[cairo] [API] Export region data type

[Behdad Esfahbod]

Kristian Høgsberg wrote:
> On Wed, Feb 25, 2009 at 3:57 PM, Behdad Esfahbod <behdad at behdad.org> wrote:
>> Kristian Høgsberg wrote:
>>> On Sat, Feb 21, 2009 at 9:44 AM, Soeren Sandmann <sandmann at daimi.au.dk> wrote:
>>>> Hi,
>>>>
>>>> I'd like to propose exporting the region data type for 1.10. There is
>>>> an implementation available in the public-region branch of this
>>>> repository:
>>> ...
>>>>    typedef struct _cairo_rectangle_int {
>>>>        int x, y;
>>>>        unsigned int width, height;
>>>>    } cairo_rectangle_int_t;
>>> If we end up exporting this, I'd suggest making width and height
>>> signed ints to avoid overflow pitfalls such as
>> With signed width/height you get overflows when doing:
>>
>>  rect->width = x2 - x1;
> 
> How so?  Getting a negative width is not an overflow situation.  It's
> potentially unexepected, but certainly not worse than having x2=100
> and x1=150 and then have width be 2^32 - 50.

What's a negative width good for?  It doesn't mean anything.  It's undefined.
 It's a hassle to handle (you have to check for width >= 0 all over the code).
 The 2^32 - 50 on the other hand will be automatically detected and handled by
whatever check you already have in place for handling large sizes.

behdad

> Kristian
>