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|
/* Pango
* syriac-ot.h: Determine what OpenType features to apply to characters based
* on the rules for Syriac from the OpenType standard.
*
* Copyright (C) 2004 Emil Soleyman-Zomalan
* Author: Emil Soleyman-Zomalan <emil@soleyman.com>
*
* This file is based on the Arabic shaping code from FreeType 1 tree; original
* copyright notice:
*
* The FreeType project -- a free and portable quality TrueType renderer.
*
* Copyright 1996-2000 by
* D. Turner, R.Wilhelm, and W. Lemberg
*
* The code, like the FreeType code it is derived from is dual-licensed
* under the GNU Public License and the FreeType license. See see
* pango/opentype/FT-license.txt for full details of the FreeType
* license.
*/
#include <config.h>
#include "syriac-ot.h"
/* Here a table of the joining classes for characters in the range
* U+0700 - U+074F.
*
* The following character also has a joining class:
*
* U+200C ZERO WIDTH NON-JOINER -> causing
*
* All other characters are given the joining class `none'.
*/
static const JoiningClass syriac[] =
{
/* U+0700 */
none, none, none, none,
none, none, none, none,
none, none, none, none,
none, none, none, transparent,
/* U+0710 */
right, none, dual, dual,
dual, right, right, right,
right, right, dual, dual,
dual, dual, right, dual,
/* U+0720 */
dual, dual, dual, dual,
dual, dual, dual, dual,
right, dual, right, dual,
right, none, none, none,
/* U+0730 */
transparent, transparent, transparent, transparent,
transparent, transparent, transparent, transparent,
transparent, transparent, transparent, transparent,
transparent, transparent, transparent, transparent,
/* U+0740 */
transparent, transparent, transparent, transparent,
transparent, transparent, transparent, transparent,
transparent, transparent, transparent, none,
none, right, dual, dual
};
/* `direction' can be -1, 0, or 1 to indicate the last non-transparent
* glyph, the current glyph, and the next non-transparent glyph,
* respectively.
*/
static JoiningClass
Get_Joining_Class (gunichar* string,
int pos,
int length,
int direction)
{
JoiningClass j;
while (1)
{
if (pos == 0 && direction < 0)
return none;
pos += direction;
if (pos >= length)
return none;
if (string[pos] < 0x0700 ||
string[pos] >= 0x074F)
{
if (string[pos] == 0x200C)
return causing;
else
return none;
}
else
j = syriac[string[pos] - 0x0700];
if (!direction || j != transparent)
return j;
}
}
/* The rules here are roughly based on the Arabic rules from the Unicode
* 2.0 standard (which differ from the Unicode-4.0 rules), augmented
* with the Syriac rules from the Unicode-4.0 standard. The numbers
* R1...R11 below do not correspond to either the Arabic or the Syriac
* rule numbering from the Unicode standard.
*
* Characters are here specified as appearing in the byte stream, i.e.
* *not* in visual order. Joining classes are given in angle brackets,
* glyph forms in square brackets. Glyphs affected by a specific rule are
* enclosed with vertical bars.
*
*
* Glyphs: 0x0715 (Dalath), 0x0716 (Dalath Rish), 0x072A (Rish),
* 0x0722 (Nun), 0x071F (Kaph)
*
*
* R1: <anything1> <transparent> <anything2>
*
* apply joining rules for
* <anything1> <anything2> -> [shape1] [shape2]
* -> [shape1] [isolated] [shape2]
*
*
* R2: <causing|right> <0x0722|0x071F> <!(causing|right|dual)>
* -> [isolated]
*
* The Nun and Kaph characters each have 3 different glyphs
* with two of those glyphs coming at the final position.
* However, one of those final glyphs should really be of the
* isolated glyph form where the preceding character cannot be
* joined to and there is no next character.
*
* This rule exists to combine similar exception for both
* characters without increasing the complexity in the other
* rules.
*
*
* R3: <causing|right|dual> && <!(0x0715|0x0716|0x072A)> |<alaph>|
*
* -> [final2]
*
* If the preceding glyph cannot be joined to the current
* glyph and the preceding character is not a Dalath, Rish,
* or Dotless Dalath Rish, then the Alaph takes this contextual
* position.
