s/NULL/`NULL`/ in documentation.

25 files changed, 107 insertions, 105 deletions

diff --git a/include/freetype/freetype.h b/include/freetype/freetype.h
index 548bf688a..f7d469ffe 100644
--- a/include/freetype/freetype.h
+++ b/include/freetype/freetype.h
@@ -927,7 +927,7 @@ FT_BEGIN_HEADER
    *     denominator used to list fonts.  Some formats (TrueType & OpenType)
    *     provide localized and Unicode versions of this string.  Applications
    *     should use the format-specific interface to access them.  Can be
-   *     NULL (e.g., in fonts embedded in a PDF file).
+   *     `NULL` (e.g., in fonts embedded in a PDF file).
    *
    *     In case the font doesn't provide a specific family name entry,
    *     FreeType tries to synthesize one, deriving it from other name
@@ -937,7 +937,7 @@ FT_BEGIN_HEADER
    *     The face's style name.  This is an ASCII string, usually in English,
    *     that describes the typeface's style (like 'Italic', 'Bold',
    *     'Condensed', etc).  Not all font formats provide a style name, so
-   *     this field is optional, and can be set to NULL.  As for
+   *     this field is optional, and can be set to `NULL`.  As for
    *     `family_name`, some formats provide localized and Unicode versions
    *     of this string.  Applications should use the format-specific
    *     interface to access them.
@@ -949,7 +949,7 @@ FT_BEGIN_HEADER
    *
    *   available_sizes ::
    *     An array of @FT_Bitmap_Size for all bitmap strikes in the face.  It
-   *     is set to NULL if there is no bitmap strike.
+   *     is set to `NULL` if there is no bitmap strike.
    *
    *     Note that FreeType tries to sanitize the strike data since they are
    *     sometimes sloppy or incorrect, but this can easily fail.
@@ -2078,7 +2078,7 @@ FT_BEGIN_HEADER
    *
    *   driver ::
    *     This field is exclusively used by @FT_Open_Face; it simply specifies
-   *     the font driver to use for opening the face.  If set to NULL,
+   *     the font driver to use for opening the face.  If set to `NULL`,
    *     FreeType tries to load the face with each one of the drivers in its
    *     list.
    *
@@ -2149,7 +2149,7 @@ FT_BEGIN_HEADER
    * @output:
    *   aface ::
    *     A handle to a new face object.  If `face_index` is greater than or
-   *     equal to zero, it must be non-NULL.
+   *     equal to zero, it must be non-`NULL`.
    *
    * @return:
    *   FreeType error code.  0~means success.
@@ -2190,7 +2190,7 @@ FT_BEGIN_HEADER
    * @output:
    *   aface ::
    *     A handle to a new face object.  If `face_index` is greater than or
-   *     equal to zero, it must be non-NULL.
+   *     equal to zero, it must be non-`NULL`.
    *
    * @return:
    *   FreeType error code.  0~means success.
@@ -2242,7 +2242,7 @@ FT_BEGIN_HEADER
    *     In general, if the `face_index` argument is negative, the function's
    *     return value is~0 if the font format is recognized, or non-zero
    *     otherwise.  The function allocates a more or less empty face handle
-   *     in `*aface` (if `aface` isn't NULL); the only two useful fields in
+   *     in `*aface` (if `aface` isn't `NULL`); the only two useful fields in
    *     this special case are `face->num_faces` and `face->style_flags`.
    *     For any negative value of `face_index`, `face->num_faces` gives the
    *     number of faces within the font file.  For the negative value
@@ -2255,7 +2255,7 @@ FT_BEGIN_HEADER
    * @output:
    *   aface ::
    *     A handle to a new face object.  If `face_index` is greater than or
-   *     equal to zero, it must be non-NULL.
+   *     equal to zero, it must be non-`NULL`.
    *
    * @return:
    *   FreeType error code.  0~means success.
@@ -3174,10 +3174,10 @@ FT_BEGIN_HEADER
    *
    * @input:
    *   matrix ::
-   *     A pointer to the transformation's 2x2 matrix.  Use NULL for the
+   *     A pointer to the transformation's 2x2 matrix.  Use `NULL` for the
    *     identity matrix.
    *   delta ::
-   *     A pointer to the translation vector.  Use NULL for the null vector.
+   *     A pointer to the translation vector.  Use `NULL` for the null vector.
    *
    * @note:
    *   The transformation is only applied to scalable image formats after the
@@ -3576,7 +3576,7 @@ FT_BEGIN_HEADER
    *     A handle to the source face object.
