add SkSfntUtils to parse some known truetype tables

add comments and cleanup to count_tables in SkFontHost_tables.cpp
fix transparency bug in gifs
use (alpha+1) for blending in srcover mode, to ensure opaque results



git-svn-id: http://skia.googlecode.com/svn/trunk/src@155 2bbb7eff-a529-9590-31e7-b0007b416f81

5 files changed, 134 insertions, 14 deletions

diff --git a/images/SkImageDecoder_libgif.cpp b/images/SkImageDecoder_libgif.cpp
index ed8817ab..86ead1fa 100644
--- a/images/SkImageDecoder_libgif.cpp
+++ b/images/SkImageDecoder_libgif.cpp
@@ -171,6 +171,7 @@ bool SkGIFImageDecoder::onDecode(SkStream* sk_stream, SkBitmap* bm,
     int width, height;
     GifRecordType recType;
     GifByteType *extData;
+    int transpIndex = -1;   // -1 means we don't have it (yet)
     
     do {
         if (DGifGetRecordType(gif, &recType) == GIF_ERROR) {
@@ -226,7 +227,7 @@ bool SkGIFImageDecoder::onDecode(SkStream* sk_stream, SkBitmap* bm,
                                                    cmap->Colors[index].Green,
                                                    cmap->Colors[index].Blue);
 
-                int transpIndex = find_transpIndex(temp_save, colorCount);
+                transpIndex = find_transpIndex(temp_save, colorCount);
                 if (transpIndex < 0)
                     ctable->setFlags(ctable->getFlags() | SkColorTable::kColorsAreOpaque_Flag);
                 else
@@ -257,12 +258,18 @@ bool SkGIFImageDecoder::onDecode(SkStream* sk_stream, SkBitmap* bm,
             if ((desc.Top | desc.Left) > 0 ||
                  innerWidth < width || innerHeight < height)
             {
-                uint8_t fill = (uint8_t)gif->SBackGroundColor;
+                int fill;
+                if (transpIndex >= 0) {
+                    fill = transpIndex;
+                } else {
+                    fill = gif->SBackGroundColor;
+                }
                 // check for valid fill index/color
-                if (fill >= (unsigned)colorCount) {
+                if (static_cast<unsigned>(fill) >=
+                        static_cast<unsigned>(colorCount)) {
                     fill = 0;
                 }
-                memset(scanline, gif->SBackGroundColor, bm->getSize());
+                memset(scanline, fill, bm->getSize());
                 // bump our starting address
                 scanline += desc.Top * rowBytes + desc.Left;
             }
diff --git a/ports/SkFontHost_tables.cpp b/ports/SkFontHost_tables.cpp
index fdf0b063..49452728 100644
--- a/ports/SkFontHost_tables.cpp
+++ b/ports/SkFontHost_tables.cpp
@@ -29,18 +29,30 @@ struct SkSFNTDirEntry {
     uint32_t    fLength;
 };
 
+/** Return the number of tables, or if this is a TTC (collection), return the
+    number of tables in the first element of the collection. In either case,
+    if offsetToDir is not-null, set it to the offset to the beginning of the
+    table headers (SkSFNTDirEntry), relative to the start of the stream.
+ 
+    On an error, return 0 for number of tables, and ignore offsetToDir
+ */
 static int count_tables(SkStream* stream, size_t* offsetToDir = NULL) {
     SkSharedTTHeader shared;
     if (stream->read(&shared, sizeof(shared)) != sizeof(shared)) {
         return 0;
     }
 
+    // by default, SkSFNTHeader is at the start of the stream
+    size_t offset = 0;
+    
+    // if we're really a collection, the first 4-bytes will be 'ttcf'
     uint32_t tag = SkEndian_SwapBE32(shared.fCollection.fTag);
     if (SkSetFourByteTag('t', 't', 'c', 'f') == tag) {
         if (shared.fCollection.fNumOffsets == 0) {
             return 0;
         }
-        size_t offset = SkEndian_SwapBE32(shared.fCollection.fOffset0);
+        // this is the offset to the first local SkSFNTHeader
+        offset = SkEndian_SwapBE32(shared.fCollection.fOffset0);
         stream->rewind();
         if (stream->skip(offset) != offset) {
             return 0;
@@ -48,13 +60,12 @@ static int count_tables(SkStream* stream, size_t* offsetToDir = NULL) {
         if (stream->read(&shared, sizeof(shared)) != sizeof(shared)) {
             return 0;
         }
-        if (offsetToDir) {
-            *offsetToDir = offset;
-        }
-    } else {
-        *offsetToDir = 0;
     }
-
+    
+    if (offsetToDir) {
+        // add the size of the header, so we will point to the DirEntries
+        *offsetToDir = offset + sizeof(SkSFNTDirEntry);
+    }
     return SkEndian_SwapBE16(shared.fSingle.fNumTables);
 }
 
@@ -64,6 +75,12 @@ struct SfntHeader {
     SfntHeader() : fCount(0), fDir(NULL) {}
     ~SfntHeader() { sk_free(fDir); }
 
