vim-patch:8.1.1038: Arabic support excludes Farsi (#19285)

Problem:    Arabic support excludes Farsi.
Solution:   Add Farsi support to the Arabic support. (Ali Gholami Rudi,
            Ameretat Reith)
https://github.com/vim/vim/commit/dc4fa190e7b9d6ba49416ce875d2192c4444d3eb

Omit Test_shape_final_to_medial(): removed in later patches.

5 files changed, 189 insertions, 894 deletions

diff --git a/src/nvim/arabic.c b/src/nvim/arabic.c
index 130ce65b86..06536e6e2b 100644
--- a/src/nvim/arabic.c
+++ b/src/nvim/arabic.c
@@ -5,6 +5,13 @@
 ///
 /// Functions for Arabic language.
 ///
+/// Author: Nadim Shaikli & Isam Bayazidi
+/// Farsi support and restructuring to make adding new letters easier by Ali
+/// Gholami Rudi.  Further work by Ameretat Reith.
+
+/// Sorted list of unicode Arabic characters.  Each entry holds the
+/// presentation forms of a letter.
+///
 /// Arabic characters are categorized into following types:
 ///
 /// Isolated    - iso-8859-6 form         char denoted with  a_*
@@ -19,12 +26,7 @@
 #include "nvim/ascii.h"
 #include "nvim/vim.h"
 
-// Arabic ISO-10646-1 character set definition
-
-// Arabic ISO-8859-6 (subset of 10646; 0600 - 06FF)
-#define a_COMMA                         0x060C
-#define a_SEMICOLON                     0x061B
-#define a_QUESTION                      0x061F
+// Unicode values for Arabic characters.
 #define a_HAMZA                         0x0621
 #define a_ALEF_MADDA                    0x0622
 #define a_ALEF_HAMZA_ABOVE              0x0623
@@ -62,7 +64,6 @@
 #define a_WAW                           0x0648
 #define a_ALEF_MAKSURA                  0x0649
 #define a_YEH                           0x064a
-
 #define a_FATHATAN                      0x064b
 #define a_DAMMATAN                      0x064c
 #define a_KASRATAN                      0x064d
@@ -71,168 +72,17 @@
 #define a_KASRA                         0x0650
 #define a_SHADDA                        0x0651
 #define a_SUKUN                         0x0652
-
 #define a_MADDA_ABOVE                   0x0653
 #define a_HAMZA_ABOVE                   0x0654
 #define a_HAMZA_BELOW                   0x0655
 
-#define a_ZERO                          0x0660
-#define a_ONE                           0x0661
-#define a_TWO                           0x0662
-#define a_THREE                         0x0663
-#define a_FOUR                          0x0664
-#define a_FIVE                          0x0665
-#define a_SIX                           0x0666
-#define a_SEVEN                         0x0667
-#define a_EIGHT                         0x0668
-#define a_NINE                          0x0669
-#define a_PERCENT                       0x066a
-#define a_DECIMAL                       0x066b
-#define a_THOUSANDS                     0x066c
-#define a_STAR                          0x066d
-#define a_MINI_ALEF                     0x0670
-// Rest of 8859-6 does not relate to Arabic
+#define a_PEH                           0x067e
+#define a_TCHEH                         0x0686
+#define a_JEH                           0x0698
+#define a_FKAF                          0x06a9
+#define a_GAF                           0x06af
+#define a_FYEH                          0x06cc
 