    *
    * @return:
-   *   A pointer to the face's PostScript name.  NULL if unavailable.
+   *   A pointer to the face's PostScript name.  `NULL` if unavailable.
    *
    * @note:
    *   The returned pointer is owned by the face and is destroyed with it.
@@ -3841,7 +3841,7 @@ FT_BEGIN_HEADER
    *     provided by the 'cff', 'type1', and 't1cid' modules; see
    *     @random-seed).
    *
-   *   Pass NULL as `data` in @FT_Parameter for a given tag to reset the
+   *   Pass `NULL` as `data` in @FT_Parameter for a given tag to reset the
    *   option and use the library or module default again.
    *
    * @input:
@@ -4056,7 +4056,7 @@ FT_BEGIN_HEADER
    *
    *   p ::
    *     An opaque pointer into `COLR` table data.  The caller must set this
-   *     to NULL before the first call of @FT_Get_Color_Glyph_Layer.
+   *     to `NULL` before the first call of @FT_Get_Color_Glyph_Layer.
    */
   typedef struct  FT_LayerIterator_
   {
@@ -4100,8 +4100,8 @@ FT_BEGIN_HEADER
    * @inout:
    *   iterator ::
    *     An @FT_LayerIterator object.  For the first call you should set
-   *     `iterator->p` to NULL.  For all following calls, simply use the same
-   *     object again.
+   *     `iterator->p` to `NULL`.  For all following calls, simply use the
+   *     same object again.
    *
    * @output:
    *   aglyph_index ::
@@ -4422,8 +4422,8 @@ FT_BEGIN_HEADER
    *     A handle to the source face object.
    *
    * @return:
-   *   A pointer to an array of selector code points, or NULL if there is no
-   *   valid variation selector cmap subtable.
+   *   A pointer to an array of selector code points, or `NULL` if there is
+   *   no valid variation selector cmap subtable.
    *
    * @note:
    *   The last item in the array is~0; the array is owned by the @FT_Face
@@ -4455,7 +4455,7 @@ FT_BEGIN_HEADER
    *
    * @return:
    *   A pointer to an array of variation selector code points that are
-   *   active for the given character, or NULL if the corresponding list is
+   *   active for the given character, or `NULL` if the corresponding list is
    *   empty.
    *
    * @note:
@@ -4489,8 +4489,8 @@ FT_BEGIN_HEADER
    *
    * @return:
    *   A list of all the code points that are specified by this selector
-   *   (both default and non-default codes are returned) or NULL if there is
-   *   no valid cmap or the variation selector is invalid.
+   *   (both default and non-default codes are returned) or `NULL` if there
+   *   is no valid cmap or the variation selector is invalid.
    *
    * @note:
    *   The last item in the array is~0; the array is owned by the @FT_Face
diff --git a/include/freetype/ftbdf.h b/include/freetype/ftbdf.h
index f860e079d..cc80d89b5 100644
--- a/include/freetype/ftbdf.h
+++ b/include/freetype/ftbdf.h
@@ -106,8 +106,8 @@ FT_BEGIN_HEADER
    *      The property type.
    *
    *    u.atom ::
-   *      The atom string, if type is @BDF_PROPERTY_TYPE_ATOM.  May be NULL,
-   *      indicating an empty string.
+   *      The atom string, if type is @BDF_PROPERTY_TYPE_ATOM.  May be
+   *      `NULL`, indicating an empty string.
    *
    *    u.integer ::
    *      A signed integer, if type is @BDF_PROPERTY_TYPE_INTEGER.
diff --git a/include/freetype/ftcache.h b/include/freetype/ftcache.h
index 7daa85932..217fc415d 100644
--- a/include/freetype/ftcache.h
+++ b/include/freetype/ftcache.h
@@ -155,7 +155,7 @@ FT_BEGIN_HEADER
    *   containing a font file path, and face index.
    *
    * @note:
-   *   Never use NULL as a valid @FTC_FaceID.
+   *   Never use `NULL` as a valid @FTC_FaceID.
    *
    *   Face IDs are passed by the client to the cache manager that calls,
    *   when needed, the @FTC_Face_Requester to translate them into new
@@ -588,7 +588,7 @@ FT_BEGIN_HEADER
    *
    * @output:
    *   acache ::
-   *     A new cache handle.  NULL in case of error.
+   *     A new cache handle.  `NULL` in case of error.
    *
    * @return:
    *   FreeType error code.  0~means success.
@@ -772,14 +772,14 @@ FT_BEGIN_HEADER
    *   Never try to transform or discard it manually!  You can however create
    *   a copy with @FT_Glyph_Copy and modify the new one.
