Microsoft KB Archive/65123

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Font-File Format

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Q65123

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The information in this article applies to:


 * Microsoft Windows Software Development Kit (SDK) versions 3.0, 3.1

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SUMMARY
This article is part of a set of seven articles, collectively called the &quot;Windows Developer's Notes.&quot; More information about the contents of the other articles can be found in the Microsoft Knowledge Base article:

"Q65260 The Windows Developer's Notes"

MORE INFORMATION
The following files are available for download from the Microsoft Download Center:

FontFmt.exe

For additional information about how to download Microsoft Support files, click the article number below to view the article in the Microsoft Knowledge Base:

"Q119591 How to Obtain Microsoft Support Files from Online Services" Microsoft used the most current virus detection software available on the date of posting to scan this file for viruses. Once posted, the file is housed on secure servers that prevent any unauthorized changes to the file.

Formats for Microsoft Windows font files are defined for both raster and vector fonts. These formats can be used by smart text generators in some GDI support modules. The vector formats, in particular, are more frequently used by GDI itself than by support modules.

Both raster and vector font files begin with information that is common to both, and then continue with information that differs for each type of file.

For Windows 3.0, the font-file header includes six new fields: dFlags, dfAspace, dfBspace, dfCspace, dfColorPointer, and dfReserved1. These fields are not used in Windows 3.0. To ensure compatibility with future versions of Windows, these fields should be set to zero.

All device drivers support the Windows 2.x fonts. However, not all device drivers support the Windows 3.0 version.

Windows 3.0 font files include the glyph table in dfCharTable, which consists of structures that describe the bits for characters in the font file. This version enables fonts to exceed 64K in size, the size limit of Windows 2.x fonts. This is made possible by the use of 32-bit offsets to the character glyphs in dfCharTable.

Because of the 32-bit offsets and their potentially large size, these fonts are designed for use on systems that are running Windows version 3.0 in protected (standard or 386 enhanced) mode with an 80386 (or higher) processor where the processor's 32-bit registers can access the character glyphs. Typically, device drivers use the Windows 3.0 version of a font only when both of these conditions are true.

Font files are stored with an .FNT extension of the form NAME.FNT. The information at the beginning of both raster and vector versions of Windows 3.0 font files is shown in the following list:

Field         Description -         ---

dfVersion     2 bytes specifying the version (0200H or 0300H) of               the file.

dfSize        4 bytes specifying the total size of the file in               bytes.

dfCopyright   60 bytes specifying copyright information.

dfType        2 bytes specifying the type of font file.

The low-order byte is exclusively for GDI use. If the low-order bit of the WORD is zero, it is a bitmap (raster) font file. If the low-order bit is 1, it is a              vector font file. The second bit is reserved and must be zero. If no bits follow in the file and the bits are located in memory at a fixed address specified in              dfBitsOffset, the third bit is set to 1; otherwise, the bit is set to 0 (zero). The high-order bit of the low byte is set if the font was realized by a device. The remaining bits in the low byte are reserved and set to              zero.

The high byte is reserved for device use and will always be set to zero for GDI-realized standard fonts. Physical fonts with the high-order bit of the low byte set may use this byte to describe themselves. GDI will never inspect the high byte.

dfPoints      2 bytes specifying the nominal point size at which this character set looks best.

dfVertRes     2 bytes specifying the nominal vertical resolution (dots-per-inch) at which this character set was digitized.

dfHorizRes    2 bytes specifying the nominal horizontal resolution (dots-per-inch) at which this character set was digitized.

dfAscent      2 bytes specifying the distance from the top of a               character definition cell to the baseline of the typographical font. It is useful for aligning the baselines of fonts of different heights.

dfInternalLeading Specifies the amount of leading inside the bounds set by dfPixHeight. Accent marks may occur in this area. This may be zero at the designer's option.

dfExternalLeading Specifies the amount of extra leading that the designer requests the application add between rows. Since this area is outside of the font proper, it contains no              marks and will not be altered by text output calls in               either the OPAQUE or TRANSPARENT mode. This may be zero at the designer's option.

dfItalic      1 (one) byte specifying whether or not the character definition data represent an italic font. The low-order bit is 1 if the flag is set. All the other bits are zero.

dfUnderline   1 byte specifying whether or not the character definition data represent an underlined font. The low-order bit is 1 if the flag is set. All the other bits are 0 (zero).

dfStrikeOut   1 byte specifying whether or not the character definition data represent a struckout font. The low- order bit is 1 if the flag is set. All the other bits are zero.

dfWeight      2 bytes specifying the weight of the characters in the character definition data, on a scale of 1 to 1000. A              dfWeight of 400 specifies a regular weight.

dfCharSet     1 byte specifying the character set defined by this font.

dfPixWidth    2 bytes. For vector fonts, specifies the width of the grid on which the font was digitized. For raster fonts, if dfPixWidth is nonzero, it represents the width for all the characters in the bitmap; if it is zero, the font has variable width characters whose widths are specified in the dfCharTable array.

