Add stub support for variable font tables#2
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…AR, MVAR) Registers parsers, tags, and typed accessors for the OpenType font variations tables without implementing full decoding of their internal structures. Co-Authored-By: Claude Sonnet 4 <noreply@anthropic.com>
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This PR adds stub implementations for variable font tables (fvar, avar, gvar, STAT, HVAR, MVAR). The implementation follows existing patterns correctly, with all tables storing raw bytes without parsing. The code is structurally sound with no security or correctness issues identified.
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This PR adds stub implementations for variable font tables (fvar, avar, gvar, STAT, HVAR, MVAR). The implementation is correct for a minimal stub but lacks input validation and has potential type safety issues with unchecked type assertions.
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This PR adds stub support for six OpenType variable font tables (fvar, avar, gvar, STAT, HVAR, MVAR) by registering parsers, tags, and typed accessor methods. The implementation stores raw bytes without parsing internal structures, which is appropriate for initial support. The README change removes Travis CI and GoDoc badges unrelated to the PR's stated purpose. Overall the code is correct and follows existing patterns, but lacks tests and has one unrelated change.
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This PR adds stub implementations for six variable font tables (fvar, avar, gvar, STAT, HVAR, MVAR), replacing a previous full fvar parser with a minimal stub. The implementations follow existing patterns and are correctly integrated. Main concern: unchecked type assertions could panic if parsers return wrong types, though this matches the existing pattern in the codebase.
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This PR adds stub implementations for variable font table support (fvar, avar, gvar, STAT, HVAR, MVAR). The implementation follows existing patterns but has critical type assertion safety issues that could cause runtime panics. All six new table accessor methods use unsafe type assertions without validation, which differs from the safer pattern used in TableLayout().
| if err != nil { | ||
| return nil, err | ||
| } | ||
| return t.(*TableFvar), nil |
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[ERROR] Security/Correctness: Unsafe type assertion
This uses an unsafe type assertion t.(*TableFvar) that will panic if the table is not of the expected type. While the parser is registered in parsers map, corrupted font files or parser bugs could return unexpected types.
Recommendation: Use the safe two-value assertion pattern like TableLayout() does:
fvar, ok := t.(*TableFvar)
if !ok {
return nil, fmt.Errorf("table %q is not an fvar table", tag)
}
return fvar, nilThis pattern is already used in TableLayout() at line 153-157 and should be applied consistently for defensive programming.
| if err != nil { | ||
| return nil, err | ||
| } | ||
| return t.(*TableAvar), nil |
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[ERROR] Security/Correctness: Unsafe type assertion
Same issue as FvarTable() - uses unsafe type assertion that will panic on type mismatch. See comment on line 176 for recommended fix pattern.
| if err != nil { | ||
| return nil, err | ||
| } | ||
| return t.(*TableGvar), nil |
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[ERROR] Security/Correctness: Unsafe type assertion
Same issue as FvarTable() - uses unsafe type assertion that will panic on type mismatch. See comment on line 176 for recommended fix pattern.
| if err != nil { | ||
| return nil, err | ||
| } | ||
| return t.(*TableStat), nil |
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[ERROR] Security/Correctness: Unsafe type assertion
Same issue as FvarTable() - uses unsafe type assertion that will panic on type mismatch. See comment on line 176 for recommended fix pattern.
| if err != nil { | ||
| return nil, err | ||
| } | ||
| return t.(*TableHvar), nil |
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[ERROR] Security/Correctness: Unsafe type assertion
Same issue as FvarTable() - uses unsafe type assertion that will panic on type mismatch. See comment on line 176 for recommended fix pattern.
| if err != nil { | ||
| return nil, err | ||
| } | ||
| return t.(*TableMvar), nil |
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[ERROR] Security/Correctness: Unsafe type assertion
Same issue as FvarTable() - uses unsafe type assertion that will panic on type mismatch. See comment on line 176 for recommended fix pattern.
| } | ||
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| func parseTableFvar(tag Tag, buf []byte) (Table, error) { | ||
| return &TableFvar{ |
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[INFO] Info: Parser does not validate table data
The parser accepts any byte slice without validation. While this matches the stub implementation pattern, consider adding basic validation in future iterations:
- Check minimum length requirements for the fvar table header
- Validate version number
- Verify axis count and instance count are reasonable
This is acceptable for a stub implementation but should be tracked for future work.
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| [](https://travis-ci.org/ConradIrwin/font) [](https://godoc.org/github.com/ConradIrwin/font) | ||
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[INFO] Info: Unrelated change
Removing the Travis CI badge appears unrelated to adding variable font stubs. Consider keeping this change in a separate commit or PR for cleaner history, unless Travis CI is no longer used.
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Summary
fvar,avar,gvar,STAT,HVAR,MVARTagconstants and wires up parsers in the parser mapFont(FvarTable(),AvarTable(), etc.) and anIsVariable()convenience methodTest plan
go build ./....ttfwithfvar) and confirmIsVariable()returns true and table accessors return non-nil🤖 Generated with Claude Code