Add pattern matchers for SkRecord

src/record/SkRecordOpts.cpp

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkRecordOpts.h"
 
-#include "SkRecordTraits.h"
+#include "SkRecordPattern.h"
 #include "SkRecords.h"
 #include "SkTDArray.h"
 
+using namespace SkRecords;
+
 void SkRecordOptimize(SkRecord* record) {
     // TODO(mtklein): fuse independent optimizations to reduce number of passes?
     SkRecordNoopSaveRestores(record);
     SkRecordAnnotateCullingPairs(record);
     SkRecordReduceDrawPosTextStrength(record);  // Helpful to run this before BoundDrawPosTextH.
     SkRecordBoundDrawPosTextH(record);
 }
 
-namespace {
+// Most of the optimizations in this file are pattern-based.  These are all defined as structs with:
+//   - a Pattern typedef
+//   - a bool onMatch(SkRceord*, Pattern*, unsigned begin, unsigned end) method,
+//     which returns true if it made changes and false if not.
 
-// Convenience base class to share some common implementation code.
-class Common : SkNoncopyable {
-public:
-    explicit Common(SkRecord* record) : fRecord(record), fIndex(0) {}
+// Run a pattern-based optimization once across the SkRecord, returning true if it made any changes.
+// It looks for spans which match Pass::Pattern, and when found calls onMatch() with the pattern,
+// record, and [begin,end) span of the commands that matched.
+template <typename Pass>
+static bool apply(Pass* pass, SkRecord* record) {
+    typename Pass::Pattern pattern;
+    bool changed = false;
+    unsigned begin, end = 0;
 
-    unsigned index() const { return fIndex; }
-    void next() { ++fIndex; }
-
-protected:
-    SkRecord* fRecord;
-    unsigned fIndex;
-};
+    while (pattern.search(record, &begin, &end)) {
+        changed |= pass->onMatch(record, &pattern, begin, end);
+    }
+    return changed;
+}
 
 // Turns logical no-op Save-[non-drawing command]*-Restore patterns into actual no-ops.
-// TODO(mtklein): state machine diagram
-class SaveRestoreNooper : public Common {
-public:
-    explicit SaveRestoreNooper(SkRecord* record)
-        : Common(record), fSave(kInactive), fChanged(false) {}
+struct SaveRestoreNooper {
+    // Star matches greedily, so we also have to exclude Save and Restore.
+    typedef Pattern3<Is<Save>,
+                     Star<Not<Or3<Is<Save>,
+                                  Is<Restore>,
+                                  IsDraw> > >,
+                     Is<Restore> >
+        Pattern;
 
-    // Drawing commands reset state to inactive without nooping.
-    template <typename T>
-    SK_WHEN(SkRecords::IsDraw<T>, void) operator()(T*) { fSave = kInactive; }
+    bool onMatch(SkRecord* record, Pattern* pattern, unsigned begin, unsigned end) {
+        // If restore doesn't revert both matrix and clip, this isn't safe to noop away.
+        if (pattern->first<Save>()->flags != SkCanvas::kMatrixClip_SaveFlag) {
+            return false;
+        }
 
-    // Most non-drawing commands can be ignored.
-    template <typename T>
-    SK_WHEN(!SkRecords::IsDraw<T>, void) operator()(T*) {}
-
-    void operator()(SkRecords::Save* r) {
-        fSave = SkCanvas::kMatrixClip_SaveFlag == r->flags ? this->index() : kInactive;
+        // The entire span between Save and Restore (inclusively) does nothing.
+        for (unsigned i = begin; i < end; i++) {
+            record->replace<NoOp>(i);
+        }
+        return true;
     }
-
-    void operator()(SkRecords::Restore* r) {
-        if (fSave != kInactive) {
-            // Remove everything between the save and restore, inclusive on both sides.
-            fChanged = true;
-            for (unsigned i = fSave; i <= this->index(); i++) {
-                fRecord->replace<SkRecords::NoOp>(i);
-            }
-            fSave = kInactive;
-        }
-    }
-
-    bool changed() const { return fChanged; }
-
-private:
-    static const unsigned kInactive = ~0;
-    unsigned fSave;
-    bool fChanged;
 };
-
-// Tries to replace PushCull with PairedPushCull, which lets us skip to the paired PopCull
-// when the canvas can quickReject the cull rect.
-class CullAnnotator : public Common {
-public:
-    explicit CullAnnotator(SkRecord* record) : Common(record) {}
-
-    // Do nothing to most ops.
-    template <typename T> void operator()(T*) {}
-
-    void operator()(SkRecords::PushCull* push) {
-        Pair pair = { this->index(), push };
-        fPushStack.push(pair);
-    }
-
-    void operator()(SkRecords::PopCull* pop) {
-        Pair push = fPushStack.top();
-        fPushStack.pop();
-
-        SkASSERT(this->index() > push.index);
-        unsigned skip = this->index() - push.index;
-
-        SkRecords::Adopted<SkRecords::PushCull> adopted(push.command);
-        SkNEW_PLACEMENT_ARGS(fRecord->replace<SkRecords::PairedPushCull>(push.index, adopted),
-                             SkRecords::PairedPushCull, (&adopted, skip));
-    }
-
-private:
-    struct Pair {
-        unsigned index;
-        SkRecords::PushCull* command;
-    };
-
-    SkTDArray<Pair> fPushStack;
-};
+void SkRecordNoopSaveRestores(SkRecord* record) {
+    SaveRestoreNooper pass;
+    while (apply(&pass, record));  // Run until it stops changing things.
+}
 
