Regularize SkGlyphCache creation.

This allows no need for downcasting for specialized use
of SkScalerContext for the remote case. This allows
cache priming to be used in a single process.

BUG=skia:7515

Change-Id: I963a50e36af9deef5a3414fc8a4c94ccfc38deaf
Reviewed-on: https://skia-review.googlesource.com/115121
Reviewed-by: Ben Wagner <bungeman@google.com>
Commit-Queue: Herb Derby <herb@google.com>

6 files changed, 64 insertions, 68 deletions

diff --git a/src/core/SkGlyphCache.cpp b/src/core/SkGlyphCache.cpp
index 4332419bbb..e030c4b9a3 100644
--- a/src/core/SkGlyphCache.cpp
+++ b/src/core/SkGlyphCache.cpp
@@ -33,15 +33,15 @@ static SkGlyphCache_Globals& get_globals() {
 }
 
 ///////////////////////////////////////////////////////////////////////////////
-
-SkGlyphCache::SkGlyphCache(const SkDescriptor& desc, std::unique_ptr<SkScalerContext> ctx)
-    : fDesc(desc.copy())
-    , fScalerContext(std::move(ctx))
+SkGlyphCache::SkGlyphCache(
+        const SkDescriptor& desc,
+        std::unique_ptr<SkScalerContext> scaler,
+        const SkPaint::FontMetrics& fontMetrics)
+    : fDesc{desc.copy()}
+    , fScalerContext{std::move(scaler)}
+    , fFontMetrics(fontMetrics)
 {
-    SkASSERT(fScalerContext);
-
-    fScalerContext->getFontMetrics(&fFontMetrics);
-
+    SkASSERT(fScalerContext != nullptr);
     fMemoryUsed = sizeof(*this);
 }
 
@@ -53,10 +53,6 @@ SkGlyphCache::~SkGlyphCache() {
     });
 }
 
-void SkGlyphCache::PurgeAll() {
-    get_globals().purgeAll();
-}
-
 SkGlyphCache::CharGlyphRec* SkGlyphCache::getCharGlyphRec(SkPackedUnicharID packedUnicharID) {
     if (!fPackedUnicharIDToPackedGlyphID) {
         fPackedUnicharIDToPackedGlyphID.reset(new CharGlyphRec[kHashCount]);
@@ -497,12 +493,32 @@ SkExclusiveStrikePtr SkGlyphCache::FindStrikeExclusive(const SkDescriptor& desc)
     return SkExclusiveStrikePtr(nullptr);
 }
 
+std::unique_ptr<SkScalerContext> SkGlyphCache::CreateScalerContext(
+        const SkDescriptor& desc,
+        const SkScalerContextEffects& effects,
+        const SkTypeface& typeface) {
+    auto scaler = typeface.createScalerContext(effects, &desc, true /* can fail */);
+
+    // Check if we can create a scaler-context before creating the glyphcache.
+    // If not, we may have exhausted OS/font resources, so try purging the
+    // cache once and try again
+    // pass true the first time, to notice if the scalercontext failed,
+    if (scaler == nullptr) {
+        get_globals().purgeAll();
+        scaler = typeface.createScalerContext(effects, &desc, false /* must succeed */);
+    }
+    return scaler;
+}
+
 SkExclusiveStrikePtr SkGlyphCache::FindOrCreateStrikeExclusive(
     const SkDescriptor& desc, const SkScalerContextEffects& effects, const SkTypeface& typeface) {
-    auto creator = [&effects, &typeface](const SkDescriptor& descriptor, bool canFail) {
-        return typeface.createScalerContext(effects, &descriptor, canFail);
-    };
-    return FindOrCreateStrikeExclusive(desc, creator);
+
+    auto cache = SkGlyphCache::FindStrikeExclusive(desc);
+    if (cache == nullptr) {
+        auto scaler = CreateScalerContext(desc, effects, typeface);
+        cache = SkGlyphCache::CreateStrikeExclusive(desc, std::move(scaler));
+    }
+    return cache;
 }
 