*
* The [final2] joining rule is placed ahead of the [final] to
* give it greater precedence when choosing the correct glyph.
* If it comes after the [final] rule, the incorrect glyph is
* inserted into position.
*
*
* R4: <0x0715|0x0715|0x072A> |<alaph>|
*
* -> [final3]
*
* If the previous glyph is a Dalath, Rish, or Dotless Dalath
* Rish, then the Alaph takes this contextual position.
*
* The [final3] joining rule is placed ahead of the [final] to
* give it greater precedence when choosing the correct glyph.
* If it comes after the [final] rule, the incorrect glyph is
* inserted into position.
*
*
* R5: <causing|right|dual> |<right>|
*
* -> [final]
*
*
* R6: <causing|right|dual> |<dual>| <!(causing|right|dual)>
*
* -> [final]
*
*
* R7: <causing|left|dual> |<dual>| <causing|right|dual>
*
* -> [medial]
*
*
* R8: <causing|right> |<alaph>| <causing|right|dual>
*
* -> [medial2]
*
* If the Alaph glyph falls in the middle of a Syriac word and
* the preceding character cannot be joined to, then the Alaph
* takes this contextual position.
*
*
* R9: |<left>| <causing|right|dual>
*
* -> [initial]
*
*
* R10: <!(causing|left|dual)> |<dual>| <causing|right|dual>
*
* -> [initial]
*
*
* R11: <anything> -> [isolated]
*
* This joining rule is placed at the end of these features
* because when it is placed at the beginning of all of them
* it tends to break the cursive nature of Syriac writing --
* it inserts the isolated glyph of each character into that
* position with no joining occurring all throughout a text
* document.
*/
FT_Error
syriac_assign_properties (gunichar *string,
gulong *properties,
int length)
{
JoiningClass previous, current, next;
int i;
if (!string || !properties || length == 0)
return FT_Err_Invalid_Argument;
for (i = 0; i < length; i++)
{
previous = Get_Joining_Class (string, i, length, -1);
current = Get_Joining_Class (string, i, length, 0);
next = Get_Joining_Class (string, i, length, 1);
/* R1 */
if (current == transparent)
{
properties[i] |= isolated_p;
continue;
}
/* R2 */
if (string[i] == 0x0722 ||
string[i] == 0x071F)
if (previous == causing ||
previous == right)
if (!(next == causing ||
next == right ||
next == dual))
{
properties[i] |= isolated_p;
continue;
}
/* R3 */
if (string[i] == 0x0710)
if (previous == causing ||
previous == right)
if (!(string[i - 1] == 0x0715 ||
string[i - 1] == 0x0716 ||
string[i - 1] == 0x072A))
{
properties[i] |= final2_p;
continue;
}
/* R4 */
if (string[i] == 0x0710)
if (previous == causing ||
previous == right)
if (string[i - 1] == 0x0715 ||
string[i - 1] == 0x0716 ||
string[i - 1] == 0x072A)
{
properties[i] |= final3_p;
continue;
}
/* R5 */
if (previous == causing ||
previous == right ||
previous == dual)
if (current == right)
{
properties[i] |= final_p;
continue;
}
/* R6 */
if (previous == causing ||
previous == right ||
previous == dual)
if (current == dual)
if (!(next == causing ||
next == right ||
next == dual ))
{
properties[i] |= final_p;
continue;
}
/* R7 */
if (previous == causing ||
previous == left ||
previous == dual)
if (current == dual)
if (next == causing ||
next == right ||
next == dual )
{
properties[i] |= medial_p;
continue;
}
/* R8 */
if (string[i] == 0x0710)
if (previous == causing ||
previous == right)
if (next == causing ||
next == right ||
next == dual)
{
properties[i] |= medial2_p;
continue;
}
/* R9 */
if (current == left)
if (next == causing ||
next == right ||
next == dual)
{
properties[i] |= initial_p;
continue;
}
/* R10 */
if (!(previous == causing ||
previous == left ||
previous == dual ))
if (current == dual)
if (next == causing ||
next == right ||
next == dual)
{
properties[i] |= initial_p;
continue;
}
/* R11 */
properties[i] |= isolated_p;
}
return FT_Err_Ok;
}
|
