Jason Harrop created FOP-3356:
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Summary: simulate-style slants an italic face again and strokes a
bold face again, and its stroke width does not scale with the font size
Key: FOP-3356
URL: https://issues.apache.org/jira/browse/FOP-3356
Project: FOP
Issue Type: Bug
Components: renderer/pdf
Affects Versions: main, 2.11
Reporter: Jason Harrop
A font entry with simulate-style="true" makes FOP synthesise the style a
triplet asks for from the face the entry registers:
PDFPainter.startSimulateStyle strokes a triplet of weight 700 (2 Tr) with a
0.31543pt line, and shears a triplet of style italic by 0.3333 in the text
matrix. It decides from the entry's flag and the triplet alone, never from the
face, although FOP has the face's italic angle (post table) and weight class
(OS/2) in CustomFont. So:
* an italic face registered for a bold italic triplet, as a family with an
italic face and no bold one needs, is slanted a second time on top of its own
slant;
* a bold face registered for a bold italic triplet, as a family with a bold
face and no bold italic one needs, is stroked a second time;
* the stroke is a fixed 0.31543pt whatever the size, which is about right at
11pt only: at 22pt it is half the weight it should be, at 8pt about 40% too
heavy.
Configuration and FO (Carlito, 24pt):
{noformat}
<font simulate-style="true"
embed-url="file:///usr/share/fonts/carlito/Carlito-Italic.ttf"><font-triplet
name="ItalFace" style="italic" weight="bold"/></font>
<font simulate-style="true"
embed-url="file:///usr/share/fonts/carlito/Carlito-Regular.ttf"><font-triplet
name="RegFace" style="italic" weight="bold"/></font>
<font simulate-style="true"
embed-url="file:///usr/share/fonts/carlito/Carlito-Bold.ttf"><font-triplet
name="BoldFace" style="italic" weight="bold"/></font>
<fo:flow flow-name="xsl-region-body" font-size="24pt" font-style="italic"
font-weight="bold">
<fo:block font-family="ItalFace">Italic face</fo:block>
<fo:block font-family="RegFace">Regular face</fo:block>
<fo:block font-family="BoldFace">Bold face</fo:block>
</fo:flow>
{noformat}
On main, the content stream draws all three the same way: 2 Tr 0.31543 w, and 1
0 0.3333 -1 ... Tm. The italic face is slanted twice and the bold face stroked
twice.
*Fix (pull request to follow)*
In PDFPainter.startSimulateStyle and endSimulateStyle: shear an italic triplet
only where the face's italic angle is 0; stroke a bold triplet only where the
face's weight class is below 700 (an unknown weight, 0, counts as not bold, as
now); and stroke at the font size / 35. A stroke of 1/35 em is what Microsoft
Word draws for a synthetic bold, measured at 7.92 to 48pt in Word's own PDFs,
and at 11.04pt it is the present 0.31543. Word also never shears a face that is
already italic, and its synthetic italic is the same 0.3333 shear FOP uses.
Measured on main with the change, the FO above: the italic face 2 Tr 0.68571 w
and 1 0 0 -1 ... Tm (stroked, not slanted again); the regular face stroked and
sheared; the bold face sheared, not stroked. Only the painted glyphs change,
never layout. PDFPainterTestCase gains three cases (the italic face, the bold
face, the stroke at 22.08pt), each failing before. The fop-core suite passes
(3679 tests) and checkstyle is clean.
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