Add asAGradient shader extraction API.

Add asAGradient shader extraction API.

Store initial gradient parameters.
Add compile asserts in GPU code for BitmapType ordering.

Committed: http://code.google.com/p/skia/source/detail?r=845

[Steve VanDeBogart, 2011-02-18 00:02:44]

See http://codereview.appspot.com/4171061/ for an example of the new API being
used.

[Steve VanDeBogart, 2011-02-18 00:03:23]

See http://codereview.appspot.com/4171061/ for an example of the new API being
used.

[reed1, 2011-02-18 12:48:48]

http://codereview.appspot.com/4178063/diff/1/include/core/SkShader.h
File include/core/SkShader.h (right):

http://codereview.appspot.com/4178063/diff/1/include/core/SkShader.h#newcode157
include/core/SkShader.h:157: kImage_BitmapType,  //<! Use a multidimensional
bitmap as a texture.
Why do we now have kDefault *and* kImage?

http://codereview.appspot.com/4178063/diff/1/include/core/SkShader.h#newcode241
include/core/SkShader.h:241: int         fColorCount;
//!< in-out parameter, specifies allocation size for fColors/Offsets on input,
and actual number of colors on output

http://codereview.appspot.com/4178063/diff/1/src/effects/SkGradientShader.cpp
File src/effects/SkGradientShader.cpp (right):

http://codereview.appspot.com/4178063/diff/1/src/effects/SkGradientShader.cpp...
src/effects/SkGradientShader.cpp:1574: void Init() {
lowercase -- init()

[Steve VanDeBogart, 2011-02-22 22:38:36]

http://codereview.appspot.com/4178063/diff/1/include/core/SkShader.h
File include/core/SkShader.h (right):

http://codereview.appspot.com/4178063/diff/1/include/core/SkShader.h#newcode157
include/core/SkShader.h:157: kImage_BitmapType,  //<! Use a multidimensional
bitmap as a texture.
On 2011/02/18 12:48:48, reed1 wrote:
> Why do we now have kDefault *and* kImage?

kDefault is used for a linear gradient, a single color gradient and maybe
something else too.  For PDF I could just check asAGradient first and assume
kDefault is fine, but and explicit kImage yields a cleaner interface.

http://codereview.appspot.com/4178063/diff/1/include/core/SkShader.h#newcode241
include/core/SkShader.h:241: int         fColorCount;
On 2011/02/18 12:48:48, reed1 wrote:
> //!< in-out parameter, specifies allocation size for fColors/Offsets on input,
> and actual number of colors on output

Done.

http://codereview.appspot.com/4178063/diff/1/src/effects/SkGradientShader.cpp
File src/effects/SkGradientShader.cpp (right):

http://codereview.appspot.com/4178063/diff/1/src/effects/SkGradientShader.cpp...
src/effects/SkGradientShader.cpp:1574: void Init() {
On 2011/02/18 12:48:48, reed1 wrote:
> lowercase -- init()

Done.

[reed1, 2011-02-23 14:33:21]

I would prefer we drop kDefault, and just use kImage, assuming it is reasonable
for your code to call asAGradient() first, and if that fails, to call
asABitmap().

[Steve VanDeBogart, 2011-02-23 17:47:10]

On 2011/02/23 14:33:21, reed1 wrote:
> I would prefer we drop kDefault, and just use kImage, assuming it is
reasonable
> for your code to call asAGradient() first, and if that fails, to call
> asABitmap().

Done; I reverted that part of the change so there is just kDefault now.

[reed1, 2011-02-23 18:21:23]

LGTM