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# Multiple Masters

## Synopsis

The following types and functions are used to manage Multiple Master fonts, i.e., the selection of specific design instances by setting design axis coordinates.

Besides Adobe MM fonts, the interface supports Apple's TrueType GX and OpenType variation fonts. Some of the routines only work with Adobe MM fonts, others will work with all three types. They are similar enough that a consistent interface makes sense.

## FT_MM_Axis

Defined in FT_MULTIPLE_MASTERS_H (freetype/ftmm.h).

      typedef struct  FT_MM_Axis_
      {
        FT_String*  name;
        FT_Long     minimum;
        FT_Long     maximum;

      } FT_MM_Axis;

A structure to model a given axis in design space for Multiple Masters fonts.

This structure can't be used for TrueType GX or OpenType variation fonts.

#### fields

name | The axis's name.
minimum | The axis's minimum design coordinate.
maximum | The axis's maximum design coordinate.

## FT_Multi_Master

Defined in FT_MULTIPLE_MASTERS_H (freetype/ftmm.h).

      typedef struct  FT_Multi_Master_
      {
        FT_UInt     num_axis;
        FT_UInt     num_designs;
        FT_MM_Axis  axis[T1_MAX_MM_AXIS];

      } FT_Multi_Master;

A structure to model the axes and space of a Multiple Masters font.

This structure can't be used for TrueType GX or OpenType variation fonts.

#### fields

num_axis | Number of axes. Cannot exceed 4.
num_designs | Number of designs; should be normally 2^num_axis even though the Type 1 specification strangely allows for intermediate designs to be present. This number cannot exceed 16.
axis | A table of axis descriptors.

## FT_Var_Axis

Defined in FT_MULTIPLE_MASTERS_H (freetype/ftmm.h).

      typedef struct  FT_Var_Axis_
      {
        FT_String*  name;

        FT_Fixed    minimum;
        FT_Fixed    def;
        FT_Fixed    maximum;

        FT_ULong    tag;
        FT_UInt     strid;

      } FT_Var_Axis;

A structure to model a given axis in design space for Multiple Masters, TrueType GX, and OpenType variation fonts.

#### fields

name | The axis's name. Not always meaningful for TrueType GX or OpenType variation fonts.
minimum | The axis's minimum design coordinate.
def | The axis's default design coordinate. FreeType computes meaningful default values for Adobe MM fonts.
maximum | The axis's maximum design coordinate.
tag | The axis's tag (the equivalent to ‘name’ for TrueType GX and OpenType variation fonts). FreeType provides default values for Adobe MM fonts if possible.
strid | The axis name entry in the font's ‘name’ table. This is another (and often better) version of the ‘name’ field for TrueType GX or OpenType variation fonts. Not meaningful for Adobe MM fonts.

#### note

The fields `minimum`, `def`, and `maximum` are 16.16 fractional values for TrueType GX and OpenType variation fonts. For Adobe MM fonts, the values are integers.

## FT_Var_Named_Style

Defined in FT_MULTIPLE_MASTERS_H (freetype/ftmm.h).

      typedef struct  FT_Var_Named_Style_
      {
        FT_Fixed*  coords;
        FT_UInt    strid;
        FT_UInt    psid;   /* since 2.7.1 */

      } FT_Var_Named_Style;

A structure to model a named instance in a TrueType GX or OpenType variation font.

This structure can't be used for Adobe MM fonts.

#### fields

coords | The design coordinates for this instance. This is an array with one entry for each axis.
strid | The entry in ‘name’ table identifying this instance.
psid | The entry in ‘name’ table identifying a PostScript name for this instance. Value 0xFFFF indicates a missing entry.

## FT_MM_Var

Defined in FT_MULTIPLE_MASTERS_H (freetype/ftmm.h).

      typedef struct  FT_MM_Var_
      {
        FT_UInt              num_axis;
        FT_UInt              num_designs;
        FT_UInt              num_namedstyles;
        FT_Var_Axis*         axis;
        FT_Var_Named_Style*  namedstyle;

      } FT_MM_Var;

A structure to model the axes and space of an Adobe MM, TrueType GX, or OpenType variation font.

Some fields are specific to one format and not to the others.

