Resolves: #i124935# fix expanded/condensed text breaking...

in the CoreText engine

the concept of an extra-width per code-unit was obsolete at least since apps
supported unicode with its different normalization forms, diacritical marks,
surrogate-pairs, non-printing characters such as ZWJ/ZWNJ/RLM, etc.  so of
course modern engines like CoreText don't aid this typographical crime.

The fix here extends the CTLayout::GetTextBreak() method to handle the obsolete
semantic of per code-unit extra-widths by successively approximating the number
of involved code-units.
(cherry picked from commit a9b9ceff86f35be1eeff5f251d24e338db760a1e)

Conflicts:
vcl/aqua/source/gdi/ctlayout.cxx

Change-Id: I52a7f7488a9e8a303ed7271df2a24a3c85098ce3

1 files changed, 27 insertions, 8 deletions

diff --git a/vcl/quartz/ctlayout.cxx b/vcl/quartz/ctlayout.cxx
index 347cc5e7fbee..8c42cc8537bb 100644
--- a/vcl/quartz/ctlayout.cxx
+++ b/vcl/quartz/ctlayout.cxx
@@ -580,20 +580,39 @@ long CTLayout::FillDXArray( sal_Int32* pDXArray ) const
     return nPixWidth;
 }
 
-sal_Int32 CTLayout::GetTextBreak( long nMaxWidth, long /*nCharExtra*/, int nFactor ) const
+sal_Int32 CTLayout::GetTextBreak( long nMaxWidth, long nCharExtra, int nFactor ) const
 {
     if( !mpCTLine )
         return -1;
 
     CTTypesetterRef aCTTypeSetter = CTTypesetterCreateWithAttributedString( mpAttrString );
-    const double fCTMaxWidth = (double)nMaxWidth / nFactor;
-    CFIndex nIndex = CTTypesetterSuggestClusterBreak( aCTTypeSetter, 0, fCTMaxWidth );
-    CFRelease( aCTTypeSetter );
-
-    if( nIndex >= mnCharCount )
-        return -1;
+    CFIndex nBestGuess = (nCharExtra >= 0) ? 0 : mnCharCount;
+    for( int i = 1; i <= mnCharCount; i *= 2 )
+    {
+        // guess the target width considering char-extra expansion/condensation
+        const double nTargetWidth = nMaxWidth - nBestGuess * nCharExtra;
+        const double fCTMaxWidth = nTargetWidth / nFactor;
+        // calculate the breaking index for the guessed target width
+        const CFIndex nNewIndex = CTTypesetterSuggestClusterBreak( aCTTypeSetter, 0, fCTMaxWidth );
+        if( nNewIndex >= mnCharCount ) {
+            CFRelease( aCTTypeSetter );
+            return -1;
+        }
+        // check if the original extra-width guess was good
+        if( !nCharExtra )
+            nBestGuess = nNewIndex;
+        if( nBestGuess == nNewIndex )
+            break;
+        // prepare another round for a different number of characters
+        CFIndex nNewGuess = (nNewIndex + nBestGuess + 1) / 2;
+        if( nNewGuess == nBestGuess )
+            nNewGuess += (nNewIndex > nBestGuess) ? +1 : -1;
+        nBestGuess = nNewGuess;
+    }
 
-    nIndex += mnMinCharPos;
+    // suggest the best fitting cluster break as breaking position
+    CFRelease( aCTTypeSetter );
+    const int nIndex = nBestGuess + mnMinCharPos;
     return nIndex;
 }