Miss Doc/Guide for some functions of class QLineF

Suggestion:
For class function QLineF::dx() & QLineF::dy(),
It's better to clearly define the return value of these 2 function. Whether the return value is an absolute value of the length of dx from P1() to P2() that means the return value must be a positive number or can be a negative number which is really the dx point from P1() to P2() .
Reason:
I single step debug the source code, find out that QLineF::dx() and QLineF::dy() return value has its orientation.
So I think its better to note this point in the document, in case that other developers needn't to debug the code to find out the true when they want to know these 2 functions has orientation or not.
Scenario:
I single step debug the source code, find out that QLineF::dx() and QLineF::dy() return value has its orientation.
So I think its better to note this point in the document, in case that other developers needn't to debug the code to find out the true when they want to know these 2 functions has orientation or not.