vim-patch:7.4.280 #745

Problem:    When using a session file the relative position of the cursor is
            not restored if there is another tab. (Nobuhiro Takasaki)
Solution:   Update w_wrow before calculating the fraction.

https://code.google.com/p/vim/source/detail?r=daf7e98675cf395e1ef96f8040567affb2782a11

src/nvim/version.c

@@ -207,7 +207,7 @@ static int included_patches[] = {
   //283,
   //282,
   //281,
-  //280,
+  280,
   //279,
   //278,
   277,

src/nvim/window.c

@@ -4457,8 +4457,8 @@ void win_drag_vsep_line(win_T *dragwin, int offset)
  */
 static void set_fraction(win_T *wp)
 {
-  wp->w_fraction = ((long)wp->w_wrow * FRACTION_MULT
-                    + FRACTION_MULT / 2) / (long)wp->w_height;
+  wp->w_fraction = ((long)wp->w_wrow * FRACTION_MULT + wp->w_height / 2)
+                   / (long)wp->w_height;
 }
 
 /*
@@ -4470,6 +4470,7 @@ void win_new_height(win_T *wp, int height)
 {
   linenr_T lnum;
   int sline, line_size;
+  int prev_height = wp->w_height;
 
   /* Don't want a negative height.  Happens when splitting a tiny window.
    * Will equalize heights soon to fix it. */
@@ -4478,8 +4479,14 @@ void win_new_height(win_T *wp, int height)
   if (wp->w_height == height)
     return;         /* nothing to do */
 
-  if (wp->w_wrow != wp->w_prev_fraction_row && wp->w_height > 0)
-    set_fraction(wp);
+  if (wp->w_height > 0) {
+    if (wp == curwin) {
+      validate_cursor();  // w_wrow needs to be valid
+    }
+    if (wp->w_wrow != wp->w_prev_fraction_row) {
+      set_fraction(wp);
+    }
+  }
 
   wp->w_height = height;
   wp->w_skipcol = 0;
@@ -4496,7 +4503,8 @@ void win_new_height(win_T *wp, int height)
     lnum = wp->w_cursor.lnum;
     if (lnum < 1)               /* can happen when starting up */
       lnum = 1;
-    wp->w_wrow = ((long)wp->w_fraction * (long)height - 1L) / FRACTION_MULT;
+    wp->w_wrow = ((long)wp->w_fraction * (long)height - 1L + FRACTION_MULT / 2)
+                 / FRACTION_MULT;
     line_size = plines_win_col(wp, lnum, (long)(wp->w_cursor.col)) - 1;
     sline = wp->w_wrow - line_size;
 
@@ -4567,7 +4575,9 @@ void win_new_height(win_T *wp, int height)
       update_topline();
     curs_columns(FALSE);        /* validate w_wrow */
   }
-  wp->w_prev_fraction_row = wp->w_wrow;
+  if (prev_height > 0) {
+    wp->w_prev_fraction_row = wp->w_wrow;
+  }
 
   win_comp_scroll(wp);
   redraw_win_later(wp, SOME_VALID);