OpenEuphoria

My Bits are Flipping (or, "Why Can't I Be Negative?")

• Posted by Travis Beaty <eucoder at travisbeaty.us> Aug 27, 2004
• 488 views

Hello all!

I've seen something a little strange while working on Midgard, and I'm hoping 
some of the other library wrapping folks out there can explain it to me, and 
tell me how to fix it.

I'm currently working on mouse events in Midgard.  When the mouse moves past 
the left or top of the widget, the mouse position is given as a negative 
number, reflecting the fact that the position is based on the widget's 
coordinate system.  This is to be expected, and is what happens in the shared 
library part of the project.

The problem is with the Euphoria function that is being used as a callback.  
The prototype for the callback function is:

-- MWidget is basically an atom.
function X(MWidget sender, integer x, integer y)

When either x or y receives a negative number from the shared library, its 
picking up on the fact that the signed bit of the number is flagged.  
However, it is seeing this not as a negative number, but as a huge positive 
number, which of course is causing a Euphoria error because the number is too 
big to be an integer.

How can I get this value, coming in from the C++ code side, to be seen by 
Euphoria as a negative number?  Or am I going to have to check the signed bit 
manually?

Any help would be greatly appreciated!


Travis.


-- 
"Well," Brahma said, "even after ten thousand explanations, a fool is no
wiser, but an intelligent man requires only two thousand five hundred."
		-- The Mahabharata.