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Add parsing anchor table format 2 #238

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merged 8 commits into from
Feb 26, 2022
Merged

Add parsing anchor table format 2 #238

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7ee119d
Add parsing anchor table format 2
brianpopow Feb 14, 2022
fb95570
Skip over x/y DeviceOffset of anchor format 3
brianpopow Feb 17, 2022
f9a9bd2
Change exception to InvalidFontFileException in case anchor format is…
brianpopow Feb 17, 2022
2063ce2
Actually implement AnchorFormat2 anchorPointIndex
JimBobSquarePants Feb 22, 2022
e12356c
Add font
JimBobSquarePants Feb 22, 2022
d963353
Merge branch 'main' into bp/anchor2
JimBobSquarePants Feb 24, 2022
bcf2bd3
Merge branch 'main' into bp/anchor2
JimBobSquarePants Feb 25, 2022
f4c9f35
Merge branch 'main' into bp/anchor2
JimBobSquarePants Feb 26, 2022
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31 changes: 30 additions & 1 deletion src/SixLabors.Fonts/Tables/AdvancedTypographic/GPos/AnchorTable.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -45,7 +45,8 @@ public static AnchorTable Load(BigEndianBinaryReader reader, long offset)
return anchorFormat switch
{
1 => AnchorFormat1.Load(reader),
_ => throw new NotSupportedException($"anchorFormat {anchorFormat} not supported. Should be '1'.")
2 => AnchorFormat2.Load(reader),
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As somebody who knows nothing about fonts, making these error messages more descriptive might be helpful too. If I knew that my font format wasn't supported, I'd just pick a different one.

 3 => throw new NotSupportedException($"Variable fonts (format 3) are not supported. Read: https://docs.sixlabors.com/articles/fonts/anchorTableFormats.html")
 _ => throw new NotSupportedException($"Fonts using anchor table format {anchorFormat} are not supported. Read: https://docs.sixlabors.com/articles/fonts/anchorTableFormats.html")

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I wouldn't link to docs from exception messages. The maintenance burden of tracking URL changes would be too much.

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that's fair enough, was just a thought

_ => throw new NotSupportedException($"anchorFormat {anchorFormat} not supported. Should be '1' or `2`.")
};
}

Expand All @@ -72,5 +73,33 @@ public static AnchorFormat1 Load(BigEndianBinaryReader reader)
return new AnchorFormat1(xCoordinate, yCoordinate);
}
}

internal sealed class AnchorFormat2 : AnchorTable
{
// TODO: actually use the anchorPointIndex.
private readonly ushort anchorPointIndex;

public AnchorFormat2(short xCoordinate, short yCoordinate, ushort anchorPointIndex)
: base(xCoordinate, yCoordinate) => this.anchorPointIndex = anchorPointIndex;

public static AnchorFormat2 Load(BigEndianBinaryReader reader)
{
// +--------------+------------------------+------------------------------------------------+
// | Type | Name | Description |
// +==============+========================+================================================+
// | uint16 | anchorFormat | Format identifier, = 1 |
// +--------------+------------------------+------------------------------------------------+
// | int16 | xCoordinate | Horizontal value, in design units. |
// +--------------+------------------------+------------------------------------------------+
// | int16 | yCoordinate | Vertical value, in design units. |
// +--------------+------------------------+------------------------------------------------+
// | uint16 + anchorPoint | Index to glyph contour point +
// +--------------+------------------------+------------------------------------------------+
short xCoordinate = reader.ReadInt16();
short yCoordinate = reader.ReadInt16();
ushort anchorPointIndex = reader.ReadUInt16();
return new AnchorFormat2(xCoordinate, yCoordinate, anchorPointIndex);
}
}
}
}