LTerm_edit: horizontal scroll wide graphemes

Author: kandu

src/lTerm_edit.ml

@@ -215,7 +215,6 @@ object(self)
   val mutable local_bindings = Bindings.empty
   method bind keys actions = local_bindings <- Bindings.add keys actions local_bindings
 
-  val mutable shift = 0
   val mutable shift_width = 0
   val mutable start = 0
   val mutable start_line = 0
@@ -228,45 +227,16 @@ object(self)
     let line_count = Zed_lines.count line_set in
     let cursor_offset = Zed_cursor.get_position cursor in
     let cursor_line = Zed_lines.line_index line_set cursor_offset in
-    let line_start= Zed_lines.line_start line_set cursor_line in
     let cursor_column = cursor_offset - Zed_lines.line_start line_set cursor_line in
     let column_display= Zed_lines.force_width line_set (Zed_lines.line_start line_set cursor_line) cursor_column in
 
-    let calc_delta width_delta=
-      let rec forward idx acc=
-        if acc < width_delta then
-          forward (idx + 1) (acc + Zed_lines.force_width line_set idx 1)
-        else
-          idx
-      in
-      let rec backward idx acc=
-        if acc > width_delta then
-          backward (idx - 1) (acc - Zed_lines.force_width line_set (idx - 1) 1)
-        else
-          idx
-      in
-      if width_delta > 0 then
-        forward (line_start + shift) 0 - (line_start + shift)
-      else if width_delta < 0 then
-        backward cursor_offset 0 - cursor_offset
-      else 0
-    in
 
     (*** check cursor position is in view *)
 
     (* Horizontal check *)
     if column_display < shift_width || column_display >= shift_width + size.cols then begin
 
-      let shift_new= max 0 (column_display - size.cols / 2) in
-      if shift_new = 0 then
-        shift <- 0
-      else
-        begin
-          let width_delta= shift_new - shift_width in
-          let shift_delta= calc_delta width_delta in
-          shift <- shift + shift_delta;
-        end;
-      shift_width <- Zed_lines.force_width line_set line_start shift;
+      shift_width <- max 0 (column_display - size.cols / 2);
     end;
 
     (* Vertical check *)
@@ -373,7 +343,7 @@ object(self)
     size <- size_of_rect rect;
     super#set_allocation rect;
     vscroll#set_page_size size.rows;
-    start <- 0; shift <- 0; shift_width <- 0; start_line <- 0;
+    start <- 0; shift_width <- 0; start_line <- 0;
     self#update_window_position
 
   initializer vscroll#on_offset_change (fun n ->
@@ -446,8 +416,8 @@ object(self)
           skip_eol row zip
 
     and skip_bol row zip remaining =
-      if remaining = 0 then
-        draw_line row 0 zip
+      if remaining <= 0 then
+        draw_line row (-remaining) zip
       else if Zed_rope.Zip.at_eos zip then
         draw_eoi (row + 1)
       else
@@ -456,13 +426,13 @@ object(self)
           let row = row + 1 in
           if row < size.rows then begin_line row zip
         end else
-          skip_bol row zip (remaining - 1)
+          skip_bol row zip (remaining - (Zed_char.width char))
 
     and begin_line row zip =
       if Zed_rope.Zip.at_eos zip then
         draw_eoi row
-      else if shift <> 0 then begin
-        skip_bol row zip shift
+      else if shift_width <> 0 then begin
+        skip_bol row zip shift_width
       end else
         draw_line row 0 zip