-// Arabic Presentation Form-B (subset of 10646; FE70 - FEFF)
-//
-//  s -> isolated
-//  i -> initial
-//  m -> medial
-//  f -> final
-#define a_s_FATHATAN                    0xfe70
-#define a_m_TATWEEL_FATHATAN            0xfe71
-#define a_s_DAMMATAN                    0xfe72
-
-#define a_s_KASRATAN                    0xfe74
-
-#define a_s_FATHA                       0xfe76
-#define a_m_FATHA                       0xfe77
-#define a_s_DAMMA                       0xfe78
-#define a_m_DAMMA                       0xfe79
-#define a_s_KASRA                       0xfe7a
-#define a_m_KASRA                       0xfe7b
-#define a_s_SHADDA                      0xfe7c
-#define a_m_SHADDA                      0xfe7d
-#define a_s_SUKUN                       0xfe7e
-#define a_m_SUKUN                       0xfe7f
-
-#define a_s_HAMZA                       0xfe80
-#define a_s_ALEF_MADDA                  0xfe81
-#define a_f_ALEF_MADDA                  0xfe82
-#define a_s_ALEF_HAMZA_ABOVE            0xfe83
-#define a_f_ALEF_HAMZA_ABOVE            0xfe84
-#define a_s_WAW_HAMZA                   0xfe85
-#define a_f_WAW_HAMZA                   0xfe86
-#define a_s_ALEF_HAMZA_BELOW            0xfe87
-#define a_f_ALEF_HAMZA_BELOW            0xfe88
-#define a_s_YEH_HAMZA                   0xfe89
-#define a_f_YEH_HAMZA                   0xfe8a
-#define a_i_YEH_HAMZA                   0xfe8b
-#define a_m_YEH_HAMZA                   0xfe8c
-#define a_s_ALEF                        0xfe8d
-#define a_f_ALEF                        0xfe8e
-#define a_s_BEH                         0xfe8f
-#define a_f_BEH                         0xfe90
-#define a_i_BEH                         0xfe91
-#define a_m_BEH                         0xfe92
-#define a_s_TEH_MARBUTA                 0xfe93
-#define a_f_TEH_MARBUTA                 0xfe94
-#define a_s_TEH                         0xfe95
-#define a_f_TEH                         0xfe96
-#define a_i_TEH                         0xfe97
-#define a_m_TEH                         0xfe98
-#define a_s_THEH                        0xfe99
-#define a_f_THEH                        0xfe9a
-#define a_i_THEH                        0xfe9b
-#define a_m_THEH                        0xfe9c
-#define a_s_JEEM                        0xfe9d
-#define a_f_JEEM                        0xfe9e
-#define a_i_JEEM                        0xfe9f
-#define a_m_JEEM                        0xfea0
-#define a_s_HAH                         0xfea1
-#define a_f_HAH                         0xfea2
-#define a_i_HAH                         0xfea3
-#define a_m_HAH                         0xfea4
-#define a_s_KHAH                        0xfea5
-#define a_f_KHAH                        0xfea6
-#define a_i_KHAH                        0xfea7
-#define a_m_KHAH                        0xfea8
-#define a_s_DAL                         0xfea9
-#define a_f_DAL                         0xfeaa
-#define a_s_THAL                        0xfeab
-#define a_f_THAL                        0xfeac
-#define a_s_REH                         0xfead
-#define a_f_REH                         0xfeae
-#define a_s_ZAIN                        0xfeaf
-#define a_f_ZAIN                        0xfeb0
-#define a_s_SEEN                        0xfeb1
-#define a_f_SEEN                        0xfeb2
-#define a_i_SEEN                        0xfeb3
-#define a_m_SEEN                        0xfeb4
-#define a_s_SHEEN                       0xfeb5
-#define a_f_SHEEN                       0xfeb6
-#define a_i_SHEEN                       0xfeb7
-#define a_m_SHEEN                       0xfeb8
-#define a_s_SAD                         0xfeb9
-#define a_f_SAD                         0xfeba
-#define a_i_SAD                         0xfebb
-#define a_m_SAD                         0xfebc
-#define a_s_DAD                         0xfebd
-#define a_f_DAD                         0xfebe
-#define a_i_DAD                         0xfebf
-#define a_m_DAD                         0xfec0
-#define a_s_TAH                         0xfec1
-#define a_f_TAH                         0xfec2
-#define a_i_TAH                         0xfec3
-#define a_m_TAH                         0xfec4
-#define a_s_ZAH                         0xfec5
-#define a_f_ZAH                         0xfec6
-#define a_i_ZAH                         0xfec7
-#define a_m_ZAH                         0xfec8
-#define a_s_AIN                         0xfec9
-#define a_f_AIN                         0xfeca
-#define a_i_AIN                         0xfecb
-#define a_m_AIN                         0xfecc
-#define a_s_GHAIN                       0xfecd
-#define a_f_GHAIN                       0xfece
-#define a_i_GHAIN                       0xfecf
-#define a_m_GHAIN                       0xfed0
-#define a_s_FEH                         0xfed1
-#define a_f_FEH                         0xfed2
-#define a_i_FEH                         0xfed3
-#define a_m_FEH                         0xfed4
-#define a_s_QAF                         0xfed5
-#define a_f_QAF                         0xfed6
-#define a_i_QAF                         0xfed7
-#define a_m_QAF                         0xfed8
-#define a_s_KAF                         0xfed9
-#define a_f_KAF                         0xfeda
-#define a_i_KAF                         0xfedb
-#define a_m_KAF                         0xfedc
-#define a_s_LAM                         0xfedd
-#define a_f_LAM                         0xfede
-#define a_i_LAM                         0xfedf
-#define a_m_LAM                         0xfee0
-#define a_s_MEEM                        0xfee1
-#define a_f_MEEM                        0xfee2
-#define a_i_MEEM                        0xfee3
-#define a_m_MEEM                        0xfee4
-#define a_s_NOON                        0xfee5
-#define a_f_NOON                        0xfee6
-#define a_i_NOON                        0xfee7
-#define a_m_NOON                        0xfee8
-#define a_s_HEH                         0xfee9
-#define a_f_HEH                         0xfeea
-#define a_i_HEH                         0xfeeb
-#define a_m_HEH                         0xfeec
-#define a_s_WAW                         0xfeed
-#define a_f_WAW                         0xfeee
-#define a_s_ALEF_MAKSURA                0xfeef
-#define a_f_ALEF_MAKSURA                0xfef0
-#define a_s_YEH                         0xfef1
-#define a_f_YEH                         0xfef2
-#define a_i_YEH                         0xfef3
-#define a_m_YEH                         0xfef4
 #define a_s_LAM_ALEF_MADDA_ABOVE        0xfef5
 #define a_f_LAM_ALEF_MADDA_ABOVE        0xfef6
 #define a_s_LAM_ALEF_HAMZA_ABOVE        0xfef7
@@ -242,664 +92,201 @@
 #define a_s_LAM_ALEF                    0xfefb
 #define a_f_LAM_ALEF                    0xfefc
 