 // Replaces DrawPosText with DrawPosTextH when all Y coordinates are equal.
-class StrengthReducer : public Common {
-public:
-    explicit StrengthReducer(SkRecord* record) : Common(record) {}
+struct StrengthReducer {
+    typedef Pattern1<Is<DrawPosText> > Pattern;
 
-    // Do nothing to most ops.
-    template <typename T> void operator()(T*) {}
+    bool onMatch(SkRecord* record, Pattern* pattern, unsigned begin, unsigned end) {
+        SkASSERT(end == begin + 1);
+        DrawPosText* draw = pattern->first<DrawPosText>();
 
-    void operator()(SkRecords::DrawPosText* r) {
-        const unsigned points = r->paint.countText(r->text, r->byteLength);
+        const unsigned points = draw->paint.countText(draw->text, draw->byteLength);
         if (points == 0) {
-            // No point (ha!).
-            return;
+            return false;  // No point (ha!).
         }
 
-        const SkScalar firstY = r->pos[0].fY;
+        const SkScalar firstY = draw->pos[0].fY;
         for (unsigned i = 1; i < points; i++) {
-            if (r->pos[i].fY != firstY) {
-                // Needs the full strength of DrawPosText.
-                return;
+            if (draw->pos[i].fY != firstY) {
+                return false;  // Needs full power of DrawPosText.
             }
         }
         // All ys are the same.  We can replace DrawPosText with DrawPosTextH.
 
-        // r->pos is points SkPoints, [(x,y),(x,y),(x,y),(x,y), ... ].
+        // draw->pos is points SkPoints, [(x,y),(x,y),(x,y),(x,y), ... ].
         // We're going to squint and look at that as 2*points SkScalars, [x,y,x,y,x,y,x,y, ...].
         // Then we'll rearrange things so all the xs are in order up front, clobbering the ys.
         SK_COMPILE_ASSERT(sizeof(SkPoint) == 2 * sizeof(SkScalar), SquintingIsNotSafe);
-        SkScalar* scalars = &r->pos[0].fX;
+        SkScalar* scalars = &draw->pos[0].fX;
         for (unsigned i = 0; i < 2*points; i += 2) {
             scalars[i/2] = scalars[i];
         }
 
-        // Extend lifetime of r to the end of the method so we can copy its parts.
-        SkRecords::Adopted<SkRecords::DrawPosText> adopted(r);
-        SkNEW_PLACEMENT_ARGS(fRecord->replace<SkRecords::DrawPosTextH>(this->index(), adopted),
-                             SkRecords::DrawPosTextH,
-                             (r->text, r->byteLength, scalars, firstY, r->paint));
+        // Extend lifetime of draw to the end of the loop so we can copy its paint.
+        Adopted<DrawPosText> adopted(draw);
+        SkNEW_PLACEMENT_ARGS(record->replace<DrawPosTextH>(begin, adopted),
+                             DrawPosTextH,
+                             (draw->text, draw->byteLength, scalars, firstY, draw->paint));
+        return true;
     }
 };
+void SkRecordReduceDrawPosTextStrength(SkRecord* record) {
+    StrengthReducer pass;
+    apply(&pass, record);
+}
 
 // Tries to replace DrawPosTextH with BoundedDrawPosTextH, which knows conservative upper and lower
 // bounds to use with SkCanvas::quickRejectY.
-class TextBounder : public Common {
-public:
-    explicit TextBounder(SkRecord* record) : Common(record) {}
+struct TextBounder {
+    typedef Pattern1<Is<DrawPosTextH> > Pattern;
 
-    // Do nothing to most ops.
-    template <typename T> void operator()(T*) {}
+    bool onMatch(SkRecord* record, Pattern* pattern, unsigned begin, unsigned end) {
+        SkASSERT(end == begin + 1);
+        DrawPosTextH* draw = pattern->first<DrawPosTextH>();
 
