Add SkTypeface::getVariationDesignPosition.

Allow users to query a typeface's position in variation design space.

Change-Id: Id7cae439e795b8c9586394f11359fb7fe55e1c0b
Reviewed-on: https://skia-review.googlesource.com/8861
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Ben Wagner <bungeman@google.com>

3 files changed, 111 insertions, 53 deletions

diff --git a/include/core/SkFontArguments.h b/include/core/SkFontArguments.h
new file mode 100644
index 0000000000..473798fb84
--- /dev/null
+++ b/include/core/SkFontArguments.h
@@ -0,0 +1,79 @@
+/*
+ * Copyright 2017 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkFontAgruments_DEFINED
+#define SkFontAgruments_DEFINED
+
+#include "SkScalar.h"
+#include "SkTypes.h"
+
+/** Represents a set of actual arguments for a font. */
+struct SkFontArguments {
+    struct VariationPosition {
+        struct Coordinate {
+            SkFourByteTag axis;
+            SkScalar value;
+        };
+        const Coordinate* coordinates;
+        int coordinateCount;
+    };
+    // deprecated, use VariationCoordinate instead
+    struct Axis {
+       SkFourByteTag fTag;
+       SkScalar fStyleValue;
+    };
+
+    SkFontArguments() : fCollectionIndex(0), fVariationDesignPosition{nullptr, 0} {}
+
+    /** Specify the index of the desired font.
+     *
+     *  Font formats like ttc, dfont, cff, cid, pfr, t42, t1, and fon may actually be indexed
+     *  collections of fonts.
+     */
+    SkFontArguments& setCollectionIndex(int collectionIndex) {
+        fCollectionIndex = collectionIndex;
+        return *this;
+    }
+
+    // deprecated, use setVariationDesignPosition instead.
+    SkFontArguments& setAxes(const Axis* axes, int axisCount) {
+        fVariationDesignPosition.coordinates =
+                reinterpret_cast<const VariationPosition::Coordinate*>(axes);
+        fVariationDesignPosition.coordinateCount = axisCount;
+        return *this;
+    }
+
+    /** Specify a position in the variation design space.
+     *
+     *  Any axis not specified will use the default value.
+     *  Any specified axis not actually present in the font will be ignored.
+     *
+     *  @param position not copied. The value must remain valid for life of SkFontArguments.
+     */
+    SkFontArguments& setVariationDesignPosition(VariationPosition position) {
+        fVariationDesignPosition.coordinates = position.coordinates;
+        fVariationDesignPosition.coordinateCount = position.coordinateCount;
+        return *this;
+    }
+
+    int getCollectionIndex() const {
+        return fCollectionIndex;
+    }
+    // deprecated, use getVariationDesignPosition instead.
+    const Axis* getAxes(int* axisCount) const {
+        *axisCount = fVariationDesignPosition.coordinateCount;
+        return reinterpret_cast<const Axis*>(fVariationDesignPosition.coordinates);
+    }
+    VariationPosition getVariationDesignPosition() const {
+        return fVariationDesignPosition;
+    }
+private:
+    int fCollectionIndex;
+    VariationPosition fVariationDesignPosition;
+};
+
+#endif
diff --git a/include/core/SkTypeface.h b/include/core/SkTypeface.h
index 51d5a0b11c..24693a9af1 100644
--- a/include/core/SkTypeface.h
+++ b/include/core/SkTypeface.h
@@ -11,6 +11,7 @@
 #include "../private/SkBitmaskEnum.h"
 #include "../private/SkOnce.h"
 #include "../private/SkWeakRefCnt.h"
+#include "SkFontArguments.h"
 #include "SkFontStyle.h"
 #include "SkRect.h"
 #include "SkString.h"
@@ -77,6 +78,20 @@ public:
      */
     bool isFixedPitch() const { return fIsFixedPitch; }
 
+    /** Copy into 'coordinates' (allocated by the caller) the design variation coordinates.
+     *
+     *  @param coordinates the buffer into which to write the design variation coordinates.
+     *  @param coordinateCount the number of entries available through 'coordinates'.
+     *
+     *  @return The number of axes, or -1 if there is an error.
+     *  If 'coordinates != nullptr' and 'coordinateCount >= numAxes' then 'coordinates' will be
+     *  filled with the variation coordinates describing the position of this typeface in design
+     *  variation space. It is possible the number of axes can be retrieved but actual position
+     *  cannot.
+     */
+    int getVariationDesignPosition(SkFontArguments::VariationPosition::Coordinate coordinates[],
+                                   int coordinateCount) const;
+
     /** Return a 32bit value for this typeface, unique for the underlying font
         data. Will never return 0.
      */
@@ -96,16 +111,16 @@ public:
     /** Returns the default typeface, which is never nullptr. */
     static sk_sp<SkTypeface> MakeDefault(Style style = SkTypeface::kNormal);
 
-  /** Creates a new reference to the typeface that most closely matches the
-      requested familyName and fontStyle. This method allows extended font
-      face specifiers as in the SkFontStyle type. Will never return null.
+    /** Creates a new reference to the typeface that most closely matches the
+        requested familyName and fontStyle. This method allows extended font
+        face specifiers as in the SkFontStyle type. Will never return null.
 