+static struct achar {
+  unsigned c;
+  unsigned isolated;
+  unsigned initial;
+  unsigned medial;
+  unsigned final;
+} achars[] = {
+  { a_HAMZA, 0xfe80, 0, 0, 0 },
+  { a_ALEF_MADDA, 0xfe81, 0, 0, 0xfe82 },
+  { a_ALEF_HAMZA_ABOVE, 0xfe83, 0, 0, 0xfe84 },
+  { a_WAW_HAMZA, 0xfe85, 0, 0, 0xfe86 },
+  { a_ALEF_HAMZA_BELOW, 0xfe87, 0, 0, 0xfe88 },
+  { a_YEH_HAMZA, 0xfe89, 0xfe8b, 0xfe8c, 0xfe8a },
+  { a_ALEF, 0xfe8d, 0, 0, 0xfe8e },
+  { a_BEH, 0xfe8f, 0xfe91, 0xfe92, 0xfe90 },
+  { a_TEH_MARBUTA, 0xfe93, 0, 0, 0xfe94 },
+  { a_TEH, 0xfe95, 0xfe97, 0xfe98, 0xfe96 },
+  { a_THEH, 0xfe99, 0xfe9b, 0xfe9c, 0xfe9a },
+  { a_JEEM, 0xfe9d, 0xfe9f, 0xfea0, 0xfe9e },
+  { a_HAH, 0xfea1, 0xfea3, 0xfea4, 0xfea2 },
+  { a_KHAH, 0xfea5, 0xfea7, 0xfea8, 0xfea6 },
+  { a_DAL, 0xfea9, 0, 0, 0xfeaa },
+  { a_THAL, 0xfeab, 0, 0, 0xfeac },
+  { a_REH, 0xfead, 0, 0, 0xfeae },
+  { a_ZAIN, 0xfeaf, 0, 0, 0xfeb0 },
+  { a_SEEN, 0xfeb1, 0xfeb3, 0xfeb4, 0xfeb2 },
+  { a_SHEEN, 0xfeb5, 0xfeb7, 0xfeb8, 0xfeb6 },
+  { a_SAD, 0xfeb9, 0xfebb, 0xfebc, 0xfeba },
+  { a_DAD, 0xfebd, 0xfebf, 0xfec0, 0xfebe },
+  { a_TAH, 0xfec1, 0xfec3, 0xfec4, 0xfec2 },
+  { a_ZAH, 0xfec5, 0xfec7, 0xfec8, 0xfec6 },
+  { a_AIN, 0xfec9, 0xfecb, 0xfecc, 0xfeca },
+  { a_GHAIN, 0xfecd, 0xfecf, 0xfed0, 0xfece },
+  { a_TATWEEL, 0, 0x0640, 0x0640, 0x0640 },
+  { a_FEH, 0xfed1, 0xfed3, 0xfed4, 0xfed2 },
+  { a_QAF, 0xfed5, 0xfed7, 0xfed8, 0xfed6 },
+  { a_KAF, 0xfed9, 0xfedb, 0xfedc, 0xfeda },
+  { a_LAM, 0xfedd, 0xfedf, 0xfee0, 0xfede },
+  { a_MEEM, 0xfee1, 0xfee3, 0xfee4, 0xfee2 },
+  { a_NOON, 0xfee5, 0xfee7, 0xfee8, 0xfee6 },
+  { a_HEH, 0xfee9, 0xfeeb, 0xfeec, 0xfeea },
+  { a_WAW, 0xfeed, 0, 0, 0xfeee },
+  { a_ALEF_MAKSURA, 0xfeef, 0, 0, 0xfef0 },
+  { a_YEH, 0xfef1, 0xfef3, 0xfef4, 0xfef2 },
+  { a_FATHATAN, 0xfe70, 0, 0, 0 },
+  { a_DAMMATAN, 0xfe72, 0, 0, 0 },
+  { a_KASRATAN, 0xfe74, 0, 0, 0 },
+  { a_FATHA, 0xfe76, 0, 0xfe77, 0 },
+  { a_DAMMA, 0xfe78, 0, 0xfe79, 0 },
+  { a_KASRA, 0xfe7a, 0, 0xfe7b, 0 },
+  { a_SHADDA, 0xfe7c, 0, 0xfe7c, 0 },
+  { a_SUKUN, 0xfe7e, 0, 0xfe7f, 0 },
+  { a_MADDA_ABOVE, 0, 0, 0, 0 },
+  { a_HAMZA_ABOVE, 0, 0, 0, 0 },
+  { a_HAMZA_BELOW, 0, 0, 0, 0 },
+  { a_PEH, 0xfb56, 0xfb58, 0xfb59, 0xfb57 },
+  { a_TCHEH, 0xfb7a, 0xfb7c, 0xfb7d, 0xfb7b },
+  { a_JEH, 0xfb8a, 0, 0, 0xfb8b },
+  { a_FKAF, 0xfb8e, 0xfb90, 0xfb91, 0xfb8f },
+  { a_GAF, 0xfb92, 0xfb94, 0xfb95, 0xfb93 },
+  { a_FYEH, 0xfbfc, 0xfbfe, 0xfbff, 0xfbfd },
+};
+
 #define a_BYTE_ORDER_MARK               0xfeff
 
 #ifdef INCLUDE_GENERATED_DECLARATIONS
 # include "arabic.c.generated.h"
 #endif
 
-// Returns true if c is an ISO-8859-6 shaped ARABIC letter (user entered).
-static bool A_is_a(int cur_c)
-{
-  switch (cur_c) {
-  case a_HAMZA:
-  case a_ALEF_MADDA:
-  case a_ALEF_HAMZA_ABOVE:
-  case a_WAW_HAMZA:
-  case a_ALEF_HAMZA_BELOW:
-  case a_YEH_HAMZA:
-  case a_ALEF:
-  case a_BEH:
-  case a_TEH_MARBUTA:
-  case a_TEH:
-  case a_THEH:
-  case a_JEEM:
-  case a_HAH:
-  case a_KHAH:
-  case a_DAL:
-  case a_THAL:
-  case a_REH:
-  case a_ZAIN:
-  case a_SEEN:
-  case a_SHEEN:
-  case a_SAD:
-  case a_DAD:
-  case a_TAH:
-  case a_ZAH:
-  case a_AIN:
-  case a_GHAIN:
-  case a_TATWEEL:
-  case a_FEH:
-  case a_QAF:
-  case a_KAF:
-  case a_LAM:
-  case a_MEEM:
-  case a_NOON:
-  case a_HEH:
-  case a_WAW:
-  case a_ALEF_MAKSURA:
-  case a_YEH:
-    return true;
-  }
-
-  return false;
-}
-
-// Returns true if c is an Isolated Form-B ARABIC letter
-static bool A_is_s(int cur_c)
+/// Find the struct achar pointer to the given Arabic char.
+/// Returns NULL if not found.
+static struct achar *find_achar(int c)
 {
-  switch (cur_c) {
-  case a_s_HAMZA:
-  case a_s_ALEF_MADDA:
-  case a_s_ALEF_HAMZA_ABOVE:
-  case a_s_WAW_HAMZA:
-  case a_s_ALEF_HAMZA_BELOW:
-  case a_s_YEH_HAMZA:
-  case a_s_ALEF:
-  case a_s_BEH:
-  case a_s_TEH_MARBUTA:
-  case a_s_TEH:
-  case a_s_THEH:
-  case a_s_JEEM:
-  case a_s_HAH:
-  case a_s_KHAH:
-  case a_s_DAL:
-  case a_s_THAL:
-  case a_s_REH:
-  case a_s_ZAIN:
-  case a_s_SEEN:
-  case a_s_SHEEN:
-  case a_s_SAD:
-  case a_s_DAD:
-  case a_s_TAH:
-  case a_s_ZAH:
-  case a_s_AIN:
-  case a_s_GHAIN:
-  case a_s_FEH:
-  case a_s_QAF:
-  case a_s_KAF:
-  case a_s_LAM:
-  case a_s_MEEM:
-  case a_s_NOON:
-  case a_s_HEH:
-  case a_s_WAW:
-  case a_s_ALEF_MAKSURA:
-  case a_s_YEH:
-    return true;
+  // using binary search to find c
+  int h = ARRAY_SIZE(achars);
+  int l = 0;
+  while (l < h) {
+    int m = (h + l) / 2;
+    if (achars[m].c == (unsigned)c) {
+      return &achars[m];
+    }
+    if ((unsigned)c < achars[m].c) {
+      h = m;
+    } else {
+      l = m + 1;
+    }
   }
-
-  return false;
+  return NULL;
 }
 
