Document and replace some magic values in sft/ttcr (vcl)

Change-Id: Id9c3f96acb7b93c7ef215ae33d98ad17ef45095c
Reviewed-on: https://gerrit.libreoffice.org/80719
Reviewed-by: Khaled Hosny <khaledhosny@eglug.org>
Tested-by: Jenkins

1 files changed, 216 insertions, 0 deletions

diff --git a/vcl/inc/sft.hxx b/vcl/inc/sft.hxx
index aa81dcd151cb..39bc2ecfd421 100644
--- a/vcl/inc/sft.hxx
+++ b/vcl/inc/sft.hxx
@@ -185,6 +185,222 @@ namespace vcl
 
     struct TrueTypeFont;
 
+/*
+  Some table OS/2 consts
+  quick history:
+  OpenType has been created from TrueType
+  - original TrueType had an OS/2 table with a length of 68 bytes
+  (cf https://developer.apple.com/fonts/TrueType-Reference-Manual/RM06/Chap6OS2.html)
+  - There have been 6 versions (from version 0 to 5)
+  (cf https://docs.microsoft.com/en-us/typography/opentype/otspec140/os2ver0)
+
+  For the record:
+  // From Initial TrueType version
+  TYPE       NAME                       FROM BYTE
+  uint16     version                    0
+  int16      xAvgCharWidth              2
+  uint16     usWeightClass              4
+  uint16     usWidthClass               6
+  uint16     fsType                     8
+  int16      ySubscriptXSize           10
+  int16      ySubscriptYSize           12
+  int16      ySubscriptXOffset         14
+  int16      ySubscriptYOffset         16
+  int16      ySuperscriptXSize         18
+  int16      ySuperscriptYSize         20
+  int16      ySuperscriptXOffset       22
+  int16      ySuperscriptYOffset       24
+  int16      yStrikeoutSize            26
+  int16      yStrikeoutPosition        28
+  int16      sFamilyClass              30
+  uint8      panose[10]                32
+  uint32     ulUnicodeRange1           42
+  uint32     ulUnicodeRange2           46
+  uint32     ulUnicodeRange3           50
+  uint32     ulUnicodeRange4           54
+  Tag        achVendID                 58
+  uint16     fsSelection               62
+  uint16     usFirstCharIndex          64
+  uint16     usLastCharIndex           66
+
+  // From Version 0 of OpenType
+  int16      sTypoAscender             68
+  int16      sTypoDescender            70
+  int16      sTypoLineGap              72
+  uint16     usWinAscent               74
+  uint16     usWinDescent              76
+
+  => length for OpenType version 0 = 78 bytes
+
+  // From Version 1 of OpenType
+  uint32     ulCodePageRange1          78
+  uint32     ulCodePageRange2          82
+
+  => length for OpenType version 1 = 86 bytes
+
+  // From Version 2 of OpenType
+  // (idem for Versions 3 and 4)
+  int16      sxHeight                  86
+  int16      sCapHeight                88
+  uint16     usDefaultChar             90
+  uint16     usBreakChar               92
+  uint16     usMaxContext              94
+
+  => length for OpenType version 2, 3 and 4 = 96 bytes
+
+  // From Version 5 of OpenType
+  uint16     usLowerOpticalPointSize   96
+  uint16     usUpperOpticalPointSize   98
+  END                                 100
+
+  => length for OS/2 table version 5 = 100 bytes
+
+*/
+static const int OS2_Legacy_length = 68;
+static const int OS2_V0_length = 78;
+static const int OS2_V1_length = 86;
+
+static const int OS2_usWeightClass_offset = 4;
+static const int OS2_usWidthClass_offset = 6;
+static const int OS2_fsType_offset = 8;
+static const int OS2_panose_offset = 32;
+static const int OS2_panoseNbBytes_offset = 10;
+static const int OS2_ulUnicodeRange1_offset = 42;
+static const int OS2_ulUnicodeRange2_offset = 46;
+static const int OS2_ulUnicodeRange3_offset = 50;
+static const int OS2_ulUnicodeRange4_offset = 54;
+static const int OS2_fsSelection_offset = 62;
+static const int OS2_typoAscender_offset = 68;
+static const int OS2_typoDescender_offset = 70;
+static const int OS2_typoLineGap_offset = 72;
+static const int OS2_winAscent_offset = 74;
+static const int OS2_winDescent_offset = 76;
+static const int OS2_ulCodePageRange1_offset = 78;
+static const int OS2_ulCodePageRange2_offset = 82;
+
+/*
+  Some table hhea consts
+  cf https://docs.microsoft.com/fr-fr/typography/opentype/spec/hhea
+  TYPE       NAME                       FROM BYTE
+  uint16     majorVersion               0
+  uint16     minorVersion               2
+  FWORD      ascender                   4
