refactor(grid): do arabic shaping in one place

The 'arabicshape' feature of vim is a transformation of unicode text to
make arabic and some related scripts look better at display time. In
particular the content of a cell will be adjusted depending on the
(original) content of the cells just before and after it.

This is implemented by the arabic_shape() function in nvim. Before this
commit, shaping was invoked in four different contexts:

- when rendering buffer text in win_line()
- in line_putchar() for rendering virtual text
- as part of grid_line_puts, used by messages and statuslines and
  similar
- as part of draw_cmdline() for drawing the cmdline

This replaces all these with a post-processing step in grid_put_linebuf(),
which has become the entry point for all text rendering after recent
refactors.

An aim of this is to make the handling of multibyte text yet simpler.
One of the main reasons multibyte chars needs to be "parsed" into
codepoint arrays of composing chars is so that these could be inspected
for the purpose of shaping. This can likely be vastly simplified in many
contexts where only the total length (in bytes) and width of composed
char is needed.

1 files changed, 0 insertions, 101 deletions

diff --git a/src/nvim/ex_getln.c b/src/nvim/ex_getln.c
index 2a1dffacb7..be0192789e 100644
--- a/src/nvim/ex_getln.c
+++ b/src/nvim/ex_getln.c
@@ -2998,16 +2998,6 @@ void realloc_cmdbuff(int len)
   }
 }
 
-static char *arshape_buf = NULL;
-
-#if defined(EXITFREE)
-void free_arshape_buf(void)
-{
-  xfree(arshape_buf);
-}
-
-#endif
-
 enum { MAX_CB_ERRORS = 1, };
 
 /// Color expression cmdline using built-in expressions parser
@@ -3317,98 +3307,7 @@ static void draw_cmdline(int start, int len)
       msg_putchar('*');
       i += utfc_ptr2len(ccline.cmdbuff + start + i) - 1;
     }
-  } else if (p_arshape && !p_tbidi && len > 0) {
-    bool do_arabicshape = false;
-    int mb_l;
-    for (int i = start; i < start + len; i += mb_l) {
-      char *p = ccline.cmdbuff + i;
-      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)) {
-        do_arabicshape = true;
-        break;
-      }
-    }
-    if (!do_arabicshape) {
-      goto draw_cmdline_no_arabicshape;
-    }
-
-    static size_t buflen = 0;
-    assert(len >= 0);
-
-    // Do arabic shaping into a temporary buffer.  This is very
-    // inefficient!
-    if ((size_t)len * 2 + 2 > buflen) {
-      // Re-allocate the buffer.  We keep it around to avoid a lot of
-      // alloc()/free() calls.
-      xfree(arshape_buf);
-      buflen = (size_t)len * 2 + 2;
-      arshape_buf = xmalloc(buflen);
-    }
-
-    int newlen = 0;
-    if (utf_iscomposing(utf_ptr2char(ccline.cmdbuff + start))) {
-      // Prepend a space to draw the leading composing char on.
-      arshape_buf[0] = ' ';
-      newlen = 1;
-    }
-
-    int prev_c = 0;
-    int prev_c1 = 0;
-    for (int i = start; i < start + len; i += mb_l) {
-      char *p = ccline.cmdbuff + i;
-      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)) {
-        int pc;
-        int pc1 = 0;
-        int nc = 0;
-        // Do Arabic shaping.
-        if (cmdmsg_rl) {
-          // Displaying from right to left.
-          pc = prev_c;
-          pc1 = prev_c1;
-          prev_c1 = u8cc[0];
-          if (i + mb_l >= start + len) {
-            nc = NUL;
-          } else {
-            nc = utf_ptr2char(p + mb_l);
-          }
-        } else {
-          // Displaying from left to right.
-          if (i + mb_l >= start + len) {
-            pc = NUL;
-          } else {
-            int pcc[MAX_MCO];
-
-            pc = utfc_ptr2char_len(p + mb_l, pcc, start + len - i - mb_l);
-            pc1 = pcc[0];
-          }
-          nc = prev_c;
-        }
-        prev_c = u8c;
-
-        u8c = arabic_shape(u8c, NULL, &u8cc[0], pc, pc1, nc);
-
-        newlen += utf_char2bytes(u8c, arshape_buf + newlen);
-        if (u8cc[0] != 0) {
-          newlen += utf_char2bytes(u8cc[0], arshape_buf + newlen);
-          if (u8cc[1] != 0) {
-            newlen += utf_char2bytes(u8cc[1], arshape_buf + newlen);
-          }
-        }
-      } else {
-        prev_c = u8c;
-        memmove(arshape_buf + newlen, p, (size_t)mb_l);
-        newlen += mb_l;
-      }
-    }
-
-    msg_outtrans_len(arshape_buf, newlen, 0);
   } else {
-draw_cmdline_no_arabicshape:
     if (kv_size(ccline.last_colors.colors)) {
       for (size_t i = 0; i < kv_size(ccline.last_colors.colors); i++) {
         CmdlineColorChunk chunk = kv_A(ccline.last_colors.colors, i);