#### fields

num_axis | The number of axes. The maximum value is 4 for Adobe MM fonts; no limit in TrueType GX or OpenType variation fonts.
num_designs | The number of designs; should be normally 2^num_axis for Adobe MM fonts. Not meaningful for TrueType GX or OpenType variation fonts (where every glyph could have a different number of designs).
num_namedstyles | The number of named styles; a ‘named style’ is a tuple of design coordinates that has a string ID (in the ‘name’ table) associated with it. The font can tell the user that, for example, [Weight=1.5,Width=1.1] is ‘Bold’. Another name for ‘named style’ is ‘named instance’. For Adobe Multiple Masters fonts, this value is always zero because the format does not support named styles.
axis | An axis descriptor table. TrueType GX and OpenType variation fonts contain slightly more data than Adobe MM fonts. Memory management of this pointer is done internally by FreeType.
namedstyle | A named style (instance) table. Only meaningful for TrueType GX and OpenType variation fonts. Memory management of this pointer is done internally by FreeType.

## FT_Get_Multi_Master

Defined in FT_MULTIPLE_MASTERS_H (freetype/ftmm.h).

      FT_EXPORT( FT_Error )
      FT_Get_Multi_Master( FT_Face           face,
                           FT_Multi_Master  *amaster );

Retrieve a variation descriptor of a given Adobe MM font.

This function can't be used with TrueType GX or OpenType variation fonts.

#### input

face | A handle to the source face.

#### output

amaster | The Multiple Masters descriptor.

#### return

FreeType error code. 0 means success.

## FT_Get_MM_Var

Defined in FT_MULTIPLE_MASTERS_H (freetype/ftmm.h).

      FT_EXPORT( FT_Error )
      FT_Get_MM_Var( FT_Face      face,
                     FT_MM_Var*  *amaster );

Retrieve a variation descriptor for a given font.

This function works with all supported variation formats.

#### input

face | A handle to the source face.

#### output

amaster | The variation descriptor. Allocates a data structure, which the user must deallocate with a call to `FT_Done_MM_Var` after use.

#### return

FreeType error code. 0 means success.

## FT_Done_MM_Var

Defined in FT_MULTIPLE_MASTERS_H (freetype/ftmm.h).

      FT_EXPORT( FT_Error )
      FT_Done_MM_Var( FT_Library   library,
                      FT_MM_Var   *amaster );

Free the memory allocated by `FT_Get_MM_Var`.

#### input

library | A handle of the face's parent library object that was used in the call to `FT_Get_MM_Var` to create `amaster`.

#### return

FreeType error code. 0 means success.

## FT_Set_MM_Design_Coordinates

Defined in FT_MULTIPLE_MASTERS_H (freetype/ftmm.h).

      FT_EXPORT( FT_Error )
      FT_Set_MM_Design_Coordinates( FT_Face   face,
                                    FT_UInt   num_coords,
                                    FT_Long*  coords );

For Adobe MM fonts, choose an interpolated font design through design coordinates.

This function can't be used with TrueType GX or OpenType variation fonts.

#### inout

face | A handle to the source face.

#### input

num_coords | The number of available design coordinates. If it is larger than the number of axes, ignore the excess values. If it is smaller than the number of axes, use default values for the remaining axes.
coords | An array of design coordinates.

#### return

FreeType error code. 0 means success.

#### note

[Since 2.8.1] To reset all axes to the default values, call the function with `num_coords` set to zero and `coords` set to `NULL`.

[Since 2.9] If `num_coords` is larger than zero, this function sets the `FT_FACE_FLAG_VARIATION` bit in `FT_Face`'s `face_flags` field (i.e., `FT_IS_VARIATION` will return true). If `num_coords` is zero, this bit flag gets unset.

## FT_Set_Var_Design_Coordinates

Defined in FT_MULTIPLE_MASTERS_H (freetype/ftmm.h).

      FT_EXPORT( FT_Error )
      FT_Set_Var_Design_Coordinates( FT_Face    face,
                                     FT_UInt    num_coords,
                                     FT_Fixed*  coords );

Choose an interpolated font design through design coordinates.

This function works with all supported variation formats.

#### inout

face | A handle to the source face.

