vhea - Vertical Header Table

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	minTopSideBearing	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	minBottomSideBearing	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	numOfLongVerMetrics	Number of advance heights in the vertical metrics 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.