Add SkTypeface::getBounds()

mirrored from https://codereview.chromium.org/666303002/

BUG=skia:
TBR=

Review URL: https://codereview.chromium.org/676523002

3 files changed, 206 insertions, 3 deletions

diff --git a/include/core/SkLazyPtr.h b/include/core/SkLazyPtr.h
new file mode 100644
index 0000000000..896dfbf88d
--- /dev/null
+++ b/include/core/SkLazyPtr.h
@@ -0,0 +1,166 @@
+/*
+ * Copyright 2014 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkLazyPtr_DEFINED
+#define SkLazyPtr_DEFINED
+
+/** Declare a lazily-chosen static pointer (or array of pointers) of type T.
+ *
+ *  Example usage:
+ *
+ *  Foo* GetSingletonFoo() {
+ *      SK_DECLARE_STATIC_LAZY_PTR(Foo, singleton);  // Created with SkNEW, destroyed with SkDELETE.
+ *      return singleton.get();
+ *  }
+ *
+ *  These macros take an optional T* (*Create)() and void (*Destroy)(T*) at the end.
+ *  If not given, we'll use SkNEW and SkDELETE.
+ *  These options are most useful when T doesn't have a public constructor or destructor.
+ *  Create comes first, so you may use a custom Create with a default Destroy, but not vice versa.
+ *
+ *  Foo* CustomCreate() { return ...; }
+ *  void CustomDestroy(Foo* ptr) { ... }
+ *  Foo* GetSingletonFooWithCustomCleanup() {
+ *      SK_DECLARE_STATIC_LAZY_PTR(Foo, singleton, CustomCreate, CustomDestroy);
+ *      return singleton.get();
+ *  }
+ *
+ *  If you have a bunch of related static pointers of the same type, you can
+ *  declare an array of lazy pointers together, and we'll pass the index to Create().
+ *
+ *  Foo* CreateFoo(int i) { return ...; }
+ *  Foo* GetCachedFoo(Foo::Enum enumVal) {
+ *      SK_DECLARE_STATIC_LAZY_PTR_ARRAY(Foo, Foo::kEnumCount, cachedFoos, CreateFoo);
+ *      return cachedFoos[enumVal];
+ *  }
+ *
+ *
+ *  You can think of SK_DECLARE_STATIC_LAZY_PTR as a cheaper specialization of
+ *  SkOnce.  There is no mutex or extra storage used past the pointer itself.
+ *
+ *  We may call Create more than once, but all threads will see the same pointer
+ *  returned from get().  Any extra calls to Create will be cleaned up.
+ *
+ *  These macros must be used in a global scope, not in function scope or as a class member.
+ */
+
+#define SK_DECLARE_STATIC_LAZY_PTR(T, name, ...) \
+    namespace {} static Private::SkStaticLazyPtr<T, ##__VA_ARGS__> name
+
+#define SK_DECLARE_STATIC_LAZY_PTR_ARRAY(T, name, N, ...) \
+    namespace {} static Private::SkStaticLazyPtrArray<T, N, ##__VA_ARGS__> name
+
+// namespace {} forces these macros to only be legal in global scopes.  Chrome has thread-safety
+// problems with them in function-local statics because it uses -fno-threadsafe-statics, and even
+// in builds with threadsafe statics, those threadsafe statics are just unnecessary overhead.
+
+// Everything below here is private implementation details.  Don't touch, don't even look.
+
+#include "SkDynamicAnnotations.h"
+#include "SkThread.h"
+#include "SkThreadPriv.h"
+
+// See FIXME below.
+class SkFontConfigInterfaceDirect;
+
+namespace Private {
+
+// Set *dst to ptr if *dst is NULL.  Returns value of *dst, destroying ptr if not swapped in.
+// Issues the same memory barriers as sk_atomic_cas: acquire on failure, release on success.
+template <typename P, void (*Destroy)(P)>
+static P try_cas(void** dst, P ptr) {
+    P prev = (P)sk_atomic_cas(dst, NULL, ptr);
+
+    if (prev) {
+        // We need an acquire barrier before returning prev, which sk_atomic_cas provided.
+        Destroy(ptr);
+        return prev;
+    } else {
+        // We need a release barrier before returning ptr, which sk_atomic_cas provided.
+        return ptr;
+    }
+}
+
+template <typename T> T* sk_new() { return SkNEW(T); }
+template <typename T> void sk_delete(T* ptr) { SkDELETE(ptr); }
+
+// We're basing these implementations here on this article:
+//   http://preshing.com/20140709/the-purpose-of-memory_order_consume-in-cpp11/
+//
+// Because the users of SkLazyPtr and SkLazyPtrArray will read the pointers
+// _through_ our atomically set pointer, there is a data dependency between our
+// atomic and the guarded data, and so we only need writer-releases /
+// reader-consumes memory pairing rather than the more general write-releases /
+// reader-acquires convention.
+//
+// This is nice, because a sk_consume_load is free on all our platforms: x86,
+// ARM, MIPS.  In contrast, sk_acquire_load issues a memory barrier on non-x86.
+
+// This has no constructor and must be zero-initalized (the macro above does this).
+template <typename T, T* (*Create)() = sk_new<T>, void (*Destroy)(T*) = sk_delete<T> >
+class SkStaticLazyPtr {
+public:
+    T* get() {
+        // If fPtr has already been filled, we need a consume barrier when loading it.
+        // If not, we need a release barrier when setting it.  try_cas will do that.
+        T* ptr = (T*)sk_consume_load(&fPtr);
+        return ptr ? ptr : try_cas<T*, Destroy>(&fPtr, Create());
+    }
+
+private:
+    void* fPtr;
+};
+
+template <typename T> T* sk_new_arg(int i) { return SkNEW_ARGS(T, (i)); }
+
+// This has no constructor and must be zero-initalized (the macro above does this).
+template <typename T, int N, T* (*Create)(int) = sk_new_arg<T>, void (*Destroy)(T*) = sk_delete<T> >
+class SkStaticLazyPtrArray {
+public:
+    T* operator[](int i) {
+        SkASSERT(i >= 0 && i < N);
+        // If fPtr has already been filled, we need an consume barrier when loading it.
+        // If not, we need a release barrier when setting it.  try_cas will do that.
+        T* ptr = (T*)sk_consume_load(&fArray[i]);
+        return ptr ? ptr : try_cas<T*, Destroy>(&fArray[i], Create(i));
+    }
+
+private:
+    void* fArray[N];
+};
+
+}  // namespace Private
+
+// This version is suitable for use as a class member.
+// It's much the same as above except:
+//   - it has a constructor to zero itself;
+//   - it has a destructor to clean up;
+//   - get() calls SkNew(T) to create the pointer;
+//   - get(functor) calls functor to create the pointer.
+template <typename T, void (*Destroy)(T*) = Private::sk_delete<T> >
+class SkLazyPtr : SkNoncopyable {
+public:
+    SkLazyPtr() : fPtr(NULL) {}
+    ~SkLazyPtr() { if (fPtr) { Destroy((T*)fPtr); } }
+
+    T* get() const {
+        T* ptr = (T*)sk_consume_load(&fPtr);
+        return ptr ? ptr : Private::try_cas<T*, Destroy>(&fPtr, SkNEW(T));
+    }
+
+    template <typename Create>
+    T* get(const Create& create) const {
+        T* ptr = (T*)sk_consume_load(&fPtr);
+        return ptr ? ptr : Private::try_cas<T*, Destroy>(&fPtr, create());
+    }
+
+private:
+    mutable void* fPtr;
+};
+
+
+#endif//SkLazyPtr_DEFINED
diff --git a/include/core/SkThreadPriv.h b/include/core/SkThreadPriv.h
new file mode 100644
index 0000000000..c44cca5350
--- /dev/null
+++ b/include/core/SkThreadPriv.h
@@ -0,0 +1,23 @@
+/*
+ * Copyright 2014 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkThreadPriv_DEFINED
+#define SkThreadPriv_DEFINED
+
+#include "SkTypes.h"
+
+// SK_ATOMICS_PLATFORM_H must provide inline implementations for the following declarations.
+
+/** Atomic compare and set, for pointers.
+ *  If *addr == before, set *addr to after.  Always returns previous value of *addr.
+ *  This must issue a release barrier on success, acquire on failure, and always a compiler barrier.
+ */
+static void* sk_atomic_cas(void** addr, void* before, void* after);
+
+#include SK_ATOMICS_PLATFORM_H
+
+#endif//SkThreadPriv_DEFINED
diff --git a/include/core/SkTypeface.h b/include/core/SkTypeface.h
index f67623674a..c3ff3641b7 100644
--- a/include/core/SkTypeface.h
+++ b/include/core/SkTypeface.h
@@ -12,6 +12,7 @@
 
