Sets the DropDownIcon for the drop down calendar mode on macOS and Linux systems. (On Windows this does nothing since the Windows control is native control that does not use icon). This property supports retina enabled Image sets.
The base size of this icon has to be 16 x 16. (and 2x and 3x if you have such should then be 32 x 32 and 48 x 48).
If setting this property to nil then the control goes back to use the default one.
Please note:
When you have image sets then all Retina capable Xojo versions at least until this is written have a bug where the biggest version is selected in the IDE design mode regardless if that is correct or not. Many things are affected by that bug including Xojo's own Bevel button.
If you are upset by it then simply put the Icon on the control in code in its open event for example.
The Xojo bug for those that want to sign on it it is: 43174