 SkExclusiveStrikePtr SkGlyphCache::FindOrCreateStrikeExclusive(
@@ -522,6 +538,21 @@ SkExclusiveStrikePtr SkGlyphCache::FindOrCreateStrikeExclusive(
     return FindOrCreateStrikeExclusive(*desc, effects, *tf);
 }
 
+SkExclusiveStrikePtr SkGlyphCache::CreateStrikeExclusive(
+        const SkDescriptor& desc,
+        std::unique_ptr<SkScalerContext> scaler,
+        SkPaint::FontMetrics* maybeMetrics)
+{
+    SkPaint::FontMetrics fontMetrics;
+    if (maybeMetrics != nullptr) {
+        fontMetrics = *maybeMetrics;
+    } else {
+        scaler->getFontMetrics(&fontMetrics);
+    }
+
+    return SkExclusiveStrikePtr(new SkGlyphCache(desc, std::move(scaler), fontMetrics));
+}
+
 void SkGlyphCache::ForEachStrike(std::function<void(const SkGlyphCache&)> visitor) {
     SkGlyphCache_Globals& globals = get_globals();
     SkAutoExclusive ac(globals.fLock);
diff --git a/src/core/SkGlyphCache.h b/src/core/SkGlyphCache.h
index f42a52bee2..3db63fe63c 100644
--- a/src/core/SkGlyphCache.h
+++ b/src/core/SkGlyphCache.h
@@ -126,21 +126,15 @@ public:
 
     void dump() const;
 
+    static std::unique_ptr<SkScalerContext> CreateScalerContext(
+            const SkDescriptor& desc,
+            const SkScalerContextEffects& effects,
+            const SkTypeface& typeface);
+
     SkScalerContext* getScalerContext() const { return fScalerContext.get(); }
 
     static SkExclusiveStrikePtr FindStrikeExclusive(const SkDescriptor& desc);
 
-    template <typename ScalerContextCreator>
-    static SkExclusiveStrikePtr FindOrCreateStrikeExclusive(
-        const SkDescriptor& desc, ScalerContextCreator&& creator)
-    {
-        auto cache = FindStrikeExclusive(desc);
-        if (cache == nullptr) {
-            cache = CreateStrikeExclusive(desc, creator);
-        }
-        return cache;
-    }
-
     static SkExclusiveStrikePtr FindOrCreateStrikeExclusive(
         const SkDescriptor& desc,
         const SkScalerContextEffects& effects,
@@ -157,24 +151,10 @@ public:
                 paint, nullptr, SkScalerContextFlags::kFakeGammaAndBoostContrast, nullptr);
     }
 
-    template <typename ScalerContextCreator>
     static SkExclusiveStrikePtr CreateStrikeExclusive(
-        const SkDescriptor& desc, ScalerContextCreator creator)
-    {
-        // Check if we can create a scaler-context before creating the glyphcache.
-        // If not, we may have exhausted OS/font resources, so try purging the
-        // cache once and try again
-        // pass true the first time, to notice if the scalercontext failed,
-        // so we can try the purge.
-        auto context = creator(desc, true/* can fail */);
-        if (!context) {
-            PurgeAll();
-            context = creator(desc, false/* must succeed */);
-            SkASSERT(context);
-        }
-
-        return SkExclusiveStrikePtr(new SkGlyphCache(desc, std::move(context)));
-    }
+        const SkDescriptor& desc,
+        std::unique_ptr<SkScalerContext> scaler,
+        SkPaint::FontMetrics* maybeMetrics = nullptr);
 
     static void Dump();
 
@@ -230,12 +210,10 @@ private:
         SkPackedGlyphID fPackedGlyphID;
     };
 
-    SkGlyphCache(const SkDescriptor& desc, std::unique_ptr<SkScalerContext> scaler);
+    SkGlyphCache(const SkDescriptor& desc, std::unique_ptr<SkScalerContext> scaler,
+                 const SkPaint::FontMetrics&);
     ~SkGlyphCache();
 
