Mixed-state toggles for multi-object editing?

Component editors can support multi-object editing when the CanEditMultipleObjects attribute is used.

The built-in editors can present 3 variations of the toggle control depending upon whether the they are checked, unchecked or contain a mixed state since one or more objects have differing values. The following screenshot illustrates each of the three states of the toggle control:

24452-toggle-states.png

This tri-state toggle control is automatically provided by the default inspector implementation of custom components, and likewise can be presented using the EditorGUI.PropertyField function.

For technical reasons I need to be able to render this control myself. How can I draw the “Mixed” variation of the toggle style within an editor GUI? Is this graphic part of the GUI.skin.toggle style or another hidden internal style?

Use EditorGUI.showMixedValue.

E.g.

EditorGUI.showMixedValue = true;
bool value = EditorGUILayout.Toggle (...);
EditorGUI.showMixedValue = false;

SerializedProperty.hasMultipleDifferentValues is very handy here to do what you need.

Also, I use to wrap properties in Begin/End calls (e.g. BeginColorGroup, BeginShowMixedValueGroup, etc… as Unity does with EditorGUI.BeginDisabledGroup), this way is easier to keep track of that property state.