screen: use UTF-8 representation

Store text in ScreenLines as UTF-8, so it can be sent as-is to the UI
layer. `utfc_char2bytes(off,buf)` is removed, as `ScreenLines[off]` now
already contains this representation.

To recover the codepoints that the screen arrays previously contained, use
utfc_ptr2char (or utf_ptr2char to ignore composing chars).

NB: This commit does NOT change how screen.c processes incoming UTF-8 data
from buffers, cmdline, messages etc. Any algorithm that operates on UCS-4
(like arabic shaping, treatment of non-printable chars)
is left unchanged for now.

1 files changed, 1 insertions, 4 deletions

diff --git a/src/nvim/eval.c b/src/nvim/eval.c
index 30c17af8c9..9ce354a0c5 100644
--- a/src/nvim/eval.c
+++ b/src/nvim/eval.c
@@ -13994,10 +13994,7 @@ static void f_screenchar(typval_T *argvars, typval_T *rettv, FunPtr fptr)
     c = -1;
   } else {
     off = LineOffset[row] + col;
-    if (enc_utf8 && ScreenLinesUC[off] != 0)
-      c = ScreenLinesUC[off];
-    else
-      c = ScreenLines[off];
+    c = utf_ptr2char(ScreenLines[off]);
   }
   rettv->vval.v_number = c;
 }