(g-object-call-set-property object-ptr property-name new-value &optional property-type)
Sets the property value of property property-name of object object-ptr to new-value.
Example:
(g-object-call-constructor "GtkButton" nil nil)
=>
#.(SB-SYS:INT-SAP #X006D8B40)
(g-object-call-set-property * "label" "Hello")
=>
; No value
(g-object-call-get-property ** "label")
=>
"Hello"