Adding an option to render only the shadow in SkDropShadowImageFilter

This is basically how blink uses the filter. Currently, I can't use it for "ShadowOnly" mode with the filter at all, but instead of copying the code and risking to have the codepaths diverge, I'm simply going to add the option here.

BUG=skia:

Review URL: https://codereview.chromium.org/646213004

5 files changed, 23 insertions, 13 deletions

diff --git a/gm/dropshadowimagefilter.cpp b/gm/dropshadowimagefilter.cpp
index a22ec43722..5a8c7a2a8b 100644
--- a/gm/dropshadowimagefilter.cpp
+++ b/gm/dropshadowimagefilter.cpp
@@ -102,7 +102,7 @@ protected:
         return SkString("dropshadowimagefilter");
     }
 
-    virtual SkISize onISize() { return SkISize::Make(400, 700); }
+    virtual SkISize onISize() { return SkISize::Make(400, 656); }
 
     void draw_frame(SkCanvas* canvas, const SkRect& r) {
         SkPaint paint;
@@ -134,12 +134,20 @@ protected:
 
         SkImageFilter* filters[] = {
             NULL,
-            SkDropShadowImageFilter::Create(7.0f, 0.0f, 0.0f, 3.0f, SK_ColorBLUE),
-            SkDropShadowImageFilter::Create(0.0f, 7.0f, 3.0f, 0.0f, SK_ColorBLUE),
-            SkDropShadowImageFilter::Create(7.0f, 7.0f, 3.0f, 3.0f, SK_ColorBLUE),
-            SkDropShadowImageFilter::Create(7.0f, 7.0f, 3.0f, 3.0f, SK_ColorBLUE, cfif),
-            SkDropShadowImageFilter::Create(7.0f, 7.0f, 3.0f, 3.0f, SK_ColorBLUE, NULL, &cropRect),
-            SkDropShadowImageFilter::Create(7.0f, 7.0f, 3.0f, 3.0f, SK_ColorBLUE, NULL, &bogusRect),
+            SkDropShadowImageFilter::Create(7.0f, 0.0f, 0.0f, 3.0f, SK_ColorBLUE,
+                SkDropShadowImageFilter::kDrawShadowAndForeground_ShadowMode),
+            SkDropShadowImageFilter::Create(0.0f, 7.0f, 3.0f, 0.0f, SK_ColorBLUE,
+                SkDropShadowImageFilter::kDrawShadowAndForeground_ShadowMode),
+            SkDropShadowImageFilter::Create(7.0f, 7.0f, 3.0f, 3.0f, SK_ColorBLUE,
+                SkDropShadowImageFilter::kDrawShadowAndForeground_ShadowMode),
+            SkDropShadowImageFilter::Create(7.0f, 7.0f, 3.0f, 3.0f, SK_ColorBLUE,
+                SkDropShadowImageFilter::kDrawShadowAndForeground_ShadowMode, cfif, NULL, 0),
+            SkDropShadowImageFilter::Create(7.0f, 7.0f, 3.0f, 3.0f, SK_ColorBLUE,
+                SkDropShadowImageFilter::kDrawShadowAndForeground_ShadowMode, NULL, &cropRect, 0),
+            SkDropShadowImageFilter::Create(7.0f, 7.0f, 3.0f, 3.0f, SK_ColorBLUE,
+                SkDropShadowImageFilter::kDrawShadowAndForeground_ShadowMode, NULL, &bogusRect, 0),
+            SkDropShadowImageFilter::Create(7.0f, 7.0f, 3.0f, 3.0f, SK_ColorBLUE,
+                SkDropShadowImageFilter::kDrawShadowOnly_ShadowMode),
         };
 
         SkRect r = SkRect::MakeWH(SkIntToScalar(64), SkIntToScalar(64));
diff --git a/gm/imagefiltersbase.cpp b/gm/imagefiltersbase.cpp
index d1bd5a72df..4546b8add2 100644
--- a/gm/imagefiltersbase.cpp
+++ b/gm/imagefiltersbase.cpp
@@ -231,7 +231,8 @@ protected:
             FailImageFilter::Create(),
             SkColorFilterImageFilter::Create(cf),
             SkBlurImageFilter::Create(12.0f, 0.0f),
-            SkDropShadowImageFilter::Create(10.0f, 5.0f, 3.0f, 3.0f, SK_ColorBLUE),
+            SkDropShadowImageFilter::Create(10.0f, 5.0f, 3.0f, 3.0f, SK_ColorBLUE,
+                SkDropShadowImageFilter::kDrawShadowAndForeground_ShadowMode),
         };
         cf->unref();
 
diff --git a/gm/imagefiltersclipped.cpp b/gm/imagefiltersclipped.cpp
index e836e40543..ae53a2e3ba 100644
--- a/gm/imagefiltersclipped.cpp
+++ b/gm/imagefiltersclipped.cpp
@@ -101,8 +101,8 @@ protected:
         SkImageFilter* filters[] = {
             SkBlurImageFilter::Create(SkIntToScalar(12), SkIntToScalar(12)),
             SkDropShadowImageFilter::Create(SkIntToScalar(10), SkIntToScalar(10),
-                                            SkIntToScalar(3), SkIntToScalar(3),
-                                            SK_ColorGREEN),
+                SkIntToScalar(3), SkIntToScalar(3), SK_ColorGREEN,
+                SkDropShadowImageFilter::kDrawShadowAndForeground_ShadowMode),
             SkDisplacementMapEffect::Create(SkDisplacementMapEffect::kR_ChannelSelectorType,
                                             SkDisplacementMapEffect::kR_ChannelSelectorType,
                                             SkIntToScalar(12),
diff --git a/gm/imagefilterscropexpand.cpp b/gm/imagefilterscropexpand.cpp
index c9601b066c..7db41e0364 100644
--- a/gm/imagefilterscropexpand.cpp
+++ b/gm/imagefilterscropexpand.cpp
@@ -142,7 +142,8 @@ protected:
 
             draw(canvas, checkerboard, rect, SkDropShadowImageFilter::Create(
                 SkIntToScalar(10), SkIntToScalar(10), SkIntToScalar(3), SkIntToScalar(3),
-                SK_ColorBLUE, noop_cropped.get(), &big_rect));
+                SK_ColorBLUE, SkDropShadowImageFilter::kDrawShadowAndForeground_ShadowMode,
+                noop_cropped.get(), &big_rect, 0));
 
             draw(canvas, checkerboard, rect, SkDisplacementMapEffect::Create(
                 SkDisplacementMapEffect::kR_ChannelSelectorType,
diff --git a/gm/imagefiltersscaled.cpp b/gm/imagefiltersscaled.cpp
index cf4dc4e8e7..8b44bd0563 100644
--- a/gm/imagefiltersscaled.cpp
+++ b/gm/imagefiltersscaled.cpp
@@ -110,8 +110,8 @@ protected:
         SkImageFilter* filters[] = {
             SkBlurImageFilter::Create(SkIntToScalar(4), SkIntToScalar(4)),
             SkDropShadowImageFilter::Create(SkIntToScalar(5), SkIntToScalar(10),
-                                            SkIntToScalar(3), SkIntToScalar(3),
-                                            SK_ColorYELLOW),
+                SkIntToScalar(3), SkIntToScalar(3), SK_ColorYELLOW,
+                SkDropShadowImageFilter::kDrawShadowAndForeground_ShadowMode),
             SkDisplacementMapEffect::Create(SkDisplacementMapEffect::kR_ChannelSelectorType,
                                             SkDisplacementMapEffect::kR_ChannelSelectorType,
                                             SkIntToScalar(12),