    *
-   *   If `anode` is _not_ NULL, it receives the address of the cache node
+   *   If `anode` is _not_ `NULL`, it receives the address of the cache node
    *   containing the glyph image, after increasing its reference count.
    *   This ensures that the node (as well as the @FT_Glyph) will always be
    *   kept in the cache until you call @FTC_Node_Unref to 'release' it.
    *
-   *   If `anode` is NULL, the cache node is left unchanged, which means that
-   *   the @FT_Glyph could be flushed out of the cache on the next call to
-   *   one of the caching sub-system APIs.  Don't assume that it is
+   *   If `anode` is `NULL`, the cache node is left unchanged, which means
+   *   that the @FT_Glyph could be flushed out of the cache on the next call
+   *   to one of the caching sub-system APIs.  Don't assume that it is
    *   persistent!
    */
   FT_EXPORT( FT_Error )
@@ -828,14 +828,14 @@ FT_BEGIN_HEADER
    *   Never try to transform or discard it manually!  You can however create
    *   a copy with @FT_Glyph_Copy and modify the new one.
    *
-   *   If `anode` is _not_ NULL, it receives the address of the cache node
+   *   If `anode` is _not_ `NULL`, it receives the address of the cache node
    *   containing the glyph image, after increasing its reference count.
    *   This ensures that the node (as well as the @FT_Glyph) will always be
    *   kept in the cache until you call @FTC_Node_Unref to 'release' it.
    *
-   *   If `anode` is NULL, the cache node is left unchanged, which means that
-   *   the @FT_Glyph could be flushed out of the cache on the next call to
-   *   one of the caching sub-system APIs.  Don't assume that it is
+   *   If `anode` is `NULL`, the cache node is left unchanged, which means
+   *   that the @FT_Glyph could be flushed out of the cache on the next call
+   *   to one of the caching sub-system APIs.  Don't assume that it is
    *   persistent!
    *
    *   Calls to @FT_Set_Char_Size and friends have no effect on cached
@@ -950,7 +950,7 @@ FT_BEGIN_HEADER
    *
    * @output:
    *   acache ::
-   *     A handle to the new sbit cache.  NULL in case of error.
+   *     A handle to the new sbit cache.  `NULL` in case of error.
    *
    * @return:
    *   FreeType error code.  0~means success.
@@ -999,14 +999,15 @@ FT_BEGIN_HEADER
    *   The descriptor's `buffer` field is set to~0 to indicate a missing
    *   glyph bitmap.
    *
-   *   If `anode` is _not_ NULL, it receives the address of the cache node
+   *   If `anode` is _not_ `NULL`, it receives the address of the cache node
    *   containing the bitmap, after increasing its reference count.  This
    *   ensures that the node (as well as the image) will always be kept in
    *   the cache until you call @FTC_Node_Unref to 'release' it.
    *
-   *   If `anode` is NULL, the cache node is left unchanged, which means that
-   *   the bitmap could be flushed out of the cache on the next call to one
-   *   of the caching sub-system APIs.  Don't assume that it is persistent!
+   *   If `anode` is `NULL`, the cache node is left unchanged, which means
+   *   that the bitmap could be flushed out of the cache on the next call to
+   *   one of the caching sub-system APIs.  Don't assume that it is
+   *   persistent!
    */
   FT_EXPORT( FT_Error )
   FTC_SBitCache_Lookup( FTC_SBitCache    cache,
@@ -1058,14 +1059,15 @@ FT_BEGIN_HEADER
    *   The descriptor's `buffer` field is set to~0 to indicate a missing
    *   glyph bitmap.
    *
-   *   If `anode` is _not_ NULL, it receives the address of the cache node
+   *   If `anode` is _not_ `NULL`, it receives the address of the cache node
    *   containing the bitmap, after increasing its reference count.  This
    *   ensures that the node (as well as the image) will always be kept in
    *   the cache until you call @FTC_Node_Unref to 'release' it.
    *
-   *   If `anode` is NULL, the cache node is left unchanged, which means that
-   *   the bitmap could be flushed out of the cache on the next call to one
-   *   of the caching sub-system APIs.  Don't assume that it is persistent!
+   *   If `anode` is `NULL`, the cache node is left unchanged, which means
+   *   that the bitmap could be flushed out of the cache on the next call to
+   *   one of the caching sub-system APIs.  Don't assume that it is
+   *   persistent!
