The vertical header table (tag name: 'vhea') contains information needed for vertical fonts. The glyphs of vertical fonts are written either top to bottom or bottom to top. This table contains information that is general to the font as a whole. Information that pertains to specific glyphs is given in the vertical metrics table (tag name: 'vmtx') described separately. The formats of these tables are similar to those for horizontal metrics (hhea and hmtx).
Data in the vertical header table must be consistent with data that appears in the vertical metrics table. The advance height and top sidebearing values in the vertical metrics table must correspond with the maximum advance height and minimum bottom sidebearing values in the vertical header table.
The vertical header table format follows:Vertical Header Table
| Type | Name | Description |
|---|---|---|
| FIXED32 | version | Version number of the vertical header table (0x00010000 for the initial version). |
| SHORT | ascent | Distance in FUnits from the centerline to the previous line's descent. |
| SHORT | descent | Distance in FUnits from the centerline to the next line's ascent. |
| SHORT | lineGap | Reserved; set to 0 |
| SHORT | advanceHeightMax | The maximum advance height measurement -in FUnits found in the font. This value must be consistent with the entries in the vertical metrics table. |
| SHORT | minTop SideBearing | The minimum top sidebearing measurement found in the font, in FUnits. This value must be consistent with the entries in the vertical metrics table. |
| SHORT | minBottom SideBearing | The minimum bottom sidebearing measurement found in the font, in FUnits. This value must be consistent with the entries in the vertical metrics table. |
| SHORT | yMaxExtent | Defined as yMaxExtent= minTopSideBearing+(yMax-yMin) |
| SHORT | caretSlopeRise | The value of the caretSlopeRise field divided by the value of the caretSlopeRun Field determines the slope of the caret. A value of 0 for the rise and a value of 1 for the run specifies a horizontal caret. A value of 1 for the rise and a value of 0 for the run specifies a vertical caret. Intermediate values are desirable for fonts whose glyphs are oblique or italic. For a vertical font, a horizontal caret is best. |
| SHORT | caretSlopeRun | See the caretSlopeRise field. Value=1 for nonslanted vertical fonts. |
| SHORT | caretOffset | The amount by which the highlight on a slanted glyph needs to be shifted away from the glyph in order to produce the best appearance. Set value equal to 0 for nonslanted fonts. |
| SHORT | reserved | Set to 0. |
| SHORT | reserved | Set to 0. |
| SHORT | reserved | Set to 0. |
| SHORT | reserved | Set to 0. |
| SHORT | metricDataFormat | Set to 0. |
| USHORT | numOf LongVerMetrics | Number of advance heights in the vertical metrics table; must be equal to the CharStrings INDEX count field in the 'CFF ' table. |
Vertical Header Table Example
| Offset/ length | Value | Name | Comment |
|---|---|---|---|
| 0/4 | 0x00010000 | version | Version number of the vertical header table, in fixed-point format, is 1.0 |
| 4/2 | 1024 | ascent | Half the em-square height. |
| 6/2 | -1024 | descent | Minus half the em-square height. |
| 8/2 | 0 | lineGap | Typographic line gap is 0 FUnits. |
| 10/2 | 2079 | advanceHeightMax | The maximum advance height measurement found in the font is 2079 FUnits. |
| 12/2 | -342 | minTopSideBearing | The minimum top sidebearing measurement found in the font is -342 FUnits. |
| 14/2 | -333 | minBottomSideBearing | The minimum bottom sidebearing measurement found in the font is -333 FUnits. |
| 16/2 | 2036 | yMaxExtent | minTopSideBearing+ (yMax-yMin)=2036. |
| 18/2 | 0 | caretSlopeRise | The caret slope rise of 0 and a caret slope run of 1 indicate a horizontal caret for a vertical font. |
| 20/2 | 1 | caretSlopeRun | The caret slope rise of 0 and a caret slope run of 1 indicate a horizontal caret for a vertical font. |
| 22/2 | 0 | caretOffset | Value set to 0 for nonslanted fonts. |
| 24/4 | 0 | reserved | Set to 0. |
| 26/2 | 0 | reserved | Set to 0. |
| 28/2 | 0 | reserved | Set to 0. |
| 30/2 | 0 | reserved | Set to 0. |
| 32/2 | 0 | metricDataFormat | Set to 0. |
| 34/2 | 258 | numOfLongVerMetrics | Number of advance heights in the vertical metrics table is 258. |