Radial Gradients as Custom Shaders

Unifies two-point normal and degenerate cases into a single class. I think GrGLRadial2Mapping::GenKey() needs fixing, although this currently passes all our tests. Other areas of concern discussed inline:

[TomH, 2012-05-24 20:28:39]

http://codereview.appspot.com/6251050/diff/1/src/gpu/gl/GrGLProgram.cpp
File src/gpu/gl/GrGLProgram.cpp (right):

http://codereview.appspot.com/6251050/diff/1/src/gpu/gl/GrGLProgram.cpp#newco...
src/gpu/gl/GrGLProgram.cpp:1441: // TODO: FIX
This *ought* to be straightforward - make sure we call
segments->setSamplerMode(), then call segments->emitTextureSetup(), but at the
moment the logic for whether or not we can do it is actually pretty nasty.

http://codereview.appspot.com/6251050/diff/1/src/gpu/gl/GrGpuGLShaders.cpp
File src/gpu/gl/GrGpuGLShaders.cpp (right):

http://codereview.appspot.com/6251050/diff/1/src/gpu/gl/GrGpuGLShaders.cpp#ne...
src/gpu/gl/GrGpuGLShaders.cpp:1055:
const_cast<GrSamplerState&>(sampler).setCustomStage(new GrRadialMapping());
This is doubly ugly, but IIRC the place where stage.fCoordMapping is set just
translates between two enums, so it's going to be ugly to do there. I'll try to
move this there before committing anyhow, just to avoid the const_cast<>.

[bsalomon, 2012-05-29 19:41:18]

http://codereview.appspot.com/6251050/diff/1/src/gpu/gl/GrGLProgram.cpp
File src/gpu/gl/GrGLProgram.cpp (right):

http://codereview.appspot.com/6251050/diff/1/src/gpu/gl/GrGLProgram.cpp#newco...
src/gpu/gl/GrGLProgram.cpp:1473: SkDEBUGFAIL("Radial Gradients should be handled
by custom stages");
GrCrash for consistency with other Gr code.

Can we start to remove these StageDesc enum values?

http://codereview.appspot.com/6251050/diff/1/src/gpu/gl/GrGpuGLShaders.cpp
File src/gpu/gl/GrGpuGLShaders.cpp (right):

http://codereview.appspot.com/6251050/diff/1/src/gpu/gl/GrGpuGLShaders.cpp#ne...
src/gpu/gl/GrGpuGLShaders.cpp:312: StageDesc::kRadialGradient_CoordMapping) {
Can we not just delete this enum value and make the guy who sets up the
GrSampleState install this guy (and similar for others)?

http://codereview.appspot.com/6251050/diff/1/src/gpu/gl/GrGpuGLShaders.cpp#ne...
src/gpu/gl/GrGpuGLShaders.cpp:1053: stage.fCoordMapping =
StageDesc::kRadialGradient_CoordMapping;
kill kill both of these enum values!

[TomH, 2012-06-01 20:30:34]

Should be completely obsoleted by http://codereview.appspot.com/6245078/ and
precursors; closing.