    */
   FT_EXPORT( FT_Error )
   FTC_SBitCache_LookupScaler( FTC_SBitCache  cache,
diff --git a/include/freetype/ftcolor.h b/include/freetype/ftcolor.h
index 842bd6312..f88eb1827 100644
--- a/include/freetype/ftcolor.h
+++ b/include/freetype/ftcolor.h
@@ -132,7 +132,7 @@ FT_BEGIN_HEADER
    *     An empty name ID in the `CPAL` table gets represented as value
    *     0xFFFF.
    *
-   *     NULL if the font's `CPAL` table doesn't contain appropriate data.
+   *     `NULL` if the font's `CPAL` table doesn't contain appropriate data.
    *
    *   palette_flags ::
    *     A read-only array of palette flags with `num_palettes` elements.
@@ -140,7 +140,7 @@ FT_BEGIN_HEADER
    *     @FT_PALETTE_FOR_LIGHT_BACKGROUND and
    *     @FT_PALETTE_FOR_DARK_BACKGROUND.
    *
-   *     NULL if the font's `CPAL` table doesn't contain appropriate data.
+   *     `NULL` if the font's `CPAL` table doesn't contain appropriate data.
    *
    *   num_palette_entries ::
    *     The number of entries in a single palette.  All palettes have the
@@ -157,7 +157,7 @@ FT_BEGIN_HEADER
    *     An empty entry name ID in the `CPAL` table gets represented as value
    *     0xFFFF.
    *
-   *     NULL if the font's `CPAL` table doesn't contain appropriate data.
+   *     `NULL` if the font's `CPAL` table doesn't contain appropriate data.
    *
    * @note:
    *   Use function @FT_Get_Sfnt_Name to map name IDs and entry name IDs to
@@ -240,10 +240,10 @@ FT_BEGIN_HEADER
    *   apalette ::
    *     An array of color entries for a palette with index `palette_index`,
    *     having `num_palette_entries` elements (as found in the
-   *     `FT_Palette_Data` structure).  If `apalette` is set to NULL, no
+   *     `FT_Palette_Data` structure).  If `apalette` is set to `NULL`, no
    *     array gets returned (and no color entries can be modified).
    *
-   *     In case the font doesn't support color palettes, NULL is returned.
+   *     In case the font doesn't support color palettes, `NULL` is returned.
    *
    * @return:
    *   FreeType error code.  0~means success.
diff --git a/include/freetype/ftfntfmt.h b/include/freetype/ftfntfmt.h
index 6ca183c45..43cd47e9f 100644
--- a/include/freetype/ftfntfmt.h
+++ b/include/freetype/ftfntfmt.h
@@ -69,7 +69,7 @@ FT_BEGIN_HEADER
    *    Input face handle.
    *
    * @return:
-   *  Font format string.  NULL in case of error.
+   *  Font format string.  `NULL` in case of error.
    *
    * @note:
    *  A deprecated name for the same function is `FT_Get_X11_Font_Format`.
diff --git a/include/freetype/ftgxval.h b/include/freetype/ftgxval.h
index adedea7eb..5aa606d41 100644
--- a/include/freetype/ftgxval.h
+++ b/include/freetype/ftgxval.h
@@ -217,7 +217,7 @@ FT_BEGIN_HEADER
    *   otherwise.
    *
    *   After use, the application should deallocate the buffers pointed to by
-   *   each `tables` element, by calling @FT_TrueTypeGX_Free.  A NULL value
+   *   each `tables` element, by calling @FT_TrueTypeGX_Free.  A `NULL` value
    *   indicates that the table either doesn't exist in the font, the
    *   application hasn't asked for validation, or the validator doesn't have
    *   the ability to validate the sfnt table.
@@ -311,7 +311,7 @@ FT_BEGIN_HEADER
    *
    * @note:
    *   After use, the application should deallocate the buffers pointed to by
-   *   `ckern_table`, by calling @FT_ClassicKern_Free.  A NULL value
+   *   `ckern_table`, by calling @FT_ClassicKern_Free.  A `NULL` value
    *   indicates that the table doesn't exist in the font.
    */
   FT_EXPORT( FT_Error )
diff --git a/include/freetype/ftimage.h b/include/freetype/ftimage.h
index 81d1cfa3e..f468cea39 100644
--- a/include/freetype/ftimage.h
+++ b/include/freetype/ftimage.h
@@ -1105,7 +1105,7 @@ FT_BEGIN_HEADER
    *
    *   pool_base ::
    *     Previously, the address in memory of the render pool.  Set this to
-   *     NULL.
+   *     `NULL`.
