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bug 553963 - part 1 - fix handling of overlong text runs in the uniscribe shaper. r=jdaggett

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This commit is contained in:
Jonathan Kew 2010-08-11 17:52:21 +01:00
parent 0b585cc0a7
commit 984c9dfea0
2 changed files with 59 additions and 58 deletions
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1
gfx/thebes/gfxFont.cpp
View File

@ -3627,6 +3627,7 @@ PRUint32
gfxTextRun::FindFirstGlyphRunContaining(PRUint32 aOffset)
{
NS_ASSERTION(aOffset <= mCharacterCount, "Bad offset looking for glyphrun");
NS_ASSERTION(mGlyphRuns.Length() > 0, "no glyph runs present!");
if (aOffset == mCharacterCount)
return mGlyphRuns.Length();
PRUint32 start = 0;

116
gfx/thebes/gfxUniscribeShaper.cpp
View File

@ -394,48 +394,15 @@ private:
PRPackedBool mFontSelected;
};
#define MAX_ITEM_LENGTH 32768
static PRUint32 FindNextItemStart(int aOffset, int aLimit,
nsTArray<SCRIPT_LOGATTR> &aLogAttr,
const PRUnichar *aString)
{
if (aOffset + MAX_ITEM_LENGTH >= aLimit) {
// The item starting at aOffset can't be longer than the max length,
// so starting the next item at aLimit won't cause ScriptShape() to fail.
return aLimit;
}
// Try to start the next item before or after a space, since spaces
// don't kern or ligate.
PRUint32 off;
int boundary = -1;
for (off = MAX_ITEM_LENGTH; off > 1; --off) {
if (aLogAttr[off].fCharStop) {
if (off > boundary) {
boundary = off;
}
if (aString[aOffset+off] == ' ' || aString[aOffset+off - 1] == ' ')
return aOffset+off;
}
}
// Try to start the next item at the last cluster boundary in the range.
if (boundary > 0) {
return aOffset+boundary;
}
// No nice cluster boundaries inside MAX_ITEM_LENGTH characters, break
// on the size limit. It won't be visually plesaing, but at least it
// won't cause ScriptShape() to fail.
return aOffset + MAX_ITEM_LENGTH;
}
#define MAX_ITEM_LENGTH 16384
class Uniscribe
{
public:
Uniscribe(const PRUnichar *aString, PRUint32 aLength, PRBool aIsRTL) :
mString(aString), mLength(aLength), mIsRTL(aIsRTL)
Uniscribe(const PRUnichar *aString,
PRUint32 aLength,
gfxTextRun *aTextRun):
mString(aString), mLength(aLength), mTextRun(aTextRun)
{
}
~Uniscribe() {
@ -446,44 +413,79 @@ public:
memset(&mState, 0, sizeof(SCRIPT_STATE));
// Lock the direction. Don't allow the itemizer to change directions
// based on character type.
mState.uBidiLevel = mIsRTL;
mState.uBidiLevel = mTextRun->IsRightToLeft() ? 1 : 0;
mState.fOverrideDirection = PR_TRUE;
}
private:
// We try to avoid calling Uniscribe with text runs that may generate
// more than this many glyphs, because of the possibility of arithmetic
// overflow of 16-bit variables. If long runs need to be split because
// of this, we'll look for whitespace to break on so that shaping needed
// (e.g. for complex scripts) should be unaffected.
#define MAX_UNISCRIBE_GLYPHS 32767
// Append mItems[aIndex] to aDest, adding extra items to aDest to ensure
// that no item is too long for ScriptShape() to handle. See bug 366643.
nsresult CopyItemSplitOversize(int aIndex, nsTArray<SCRIPT_ITEM> &aDest) {
aDest.AppendElement(mItems[aIndex]);
const int itemLength = mItems[aIndex+1].iCharPos - mItems[aIndex].iCharPos;
if (ESTIMATE_MAX_GLYPHS(itemLength) > 65535) {
// This items length would cause ScriptShape() to fail. We need to
// add extra items here so that no item's length could cause the fail.
// Get cluster boundaries, so we can break cleanly if possible.
nsTArray<SCRIPT_LOGATTR> logAttr;
if (!logAttr.SetLength(itemLength))
return NS_ERROR_FAILURE;
HRESULT rv = ScriptBreak(mString+mItems[aIndex].iCharPos, itemLength,
&mItems[aIndex].a, logAttr.Elements());
if (FAILED(rv))
return NS_ERROR_FAILURE;
const int itemLength =
mItems[aIndex+1].iCharPos - mItems[aIndex].iCharPos;
if (ESTIMATE_MAX_GLYPHS(itemLength) > MAX_UNISCRIBE_GLYPHS) {
// This item's length would cause ScriptShape() to fail.
// We need to add extra items here so that no item's length
// could cause the fail.
// We break on whitespace or cluster boundaries if possible.
const int nextItemStart = mItems[aIndex+1].iCharPos;
int start = FindNextItemStart(mItems[aIndex].iCharPos,
nextItemStart, logAttr, mString);
nextItemStart);
while (start < nextItemStart) {
SCRIPT_ITEM item = mItems[aIndex];
item.iCharPos = start;
aDest.AppendElement(item);
start = FindNextItemStart(start, nextItemStart, logAttr, mString);
start = FindNextItemStart(start, nextItemStart);
}
}
return NS_OK;
}
PRUint32 FindNextItemStart(int aOffset, int aLimit) {
if (aOffset + MAX_ITEM_LENGTH >= aLimit) {
// The item starting at aOffset can't be longer than max length,
// so starting the next item at aLimit won't cause ScriptShape()
// to fail.
return aLimit;
}
// Try to start the next item before or after a space, since spaces
// don't kern or ligate.
PRInt32 off;
int boundary = -1;
for (off = MAX_ITEM_LENGTH; off > 1; --off) {
if (mTextRun->IsClusterStart(off)) {
if (off > boundary) {
boundary = off;
}
if (mString[aOffset+off] == ' ' ||
mString[aOffset+off - 1] == ' ') {
return aOffset+off;
}
}
}
// Try to start the next item at last cluster boundary in the range.
if (boundary > 0) {
return aOffset+boundary;
}
// No nice cluster boundaries inside MAX_ITEM_LENGTH characters, break
// on the size limit. It won't be visually pleasing, but at least it
// won't cause ScriptShape() to fail.
return aOffset + MAX_ITEM_LENGTH;
}
public:
int Itemize() {
@ -537,7 +539,7 @@ public:
private:
const PRUnichar *mString;
const PRUint32 mLength;
const PRBool mIsRTL;
gfxTextRun *mTextRun;
SCRIPT_CONTROL mControl;
SCRIPT_STATE mState;
@ -556,15 +558,13 @@ gfxUniscribeShaper::InitTextRun(gfxContext *aContext,
{
DCFromContext aDC(aContext);
const PRBool isRTL = aTextRun->IsRightToLeft();
PRBool result = PR_TRUE;
HRESULT rv;
gfxGDIFont *font = static_cast<gfxGDIFont*>(mFont);
AutoSelectFont fs(aDC, font->GetHFONT());
Uniscribe us(aString + aRunStart, aRunLength, isRTL);
Uniscribe us(aString + aRunStart, aRunLength, aTextRun);
/* itemize the string */
int numItems = us.Itemize();