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https://issues.apache.org/jira/browse/PDFBOX-2946?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14725624#comment-14725624
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Tilman Hausherr commented on PDFBOX-2946:
-----------------------------------------
It's the leftsidebearing.
I did have some suspicion because of the "contradiction" between
leftsidebearing and the bbox (see table below) after reading the TT font
specification but wasn't sure what to do. So I had a look at the ghostscript
sources (base/ttfmain.c), because it displays the file correctly, and these
guys are usually 10 years ahead of us :-)
{code}
/* Lets do X */
{ short coord = (self->bVertical ? 0 : sideBearing -
subglyph.bbox.xMin);
F26Dot6* x = pts->org_x;
onCurve = pts->touch;
while (onCurve < stop) {
if ((flag = *onCurve++) & XSHORT) {
if (flag & SHORT_X_IS_POS)
coord += ttfReader__Byte(r);
else
coord -= ttfReader__Byte(r);
} else if (!(flag & NEXT_X_IS_ZERO))
coord += ttfReader__Short(r);
*x++ = Scale_X(&exec->metrics, coord);
}
}
{code}
Our code for "Lets do X" is in GlyfSimpleDescript.java:
{code}
short x = 0;
short y = 0;
for (int i = 0; i < count; i++)
{
if ((flags[i] & X_DUAL) != 0)
{
if ((flags[i] & X_SHORT_VECTOR) != 0)
{
x += (short) bais.readUnsignedByte();
}
}
else
{
if ((flags[i] & X_SHORT_VECTOR) != 0)
{
x += (short) -((short) bais.readUnsignedByte());
}
else
{
x += bais.readSignedShort();
}
}
xCoordinates[i] = x;
}
{code}
The main difference is this line:
{code}
short coord = (self->bVertical ? 0 : sideBearing - subglyph.bbox.xMin);
{code}
some font data for the test file:
{code}
leftSideBearing boundingBox
bracelefttp: 420 [0.0,-167.0,490.0,1897.0]
braceleftmid: 28 [0.0,-166.0,490.0,1897.0]
braceleftbt: 420 [420.0,-167.0,910.0,1897.0]
{code}
bracelefttp is the "wrong" one, drawing starts at 0 despire having a left side
bearing of 420.
(Btw fontforge -sucks- is not helpful. It shows the (correct) path without
showing the raw data leading to it).
Proposed patch attached.
> Symbol glyphs not aligned
> -------------------------
>
> Key: PDFBOX-2946
> URL: https://issues.apache.org/jira/browse/PDFBOX-2946
> Project: PDFBox
> Issue Type: Bug
> Components: Rendering
> Affects Versions: 2.0.0
> Environment: W7, JDK7
> Reporter: Tilman Hausherr
> Assignee: John Hewson
> Fix For: 2.0.0
>
> Attachments: PDFJS-3599.pdf-1-bad.png, PDFJS-3599.pdf-1-good.png,
> PDFJS-3599_reduced.pdf, PDFJS-3599_reduced1.png, leftsidebearing.diff
>
>
> Symbol glyphs not aligned in rendering
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