-// Returns true if c is a Final shape of an ARABIC letter
-static bool A_is_f(int cur_c)
+/// Change shape - from Combination (2 char) to an Isolated
+static int chg_c_laa2i(int hid_c)
 {
-  switch (cur_c) {
-  case a_f_ALEF_MADDA:
-  case a_f_ALEF_HAMZA_ABOVE:
-  case a_f_WAW_HAMZA:
-  case a_f_ALEF_HAMZA_BELOW:
-  case a_f_YEH_HAMZA:
-  case a_f_ALEF:
-  case a_f_BEH:
-  case a_f_TEH_MARBUTA:
-  case a_f_TEH:
-  case a_f_THEH:
-  case a_f_JEEM:
-  case a_f_HAH:
-  case a_f_KHAH:
-  case a_f_DAL:
-  case a_f_THAL:
-  case a_f_REH:
-  case a_f_ZAIN:
-  case a_f_SEEN:
-  case a_f_SHEEN:
-  case a_f_SAD:
-  case a_f_DAD:
-  case a_f_TAH:
-  case a_f_ZAH:
-  case a_f_AIN:
-  case a_f_GHAIN:
-  case a_f_FEH:
-  case a_f_QAF:
-  case a_f_KAF:
-  case a_f_LAM:
-  case a_f_MEEM:
-  case a_f_NOON:
-  case a_f_HEH:
-  case a_f_WAW:
-  case a_f_ALEF_MAKSURA:
-  case a_f_YEH:
-  case a_f_LAM_ALEF_MADDA_ABOVE:
-  case a_f_LAM_ALEF_HAMZA_ABOVE:
-  case a_f_LAM_ALEF_HAMZA_BELOW:
-  case a_f_LAM_ALEF:
-    return true;
-  }
-  return false;
-}
+  int tempc;
 
-// Change shape - from ISO-8859-6/Isolated to Form-B Isolated
-static int chg_c_a2s(int cur_c)
-{
-  switch (cur_c) {
-  case a_HAMZA:
-    return a_s_HAMZA;
+  switch (hid_c) {
   case a_ALEF_MADDA:
-    return a_s_ALEF_MADDA;
+    tempc = a_s_LAM_ALEF_MADDA_ABOVE;
+    break;
   case a_ALEF_HAMZA_ABOVE:
-    return a_s_ALEF_HAMZA_ABOVE;
-  case a_WAW_HAMZA:
-    return a_s_WAW_HAMZA;
+    tempc = a_s_LAM_ALEF_HAMZA_ABOVE;
+    break;
   case a_ALEF_HAMZA_BELOW:
-    return a_s_ALEF_HAMZA_BELOW;
-  case a_YEH_HAMZA:
-    return a_s_YEH_HAMZA;
+    tempc = a_s_LAM_ALEF_HAMZA_BELOW;
+    break;
   case a_ALEF:
-    return a_s_ALEF;
-  case a_TEH_MARBUTA:
-    return a_s_TEH_MARBUTA;
-  case a_DAL:
-    return a_s_DAL;
-  case a_THAL:
-    return a_s_THAL;
-  case a_REH:
-    return a_s_REH;
-  case a_ZAIN:
-    return a_s_ZAIN;
-  case a_TATWEEL:
-    return cur_c;   // exceptions
-  case a_WAW:
-    return a_s_WAW;
-  case a_ALEF_MAKSURA:
-    return a_s_ALEF_MAKSURA;
-  case a_BEH:
-    return a_s_BEH;
-  case a_TEH:
-    return a_s_TEH;
-  case a_THEH:
-    return a_s_THEH;
-  case a_JEEM:
-    return a_s_JEEM;
-  case a_HAH:
-    return a_s_HAH;
-  case a_KHAH:
-    return a_s_KHAH;
-  case a_SEEN:
-    return a_s_SEEN;
-  case a_SHEEN:
-    return a_s_SHEEN;
-  case a_SAD:
-    return a_s_SAD;
-  case a_DAD:
-    return a_s_DAD;
-  case a_TAH:
-    return a_s_TAH;
-  case a_ZAH:
-    return a_s_ZAH;
-  case a_AIN:
-    return a_s_AIN;
-  case a_GHAIN:
-    return a_s_GHAIN;
-  case a_FEH:
-    return a_s_FEH;
-  case a_QAF:
-    return a_s_QAF;
-  case a_KAF:
-    return a_s_KAF;
-  case a_LAM:
-    return a_s_LAM;
-  case a_MEEM:
-    return a_s_MEEM;
-  case a_NOON:
-    return a_s_NOON;
-  case a_HEH:
-    return a_s_HEH;
-  case a_YEH:
-    return a_s_YEH;
+    tempc = a_s_LAM_ALEF;
+    break;
+  default:
+    tempc = 0;
   }
-  return 0;
-}
 
