From 24db94b1a6d821699222564856f8e1d89841dfa6 Mon Sep 17 00:00:00 2001
From: Jonathan de Boyne Pollard <J.deBoynePollard-newsgroups@NTLWorld.com>
Date: Sun, 28 May 2017 00:55:04 +0100
Subject: [PATCH] tui: Fix Interix and account for deferred wrap. The Interix
 termcap entry is missing the carriage_return capability which nvim relies
 upon.  And Interix is one of the few terminal emulators that does not defer
 automatic wrap at the right margin, which is now accounted for when moving
 the cursor left and when outputting whole lines at a time.

---
 src/nvim/tui/tui.c | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/src/nvim/tui/tui.c b/src/nvim/tui/tui.c
index 5c191d94a8..3d27758b01 100644
--- a/src/nvim/tui/tui.c
+++ b/src/nvim/tui/tui.c
@@ -76,6 +76,7 @@ typedef struct {
   bool can_change_scroll_region;
   bool can_set_lr_margin;
   bool can_set_left_right_margin;
+  bool immediate_wrap_after_last_column;
   bool mouse_enabled;
   bool busy;
   cursorentry_T cursor_shapes[SHAPE_IDX_COUNT];
@@ -184,6 +185,8 @@ static void terminfo_start(UI *ui)
   data->can_set_left_right_margin =
     !!unibi_get_str(data->ut, unibi_set_left_margin_parm)
     && !!unibi_get_str(data->ut, unibi_set_right_margin_parm);
+  data->immediate_wrap_after_last_column =
+    term && STARTS_WITH(term, "interix");
   // Set 't_Co' from the result of unibilium & fix_terminfo.
   t_colors = unibi_get_num(data->ut, unibi_max_colors);
   // Enter alternate screen and clear
@@ -423,6 +426,23 @@ static bool cheap_to_print(UI *ui, int row, int col, int next)
   return true;
 }
 
+/// The behaviour that this is checking for the absence of is undocumented,
+/// but is implemented in the majority of terminals and terminal emulators.
+/// Printing at the right margin does not cause an automatic wrap until the
+/// next character is printed, holding the cursor in place until then.
+static void check_final_column_wrap(UI *ui)
+{
+  TUIData *data = ui->data;
+  if (!data->immediate_wrap_after_last_column) {
+    return;
+  }
+  UGrid *grid = &data->grid;
+  if (grid->col == ui->width) {
+    grid->col = 0;
+    ++grid->row;
+  }
+}
+
 /// This optimizes several cases where it is cheaper to do something other
 /// than send a full cursor positioning control sequence.  However, there are
 /// some further optimizations that may seem obvious but that will not work.
@@ -460,6 +480,7 @@ static void cursor_goto(UI *ui, int row, int col)
           grid->col, col - 1, {
           print_cell(ui, cell);
           ++grid->col;
+          check_final_column_wrap(ui);
         });
       }
   }
@@ -471,6 +492,9 @@ static void cursor_goto(UI *ui, int row, int col)
           unibi_out(ui, unibi_cursor_left);
         }
       } else {
+        if (!data->immediate_wrap_after_last_column && grid->col >= ui->width) {
+          --n;  // We have calculated one too many columns because of delayed wrap.
+        }
         data->params[0].i = n;
         unibi_out(ui, unibi_parm_left_cursor);
       }
@@ -565,6 +589,7 @@ static void clear_region(UI *ui, int top, int bot, int left, int right)
       cursor_goto(ui, row, col);
       print_cell(ui, cell);
       ++grid->col;
+      check_final_column_wrap(ui);
     });
   }
 
@@ -879,6 +904,7 @@ static void tui_put(UI *ui, String text)
 {
   TUIData *data = ui->data;
   print_cell(ui, ugrid_put(&data->grid, (uint8_t *)text.data, text.size));
+  check_final_column_wrap(ui);
 }
 
 static void tui_bell(UI *ui)
@@ -932,6 +958,7 @@ static void tui_flush(UI *ui)
       cursor_goto(ui, row, col);
       print_cell(ui, cell);
       ++grid->col;
+      check_final_column_wrap(ui);
     });
   }
 
@@ -2408,6 +2435,8 @@ static void patch_terminfo_bugs(TUIData *data, const char *term,
   } else if (term && STARTS_WITH(term, "tmux")) {
     unibi_set_if_empty(ut, unibi_to_status_line, "\x1b_");
     unibi_set_if_empty(ut, unibi_from_status_line, "\x1b\\");
+  } else if (term && STARTS_WITH(term, "interix")) {
+    unibi_set_if_empty(ut, unibi_carriage_return, "\x0d");
   } else if (linuxvt) {
     // No deviations from the vanilla terminfo.
   } else if (term && STARTS_WITH(term, "putty")) {