-    // Purge all the things.
-    static void PurgeAll();
-
     // Return the SkGlyph* associated with MakeID. The id parameter is the
     // combined glyph/x/y id generated by MakeID. If it is just a glyph id
     // then x and y are assumed to be zero.
diff --git a/src/core/SkScalerContext.cpp b/src/core/SkScalerContext.cpp
index b8778282e2..6302a80dc1 100644
--- a/src/core/SkScalerContext.cpp
+++ b/src/core/SkScalerContext.cpp
@@ -805,6 +805,10 @@ std::unique_ptr<SkScalerContext> SkTypeface::createScalerContext(
         c = skstd::make_unique<SkScalerContext_Empty>(sk_ref_sp(const_cast<SkTypeface*>(this)),
                                                       effects, desc);
     }
+
+    // !allowFailure implies c != nullptr
+    SkASSERT(c || allowFailure);
+
     return c;
 }
 
diff --git a/src/core/SkTypeface_remote.cpp b/src/core/SkTypeface_remote.cpp
index ce3c7f5ba6..504d2413ec 100644
--- a/src/core/SkTypeface_remote.cpp
+++ b/src/core/SkTypeface_remote.cpp
@@ -31,11 +31,7 @@ void SkScalerContextProxy::generatePath(SkGlyphID glyphID, SkPath* path) {
 }
 
 void SkScalerContextProxy::generateFontMetrics(SkPaint::FontMetrics* metrics) {
-    if (!fHaveFontMetrics) {
-        fRemote->generateFontMetrics(*this->typefaceProxy(), this->getRec(), &fFontMetrics);
-    }
-    fHaveFontMetrics = true;
-    *metrics = fFontMetrics;
+    fRemote->generateFontMetrics(*this->typefaceProxy(), this->getRec(), metrics);
 }
 
 SkTypefaceProxy* SkScalerContextProxy::typefaceProxy() {
diff --git a/src/core/SkTypeface_remote.h b/src/core/SkTypeface_remote.h
index 750ec21ebe..03516be481 100644
--- a/src/core/SkTypeface_remote.h
+++ b/src/core/SkTypeface_remote.h
@@ -47,11 +47,6 @@ public:
             const SkDescriptor* desc,
             SkRemoteScalerContext* rsc);
 
-    void setFontMetrics(const SkPaint::FontMetrics& fontMetrics) {
-        fFontMetrics = fontMetrics;
-        fHaveFontMetrics = true;
-    }
-
 protected:
     unsigned generateGlyphCount(void) override { SK_ABORT("Should never be called."); return 0;}
     uint16_t generateCharToGlyph(SkUnichar uni) override {
@@ -75,8 +70,6 @@ private:
 
     SkArenaAlloc  fAlloc{kMinAllocAmount};
     SkRemoteScalerContext* const fRemote;
-    bool fHaveFontMetrics{false};
-    SkPaint::FontMetrics fFontMetrics;
     typedef SkScalerContext INHERITED;
 };
 
diff --git a/tools/remote_demo.cpp b/tools/remote_demo.cpp
index 8ff7d2986d..7cedaea00b 100644
--- a/tools/remote_demo.cpp
+++ b/tools/remote_demo.cpp
@@ -774,14 +774,8 @@ static void prepopulate_cache(
         // TODO: implement effects handling.
         SkScalerContextEffects effects;
         if ((strike = SkGlyphCache::FindStrikeExclusive(*desc)) == nullptr) {
-            auto creator = [&effects, &tf, &fontMetrics](
-                const SkDescriptor& descriptor, bool canFail)
-            {
-                auto scaler = tf->createScalerContext(effects, &descriptor, canFail);
-                ((SkScalerContextProxy*)scaler.get())->setFontMetrics(*fontMetrics);
-                return scaler;
-            };
-            strike = SkGlyphCache::CreateStrikeExclusive(*desc,creator);
+            auto scaler = SkGlyphCache::CreateScalerContext(*desc, effects, *tf);
+            strike = SkGlyphCache::CreateStrikeExclusive(*desc, std::move(scaler), fontMetrics);
         }
 #if INSTRUMENT
         std::cout << std::hex << "prepop cache " << (intptr_t)cache