-// Change shape - from ISO-8859-6/Isolated to Initial
-static int chg_c_a2i(int cur_c)
-{
-  switch (cur_c) {
-  case a_YEH_HAMZA:
-    return a_i_YEH_HAMZA;
-  case a_HAMZA:
-    return a_s_HAMZA;  // exceptions
-  case a_ALEF_MADDA:
-    return a_s_ALEF_MADDA;  // exceptions
-  case a_ALEF_HAMZA_ABOVE:
-    return a_s_ALEF_HAMZA_ABOVE;  // exceptions
-  case a_WAW_HAMZA:
-    return a_s_WAW_HAMZA;  // exceptions
-  case a_ALEF_HAMZA_BELOW:
-    return a_s_ALEF_HAMZA_BELOW;  // exceptions
-  case a_ALEF:
-    return a_s_ALEF;  // exceptions
-  case a_TEH_MARBUTA:
-    return a_s_TEH_MARBUTA;  // exceptions
-  case a_DAL:
-    return a_s_DAL;  // exceptions
-  case a_THAL:
-    return a_s_THAL;  // exceptions
-  case a_REH:
-    return a_s_REH;  // exceptions
-  case a_ZAIN:
-    return a_s_ZAIN;  // exceptions
-  case a_TATWEEL:
-    return cur_c;  // exceptions
-  case a_WAW:
-    return a_s_WAW;  // exceptions
-  case a_ALEF_MAKSURA:
-    return a_s_ALEF_MAKSURA;  // exceptions
-  case a_BEH:
-    return a_i_BEH;
-  case a_TEH:
-    return a_i_TEH;
-  case a_THEH:
-    return a_i_THEH;
-  case a_JEEM:
-    return a_i_JEEM;
-  case a_HAH:
-    return a_i_HAH;
-  case a_KHAH:
-    return a_i_KHAH;
-  case a_SEEN:
-    return a_i_SEEN;
-  case a_SHEEN:
-    return a_i_SHEEN;
-  case a_SAD:
-    return a_i_SAD;
-  case a_DAD:
-    return a_i_DAD;
-  case a_TAH:
-    return a_i_TAH;
-  case a_ZAH:
-    return a_i_ZAH;
-  case a_AIN:
-    return a_i_AIN;
-  case a_GHAIN:
-    return a_i_GHAIN;
-  case a_FEH:
-    return a_i_FEH;
-  case a_QAF:
-    return a_i_QAF;
-  case a_KAF:
-    return a_i_KAF;
-  case a_LAM:
-    return a_i_LAM;
-  case a_MEEM:
-    return a_i_MEEM;
-  case a_NOON:
-    return a_i_NOON;
-  case a_HEH:
-    return a_i_HEH;
-  case a_YEH:
-    return a_i_YEH;
-  }
-  return 0;
+  return tempc;
 }
 
-// Change shape - from ISO-8859-6/Isolated to Medial
-static int chg_c_a2m(int cur_c)
+/// Change shape - from Combination-Isolated to Final
+static int chg_c_laa2f(int hid_c)
 {
-  switch (cur_c) {
-  case a_HAMZA:
-    return a_s_HAMZA;  // exception
+  int tempc;
+
+  switch (hid_c) {
   case a_ALEF_MADDA:
-    return a_f_ALEF_MADDA;    // exception
+    tempc = a_f_LAM_ALEF_MADDA_ABOVE;
+    break;
   case a_ALEF_HAMZA_ABOVE:
-    return a_f_ALEF_HAMZA_ABOVE;    // exception
-  case a_WAW_HAMZA:
-    return a_f_WAW_HAMZA;  // exception
+    tempc = a_f_LAM_ALEF_HAMZA_ABOVE;
+    break;
   case a_ALEF_HAMZA_BELOW:
-    return a_f_ALEF_HAMZA_BELOW;    // exception
-  case a_YEH_HAMZA:
-    return a_m_YEH_HAMZA;
+    tempc = a_f_LAM_ALEF_HAMZA_BELOW;
+    break;
   case a_ALEF:
-    return a_f_ALEF;    // exception
-  case a_BEH:
-    return a_m_BEH;
-  case a_TEH_MARBUTA:
-    return a_f_TEH_MARBUTA;  // exception
-  case a_TEH:
-    return a_m_TEH;
-  case a_THEH:
-    return a_m_THEH;
-  case a_JEEM:
-    return a_m_JEEM;
-  case a_HAH:
-    return a_m_HAH;
-  case a_KHAH:
-    return a_m_KHAH;
-  case a_DAL:
-    return a_f_DAL;  // exception
-  case a_THAL:
-    return a_f_THAL;    // exception
-  case a_REH:
-    return a_f_REH;  // exception
-  case a_ZAIN:
-    return a_f_ZAIN;    // exception
-  case a_SEEN:
-    return a_m_SEEN;
-  case a_SHEEN:
-    return a_m_SHEEN;
-  case a_SAD:
-    return a_m_SAD;
-  case a_DAD:
-    return a_m_DAD;
-  case a_TAH:
-    return a_m_TAH;
-  case a_ZAH:
-    return a_m_ZAH;
-  case a_AIN:
-    return a_m_AIN;
-  case a_GHAIN:
-    return a_m_GHAIN;
-  case a_TATWEEL:
-    return cur_c;    // exception
-  case a_FEH:
-    return a_m_FEH;
-  case a_QAF:
-    return a_m_QAF;
-  case a_KAF:
-    return a_m_KAF;
-  case a_LAM:
-    return a_m_LAM;
-  case a_MEEM:
-    return a_m_MEEM;
-  case a_NOON:
-    return a_m_NOON;
-  case a_HEH:
-    return a_m_HEH;
-  case a_WAW:
-    return a_f_WAW;  // exception
-  case a_ALEF_MAKSURA:
-    return a_f_ALEF_MAKSURA;    // exception
-  case a_YEH:
-    return a_m_YEH;
+    tempc = a_f_LAM_ALEF;
+    break;
+  default:
+    tempc = 0;
   }
-  return 0;
+
+  return tempc;
 }
 
-// Change shape - from ISO-8859-6/Isolated to final
-static int chg_c_a2f(int cur_c)
+/// Returns whether it is possible to join the given letters
+static int can_join(int c1, int c2)
 {
-  // NOTE: these encodings need to be accounted for
-  //
-  // a_f_ALEF_MADDA;
-  // a_f_ALEF_HAMZA_ABOVE;
-  // a_f_ALEF_HAMZA_BELOW;
-  // a_f_LAM_ALEF_MADDA_ABOVE;
-  // a_f_LAM_ALEF_HAMZA_ABOVE;
-  // a_f_LAM_ALEF_HAMZA_BELOW;
+  struct achar *a1 = find_achar(c1);
+  struct achar *a2 = find_achar(c2);
 
