[Gtk2hs-commit] (main branch): Add support for getting the stride and image data of an image surface

[Duncan C. <dun...@wo...>]

Tue Oct 30 11:38:25 PDT 2007  ag...@im...
  * Add support for getting the stride and image data of an image surface
  
    This wraps the cairo functions:
      cairo_image_surface_get_stride
      cairo_image_surface_get_data
  
    Note that these functions were introduced in cairo 1.2, and so this sets a new
    high bar for gtk2hs cairo.
  

    hunk ./cairo/Graphics/Rendering/Cairo/Internal/Surfaces/Image.chs 26
    +{#fun image_surface_get_stride as imageSurfaceGetStride { withSurface* `Surface' } -> `Int'#}
    +{#fun image_surface_get_data   as imageSurfaceGetData   { withSurface* `Surface' } -> `(Ptr CUChar)' id#}
    hunk ./cairo/Graphics/Rendering/Cairo.hs.pp 172
    +  , imageSurfaceGetStride
    +  , imageSurfaceGetData
    hunk ./cairo/Graphics/Rendering/Cairo.hs.pp 242
    +import Foreign.Ptr (castPtr)
    +import qualified Data.ByteString as BS
    hunk ./cairo/Graphics/Rendering/Cairo.hs.pp 1526
    --- [_$_]
    +--
    hunk ./cairo/Graphics/Rendering/Cairo.hs.pp 1552
    +-- | Get the number of bytes from the start of one row to the start of the
    +--   next. If the image data contains no padding, then this is equal to
    +--   the pixel depth * the width.
    +imageSurfaceGetStride :: Surface -> Render Int
    +imageSurfaceGetStride = liftIO . Internal.imageSurfaceGetStride
    +
    +-- | Return a ByteString of the image data for a surface. In order to remain
    +--   safe the returned ByteString is a copy of the data. This is a little
    +--   slower than returning a pointer into the image surface object itself, but
    +--   much safer
    +imageSurfaceGetData :: Surface -> IO BS.ByteString
    +imageSurfaceGetData a = do
    +  height <- Internal.imageSurfaceGetHeight a
    +  stride <- Internal.imageSurfaceGetStride a
    +  ptr <- Internal.imageSurfaceGetData a
    +  BS.copyCStringLen (castPtr ptr, height * stride)
    +