#### input

num_coords | The number of available design coordinates. If it is larger than the number of axes, ignore the excess values. If it is smaller than the number of axes, use default values for the remaining axes.
coords | An array of design coordinates.

#### return

FreeType error code. 0 means success.

#### note

[Since 2.8.1] To reset all axes to the default values, call the function with `num_coords` set to zero and `coords` set to `NULL`. [Since 2.9] ‘Default values’ means the currently selected named instance (or the base font if no named instance is selected).

[Since 2.9] If `num_coords` is larger than zero, this function sets the `FT_FACE_FLAG_VARIATION` bit in `FT_Face`'s `face_flags` field (i.e., `FT_IS_VARIATION` will return true). If `num_coords` is zero, this bit flag gets unset.

## FT_Get_Var_Design_Coordinates

Defined in FT_MULTIPLE_MASTERS_H (freetype/ftmm.h).

      FT_EXPORT( FT_Error )
      FT_Get_Var_Design_Coordinates( FT_Face    face,
                                     FT_UInt    num_coords,
                                     FT_Fixed*  coords );

Get the design coordinates of the currently selected interpolated font.

This function works with all supported variation formats.

#### input

face | A handle to the source face.
num_coords | The number of design coordinates to retrieve. If it is larger than the number of axes, set the excess values to 0.

#### output

coords | The design coordinates array.

#### return

FreeType error code. 0 means success.

#### since

2.7.1

## FT_Set_MM_Blend_Coordinates

Defined in FT_MULTIPLE_MASTERS_H (freetype/ftmm.h).

      FT_EXPORT( FT_Error )
      FT_Set_MM_Blend_Coordinates( FT_Face    face,
                                   FT_UInt    num_coords,
                                   FT_Fixed*  coords );

Choose an interpolated font design through normalized blend coordinates.

This function works with all supported variation formats.

#### inout

face | A handle to the source face.

#### input

num_coords | The number of available design coordinates. If it is larger than the number of axes, ignore the excess values. If it is smaller than the number of axes, use default values for the remaining axes.
coords | The design coordinates array (each element must be between 0 and 1.0 for Adobe MM fonts, and between -1.0 and 1.0 for TrueType GX and OpenType variation fonts).

#### return

FreeType error code. 0 means success.

#### note

[Since 2.8.1] To reset all axes to the default values, call the function with `num_coords` set to zero and `coords` set to `NULL`. [Since 2.9] ‘Default values’ means the currently selected named instance (or the base font if no named instance is selected).

[Since 2.9] If `num_coords` is larger than zero, this function sets the `FT_FACE_FLAG_VARIATION` bit in `FT_Face`'s `face_flags` field (i.e., `FT_IS_VARIATION` will return true). If `num_coords` is zero, this bit flag gets unset.

## FT_Get_MM_Blend_Coordinates

Defined in FT_MULTIPLE_MASTERS_H (freetype/ftmm.h).

      FT_EXPORT( FT_Error )
      FT_Get_MM_Blend_Coordinates( FT_Face    face,
                                   FT_UInt    num_coords,
                                   FT_Fixed*  coords );

Get the normalized blend coordinates of the currently selected interpolated font.

This function works with all supported variation formats.

#### input

face | A handle to the source face.
num_coords | The number of normalized blend coordinates to retrieve. If it is larger than the number of axes, set the excess values to 0.5 for Adobe MM fonts, and to 0 for TrueType GX and OpenType variation fonts.

#### output

coords | The normalized blend coordinates array.

#### return

FreeType error code. 0 means success.

#### since

2.7.1

## FT_Set_Var_Blend_Coordinates

Defined in FT_MULTIPLE_MASTERS_H (freetype/ftmm.h).

      FT_EXPORT( FT_Error )
      FT_Set_Var_Blend_Coordinates( FT_Face    face,
                                    FT_UInt    num_coords,
                                    FT_Fixed*  coords );

This is another name of `FT_Set_MM_Blend_Coordinates`.

## FT_Get_Var_Blend_Coordinates

Defined in FT_MULTIPLE_MASTERS_H (freetype/ftmm.h).

      FT_EXPORT( FT_Error )
      FT_Get_Var_Blend_Coordinates( FT_Face    face,
                                    FT_UInt    num_coords,
                                    FT_Fixed*  coords );

This is another name of `FT_Get_MM_Blend_Coordinates`.