-  switch (cur_c) {
-  case a_HAMZA:
-    return a_s_HAMZA;  // exception
-  case a_ALEF_MADDA:
-    return a_f_ALEF_MADDA;
-  case a_ALEF_HAMZA_ABOVE:
-    return a_f_ALEF_HAMZA_ABOVE;
-  case a_WAW_HAMZA:
-    return a_f_WAW_HAMZA;
-  case a_ALEF_HAMZA_BELOW:
-    return a_f_ALEF_HAMZA_BELOW;
-  case a_YEH_HAMZA:
-    return a_f_YEH_HAMZA;
-  case a_ALEF:
-    return a_f_ALEF;
-  case a_BEH:
-    return a_f_BEH;
-  case a_TEH_MARBUTA:
-    return a_f_TEH_MARBUTA;
-  case a_TEH:
-    return a_f_TEH;
-  case a_THEH:
-    return a_f_THEH;
-  case a_JEEM:
-    return a_f_JEEM;
-  case a_HAH:
-    return a_f_HAH;
-  case a_KHAH:
-    return a_f_KHAH;
-  case a_DAL:
-    return a_f_DAL;
-  case a_THAL:
-    return a_f_THAL;
-  case a_REH:
-    return a_f_REH;
-  case a_ZAIN:
-    return a_f_ZAIN;
-  case a_SEEN:
-    return a_f_SEEN;
-  case a_SHEEN:
-    return a_f_SHEEN;
-  case a_SAD:
-    return a_f_SAD;
-  case a_DAD:
-    return a_f_DAD;
-  case a_TAH:
-    return a_f_TAH;
-  case a_ZAH:
-    return a_f_ZAH;
-  case a_AIN:
-    return a_f_AIN;
-  case a_GHAIN:
-    return a_f_GHAIN;
-  case a_TATWEEL:
-    return cur_c;   // exception
-  case a_FEH:
-    return a_f_FEH;
-  case a_QAF:
-    return a_f_QAF;
-  case a_KAF:
-    return a_f_KAF;
-  case a_LAM:
-    return a_f_LAM;
-  case a_MEEM:
-    return a_f_MEEM;
-  case a_NOON:
-    return a_f_NOON;
-  case a_HEH:
-    return a_f_HEH;
-  case a_WAW:
-    return a_f_WAW;
-  case a_ALEF_MAKSURA:
-    return a_f_ALEF_MAKSURA;
-  case a_YEH:
-    return a_f_YEH;
-  }
-  return 0;
+  return a1 && a2 && (a1->initial || a1->medial) && (a2->final || a2->medial);
 }
 
-// Change shape - from Initial to Medial
-// This code is unreachable, because for the relevant characters ARABIC_CHAR()
-// is FALSE;
-#if 0
-static int chg_c_i2m(int cur_c)
+/// Check whether we are dealing with a character that could be regarded as an
+/// Arabic combining character, need to check the character before this.
+bool arabic_maycombine(int two)
+  FUNC_ATTR_PURE
 {
-  switch (cur_c) {
-  case a_i_YEH_HAMZA:
-    return a_m_YEH_HAMZA;
-  case a_i_BEH:
-    return a_m_BEH;
-  case a_i_TEH:
-    return a_m_TEH;
-  case a_i_THEH:
-    return a_m_THEH;
-  case a_i_JEEM:
-    return a_m_JEEM;
-  case a_i_HAH:
-    return a_m_HAH;
-  case a_i_KHAH:
-    return a_m_KHAH;
-  case a_i_SEEN:
-    return a_m_SEEN;
-  case a_i_SHEEN:
-    return a_m_SHEEN;
-  case a_i_SAD:
-    return a_m_SAD;
-  case a_i_DAD:
-    return a_m_DAD;
-  case a_i_TAH:
-    return a_m_TAH;
-  case a_i_ZAH:
-    return a_m_ZAH;
-  case a_i_AIN:
-    return a_m_AIN;
-  case a_i_GHAIN:
-    return a_m_GHAIN;
-  case a_i_FEH:
-    return a_m_FEH;
-  case a_i_QAF:
-    return a_m_QAF;
-  case a_i_KAF:
-    return a_m_KAF;
-  case a_i_LAM:
-    return a_m_LAM;
-  case a_i_MEEM:
-    return a_m_MEEM;
-  case a_i_NOON:
-    return a_m_NOON;
-  case a_i_HEH:
-    return a_m_HEH;
-  case a_i_YEH:
-    return a_m_YEH;
+  if (p_arshape && !p_tbidi) {
+    return two == a_ALEF_MADDA
+           || two == a_ALEF_HAMZA_ABOVE
+           || two == a_ALEF_HAMZA_BELOW
+           || two == a_ALEF;
   }
-  return 0;
+  return false;
 }
-#endif
 
-// Change shape - from Final to Medial
-static int chg_c_f2m(int cur_c)
+/// Check whether we are dealing with Arabic combining characters.
+/// Note: these are NOT really composing characters!
+///
+/// @param one First character.
+/// @param two Character just after "one".
+bool arabic_combine(int one, int two)
+  FUNC_ATTR_PURE
 {
-  switch (cur_c) {
-  // NOTE: these encodings are multi-positional, no ?
-  // case a_f_ALEF_MADDA:
-  // case a_f_ALEF_HAMZA_ABOVE:
-  // case a_f_ALEF_HAMZA_BELOW:
-  case a_f_YEH_HAMZA:
-    return a_m_YEH_HAMZA;
-  case a_f_WAW_HAMZA:  // exceptions
-  case a_f_ALEF:
-  case a_f_TEH_MARBUTA:
-  case a_f_DAL:
-  case a_f_THAL:
-  case a_f_REH:
-  case a_f_ZAIN:
-  case a_f_WAW:
-  case a_f_ALEF_MAKSURA:
-    return cur_c;
-  case a_f_BEH:
-    return a_m_BEH;
-  case a_f_TEH:
-    return a_m_TEH;
-  case a_f_THEH:
-    return a_m_THEH;
-  case a_f_JEEM:
-    return a_m_JEEM;
-  case a_f_HAH:
-    return a_m_HAH;
-  case a_f_KHAH:
-    return a_m_KHAH;
-  case a_f_SEEN:
-    return a_m_SEEN;
-  case a_f_SHEEN:
-    return a_m_SHEEN;
-  case a_f_SAD:
-    return a_m_SAD;
-  case a_f_DAD:
-    return a_m_DAD;
-  case a_f_TAH:
-    return a_m_TAH;
-  case a_f_ZAH:
-    return a_m_ZAH;
-  case a_f_AIN:
-    return a_m_AIN;
-  case a_f_GHAIN:
-    return a_m_GHAIN;
-  case a_f_FEH:
-    return a_m_FEH;
-  case a_f_QAF:
-    return a_m_QAF;
-  case a_f_KAF:
-    return a_m_KAF;
-  case a_f_LAM:
-    return a_m_LAM;
-  case a_f_MEEM:
-    return a_m_MEEM;
-  case a_f_NOON:
-    return a_m_NOON;
-  case a_f_HEH:
-    return a_m_HEH;
-  case a_f_YEH:
-    return a_m_YEH;
-    // NOTE: these encodings are multi-positional, no ?
-    //   case a_f_LAM_ALEF_MADDA_ABOVE:
-    //   case a_f_LAM_ALEF_HAMZA_ABOVE:
-    //   case a_f_LAM_ALEF_HAMZA_BELOW:
-    //   case a_f_LAM_ALEF:
+  if (one == a_LAM) {
+    return arabic_maycombine(two);
   }
-  return 0;
+  return false;
 }
 