    *
    *   pool_size ::
    *     Previously, the size in bytes of the render pool.  Set this to 0.
diff --git a/include/freetype/ftlist.h b/include/freetype/ftlist.h
index e127ac286..582a7cfe6 100644
--- a/include/freetype/ftlist.h
+++ b/include/freetype/ftlist.h
@@ -90,7 +90,7 @@ FT_BEGIN_HEADER
    *     The address of the listed object.
    *
    * @return:
-   *   List node.  NULL if it wasn't found.
+   *   List node.  `NULL` if it wasn't found.
    */
   FT_EXPORT( FT_ListNode )
   FT_List_Find( FT_List  list,
@@ -267,7 +267,7 @@ FT_BEGIN_HEADER
    *
    *   destroy ::
    *     A list destructor that will be applied to each element of the list.
-   *     Set this to NULL if not needed.
+   *     Set this to `NULL` if not needed.
    *
    *   memory ::
    *     The current memory object that handles deallocation.
diff --git a/include/freetype/ftmm.h b/include/freetype/ftmm.h
index 7c6b40502..db99ef88b 100644
--- a/include/freetype/ftmm.h
+++ b/include/freetype/ftmm.h
@@ -356,7 +356,7 @@ FT_BEGIN_HEADER
    *
    * @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.
+   *   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
@@ -397,7 +397,7 @@ FT_BEGIN_HEADER
    *
    * @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.
+   *   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).
    *
@@ -478,7 +478,7 @@ FT_BEGIN_HEADER
    *
    * @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.
+   *   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).
    *
@@ -593,7 +593,7 @@ FT_BEGIN_HEADER
    *   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
+   *   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
diff --git a/include/freetype/ftotval.h b/include/freetype/ftotval.h
index 12bcc89bd..e18588bd4 100644
--- a/include/freetype/ftotval.h
+++ b/include/freetype/ftotval.h
@@ -157,7 +157,7 @@ FT_BEGIN_HEADER
    *   otherwise.
    *
    *   After use, the application should deallocate the five tables with
-   *   @FT_OpenType_Free.  A NULL value indicates that the table either
+   *   @FT_OpenType_Free.  A `NULL` value indicates that the table either
    *   doesn't exist in the font, or the application hasn't asked for
    *   validation.
    */
diff --git a/include/freetype/ftpfr.h b/include/freetype/ftpfr.h
index c2df2736a..4435aa6fe 100644
--- a/include/freetype/ftpfr.h
+++ b/include/freetype/ftpfr.h
@@ -64,21 +64,21 @@ FT_BEGIN_HEADER
    * @output:
    *    aoutline_resolution ::
    *      Outline resolution.  This is equivalent to `face->units_per_EM` for
-   *      non-PFR fonts.  Optional (parameter can be NULL).
+   *      non-PFR fonts.  Optional (parameter can be `NULL`).
    *
    *    ametrics_resolution ::
    *      Metrics resolution.  This is equivalent to `outline_resolution` for
-   *      non-PFR fonts.  Optional (parameter can be NULL).
+   *      non-PFR fonts.  Optional (parameter can be `NULL`).
    *
    *    ametrics_x_scale ::
    *      A 16.16 fixed-point number used to scale distance expressed in
    *      metrics units to device subpixels.  This is equivalent to
    *      `face->size->x_scale`, but for metrics only.  Optional (parameter
-   *      can be NULL).
+   *      can be `NULL`).
    *
    *    ametrics_y_scale ::
    *      Same as `ametrics_x_scale` but for the vertical direction.
-   *      optional (parameter can be NULL).
+   *      optional (parameter can be `NULL`).
    *
    * @return:
    *    FreeType error code.  0~means success.
diff --git a/include/freetype/ftrender.h b/include/freetype/ftrender.h
index eefdb69dc..4cb48eee9 100644
--- a/include/freetype/ftrender.h
+++ b/include/freetype/ftrender.h
@@ -226,7 +226,7 @@ FT_BEGIN_HEADER
    *   This doesn't change the current renderer for other formats.
    *
    *   Currently, no FreeType renderer module uses `parameters`; you should
-   *   thus always pass NULL as the value.
+   *   thus always pass `NULL` as the value.
    */
   FT_EXPORT( FT_Error )
   FT_Set_Renderer( FT_Library     library,
diff --git a/include/freetype/ftsnames.h b/include/freetype/ftsnames.h
index f37e82b71..de6858b06 100644
--- a/include/freetype/ftsnames.h
+++ b/include/freetype/ftsnames.h
@@ -96,7 +96,7 @@ FT_BEGIN_HEADER
    *   string ::
    *     The 'name' string.  Note that its format differs depending on the
    *     (platform,encoding) pair, being either a string of bytes (without a
-   *     terminating NULL byte) or containing UTF-16BE entities.
