From eb9c9884606212ea89f9af35c6a6913eec45452c Mon Sep 17 00:00:00 2001
From: Jonathan Kew <jkew@mozilla.com>
Date: Thu, 15 Jan 2015 11:07:26 +0000
Subject: [PATCH] Bug 1120101 - Calculate vertical glyph origin based on 'vmtx'
 table in TrueType fonts. r=jdaggett

---
 gfx/thebes/gfxHarfBuzzShaper.cpp | 97 +++++++++++++++++++++++++++++++-
 gfx/thebes/gfxHarfBuzzShaper.h   |  5 ++
 2 files changed, 101 insertions(+), 1 deletion(-)

diff --git a/gfx/thebes/gfxHarfBuzzShaper.cpp b/gfx/thebes/gfxHarfBuzzShaper.cpp
index c7fd9990864..7df10a42b30 100644
--- a/gfx/thebes/gfxHarfBuzzShaper.cpp
+++ b/gfx/thebes/gfxHarfBuzzShaper.cpp
@@ -41,6 +41,8 @@ gfxHarfBuzzShaper::gfxHarfBuzzShaper(gfxFont *aFont)
       mHmtxTable(nullptr),
       mVmtxTable(nullptr),
       mVORGTable(nullptr),
+      mLocaTable(nullptr),
+      mGlyfTable(nullptr),
       mCmapTable(nullptr),
       mCmapFormat(-1),
       mSubtableOffset(0),
@@ -50,7 +52,8 @@ gfxHarfBuzzShaper::gfxHarfBuzzShaper(gfxFont *aFont)
       mUseFontGetGlyph(aFont->ProvidesGetGlyph()),
       mUseFontGlyphWidths(false),
       mInitialized(false),
-      mVerticalInitialized(false)
+      mVerticalInitialized(false),
+      mLocaLongOffsets(false)
 {
 }
 
@@ -65,6 +68,18 @@ gfxHarfBuzzShaper::~gfxHarfBuzzShaper()
     if (mKernTable) {
         hb_blob_destroy(mKernTable);
     }
+    if (mVmtxTable) {
+        hb_blob_destroy(mVmtxTable);
+    }
+    if (mVORGTable) {
+        hb_blob_destroy(mVORGTable);
+    }
+    if (mLocaTable) {
+        hb_blob_destroy(mLocaTable);
+    }
+    if (mGlyfTable) {
+        hb_blob_destroy(mGlyfTable);
+    }
     if (mHBFont) {
         hb_font_destroy(mHBFont);
     }
@@ -330,6 +345,72 @@ gfxHarfBuzzShaper::GetGlyphVOrigin(hb_codepoint_t aGlyph,
         return;
     }
 