-// Change shape - from Combination (2 char) to an Isolated.
-static int chg_c_laa2i(int hid_c)
+/// A_is_iso returns true if 'c' is an Arabic ISO-8859-6 character
+///          (alphabet/number/punctuation)
+static int A_is_iso(int c)
 {
-  switch (hid_c) {
-  case a_ALEF_MADDA:
-    return a_s_LAM_ALEF_MADDA_ABOVE;
-  case a_ALEF_HAMZA_ABOVE:
-    return a_s_LAM_ALEF_HAMZA_ABOVE;
-  case a_ALEF_HAMZA_BELOW:
-    return a_s_LAM_ALEF_HAMZA_BELOW;
-  case a_ALEF:
-    return a_s_LAM_ALEF;
-  }
-  return 0;
+  return find_achar(c) != NULL;
 }
 
-// Change shape - from Combination-Isolated to Final.
-static int chg_c_laa2f(int hid_c)
+/// A_is_ok returns true if 'c' is an Arabic 10646 (8859-6 or Form-B)
+static int A_is_ok(int c)
 {
-  switch (hid_c) {
-  case a_ALEF_MADDA:
-    return a_f_LAM_ALEF_MADDA_ABOVE;
-  case a_ALEF_HAMZA_ABOVE:
-    return a_f_LAM_ALEF_HAMZA_ABOVE;
-  case a_ALEF_HAMZA_BELOW:
-    return a_f_LAM_ALEF_HAMZA_BELOW;
-  case a_ALEF:
-    return a_f_LAM_ALEF;
-  }
-  return 0;
+  return (A_is_iso(c) || c == a_BYTE_ORDER_MARK);
 }
 
-// Do "half-shaping" on character "c". Return zero if no shaping.
-static int half_shape(int c)
+/// A_is_valid returns true if 'c' is an Arabic 10646 (8859-6 or Form-B)
+///            with some exceptions/exclusions
+static int A_is_valid(int c)
 {
-  if (A_is_a(c)) {
-    return chg_c_a2i(c);
-  }
-
-  if (A_is_valid(c) && A_is_f(c)) {
-    return chg_c_f2m(c);
-  }
-  return 0;
+  return (A_is_ok(c) && c != a_HAMZA);
 }
 
 // Do Arabic shaping on character "c".  Returns the shaped character.
@@ -916,37 +303,35 @@ int arabic_shape(int c, int *ccp, int *c1p, int prev_c, int prev_c1, int next_c)
     return c;
   }
 
-  // half-shape current and previous character
-  int shape_c = half_shape(prev_c);
-
   int curr_c;
-  int curr_laa = A_firstc_laa(c, *c1p);
-  int prev_laa = A_firstc_laa(prev_c, prev_c1);
+  int curr_laa = arabic_combine(c, *c1p);
+  int prev_laa = arabic_combine(prev_c, prev_c1);
 
   if (curr_laa) {
-    if (A_is_valid(prev_c) && !A_is_f(shape_c) && !A_is_s(shape_c)
-        && !prev_laa) {
-      curr_c = chg_c_laa2f(curr_laa);
+    if (A_is_valid(prev_c) && can_join(prev_c, a_LAM) && !prev_laa) {
+      curr_c = chg_c_laa2f(*c1p);
     } else {
-      curr_c = chg_c_laa2i(curr_laa);
+      curr_c = chg_c_laa2i(*c1p);
     }
-
     // Remove the composing character
     *c1p = 0;
-  } else if (!A_is_valid(prev_c) && A_is_valid(next_c)) {
-    curr_c = chg_c_a2i(c);
-  } else if (!shape_c || A_is_f(shape_c) || A_is_s(shape_c) || prev_laa) {
-    curr_c = A_is_valid(next_c) ? chg_c_a2i(c) : chg_c_a2s(c);
-  } else if (A_is_valid(next_c)) {
-#if 0
-    curr_c = A_is_iso(c) ? chg_c_a2m(c) : chg_c_i2m(c);
-#else
-    curr_c = A_is_iso(c) ? chg_c_a2m(c) : 0;
-#endif
-  } else if (A_is_valid(prev_c)) {
-    curr_c = chg_c_a2f(c);
   } else {
-    curr_c = chg_c_a2s(c);
+    struct achar *curr_a = find_achar(c);
+    int backward_combine = !prev_laa && can_join(prev_c, c);
+    int forward_combine = can_join(c, next_c);
+
+    if (backward_combine && forward_combine) {
+      curr_c = (int)curr_a->medial;
+    }
+    if (backward_combine && !forward_combine) {
+      curr_c = (int)curr_a->final;
+    }
+    if (!backward_combine && forward_combine) {
+      curr_c = (int)curr_a->initial;
+    }
+    if (!backward_combine && !forward_combine) {
+      curr_c = (int)curr_a->isolated;
+    }
   }
 