+   *     terminating `NULL` byte) or containing UTF-16BE entities.
    *
    *   string_len ::
    *     The length of `string` in bytes.
@@ -194,8 +194,8 @@ FT_BEGIN_HEADER
    *
    * @fields:
    *   string ::
-   *     The language tag string, encoded in UTF-16BE (without trailing NULL
-   *     bytes).
+   *     The language tag string, encoded in UTF-16BE (without trailing
+   *     `NULL` bytes).
    *
    *   string_len ::
    *     The length of `string` in **bytes**.
diff --git a/include/freetype/ftstroke.h b/include/freetype/ftstroke.h
index ad6560dda..811fbf77d 100644
--- a/include/freetype/ftstroke.h
+++ b/include/freetype/ftstroke.h
@@ -264,7 +264,7 @@ FT_BEGIN_HEADER
    *
    * @output:
    *   astroker ::
-   *     A new stroker object handle.  NULL in case of error.
+   *     A new stroker object handle.  `NULL` in case of error.
    *
    * @return:
    *    FreeType error code.  0~means success.
@@ -674,7 +674,7 @@ FT_BEGIN_HEADER
    *
    * @input:
    *   stroker ::
-   *     A stroker handle.  Can be NULL.
+   *     A stroker handle.  Can be `NULL`.
    */
   FT_EXPORT( void )
   FT_Stroker_Done( FT_Stroker  stroker );
diff --git a/include/freetype/ftsystem.h b/include/freetype/ftsystem.h
index c71898065..b9e833afd 100644
--- a/include/freetype/ftsystem.h
+++ b/include/freetype/ftsystem.h
@@ -281,7 +281,7 @@ FT_BEGIN_HEADER
    * @input:
    *   base ::
    *     For memory-based streams, this is the address of the first stream
-   *     byte in memory.  This field should always be set to NULL for
+   *     byte in memory.  This field should always be set to `NULL` for
    *     disk-based streams.
    *
    *   size ::
diff --git a/include/freetype/fttypes.h b/include/freetype/fttypes.h
index 67aa719d1..ee0576cbc 100644
--- a/include/freetype/fttypes.h
+++ b/include/freetype/fttypes.h
@@ -461,8 +461,8 @@ FT_BEGIN_HEADER
    *
    *   finalizer ::
    *     A pointer to a 'generic finalizer' function, which will be called
-   *     when the object is destroyed.  If this field is set to NULL, no code
-   *     will be called.
+   *     when the object is destroyed.  If this field is set to `NULL`, no
+   *     code will be called.
    */
   typedef struct  FT_Generic_
   {
@@ -544,10 +544,10 @@ FT_BEGIN_HEADER
    *
    * @fields:
    *   prev ::
-   *     The previous element in the list.  NULL if first.
+   *     The previous element in the list.  `NULL` if first.
    *
    *   next ::
-   *     The next element in the list.  NULL if last.
+   *     The next element in the list.  `NULL` if last.
    *
    *   data ::
    *     A typeless pointer to the listed object.
diff --git a/include/freetype/internal/ftdebug.h b/include/freetype/internal/ftdebug.h
index 228f03011..9988784b7 100644
--- a/include/freetype/internal/ftdebug.h
+++ b/include/freetype/internal/ftdebug.h
@@ -135,8 +135,8 @@ FT_BEGIN_HEADER
    *
    * @return:
    *   The name of the trace component.  This is a statically allocated
-   *   C~string, so do not free it after use.  NULL if FreeType is not built
-   *   with FT_DEBUG_LEVEL_TRACE definition.
+   *   C~string, so do not free it after use.  `NULL` if FreeType is not
+   *   built with FT_DEBUG_LEVEL_TRACE definition.
    *
    * @note:
    *   Use @FT_Trace_Get_Count to get the number of available trace
diff --git a/include/freetype/internal/ftrfork.h b/include/freetype/internal/ftrfork.h
index 01e8a9030..1ce1b0b2c 100644
--- a/include/freetype/internal/ftrfork.h
+++ b/include/freetype/internal/ftrfork.h
@@ -118,8 +118,8 @@ FT_BEGIN_HEADER
    * @output:
    *   new_names ::
    *     An array of guessed file names in which the resource forks may
-   *     exist.  If 'new_names[N]' is NULL, the guessed file name is equal to
-   *     `base_name`.
