HyphenEdit in support of hyphenation

Adds a "HyphenEdit" field to the Minikin Paint object, which represents
an edit to the text to add a hyphen (and, in the future, other edits to
support nonstandard hyphenation).

Change-Id: Ib4ee690b0fe2137e1d1e2c9251e5526b274ec3a7

engine/src/flutter/include/minikin/MinikinFont.h

@@ -27,6 +27,18 @@
 
 namespace android {
 
+// The hyphen edit represents an edit to the string when a word is
+// hyphenated. The most common hyphen edit is adding a "-" at the end
+// of a syllable, but nonstandard hyphenation allows for more choices.
+class HyphenEdit {
+public:
+    HyphenEdit() : hyphen(0) { }
+    HyphenEdit(uint32_t hyphenInt) : hyphen(hyphenInt) { }
+    bool hasHyphen() const { return hyphen != 0; }
+private:
+    uint32_t hyphen;
+};
+
 class MinikinFont;
 
 // Possibly move into own .h file?
@@ -36,7 +48,8 @@ struct MinikinPaint {
             fakery(), fontFeatureSettings() { }
 
     bool skipCache() const {
-      return !fontFeatureSettings.empty();
+        // TODO: add hyphen to cache
+        return !fontFeatureSettings.empty() || hyphenEdit.hasHyphen();
     }
 
     MinikinFont *font;
@@ -46,6 +59,7 @@ struct MinikinPaint {
     float letterSpacing;
     uint32_t paintFlags;
     FontFakery fakery;
+    HyphenEdit hyphenEdit;
     std::string fontFeatureSettings;
 };
 

engine/src/flutter/libs/minikin/Layout.cpp

@@ -594,12 +594,15 @@ void Layout::doLayout(const uint16_t* buf, size_t start, size_t count, size_t bu
 
 void Layout::doLayoutRunCached(const uint16_t* buf, size_t start, size_t count, size_t bufSize,
         bool isRtl, LayoutContext* ctx, size_t dstStart) {
+    HyphenEdit hyphen = ctx->paint.hyphenEdit;
     if (!isRtl) {
         // left to right
         size_t wordstart = start == bufSize ? start : getPrevWordBreak(buf, start + 1);
         size_t wordend;
         for (size_t iter = start; iter < start + count; iter = wordend) {
             wordend = getNextWordBreak(buf, iter, bufSize);
+            // Only apply hyphen to the last word in the string.
+            ctx->paint.hyphenEdit = wordend >= start + count ? hyphen : HyphenEdit();
             size_t wordcount = std::min(start + count, wordend) - iter;
             doLayoutWord(buf + wordstart, iter - wordstart, wordcount, wordend - wordstart,
                     isRtl, ctx, iter - dstStart);
@@ -612,6 +615,8 @@ void Layout::doLayoutRunCached(const uint16_t* buf, size_t start, size_t count,
         size_t wordend = end == 0 ? 0 : getNextWordBreak(buf, end - 1, bufSize);
         for (size_t iter = end; iter > start; iter = wordstart) {
             wordstart = getPrevWordBreak(buf, iter);
+            // Only apply hyphen to the last (leftmost) word in the string.
+            ctx->paint.hyphenEdit = iter == end ? hyphen : HyphenEdit();
             size_t bufStart = std::max(start, wordstart);
             doLayoutWord(buf + wordstart, bufStart - wordstart, iter - bufStart,
                     wordend - wordstart, isRtl, ctx, bufStart - dstStart);
@@ -729,6 +734,12 @@ void Layout::doLayoutRun(const uint16_t* buf, size_t start, size_t count, size_t
                 hb_buffer_set_language(buffer, hb_language_from_string(lang.c_str(), -1));
             }
             hb_buffer_add_utf16(buffer, buf, bufSize, srunstart + start, srunend - srunstart);
+            if (ctx->paint.hyphenEdit.hasHyphen() && srunend > srunstart) {
+                // TODO: check whether this is really the desired semantics. It could have the
+                // effect of assigning the hyphen width to a nonspacing mark
+                unsigned int lastCluster = srunend - 1;
+                hb_buffer_add(buffer, 0x2010, lastCluster);
+            }
             hb_shape(hbFont, buffer, features.empty() ? NULL : &features[0], features.size());
             unsigned int numGlyphs;
             hb_glyph_info_t* info = hb_buffer_get_glyph_infos(buffer, &numGlyphs);
@@ -763,7 +774,12 @@ void Layout::doLayoutRun(const uint16_t* buf, size_t start, size_t count, size_t
                 ctx->paint.font->GetBounds(&glyphBounds, glyph_ix, ctx->paint);
                 glyphBounds.offset(x + xoff, y + yoff);
                 mBounds.join(glyphBounds);
+                if (info[i].cluster - start < count) {
                     mAdvances[info[i].cluster - start] += xAdvance;
+                } else {
+                    ALOGE("cluster %d (start %d) out of bounds of count %d",
+                        info[i].cluster - start, start, count);
+                }
                 x += xAdvance;
             }
             if (numGlyphs)