dfPixHeight   2 bytes specifying the height of the character bitmap (raster fonts), or the height of the grid on which a              vector font was digitized.

dfPitchAndFamily Specifies the pitch and font family. The low bit is set if the font is variable pitch. The high four bits give the family name of the font. Font families describe in              a general way the look of a font. They are intended for specifying fonts when the exact face name desired is              not available. The families are as follows:

Family              Description --              ---                  FF_DONTCARE (0<<4)   Don't care or don't know. FF_ROMAN (1<<4)     Proportionally spaced fonts with serifs. FF_SWISS (2<<4)     Proportionally spaced fonts without serifs. FF_MODERN (3<<4)    Fixed-pitch fonts. FF_SCRIPT (4<<4) FF_DECORATIVE (5<<4)

dfAvgWidth    2 bytes specifying the width of characters in the font. For fixed-pitch fonts, this is the same as dfPixWidth. For variable-pitch fonts, this is the width of the character &quot;X.&quot;

dfMaxWidth    2 bytes specifying the maximum pixel width of any character in the font. For fixed-pitch fonts, this is              simply dfPixWidth.

dfFirstChar   1 byte specifying the first character code defined by               this font. Character definitions are stored only for the characters actually present in a font. Therefore, use this field when calculating indexes into either dfBits or dfCharOffset.

dfLastChar    1 byte specifying the last character code defined by               this font. Note that all the characters with codes between dfFirstChar and dfLastChar must be present in              the font character definitions.

dfDefaultChar 1 byte specifying the character to substitute whenever a string contains a character out of the range. The character is given relative to dfFirstChar so that dfDefaultChar is the actual value of the character, less dfFirstChar. The dfDefaultChar should indicate a special character that is not a space.

dfBreakChar   1 byte specifying the character that will define word breaks. This character defines word breaks for word wrapping and word spacing justification. The character is given relative to dfFirstChar so that dfBreakChar is              the actual value of the character, less that of               dfFirstChar. The dfBreakChar is normally (32 -              dfFirstChar), which is an ASCII space.

dfWidthBytes  2 bytes specifying the number of bytes in each row of               the bitmap. This is always even, so that the rows start on WORD boundaries. For vector fonts, this field has no              meaning.

dfDevice      4 bytes specifying the offset in the file to the string giving the device name. For a generic font, this value is zero.

dfFace        4 bytes specifying the offset in the file to the null-terminated string that names the face.

dfBitsPointer 4 bytes specifying the absolute machine address of               the bitmap. This is set by GDI at load time. The dfBitsPointer is guaranteed to be even.

dfBitsOffset  4 bytes specifying the offset in the file to the beginning of the bitmap information. If the 04H bit in              the dfType is set, then dfBitsOffset is an absolute address of the bitmap (probably in ROM).

For raster fonts, dfBitsOffset points to a sequence of              bytes that make up the bitmap of the font, whose height is the height of the font, and whose width is the sum of the widths of the characters in the font rounded up              to the next WORD boundary.

For vector fonts, it points to a string of bytes or              words (depending on the size of the grid on which the               font was digitized) that specify the strokes for each character of the font. The dfBitsOffset field must be              even.

dfReserved    1 byte, not used.

dfFlags       4 bytes specifying the bits flags, which are additional flags that define the format of the Glyph bitmap, as              follows:

DFF_FIXED           equ  0001h ; font is fixed pitch DFF_PROPORTIONAL    equ  0002h ; font is proportional ; pitch DFF_ABCFIXED        equ  0004h ; font is an ABC fixed ; font DFF_ABCPROPORTIONAL equ  0008h ; font is an ABC pro- ; portional font DFF_1COLOR          equ  0010h ; font is one color DFF_16COLOR         equ  0020h ; font is 16 color DFF_256COLOR        equ  0040h ; font is 256 color DFF_RGBCOLOR        equ  0080h ; font is RGB color

dfAspace      2 bytes specifying the global A space, if any. The dfAspace is the distance from the current position to              the left edge of the bitmap.

dfBspace      2 bytes specifying the global B space, if any. The dfBspace is the width of the character.

dfCspace      2 bytes specifying the global C space, if any. The dfCspace is the distance from the right edge of the bitmap to the new current position. The increment of a              character is the sum of the three spaces. These apply to all glyphs and is the case for DFF_ABCFIXED.

dfColorPointer 4 bytes specifying the offset to the color table for color fonts, if any. The format of the bits is similar to a DIB, but without the header. That is, the characters are not split up into disjoint bytes. Instead, they are left intact. If no color table is              needed, this entry is NULL. [NOTE: This information is different from that in the hard-copy Developer's Notes and reflects a correction.]

dfReserved1   16 bytes, not used. [NOTE: This information is different from that in the hard-copy Developer's Notes and reflects a correction.]

dfCharTable   For raster fonts, the CharTable is an array of entries each consisting of two 2-byte WORDs for Windows 2.x and three 2-byte WORDs for Windows 3.0. The first WORD of              each entry is the character width. The second WORD of              each entry is the byte offset from the beginning of the FONTINFO structure to the character bitmap. For Windows 3.0, the second and third WORDs are used for the offset.