+   *     exist.  If 'new_names[N]' is `NULL`, the guessed file name is equal
+   *     to `base_name`.
    *
    *   offsets ::
    *     An array of guessed file offsets.  'offsets[N]' holds the file
diff --git a/include/freetype/internal/ftserv.h b/include/freetype/internal/ftserv.h
index 33e0b4f30..21f6a2631 100644
--- a/include/freetype/internal/ftserv.h
+++ b/include/freetype/internal/ftserv.h
@@ -54,7 +54,7 @@ FT_BEGIN_HEADER
    *
    * @output:
    *   ptr ::
-   *     A variable that receives the service pointer.  Will be NULL if not
+   *     A variable that receives the service pointer.  Will be `NULL` if not
    *     found.
    */
 #ifdef __cplusplus
@@ -106,7 +106,7 @@ FT_BEGIN_HEADER
    *
    * @output:
    *   ptr ::
-   *     A variable that receives the service pointer.  Will be NULL if not
+   *     A variable that receives the service pointer.  Will be `NULL` if not
    *     found.
    */
 #ifdef __cplusplus
@@ -426,7 +426,7 @@ FT_BEGIN_HEADER
    *
    * @output:
    *   ptr ::
-   *     A variable receiving the service data.  NULL if not available.
+   *     A variable receiving the service data.  `NULL` if not available.
    */
 #ifdef __cplusplus
 
diff --git a/include/freetype/internal/services/svpostnm.h b/include/freetype/internal/services/svpostnm.h
index 67106d1c2..53156af6a 100644
--- a/include/freetype/internal/services/svpostnm.h
+++ b/include/freetype/internal/services/svpostnm.h
@@ -26,9 +26,9 @@ FT_BEGIN_HEADER
 
   /*
    * A trivial service used to retrieve the PostScript name of a given font
-   * when available.  The `get_name' field should never be NULL.
+   * when available.  The `get_name' field should never be `NULL`.
    *
-   * The corresponding function can return NULL to indicate that the
+   * The corresponding function can return `NULL` to indicate that the
    * PostScript name is not available.
    *
    * The name is owned by the face and will be destroyed with it.
diff --git a/include/freetype/internal/services/svpscmap.h b/include/freetype/internal/services/svpscmap.h
index 3ef0f6b31..8691a9a65 100644
--- a/include/freetype/internal/services/svpscmap.h
+++ b/include/freetype/internal/services/svpscmap.h
@@ -35,13 +35,13 @@ FT_BEGIN_HEADER
   (*PS_Unicode_ValueFunc)( const char*  glyph_name );
 
   /*
-   * Macintosh name id to glyph name.  NULL if invalid index.
+   * Macintosh name id to glyph name.  `NULL` if invalid index.
    */
   typedef const char*
   (*PS_Macintosh_NameFunc)( FT_UInt  name_index );
 
   /*
-   * Adobe standard string ID to glyph name.  NULL if invalid index.
+   * Adobe standard string ID to glyph name.  `NULL` if invalid index.
    */
   typedef const char*
   (*PS_Adobe_Std_StringsFunc)( FT_UInt  string_index );
@@ -70,8 +70,8 @@ FT_BEGIN_HEADER
 
 
   /*
-   * A function which returns a glyph name for a given index.  Returns NULL
-   * if invalid index.
+   * A function which returns a glyph name for a given index.  Returns
+   * `NULL` if invalid index.
    */
   typedef const char*
   (*PS_GetGlyphNameFunc)( FT_Pointer  data,
diff --git a/include/freetype/internal/sfnt.h b/include/freetype/internal/sfnt.h
index 7cdad648f..5b6f5f8af 100644
--- a/include/freetype/internal/sfnt.h
+++ b/include/freetype/internal/sfnt.h
@@ -160,13 +160,13 @@ FT_BEGIN_HEADER
    *   length ::
    *     The address of the decision variable:
    *
-   *     If length == NULL: Loads the whole table.  Returns an error if
+   *     If `length == NULL`: Loads the whole table.  Returns an error if
    *     'offset' == 0!
    *
-   *     If *length == 0: Exits immediately; returning the length of the
+   *     If `*length == 0`: Exits immediately; returning the length of the
    *     given table or of the font file, depending on the value of 'tag'.
    *
-   *     If *length != 0: Loads the next 'length' bytes of table or font,
+   *     If `*length != 0`: Loads the next 'length' bytes of table or font,
    *     starting at offset 'offset' (in table or font too).
    *
    * @output:
@@ -382,7 +382,7 @@ FT_BEGIN_HEADER
    *     The glyph index.
