SkPDF: Refactor PDFShader to use ShTHashMap<>

my tests run ~14% faster.

  - Split out gradient shaders from image shaders.  new compilation
    unit: SkPDFGradientShader
  - Common functions InverseTransformBBox and PopulateTilingPatternDict
    moved to SkPDFUtils
  - Split SkPDFShader::State into image and gradient structures.
  - SkPDFCanon is now a simpler structure, with no logic of its own.
    I am considering just moving all of its fields into SkPDFDocument
  - SkPDFShader::State (the image/fallback shader) now is POD, making
    the use of a hashmap for canonicalization straightforward.
    Formerly, we used a linear search.
  - Do not bother trying to canonicalize the falback image shader.
  - SkPDFGradientShader::Key is not POD; comparison of two objects
    requires looking at the contents of two variable-sized arrays.
    We now pre-calculate the hash of the arrays using SkOpts::hash and
    store a hash for the object in the fHash field.
    Using that hash, we can now canonicalize using a hashmap instead
    of a linar search!
  - several static functions renamed to follow style guidelines
  - stop using codeFunction function pointer; I find that less
    clear than it could be.
  - operator==() for SkPDFShader::State and SkPDFGradientShader::Key is
    now much simpler and can now be inlined.
  - SkArrayEqual template in SkPDFUtils.h

No change to PDF output.

BUG=skia:3585
Change-Id: I354ad1b600be6d6749abccb58d13db257370bc0b
Reviewed-on: https://skia-review.googlesource.com/21376
Reviewed-by: Ben Wagner <bungeman@google.com>
Commit-Queue: Hal Canary <halcanary@google.com>

1 files changed, 8 insertions, 17 deletions

diff --git a/src/pdf/SkPDFCanon.h b/src/pdf/SkPDFCanon.h
index d876443c17..1085387242 100644
--- a/src/pdf/SkPDFCanon.h
+++ b/src/pdf/SkPDFCanon.h
@@ -9,6 +9,7 @@
 
 #include "SkPDFGraphicState.h"
 #include "SkPDFShader.h"
+#include "SkPDFGradientShader.h"
 #include "SkPixelSerializer.h"
 #include "SkTDArray.h"
 #include "SkTHash.h"
@@ -21,18 +22,17 @@ struct SkAdvancedTypefaceMetrics;
  *  The SkPDFCanon canonicalizes objects across PDF pages
  *  (SkPDFDevices) and across draw calls.
  */
-class SkPDFCanon : SkNoncopyable {
+class SkPDFCanon {
 public:
     ~SkPDFCanon();
+    SkPDFCanon();
+    SkPDFCanon(const SkPDFCanon&) = delete;
+    SkPDFCanon& operator=(const SkPDFCanon&) = delete;
 
-    sk_sp<SkPDFObject> findFunctionShader(const SkPDFShader::State&) const;
-    void addFunctionShader(sk_sp<SkPDFObject>, SkPDFShader::State);
+    SkTHashMap<SkPDFShader::State, sk_sp<SkPDFObject>> fImageShaderMap;
 
-    sk_sp<SkPDFObject> findAlphaShader(const SkPDFShader::State&) const;
-    void addAlphaShader(sk_sp<SkPDFObject>, SkPDFShader::State);
-
-    sk_sp<SkPDFObject> findImageShader(const SkPDFShader::State&) const;
-    void addImageShader(sk_sp<SkPDFObject>, SkPDFShader::State);
+    SkPDFGradientShader::HashMap fAlphaGradientMap;
+    SkPDFGradientShader::HashMap fOpaqueGradientMap;
 
     SkTHashMap<SkBitmapKey, sk_sp<SkPDFObject>> fPDFBitmapMap;
 
@@ -47,14 +47,5 @@ public:
     sk_sp<SkPDFStream> fInvertFunction;
     sk_sp<SkPDFDict> fNoSmaskGraphicState;
     sk_sp<SkPDFArray> fRangeObject;
-
-private:
-    struct ShaderRec {
-        SkPDFShader::State fShaderState;
-        sk_sp<SkPDFObject> fShaderObject;
-    };
-    SkTArray<ShaderRec> fFunctionShaderRecords;
-    SkTArray<ShaderRec> fAlphaShaderRecords;
-    SkTArray<ShaderRec> fImageShaderRecords;
 };
 #endif  // SkPDFCanon_DEFINED