   // Sanity check -- curr_c should, in the future, never be 0.
@@ -966,88 +351,3 @@ int arabic_shape(int c, int *ccp, int *c1p, int prev_c, int prev_c1, int next_c)
   // Return the shaped character
   return curr_c;
 }
-
-/// Check whether we are dealing with Arabic combining characters.
-/// Note: these are NOT really composing characters!
-///
-/// @param one First character.
-/// @param two Character just after "one".
-bool arabic_combine(int one, int two)
-  FUNC_ATTR_PURE
-{
-  if (one == a_LAM) {
-    return arabic_maycombine(two);
-  }
-  return false;
-}
-
-/// Check whether we are dealing with a character that could be regarded as an
-/// Arabic combining character, need to check the character before this.
-bool arabic_maycombine(int two)
-  FUNC_ATTR_PURE
-{
-  if (p_arshape && !p_tbidi) {
-    return two == a_ALEF_MADDA
-           || two == a_ALEF_HAMZA_ABOVE
-           || two == a_ALEF_HAMZA_BELOW
-           || two == a_ALEF;
-  }
-  return false;
-}
-
-// A_firstc_laa returns first character of LAA combination if it exists
-// in: "c" base character
-// in: "c1" first composing character
-static int A_firstc_laa(int c, int c1)
-{
-  if ((c1 != NUL) && (c == a_LAM) && !A_is_harakat(c1)) {
-    return c1;
-  }
-  return 0;
-}
-
-// A_is_harakat returns true if 'c' is an Arabic Harakat character.
-//     (harakat/tanween)
-static bool A_is_harakat(int c)
-{
-  return c >= a_FATHATAN && c <= a_SUKUN;
-}
-
-// A_is_iso returns true if 'c' is an Arabic ISO-8859-6 character.
-//     (alphabet/number/punctuation)
-static bool A_is_iso(int c)
-{
-  return ((c >= a_HAMZA && c <= a_GHAIN)
-          || (c >= a_TATWEEL && c <= a_HAMZA_BELOW)
-          || c == a_MINI_ALEF);
-}
-
-// A_is_formb returns true if 'c' is an Arabic 10646-1 FormB character.
-//     (alphabet/number/punctuation)
-static bool A_is_formb(int c)
-{
-  return ((c >= a_s_FATHATAN && c <= a_s_DAMMATAN)
-          || c == a_s_KASRATAN
-          || (c >= a_s_FATHA && c <= a_f_LAM_ALEF)
-          || c == a_BYTE_ORDER_MARK);
-}
-
-// A_is_ok returns true if 'c' is an Arabic 10646 (8859-6 or Form-B).
-static bool A_is_ok(int c)
-{
-  return A_is_iso(c) || A_is_formb(c);
-}
-
-// A_is_valid returns true if 'c' is an Arabic 10646 (8859-6 or Form-B),
-// with some exceptions/exclusions.
-static bool A_is_valid(int c)
-{
-  return A_is_ok(c) && !A_is_special(c);
-}
-
-// A_is_special returns true if 'c' is not a special Arabic character.
-// Specials don't adhere to most of the rules.
-static bool A_is_special(int c)
-{
-  return c == a_HAMZA || c == a_s_HAMZA;
-}
diff --git a/src/nvim/arabic.h b/src/nvim/arabic.h
index eaab463777..3c34de1449 100644
--- a/src/nvim/arabic.h
+++ b/src/nvim/arabic.h
@@ -3,12 +3,7 @@
 
 #include <stdbool.h>
 
-/// Whether c belongs to the range of Arabic characters that might be shaped.
-static inline bool arabic_char(int c)
-{
-  // return c >= a_HAMZA && c <= a_MINI_ALEF;
-  return c >= 0x0621 && c <= 0x0670;
-}
+#define ARABIC_CHAR(ch)            (((ch) & 0xFF00) == 0x0600)
 
 #ifdef INCLUDE_GENERATED_DECLARATIONS
 # include "arabic.h.generated.h"
diff --git a/src/nvim/ex_getln.c b/src/nvim/ex_getln.c
index 7e22ed55cb..32977569c3 100644
--- a/src/nvim/ex_getln.c
+++ b/src/nvim/ex_getln.c
@@ -3224,7 +3224,7 @@ static void draw_cmdline(int start, int len)
       int u8cc[MAX_MCO];
       int u8c = utfc_ptr2char_len(p, u8cc, start + len - i);
       mb_l = utfc_ptr2len_len(p, start + len - i);
-      if (arabic_char(u8c)) {
+      if (ARABIC_CHAR(u8c)) {
         do_arabicshape = true;
         break;
       }
@@ -3260,7 +3260,7 @@ static void draw_cmdline(int start, int len)
       int u8cc[MAX_MCO];
       int u8c = utfc_ptr2char_len(p, u8cc, start + len - i);
       mb_l = utfc_ptr2len_len(p, start + len - i);
-      if (arabic_char(u8c)) {
+      if (ARABIC_CHAR(u8c)) {
         int pc;
         int pc1 = 0;
         int nc = 0;
diff --git a/src/nvim/grid.c b/src/nvim/grid.c
index 7d407bd3d1..1268f987e1 100644
--- a/src/nvim/grid.c
+++ b/src/nvim/grid.c
@@ -241,7 +241,7 @@ void grid_puts_len(ScreenGrid *grid, char_u *text, int textlen, int row, int col
       u8c = utfc_ptr2char(ptr, u8cc);
     }
     mbyte_cells = utf_char2cells(u8c);
-    if (p_arshape && !p_tbidi && arabic_char(u8c)) {
+    if (p_arshape && !p_tbidi && ARABIC_CHAR(u8c)) {
       // Do Arabic shaping.
       if (len >= 0 && (int)(ptr - text) + mbyte_blen >= len) {
         // Past end of string to be displayed.
diff --git a/src/nvim/screen.c b/src/nvim/screen.c
index 32e2d515e1..03d7cb1783 100644
--- a/src/nvim/screen.c
+++ b/src/nvim/screen.c
@@ -1869,7 +1869,7 @@ static int line_putchar(buf_T *buf, LineState *s, schar_T *dest, int maxcells, b
     schar_from_ascii(dest[0], *p);
     s->prev_c = u8c;
   } else {
-    if (p_arshape && !p_tbidi && arabic_char(u8c)) {
+    if (p_arshape && !p_tbidi && ARABIC_CHAR(u8c)) {
       // Do Arabic shaping.
       int pc, pc1, nc;
       int pcc[MAX_MCO];
@@ -3157,7 +3157,7 @@ static int win_line(win_T *wp, linenr_T lnum, int startrow, int endrow, bool noc
         }
       } else if (mb_l == 0) {        // at the NUL at end-of-line
         mb_l = 1;
-      } else if (p_arshape && !p_tbidi && arabic_char(mb_c)) {
+      } else if (p_arshape && !p_tbidi && ARABIC_CHAR(mb_c)) {
         // Do Arabic shaping.
         int pc, pc1, nc;
         int pcc[MAX_MCO];