+    /** If it returns true, then fCount and fDir are properly initialized.
+        Note: fDir will point to the raw array of SkSFNTDirEntry values,
+        meaning they will still be in the file's native endianness (BE).
+     
+        fDir will be automatically freed when this object is destroyed
+     */
     bool init(SkStream* stream) {
         size_t offsetToDir;
         fCount = count_tables(stream, &offsetToDir);
@@ -72,8 +89,7 @@ struct SfntHeader {
         }
 
         stream->rewind();
-        const size_t tableRecordOffset = offsetToDir + sizeof(SkSFNTHeader);
-        if (stream->skip(tableRecordOffset) != tableRecordOffset) {
+        if (stream->skip(offsetToDir) != offsetToDir) {
             return false;
         }
 
diff --git a/utils/SkNinePatch.cpp b/utils/SkNinePatch.cpp
index b8e11fbc..3d85edcf 100644
--- a/utils/SkNinePatch.cpp
+++ b/utils/SkNinePatch.cpp
@@ -186,7 +186,7 @@ void SkNinePatch::DrawMesh(SkCanvas* canvas, const SkRect& bounds,
     if (numXDivs == 2 && numYDivs <= 2) {
         mesh.fIndices = g3x3Indices;
     } else {
-        int n = fillIndices(indices, numXDivs + 1, numYDivs + 1);
+        SkDEBUGCODE(int n =) fillIndices(indices, numXDivs + 1, numYDivs + 1);
         SkASSERT(n == indexCount);
         mesh.fIndices = indices;
     }
diff --git a/utils/SkSfntUtils.cpp b/utils/SkSfntUtils.cpp
new file mode 100644
index 00000000..36f1f97d
--- /dev/null
+++ b/utils/SkSfntUtils.cpp
@@ -0,0 +1,87 @@
+#include "SkEndian.h"
+#include "SkSfntUtils.h"
+
+static uint16_t parse_be16(const uint8_t*& p) {
+    uint16_t value = (p[0] << 8) | p[1];
+    p += 2;
+    return value;
+}
+
+static uint32_t parse_be32(const uint8_t*& p) {
+    uint32_t value = (p[0] << 24) | (p[1] << 16) | (p[2] << 8) | p[3];
+    p += 4;
+    return value;
+}
+
+static Sk64 parse_be64(const uint8_t*& p) {
+    Sk64 value;
+    value.fHi = (p[0] << 24) | (p[1] << 16) | (p[2] << 8) | p[3];
+    value.fLo = (p[4] << 24) | (p[5] << 16) | (p[6] << 8) | p[7];
+    p += 8;
+    return value;
+}
+
+///////////////////////////////////////////////////////////////////////////////
+
+bool SkSfntUtils::ReadTable_head(SkFontID fontID, SkSfntTable_head* head) {
+    static const uint32_t gTag = SkSetFourByteTag('h', 'e', 'a', 'd');
+    static const ssize_t gSize = 54;
+    
+    uint8_t storage[gSize];
+    ssize_t size = SkFontHost::GetTableData(fontID, gTag, 0, gSize, storage);
+    if (size != gSize) {
+        return false;
+    }
+    
+    const uint8_t* p = storage;
+    head->fVersion = parse_be32(p);
+    head->fRevision = parse_be32(p);
+    head->fCheckSumAdjustment = parse_be32(p);
+    head->fMagicNumber = parse_be32(p);
+    head->fFlags = parse_be16(p);
+    head->fUnitsPerEm = parse_be16(p);
+    head->fDateCreated = parse_be64(p);
+    head->fDateModified = parse_be64(p);
+    head->fXMin = parse_be16(p);
+    head->fXMin = parse_be16(p);
+    head->fXMin = parse_be16(p);
+    head->fXMin = parse_be16(p);
+    head->fMacStyle = parse_be16(p);
+    head->fLowestPPEM = parse_be16(p);
+    head->fFontDirectionHint = parse_be16(p);
+    head->fIndexToLocFormat = parse_be16(p);
+    head->fGlyphDataFormat = parse_be16(p);
+    SkASSERT(p - storage == size);
+    return true;
+}
+
+bool SkSfntUtils::ReadTable_maxp(SkFontID fontID, SkSfntTable_maxp* maxp) {
+    static const uint32_t gTag = SkSetFourByteTag('m', 'a', 'x', 'p');
+    static const ssize_t gSize = 32;
+    
+    uint8_t storage[gSize];
+    ssize_t size = SkFontHost::GetTableData(fontID, gTag, 0, gSize, storage);
+    if (size != gSize) {
+        return false;
+    }
+    
+    const uint8_t* p = storage;
+    maxp->fVersion = parse_be32(p);
+    maxp->fNumGlyphs = parse_be16(p);
+    maxp->fMaxPoints = parse_be16(p);
+    maxp->fMaxContours = parse_be16(p);
+    maxp->fMaxComponentPoints = parse_be16(p);
+    maxp->fMaxComponentContours = parse_be16(p);
+    maxp->fMaxZones = parse_be16(p);
+    maxp->fMaxTwilightPoints = parse_be16(p);
+    maxp->fMaxStorage = parse_be16(p);
+    maxp->fMaxFunctionDefs = parse_be16(p);
+    maxp->fMaxInstructionDefs = parse_be16(p);
+    maxp->fMaxStackElements = parse_be16(p);
+    maxp->fMaxSizeOfInstructions = parse_be16(p);
+    maxp->fMaxComponentElements = parse_be16(p);
+    maxp->fMaxComponentDepth = parse_be16(p);
+    SkASSERT(p - storage == size);
+    return true;
+}
+
diff --git a/utils/utils_files.mk b/utils/utils_files.mk
new file mode 100644
index 00000000..a8c9496a
--- /dev/null
+++ b/utils/utils_files.mk
@@ -0,0 +1,10 @@
+SOURCE := \
+	SkCamera.cpp \
+	SkColorMatrix.cpp \
+	SkCullPoints.cpp \
+	SkDumpCanvas.cpp \
+	SkInterpolator.cpp \
+	SkNinePatch.cpp \
+	SkProxyCanvas.cpp \
+	SkSfntUtils.cpp \
+	SkUnitMappers.cpp