 #include "SkAdvancedTypefaceMetrics.h"
 #include "SkFontStyle.h"
+#include "SkLazyPtr.h"
 #include "SkWeakRefCnt.h"
 
 class SkDescriptor;
@@ -282,6 +283,13 @@ public:
     SkScalerContext* createScalerContext(const SkDescriptor*,
                                          bool allowFailure = false) const;
 
+    /**
+     *  Return a rectangle (scaled to 1-pt) that represents the union of the bounds of all
+     *  of the glyphs, but each one positioned at (0,). This may be conservatively large, and
+     *  will not take into account any hinting or other size-specific adjustments.
+     */
+    SkRect getBounds() const;
+
     // PRIVATE / EXPERIMENTAL -- do not call
     void filterRec(SkScalerContextRec* rec) const {
         this->onFilterRec(rec);
@@ -333,6 +341,8 @@ protected:
     virtual size_t onGetTableData(SkFontTableTag, size_t offset,
                                   size_t length, void* data) const = 0;
 
+    virtual bool onComputeBounds(SkRect*) const;
+
 private:
     friend class SkGTypeface;
     friend class SkPDFFont;
@@ -359,9 +369,13 @@ private:
     static SkTypeface* CreateDefault(int style);  // SkLazyPtr requires an int, not a Style.
     static void        DeleteDefault(SkTypeface*);
 
-    SkFontID    fUniqueID;
-    SkFontStyle fStyle;
-    bool        fIsFixedPitch;
+    struct BoundsComputer;
+//    friend struct BoundsComputer;
+
+    SkLazyPtr<SkRect>   fLazyBounds;
+    SkFontID            fUniqueID;
+    SkFontStyle         fStyle;
+    bool                fIsFixedPitch;
 
     friend class SkPaint;
     friend class SkGlyphCache;  // GetDefaultTypeface