There is one extra entry at the end of this table that describes an absolute-space character. This entry corresponds to a character that is guaranteed to be              blank; this character is not part of the normal character set.

The number of entries in the table is calculated as              ((dfLastChar - dfFirstChar) + 2). This includes a              spare, the sentinel offset mentioned in the following paragraph.

For fixed-pitch vector fonts, each 2-byte entry in this array specifies the offset from the start of the bitmap to the beginning of the string of stroke specification units for the character. The number of bytes or WORDs to be used for a particular character is calculated by              subtracting its entry from the next one, so that there is a sentinel at the end of the array of values.

For proportionally spaced vector fonts, each 4-byte entry is divided into two 2-byte fields. The first field gives the starting offset from the start of the bitmap of the character strokes. The second field gives the pixel width of the character.

An ASCII character string specifying the name of the font face. The size of this field is the length of the string plus a NULL terminator.

An ASCII character string specifying the name of the device if this font file is for a specific device. The size of this field is the length of the string plus a              NULL terminator.

This field contains the character bitmap definitions. Each character is stored as a contiguous set of bytes. (In the old font format, this was not the case.)

The first byte contains the first 8 bits of the first scanline (that is, the top line of the character). The second byte contains the first 8 bits of the second scanline. This continues until a first &quot;column&quot; is              completely defined.

The following byte contains the next 8 bits of the first scanline, padded with zeros on the right if              necessary (and so on, down through the second               &quot;column&quot;). If the glyph is quite narrow, each scanline is covered by 1 byte, with bits set to zero as              necessary for padding. If the glyph is very wide, a              third or even fourth set of bytes can be present.

NOTE: The character bitmaps must be stored contiguously and arranged in ascending order.

The following is a single-character example, in which are given the bytes for a 12 x 14 pixel character, as              shown here schematically.

............                 .....**.....                  ....*..*....                  ...*....*...                  ..*......*..                  ..*......*..                  ..*......*..                  ..********..                  ..*......*..                  ..*......*..                  ..*......*..                  ............                  ............                  ............

The bytes are given here in two sets, because the character is less than 17 pixels wide.

00 06 09 10 20 20 20 3F 20 20 20 00 00 00 00 00 00 80 40 40 40 C0 40 40 40 00 00 00

Note that in the second set of bytes, the second digit of each is always zero. It would correspond to the 13th through 16th pixels on the right side of the character, if they were present. The Windows 2.x version of dfCharTable has a GlyphEntry structure with the following format:

GlyphEntry   struc geWidth      dw     ? ; width of character bitmap in pixels geOffset     dw     ? ; pointer to the bits GlyphEntry   ends The Windows 3.0 version of the dfCharTable is dependent on the format of the Glyph bitmap.

NOTE: The only formats supported in Windows 3.0 will be DFF_FIXED and DFF_PROPORTIONAL.

DFF_FIXED

DFF_PROPORTIONAL

GlyphEntry   struc geWidth      dw     ? ; width of character bitmap in pixels geOffset     dd     ? ; pointer to the bits GlyphEntry   ends DFF_ABCFIXED

DFF_ABCPROPORTIONAL

GlyphEntry   struc geWidth      dw     ? ; width of character bitmap in pixels geOffset     dd     ? ; pointer to the bits geAspace     dd     ? ; A space in fractional pixels (16.16) geBspace     dd     ? ; B space in fractional pixels (16.16) geCspace     dw     ? ; C space in fractional pixels (16.16) GlyphEntry   ends The fractional pixels are expressed as a 32-bit signed number with an implicit binary point between bits 15 and 16. This is referred to as a 16.16 (&quot;sixteen dot sixteen&quot;) fixed-point number.

The ABC spacing here is the same as that defined above. However, here there are specific sets for each character.

DFF_1COLOR

DFF_16COLOR

DFF_256COLOR

DFF_RGBCOLOR

GlyphEntry   struc geWidth      dw     ? ; width of character bitmap in pixels geOffset     dd     ? ; pointer to the bits geHeight     dw     ? ; height of character bitmap in pixels geAspace     dd     ? ; A space in fractional pixels (16.16) geBspace     dd     ? ; B space in fractional pixels (16.16) geCspace     dd     ? ; C space in fractional pixels (16.16) GlyphEntry   ends DFF_1COLOR means 8 pixels per byte

DFF_16COLOR means 2 pixels per byte

DFF_256COLOR means 1 pixel per byte

DFF_RGBCOLOR means RGBquads

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