Re: [cairo] Re: Notes on cairo/win32

On 13/01/05 22:06:46, J. Ali Harlow wrote:
On 13/01/05 20:27:43, Owen Taylor wrote:

> I think that the claim is that the flat API is C++ based too...

Concern, at least, yes.

> GpPath *is* defined as a class, but only in the most trivial way.
> As far as I can see, it's really just an opaque pointer and you
> could use a C definition like:
>  typedef struct GpPath_ GpPath;
> and it should work fine.

Let's hope you're right. I'll try and have a play tomorrow and see if
I can put together a gdiplusflat.h which uses opaque pointers or drops functions that take classes that appear to be wrappers themselves (eg., GdipAddPathRectanglesI which probably just wraps

Okay, I've had a quick play. It's possible to produce header files which will compile with a C compiler as long as you avoid certain functions which use the C++ '&' operator. Mine are pretty raw, but if anybody wants them, please shout.

However, in trying to use these headers to compile a test program[1], I ran into trouble with trying to lock a bitmap. It seems as though you have to have a Rect (which is a class) to lock a bitmap and there is no way to create one in C.

Some half-baked ideas for how to proceed:

- It's possible that you could try and hack one up using a structure if you assumed that the public members came at the start but I've no idea if this would work and in any case it doesn't sound like a sensible way to proceed to me.

- We could set aside a hopefully-large-enough block of memory and then set and get the clip rect as another gross hack.

- Another possibility would be to try and see if we could pass NULL into the locking function. We'd loose the ability to lock a portion of a bitmap, but that might be acceptable if it happens to work. It's still breaking the published API of course.

- There may be a method of creating a Rect using one of the functions which I have excluded because they use the C++ '&' operator. Somebody who understands C++ rather more than me (ie., at all) will need to advise here.

- Assume we don't need this functionality for cairo and soldier on.



[Date Prev][Date Next]   [Thread Prev][Thread Next]   [Thread Index] [Date Index] [Author Index]