Disable blend for edge AA, not general AA

Blending was being turned off for smooth lines, so didn't affect Chrome.

[bsalomon, 2011-05-12 20:24:32]

A side effect of returning false in canDisableBlend is that we can't use smooth
lines:

bool GrGpuGL::useSmoothLines() {
    // there is a conflict between using smooth lines and our use of
    // premultiplied alpha. Smooth lines tweak the incoming alpha value
    // but not in a premul-alpha way. So we only use them when our alpha
    // is 0xff.

    // TODO: write a smarter line frag shader.

    return (kAntialias_StateBit & fCurrDrawState.fFlagBits) &&
           canDisableBlend();
}

Smooth lines aren't supported in ES2. That combined with the above consideration
means we need to write a line AA path. For now, though, let's limit the
canDisableBlend() to checking the edgeAA flag since the gm test draws aa lines.

[Stephen White, 2011-05-12 20:28:53]

LGTM.  Thanks!

http://codereview.appspot.com/4526051/diff/1/gpu/src/GrDrawTarget.cpp
File gpu/src/GrDrawTarget.cpp (right):

http://codereview.appspot.com/4526051/diff/1/gpu/src/GrDrawTarget.cpp#newcode482
gpu/src/GrDrawTarget.cpp:482: if (fCurrDrawState.fFlagBits & kEdgeAA_StateBit) {
Argh, sorry.  That's what this code should've been in the first place.

[bsalomon, 2011-05-12 20:35:10]

On 2011/05/12 20:28:53, Stephen White wrote:
> LGTM.  Thanks!
> 
> http://codereview.appspot.com/4526051/diff/1/gpu/src/GrDrawTarget.cpp
> File gpu/src/GrDrawTarget.cpp (right):
> 
>
http://codereview.appspot.com/4526051/diff/1/gpu/src/GrDrawTarget.cpp#newcode482
> gpu/src/GrDrawTarget.cpp:482: if (fCurrDrawState.fFlagBits & kEdgeAA_StateBit)
{
> Argh, sorry.  That's what this code should've been in the first place.


np, I forgot about that side-effect. Checked in at r1316.