Add Text Justification Options

[JimBobSquarePants]

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• I have written a descriptive pull-request title
• I have verified that there are no overlapping pull-requests open
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• I have provided test coverage for my change (where applicable)

Description

Prompted by this Stack Overflow question This PR adds a new TextJustification enum to TextOptions. The options and implementation supporting the
CSS Text Module Level 3 text-justify property.

Horizontal

TextJustification.None

TextJustification.InterWord

TextJustification.InterCharacter

Vertical

TextJustification.None

TextJustification.InterWord

TextJustification.InterCharacter

[codecov]

Codecov Report

Merging #285 (dd419f4) into main (cab42e5) will increase coverage by 0%.
The diff coverage is 82%.

@@          Coverage Diff          @@
##            main    #285   +/-   ##
=====================================
  Coverage     83%     83%           
=====================================
  Files        222     222           
  Lines      12211   12266   +55     
  Branches    1761    1779   +18     
=====================================
+ Hits       10191   10248   +57     
+ Misses      1591    1586    -5     
- Partials     429     432    +3     

Flag	Coverage Δ
unittests	83% <82%> (+<1%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
src/SixLabors.Fonts/TextMeasurer.cs	83% <58%> (-8%)	⬇️
src/SixLabors.Fonts/TextLayout.cs	87% <90%> (+1%)	⬆️
src/SixLabors.Fonts/TextOptions.cs	100% <100%> (ø)
src/SixLabors.Fonts/Unicode/UnicodeTrie.cs	88% <100%> (ø)
src/SixLabors.Fonts/GlyphLayout.cs	80% <0%> (+3%)	⬆️
src/SixLabors.Fonts/Unicode/BidiData.cs	85% <0%> (+9%)	⬆️

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[tocsoft]

You seem to have zero test coverage for validating the justification.

2 test cases I can think of,

1. For both justification types you want to run TextMeasurer.TryMeasureCharacterBounds and validate the first and last visible character of each line approximately aligns with the target bounding box.

2. for all justification types track the location of a few well distributed characters (i.e. the position of the e in elit and the m in maximus on the 2nd line of your samples.) that have different locations in all the layouts. and validate those.

Additionally how does this effect rtl and ttb etc, they should also be accounted for in the tests.

[JimBobSquarePants]

@tocsoft Yeah... Trying to figure out some way of testing things. It's a meaty gap.

I think I can also calculate for the InterCharacter value that the sum of each glyph advance is equal to the wrapping length.

Regarding RTL and TTB layouts. They all use the same ScaledAdvance to operate so this will automatically work for all layout versions. I'll try and add tests though.

[JimBobSquarePants]

@tocsoft I've added some tests. In order to do so I was required to add a new method to TextMeasurer which allows getting the size of each glyph. This end up making the class more symmetrical.