Pen width and XOR drawing

[enonod]

I have searched but not found (almost always no hits). I wish to alter/set the pen width when drawing.
I cannot find how to set the pen to XOR so that a second drawing of the same line removes it (for rubber banding).
Any pointers please?

 

[klaus]

There is no line thickness parameter in B4PPC.
Have look at Erel's proposals:
http://www.b4x.com/forum/code-samples-tips/2331-different-line-types.html

The XOR mode is not supported by B4PPC, for the rubber banding you should use the ForeLayer.
You can have a look at this:
http://www.b4x.com/forum/code-samples-tips/1821-rubber-banding.html

Best regards

 

[enonod]

Thank you klaus for those pointers, I don't know why my search didn't find them.
A question now occurs to me. I have never come across ForeLayer in any other language, is there only one? If so does that mean a form has two layers and can they just be switched between etc?
What is its main purpose (why was it invented )
Any further info and common usage would be appreciated.