Re: [XaraXtreme-dev] Cairo Port

[Jonas Diemer <diemer@xxxxxx>]

Alex Bligh schrieb:
> > Also, the code above must certainly be able to get at the image buffer
> > contents somehow in order to be able to actually display them. But I'm
> > not sure how that happens.
>
> The image buffer is allocated (and, I believe, blanked) in the 
> application.
> For extra bonus confusion value the bitmap bit itself needs to be in
> windows DIB format. Given that it's (almost) exclusively used in 32 bit
> mode these days, this is simply one 32-bit word per pixel, and row
> alignment etc. aren't a problem, so we are merely talking byte 
> ordering and
> "where T goes" considerations. 

Well, I have added code to the GDraw_SetDIBitmap function, which I think 
should be the place to set up a cairo surface to draw on.

AFAIK, a cairo_t context requires a surface to be created, so I create 
the cairo_t here as well. Hence, a cairo_t context does not perfectly 
map to the GDRAW context...

So far, I ignore calls with Bitmap==NULL, I don't know if that is the 
expected behaviour though.

It looks like, cairo and gdraw use the same bitmap format. I could set 
up a surface to draw on like this:

   cairo_surface_t *surface = cairo_image_surface_create_for_data(
           Bitmap, // This is the Bitmap pointer passed to 
GDraw_SetDIBitmap
           CAIRO_FORMAT_ARGB32,
           BitmapInfo->biWidth,
           BitmapInfo->biHeight,
           4*BitmapInfo->biWidth /*stride is 4*width bytes*/ );

I have sucessfully drawn some shapes to the "stroke shape / pressure 
profile" selector by just drawing something directly from 
GDraw_SetDIBitmap. However, I have not yet been able to draw to the main 
canvas (which shows the actual image)...

I know, I am moving forward in very little steps, since I am new to all 
this :-)

Jonas