperty.longValue = fixedValue.RawValue;
                rawProperty.serializedObject.ApplyModifiedProperties();
            }
        }
    }

Would be great to have a drawer added to the package out of the box.