-      @param familyName  May be NULL. The name of the font family.
-      @param fontStyle   The style of the typeface.
-      @return reference to the closest-matching typeface. Call must call
+        @param familyName  May be NULL. The name of the font family.
+        @param fontStyle   The style of the typeface.
+        @return reference to the closest-matching typeface. Call must call
               unref() when they are done.
     */
-  static sk_sp<SkTypeface> MakeFromName(const char familyName[], SkFontStyle fontStyle);
+    static sk_sp<SkTypeface> MakeFromName(const char familyName[], SkFontStyle fontStyle);
 
     /** Return the typeface that most closely matches the requested typeface and style.
         Use this to pick a new style from the same family of the existing typeface.
@@ -341,6 +356,11 @@ protected:
     // TODO: make pure virtual.
     virtual std::unique_ptr<SkFontData> onMakeFontData() const;
 
+    // TODO: make pure virtual.
+    virtual int onGetVariationDesignPosition(
+        SkFontArguments::VariationPosition::Coordinate coordinates[],
+        int coordinateCount) const;
+
     virtual void onGetFontDescriptor(SkFontDescriptor*, bool* isLocal) const = 0;
 
     virtual int onCharsToGlyphs(const void* chars, Encoding, SkGlyphID glyphs[],
diff --git a/include/ports/SkFontMgr.h b/include/ports/SkFontMgr.h
index 4103e8747e..b5879d35b8 100644
--- a/include/ports/SkFontMgr.h
+++ b/include/ports/SkFontMgr.h
@@ -8,9 +8,9 @@
 #ifndef SkFontMgr_DEFINED
 #define SkFontMgr_DEFINED
 
+#include "SkFontArguments.h"
 #include "SkFontStyle.h"
 #include "SkRefCnt.h"
-#include "SkScalar.h"
 #include "SkTypes.h"
 
 class SkData;
@@ -102,51 +102,10 @@ public:
      */
     SkTypeface* createFromStream(SkStreamAsset*, int ttcIndex = 0) const;
 
-    struct FontParameters {
-        struct Axis {
-            SkFourByteTag fTag;
-            SkScalar fStyleValue;
-        };
-
-        FontParameters() : fCollectionIndex(0), fAxisCount(0), fAxes(nullptr) {}
-
-        /** Specify the index of the desired font.
-         *
-         *  Font formats like ttc, dfont, cff, cid, pfr, t42, t1, and fon may actually be indexed
-         *  collections of fonts.
-         */
-        FontParameters& setCollectionIndex(int collectionIndex) {
-            fCollectionIndex = collectionIndex;
-            return *this;
-        }
-
-        /** Specify the GX variation axis values.
-         *
-         *  Any axes not specified will use the default value. Specified axes not present in the
-         *  font will be ignored.
-         *
-         *  @param axes not copied. This pointer must remain valid for life of FontParameters.
-         */
-        FontParameters& setAxes(const Axis* axes, int axisCount) {
-            fAxisCount = axisCount;
-            fAxes = axes;
-            return *this;
-        }
-
-        int getCollectionIndex() const {
-            return fCollectionIndex;
-        }
-        const Axis* getAxes(int* axisCount) const {
-            *axisCount = fAxisCount;
-            return fAxes;
-        }
-    private:
-        int fCollectionIndex;
-        int fAxisCount;
-        const Axis* fAxes;
-    };
+    // deprecated, use SkFontArguments instead.
+    using FontParameters = SkFontArguments;
     /* Experimental, API subject to change. */
-    SkTypeface* createFromStream(SkStreamAsset*, const FontParameters&) const;
+    SkTypeface* createFromStream(SkStreamAsset*, const SkFontArguments&) const;
 
     /**
      *  Create a typeface from the specified font data.
@@ -187,7 +146,7 @@ protected:
     virtual SkTypeface* onCreateFromData(SkData*, int ttcIndex) const = 0;
     virtual SkTypeface* onCreateFromStream(SkStreamAsset*, int ttcIndex) const = 0;
     // TODO: make pure virtual.
-    virtual SkTypeface* onCreateFromStream(SkStreamAsset*, const FontParameters&) const;
+    virtual SkTypeface* onCreateFromStream(SkStreamAsset*, const SkFontArguments&) const;
     virtual SkTypeface* onCreateFromFontData(std::unique_ptr<SkFontData>) const;
     virtual SkTypeface* onCreateFromFile(const char path[], int ttcIndex) const = 0;