-    void operator()(SkRecords::DrawPosTextH* r) {
         // If we're drawing vertical text, none of the checks we're about to do make any sense.
         // We'll need to call SkPaint::computeFastBounds() later, so bail if that's not possible.
-        if (r->paint.isVerticalText() || !r->paint.canComputeFastBounds()) {
-            return;
+        if (draw->paint.isVerticalText() || !draw->paint.canComputeFastBounds()) {
+            return false;
         }
 
         // Rather than checking the top and bottom font metrics, we guess.  Actually looking up the
         // top and bottom metrics is slow, and this overapproximation should be good enough.
-        const SkScalar buffer = r->paint.getTextSize() * 1.5f;
+        const SkScalar buffer = draw->paint.getTextSize() * 1.5f;
         SkDEBUGCODE(SkPaint::FontMetrics metrics;)
-        SkDEBUGCODE(r->paint.getFontMetrics(&metrics);)
+        SkDEBUGCODE(draw->paint.getFontMetrics(&metrics);)
         SkASSERT(-buffer <= metrics.fTop);
         SkASSERT(+buffer >= metrics.fBottom);
 
         // Let the paint adjust the text bounds.  We don't care about left and right here, so we use
         // 0 and 1 respectively just so the bounds rectangle isn't empty.
         SkRect bounds;
-        bounds.set(0, r->y - buffer, SK_Scalar1, r->y + buffer);
-        SkRect adjusted = r->paint.computeFastBounds(bounds, &bounds);
+        bounds.set(0, draw->y - buffer, SK_Scalar1, draw->y + buffer);
+        SkRect adjusted = draw->paint.computeFastBounds(bounds, &bounds);
 
-        SkRecords::Adopted<SkRecords::DrawPosTextH> adopted(r);
-        SkNEW_PLACEMENT_ARGS(
-                fRecord->replace<SkRecords::BoundedDrawPosTextH>(this->index(), adopted),
-                SkRecords::BoundedDrawPosTextH,
-                (&adopted, adjusted.fTop, adjusted.fBottom));
+        Adopted<DrawPosTextH> adopted(draw);
+        SkNEW_PLACEMENT_ARGS(record->replace<BoundedDrawPosTextH>(begin, adopted),
+                             BoundedDrawPosTextH,
+                             (&adopted, adjusted.fTop, adjusted.fBottom));
+        return true;
     }
 };
-
-
-template <typename Pass>
-static void run_pass(Pass& pass, SkRecord* record) {
-    for (; pass.index() < record->count(); pass.next()) {
-        record->mutate(pass.index(), pass);
-    }
+void SkRecordBoundDrawPosTextH(SkRecord* record) {
+    TextBounder pass;
+    apply(&pass, record);
 }
 
-}  // namespace
+// Replaces PushCull with PairedPushCull, which lets us skip to the paired PopCull when the canvas
+// can quickReject the cull rect.
+// There's no efficient way (yet?) to express this one as a pattern, so we write a custom pass.
+class CullAnnotator {
+public:
+    // Do nothing to most ops.
+    template <typename T> void operator()(T*) {}
 
+    void operator()(PushCull* push) {
+        Pair pair = { fIndex, push };
+        fPushStack.push(pair);
+    }
 
-void SkRecordNoopSaveRestores(SkRecord* record) {
-    // Run SaveRestoreNooper until it doesn't make any more changes.
-    bool changed;
-    do {
-        SaveRestoreNooper nooper(record);
-        run_pass(nooper, record);
-        changed = nooper.changed();
-    } while (changed);
+    void operator()(PopCull* pop) {
+        Pair push = fPushStack.top();
+        fPushStack.pop();
+
+        SkASSERT(fIndex > push.index);
+        unsigned skip = fIndex - push.index;
+
+        Adopted<PushCull> adopted(push.command);
+        SkNEW_PLACEMENT_ARGS(fRecord->replace<PairedPushCull>(push.index, adopted),
+                             PairedPushCull, (&adopted, skip));
+    }
+
+    void apply(SkRecord* record) {
+        for (fRecord = record, fIndex = 0; fIndex < record->count(); fIndex++) {
+            fRecord->mutate(fIndex, *this);
+        }
+    }
+
+private:
+    struct Pair {
+        unsigned index;
+        PushCull* command;
+    };
+
+    SkTDArray<Pair> fPushStack;
+    SkRecord* fRecord;
+    unsigned fIndex;
+};
+void SkRecordAnnotateCullingPairs(SkRecord* record) {
+    CullAnnotator pass;
+    pass.apply(record);
 }
-
-void SkRecordAnnotateCullingPairs(SkRecord* record) {
-    CullAnnotator annotator(record);
-    run_pass(annotator, record);
-}
-
-void SkRecordReduceDrawPosTextStrength(SkRecord* record) {
-    StrengthReducer reducer(record);
-    run_pass(reducer, record);
-}
-
-void SkRecordBoundDrawPosTextH(SkRecord* record) {
-    TextBounder bounder(record);
-    run_pass(bounder, record);
-}