X, Y, Width, and Height are the dimensions of the check box.
Value is the checkbox state: CheckBox.False, CheckBox.True or CheckBox.None for an unknown state.
Flag is a combination of style drawing flags.

Note:

Different toolkits behave differently with this function.

As a general example if you supply width and height size as 32x32px QT5 will paint a checkbox 32x32px in size but GTK3 will only paint a box of 16x16px inside a 32x32 frame regardless of what size you request.

To get a truly different size checkbox with gtk3 you must paint the 16x16 box and then stretch the image.