#### since

2.7.1

## FT_Set_MM_WeightVector

Defined in FT_MULTIPLE_MASTERS_H (freetype/ftmm.h).

      FT_EXPORT( FT_Error )
      FT_Set_MM_WeightVector( FT_Face    face,
                              FT_UInt    len,
                              FT_Fixed*  weightvector );

For Adobe MM fonts, choose an interpolated font design by directly setting the weight vector.

This function can't be used with TrueType GX or OpenType variation fonts.

#### inout

face | A handle to the source face.

#### input

len | The length of the weight vector array. If it is larger than the number of designs, the extra values are ignored. If it is less than the number of designs, the remaining values are set to zero.
weightvector | An array representing the weight vector.

#### return

FreeType error code. 0 means success.

#### note

Adobe Multiple Master fonts limit the number of designs, and thus the length of the weight vector to 16.

If `len` is zero and `weightvector` is `NULL`, the weight vector array is reset to the default values.

The Adobe documentation also states that the values in the WeightVector array must total 1.0 ± 0.001. In practice this does not seem to be enforced, so is not enforced here, either.

#### since

2.10

## FT_Get_MM_WeightVector

Defined in FT_MULTIPLE_MASTERS_H (freetype/ftmm.h).

      FT_EXPORT( FT_Error )
      FT_Get_MM_WeightVector( FT_Face    face,
                              FT_UInt*   len,
                              FT_Fixed*  weightvector );

For Adobe MM fonts, retrieve the current weight vector of the font.

This function can't be used with TrueType GX or OpenType variation fonts.

#### inout

face | A handle to the source face.
len | A pointer to the size of the array to be filled. If the size of the array is less than the number of designs, `FT_Err_Invalid_Argument` is returned, and `len` is set to the required size (the number of designs). If the size of the array is greater than the number of designs, the remaining entries are set to 0. On successful completion, `len` is set to the number of designs (i.e., the number of values written to the array).

#### output

weightvector | An array to be filled.

#### return

FreeType error code. 0 means success.

#### note

Adobe Multiple Master fonts limit the number of designs, and thus the length of the WeightVector to 16.

#### since

2.10

## FT_VAR_AXIS_FLAG_XXX

Defined in FT_MULTIPLE_MASTERS_H (freetype/ftmm.h).

    #define FT_VAR_AXIS_FLAG_HIDDEN  1

A list of bit flags used in the return value of `FT_Get_Var_Axis_Flags`.

#### values

FT_VAR_AXIS_FLAG_HIDDEN | The variation axis should not be exposed to user interfaces.

#### since

2.8.1

## FT_Get_Var_Axis_Flags

Defined in FT_MULTIPLE_MASTERS_H (freetype/ftmm.h).

      FT_EXPORT( FT_Error )
      FT_Get_Var_Axis_Flags( FT_MM_Var*  master,
                             FT_UInt     axis_index,
                             FT_UInt*    flags );

Get the ‘flags’ field of an OpenType Variation Axis Record.

Not meaningful for Adobe MM fonts (`*flags` is always zero).

#### input

master | The variation descriptor.
axis_index | The index of the requested variation axis.

#### output

flags | The ‘flags’ field. See `FT_VAR_AXIS_FLAG_XXX` for possible values.

#### return

FreeType error code. 0 means success.

#### since

2.8.1

## FT_Set_Named_Instance

Defined in FT_MULTIPLE_MASTERS_H (freetype/ftmm.h).

      FT_EXPORT( FT_Error )
      FT_Set_Named_Instance( FT_Face  face,
                             FT_UInt  instance_index );

Set or change the current named instance.

#### input

face | A handle to the source face.
instance_index | The index of the requested instance, starting with value 1. If set to value 0, FreeType switches to font access without a named instance.

#### return

FreeType error code. 0 means success.

#### note

The function uses the value of `instance_index` to set bits 16-30 of the face's `face_index` field. It also resets any variation applied to the font, and the `FT_FACE_FLAG_VARIATION` bit of the face's `face_flags` field gets reset to zero (i.e., `FT_IS_VARIATION` will return false).

For Adobe MM fonts (which don't have named instances) this function simply resets the current face to the default instance.

#### since

2.9