Change GrTextContext fallbacks to be a linked list chain.

src/gpu/SkGpuDevice.cpp

Index: src/gpu/SkGpuDevice.cpp
diff --git a/src/gpu/SkGpuDevice.cpp b/src/gpu/SkGpuDevice.cpp
index 6f4d1a6f99ea6b83fc5ac1ae99a78704678e8228..f0abf4463f5790001d178e2ab3d1878fa1d35839 100644
--- a/src/gpu/SkGpuDevice.cpp
+++ b/src/gpu/SkGpuDevice.cpp
@@ -147,8 +147,7 @@ SkGpuDevice::SkGpuDevice(GrSurface* surface, const SkSurfaceProps& props, unsign
     this->setPixelGeometry(props.pixelGeometry());
 
     bool useDFFonts = !!(flags & kDFFonts_Flag);
-    fMainTextContext = fContext->createTextContext(fRenderTarget, this->getLeakyProperties(), useDFFonts);
-    fFallbackTextContext = SkNEW_ARGS(GrBitmapTextContext, (fContext, this->getLeakyProperties()));
+    fTextContext = fContext->createTextContext(fRenderTarget, this->getLeakyProperties(), useDFFonts);
 }
 
 SkGpuDevice* SkGpuDevice::Create(GrContext* context, const SkImageInfo& origInfo,
@@ -192,8 +191,7 @@ SkGpuDevice::~SkGpuDevice() {
         delete fDrawProcs;
     }
 
-    delete fMainTextContext;
-    delete fFallbackTextContext;
+    delete fTextContext;
 
     // The GrContext takes a ref on the target. We don't want to cause the render
     // target to be unnecessarily kept alive.
@@ -1685,24 +1683,22 @@ void SkGpuDevice::drawText(const SkDraw& draw, const void* text,
     CHECK_SHOULD_DRAW(draw, false);
     GR_CREATE_TRACE_MARKER_CONTEXT("SkGpuDevice::drawText", fContext);
 
-    if (fMainTextContext->canDraw(paint)) {
-        GrPaint grPaint;
-        SkPaint2GrPaintShader(this->context(), paint, true, &grPaint);
-
-        SkDEBUGCODE(this->validate();)
+    GrTextContext* textContext = fTextContext;
+    do {
+        if (textContext->canDraw(paint)) {
+            GrPaint grPaint;
+            SkPaint2GrPaintShader(this->context(), paint, true, &grPaint);
 
-        fMainTextContext->drawText(grPaint, paint, (const char *)text, byteLength, x, y);
-    } else if (fFallbackTextContext && fFallbackTextContext->canDraw(paint)) {
-        GrPaint grPaint;
-        SkPaint2GrPaintShader(this->context(), paint, true, &grPaint);
+            SkDEBUGCODE(this->validate();)
 
-        SkDEBUGCODE(this->validate();)
+            textContext->drawText(grPaint, paint, (const char *)text, byteLength, x, y);
+            return;
+        }
+        textContext = textContext->getFallbackTextContext();

[bsalomon, 2014/10/13 18:46:36]

Would it make sense for this to just happen within the text context? Maybe make
drawText() non-virtual with a virtual onDrawText() put the the fallback code on
drawText()?

[jvanverth1, 2014/10/13 18:54:48]

I thought of that, but you'd have to call canDraw() twice -- once to see if you
can draw at all (for the path fallback) and then again to see which your chain
to use. CanDraw() is  currently a little expensive on the DFF side, so I'm
trying to avoid that.

[bsalomon, 2014/10/13 19:01:44]

I'm not sure I see why... 

GrTextContext::drawText() {
    GrTextContext* context = this;
    do {
        if (context->canDrawText()) {
           context->onDrawText();
           return;
        }
    } while (context = context->getFallback());
}

[jvanverth1, 2014/10/13 19:06:18]

Got it. And GrTextContext::drawText can return false if all of them fail, and
SkGpuDevice will draw paths in that case.

+    } while (textContext);
 
-        fFallbackTextContext->drawText(grPaint, paint, (const char *)text, byteLength, x, y);
-    } else {
-        // this guy will just call our drawPath()
-        draw.drawText_asPaths((const char*)text, byteLength, x, y, paint);
-    }
+    // this will just call our drawPath()
+    draw.drawText_asPaths((const char*)text, byteLength, x, y, paint);
 }
 
 void SkGpuDevice::drawPosText(const SkDraw& draw, const void* text, size_t byteLength,
@@ -1711,25 +1707,22 @@ void SkGpuDevice::drawPosText(const SkDraw& draw, const void* text, size_t byteL
     GR_CREATE_TRACE_MARKER_CONTEXT("SkGpuDevice::drawPosText", fContext);
     CHECK_SHOULD_DRAW(draw, false);
 
-    if (fMainTextContext->canDraw(paint)) {
-        GrPaint grPaint;
-        SkPaint2GrPaintShader(this->context(), paint, true, &grPaint);
-
-        SkDEBUGCODE(this->validate();)
+    GrTextContext* textContext = fTextContext;
+    do {
+        if (textContext->canDraw(paint)) {
+            GrPaint grPaint;
+            SkPaint2GrPaintShader(this->context(), paint, true, &grPaint);
 
-        fMainTextContext->drawPosText(grPaint, paint, (const char *)text, byteLength, pos,
-                                      scalarsPerPos, offset);
-    } else if (fFallbackTextContext && fFallbackTextContext->canDraw(paint)) {
-        GrPaint grPaint;
-        SkPaint2GrPaintShader(this->context(), paint, true, &grPaint);
+            SkDEBUGCODE(this->validate();)
 
-        SkDEBUGCODE(this->validate();)
+            textContext->drawPosText(grPaint, paint, (const char *)text, byteLength, pos,
+                                     scalarsPerPos, offset);
+            return;
+        }
+        textContext = textContext->getFallbackTextContext();
+    } while (textContext);
 
-        fFallbackTextContext->drawPosText(grPaint, paint, (const char *)text, byteLength, pos,
-                                          scalarsPerPos, offset);
-    } else {
-        draw.drawPosText_asPaths((const char*)text, byteLength, pos, scalarsPerPos, offset, paint);
-    }
+    draw.drawPosText_asPaths((const char*)text, byteLength, pos, scalarsPerPos, offset, paint);
 }
 
 void SkGpuDevice::drawTextOnPath(const SkDraw& draw, const void* text,