+  FWORD      descender                  6
+  FWORD      lineGap                    8
+  UFWORD     advanceWidthMax           10
+  FWORD      minLeftSideBearing        12
+  FWORD      minRightSideBearing       14
+  FWORD      xMaxExtent                16
+  int16      caretSlopeRise            18
+  int16      caretSlopeRun             20
+  int16      caretOffset               22
+  int16      (reserved)                24
+  int16      (reserved)                26
+  int16      (reserved)                28
+  int16      (reserved)                30
+  int16      metricDataFormat          32
+  uint16     numberOfHMetrics          34
+  END                                  36
+
+  => length for hhea table = 36 bytes
+
+*/
+static const int HHEA_Length = 36;
+
+static const int HHEA_ascender_offset = 4;
+static const int HHEA_descender_offset = 6;
+static const int HHEA_lineGap_offset = 8;
+static const int HHEA_caretSlopeRise_offset = 18;
+static const int HHEA_caretSlopeRun_offset = 20;
+
+/*
+  Some table post consts
+  cf https://docs.microsoft.com/fr-fr/typography/opentype/spec/post
+  TYPE       NAME                       FROM BYTE
+  Fixed      version                    0
+  Fixed      italicAngle                4
+  FWord      underlinePosition          8
+  FWord      underlineThickness        10
+  uint32     isFixedPitch              12
+  ...
+
+*/
+static const int POST_italicAngle_offset = 4;
+static const int POST_underlinePosition_offset = 8;
+static const int POST_underlineThickness_offset = 10;
+static const int POST_isFixedPitch_offset = 12;
+
+/*
+  Some table head consts
+  cf https://docs.microsoft.com/fr-fr/typography/opentype/spec/head
+  TYPE       NAME                       FROM BYTE
+  uit16      majorVersion               0
+  uit16      minorVersion               2
+  Fixed      fontRevision               4
+  uint32     checkSumAdjustment         8
+  uint32     magicNumber               12 (= 0x5F0F3CF5)
+  uint16     flags                     16
+  uint16     unitsPerEm                18
+  LONGDATETIME created                 20
+  LONGDATETIME modified                28
+  int16      xMin                      36
+  int16      yMin                      38
+  int16      xMax                      40
+  int16      yMax                      42
+  uint16     macStyle                  44
+  uint16     lowestRecPPEM             46
+  int16      fontDirectionHint         48
+  int16      indexToLocFormat          50
+  int16      glyphDataFormat           52
+
+  END                                  54
+
+  => length head table = 54 bytes
+*/
+static const int HEAD_Length_offset = 54;
+
+static const int HEAD_majorVersion_offset = 0;
+static const int HEAD_fontRevision_offset = 4;
+static const int HEAD_magicNumber_offset = 12;
+static const int HEAD_flags_offset = 16;
+static const int HEAD_unitsPerEm_offset = 18;
+static const int HEAD_created_offset = 20;
+static const int HEAD_xMin_offset = 36;
+static const int HEAD_yMin_offset = 38;
+static const int HEAD_xMax_offset = 40;
+static const int HEAD_yMax_offset = 42;
+static const int HEAD_macStyle_offset = 44;
+static const int HEAD_lowestRecPPEM_offset = 46;
+static const int HEAD_fontDirectionHint_offset = 48;
+static const int HEAD_indexToLocFormat_offset = 50;
+static const int HEAD_glyphDataFormat_offset = 52;
+
+/*
+  Some table maxp consts
+  cf https://docs.microsoft.com/fr-fr/typography/opentype/spec/maxp
+  For 0.5 version
+  TYPE       NAME                       FROM BYTE
+  Fixed      version                    0
+  uint16     numGlyphs                  4
+
+  For 1.0 Version
+  Fixed      version                    0
+  uint16     numGlyphs                  4
+  uint16     maxPoints                  6
+  uint16     maxContours                8
+  uint16     maxCompositePoints        10
+  uint16     maxCompositeContours      12
+  ...
+
+*/
+static const int MAXP_Version1Length_offset = 32;
+
+static const int MAXP_numGlyphs_offset = 4;
+static const int MAXP_maxPoints_offset = 6;
+static const int MAXP_maxContours_offset = 8;
+static const int MAXP_maxCompositePoints_offset = 10;
+static const int MAXP_maxCompositeContours_offset = 12;
+
 /**
  * @defgroup sft Sun Font Tools Exported Functions
  */