    *
    *   PSname ::
-   *     The address of a string pointer.  Will be NULL in case of error,
+   *     The address of a string pointer.  Will be `NULL` in case of error,
    *     otherwise it is a pointer to the glyph name.
    *
    *     You must not modify the returned string!
@@ -498,8 +498,8 @@ FT_BEGIN_HEADER
    * @inout:
    *   iterator ::
    *     An @FT_LayerIterator object.  For the first call you should set
-   *     `iterator->p` to NULL.  For all following calls, simply use the same
-   *     object again.
+   *     `iterator->p` to `NULL`.  For all following calls, simply use the
+   *     same object again.
    *
    * @output:
    *   aglyph_index ::
@@ -579,7 +579,7 @@ FT_BEGIN_HEADER
    *
    * @inout:
    *   name ::
-   *     The address of an allocated string pointer.  NULL if no name is
+   *     The address of an allocated string pointer.  `NULL` if no name is
    *     present.
    *
    * @return:
diff --git a/include/freetype/internal/tttypes.h b/include/freetype/internal/tttypes.h
index 268bb7b85..24f2e46a8 100644
--- a/include/freetype/internal/tttypes.h
+++ b/include/freetype/internal/tttypes.h
@@ -1485,12 +1485,12 @@ FT_BEGIN_HEADER
    *     indices used in the font's sbit table.
    *
    *   cpal ::
-   *     A pointer to data related to the 'CPAL' table.  NULL if the table is
-   *     not available.
+   *     A pointer to data related to the 'CPAL' table.  `NULL` if the table
+   *     is not available.
    *
    *   colr ::
-   *     A pointer to data related to the 'COLR' table.  NULL if the table is
-   *     not available.
+   *     A pointer to data related to the 'COLR' table.  `NULL` if the table
+   *     is not available.
    *
    *   kern_table ::
    *     A pointer to the 'kern' table.
diff --git a/include/freetype/t1tables.h b/include/freetype/t1tables.h
index 81da156a4..307a4166f 100644
--- a/include/freetype/t1tables.h
+++ b/include/freetype/t1tables.h
@@ -499,7 +499,7 @@ FT_BEGIN_HEADER
    * @note:
    *    String pointers within the @PS_FontInfoRec structure are owned by the
    *    face and don't need to be freed by the caller.  Missing entries in
-   *    the font's FontInfo dictionary are represented by NULL pointers.
+   *    the font's FontInfo dictionary are represented by `NULL` pointers.
    *
    *    If the font's format is not PostScript-based, this function will
    *    return the `FT_Err_Invalid_Argument` error code.
@@ -733,7 +733,7 @@ FT_BEGIN_HEADER
    *    `value` is a void pointer because the values returned can be of
    *    various types.
    *
-   *    If either `value` is NULL or `value_len` is too small, just the
+   *    If either `value` is `NULL` or `value_len` is too small, just the
    *    required memory size for the requested entry is returned.
    *
    *    The `idx` parameter is used, not only to retrieve elements of, for
diff --git a/include/freetype/tttables.h b/include/freetype/tttables.h
index c30609fb5..20b8c8884 100644
--- a/include/freetype/tttables.h
+++ b/include/freetype/tttables.h
@@ -659,9 +659,9 @@ FT_BEGIN_HEADER
    *     The index of the SFNT table.
    *
    * @return:
-   *   A type-less pointer to the table.  This will be NULL in case of error,
-   *   or if the corresponding table was not found **OR** loaded from the
-   *   file.
+   *   A type-less pointer to the table.  This will be `NULL` in case of
+   *   error, or if the corresponding table was not found **OR** loaded from
+   *   the file.
    *
    *   Use a typecast according to `tag` to access the structure elements.
    *
@@ -716,7 +716,7 @@ FT_BEGIN_HEADER
    *
    * @inout:
    *   length ::
-   *     If the `length` parameter is NULL, try to load the whole table.
+   *     If the `length` parameter is `NULL`, try to load the whole table.
    *     Return an error code if it fails.
    *
    *     Else, if `*length` is~0, exit immediately while returning the
@@ -778,9 +778,9 @@ FT_BEGIN_HEADER
    *
    * @inout:
    *   tag ::
-   *     The name tag of the SFNT table.  If the value is NULL, `table_index`
-   *     is ignored, and `length` returns the number of SFNT tables in the
-   *     font.
+   *     The name tag of the SFNT table.  If the value is `NULL`,
+   *     `table_index` is ignored, and `length` returns the number of SFNT
+   *     tables in the font.
    *
    * @output:
    *   length ::