+    if (mVmtxTable) {
+        if (mLocaTable && mGlyfTable) {
+            // TrueType outlines: use glyph bbox + top sidebearing
+            uint32_t offset; // offset of glyph record in the 'glyf' table
+            uint32_t len;
+            const char* data = hb_blob_get_data(mLocaTable, &len);
+            if (mLocaLongOffsets) {
+                if ((aGlyph + 1) * sizeof(AutoSwap_PRUint32) > len) {
+                    *aY = 0;
+                    return;
+                }
+                const AutoSwap_PRUint32* offsets =
+                    reinterpret_cast<const AutoSwap_PRUint32*>(data);
+                offset = offsets[aGlyph];
+                if (offset == offsets[aGlyph + 1]) {
+                    // empty glyph
+                    *aY = 0;
+                    return;
+                }
+            } else {
+                if ((aGlyph + 1) * sizeof(AutoSwap_PRUint16) > len) {
+                    *aY = 0;
+                    return;
+                }
+                const AutoSwap_PRUint16* offsets =
+                    reinterpret_cast<const AutoSwap_PRUint16*>(data);
+                offset = uint16_t(offsets[aGlyph]);
+                if (offset == uint16_t(offsets[aGlyph + 1])) {
+                    // empty glyph
+                    *aY = 0;
+                    return;
+                }
+                offset *= 2;
+            }
+
+            struct Glyf { // we only need the bounding-box at the beginning
+                          // of the glyph record, not the actual outline data
+                AutoSwap_PRInt16 numberOfContours;
+                AutoSwap_PRInt16 xMin;
+                AutoSwap_PRInt16 yMin;
+                AutoSwap_PRInt16 xMax;
+                AutoSwap_PRInt16 yMax;
+            };
+            data = hb_blob_get_data(mGlyfTable, &len);
+            if (offset + sizeof(Glyf) > len) {
+                *aY = 0;
+                return;
+            }
+            const Glyf* glyf = reinterpret_cast<const Glyf*>(data + offset);
+
+            if (aGlyph >= uint32_t(mNumLongVMetrics)) {
+                aGlyph = mNumLongVMetrics - 1;
+            }
+            const GlyphMetrics* metrics =
+                reinterpret_cast<const GlyphMetrics*>
+                    (hb_blob_get_data(mVmtxTable, nullptr));
+            *aY = -FloatToFixed(mFont->FUnitsToDevUnitsFactor() *
+                                (int16_t(metrics->metrics[aGlyph].lsb) +
+                                 int16_t(glyf->yMax)));
+            return;
+        } else {
+            // XXX TODO: CFF outlines - need to get glyph extents.
+            // For now, fall through to default code below.
+        }
+    }
+
     // XXX should we consider using OS/2 sTypo* metrics if available?
 
     gfxFontEntry::AutoTable hheaTable(GetFont()->GetFontEntry(),
@@ -1144,6 +1225,20 @@ gfxHarfBuzzShaper::InitializeVertical()
                 mVORGTable = nullptr;
             }
         }
+    } else if (mVmtxTable) {
+        // Otherwise, try to load loca and glyf tables so that we can read
+        // bounding boxes (needed to support vertical glyph origin).
+        uint32_t len;
+        gfxFontEntry::AutoTable headTable(entry,
+                                          TRUETYPE_TAG('h','e','a','d'));
+        const HeadTable* head =
+            reinterpret_cast<const HeadTable*>(hb_blob_get_data(headTable,
+                                                                &len));
+        if (len >= sizeof(HeadTable)) {
+            mLocaLongOffsets = int16_t(head->indexToLocFormat) > 0;
+            mLocaTable = entry->GetFontTable(TRUETYPE_TAG('l','o','c','a'));
+            mGlyfTable = entry->GetFontTable(TRUETYPE_TAG('g','l','y','f'));
+        }
     }
 
     return true;
diff --git a/gfx/thebes/gfxHarfBuzzShaper.h b/gfx/thebes/gfxHarfBuzzShaper.h
index 54ed5bdd73b..10ca6459ab3 100644
--- a/gfx/thebes/gfxHarfBuzzShaper.h
+++ b/gfx/thebes/gfxHarfBuzzShaper.h
@@ -130,6 +130,10 @@ protected:
     // For vertical fonts, cached vmtx and VORG table, if present.
     mutable hb_blob_t *mVmtxTable;
     mutable hb_blob_t *mVORGTable;
+    // And for vertical TrueType (not CFF) fonts that have vmtx,
+    // we also use loca and glyf to get glyph bounding boxes.
+    mutable hb_blob_t *mLocaTable;
+    mutable hb_blob_t *mGlyfTable;
 
     // Cached pointer to cmap subtable to be used for char-to-glyph mapping.
     // This comes from GetFontTablePtr; if it is non-null, our destructor
@@ -157,6 +161,7 @@ protected:
 
     bool mInitialized;
     bool mVerticalInitialized;
+    bool mLocaLongOffsets;
 };
 
 #endif /* GFX_HARFBUZZSHAPER_H */