Glyph layout - See Issue #442

[vk-github18]

Pull request for issue #442 Accented Letters composed of Unicode base letter and combining accent are rendered incorrectly.

The position of glyphs is computed with statndard Java AWT methods.
The output should be correct for all characters and sequences of DIN SPEC 91379.
Eventually other scripts are also rendered correctly especially with Java versions >= 1.9 using HarfBuzz for rendering - this is not in the scope of this change.

See the example GlyphLayoutDinSpec91379.java

[codecracker2014]

@vk-github18 can you check this wiki and see if this can solve notofonts/noto-fonts#442

[vk-github18]

@codecracker2014 FopGlyphProcessor does glyph substitution, not glyph positioning, so it can not solve notofonts/noto-fonts#442

[codecracker2014]

@vk-github18 can you share output with FopGlyphProcessor enabled.

[vk-github18]

@codecracker2014 The output would not change with FopGlyphProcessor enabled, because it will not be called. The LayoutProcessor always calls showText(glyphVector),

Output of Hindi example with LayoutProcessor enabled:
helloworld-hindi.pdf

[vk-github18]

Output of example programs:
GlyphLayoutDocumentDinSpec91379.pdf
GlyphLayoutFormDinSpec91379.pdf

[asturio]

@codecracker2014 , @vk-github18
Any objections in this PR? It looks OK for me. (will merge in 3 days, if no one is against it :-) )

[asturio]

The results look good. Code is clean!

[vk-github18]

I need to provide another correction before merging.

[sonarcloud]

Kudos, SonarCloud Quality Gate passed!

0 Bugs
0 Vulnerabilities (and 0 Security Hotspots to review)
0 Code Smells

No Coverage information
No Duplication information

[vk-github18]

Code should be ok now, the result of the examples is:

GlyphLayoutDocumentDinSpec91379.pdf
GlyphLayoutFormDinSpec91379.pdf

[asturio]

It's a nice improvement. I think there still some issues with "apostrophes" or "acutes" like in c', or t'. But other glyphs are looking great.

[vk-github18]

Thanks for merging the request.
I am not sure, which combinations you refer to. Some problems are addressed in https://github.com/googlefonts/noto-fonts/issues/1882

[vk-github18]

For reference I am adding a list of the sequences with codepoint and name.
GlyphLayoutDinSpec91379Sequences.pdf

[asturio]

For reference I am adding a list of the sequences with codepoint and name.
GlyphLayoutDinSpec91379Sequences.pdf

Everything fine. I assumed the display of "LATIN CAPITAL LETTER * WITH COMBINING COMMA ABOVE RIGHT" was wrong. But it is exactly as in the reference.

Thank you again for this very nice PR 👍

[vk-github18]

@asturio You are right, the display of some letters with "COMBINING COMMA ABOVE RIGHT" is wrong, this is caused by a bug of the Noto Sans fonts, see https://github.com/googlefonts/noto-fonts/issues/1882