vim-patch:8.0.1037: "icase" of 'diffopt' is not used for highlighting

Problem:    "icase" of 'diffopt' is not used for highlighting differences.
Solution:   Also use "icase". (Rick Howe)
da22b8cc8b

src/nvim/diff.c

@@ -1870,6 +1870,35 @@ bool diffopt_horizontal(void)
   return (diff_flags & DIFF_HORIZONTAL) != 0;
 }
 
+// Compare the characters at "p1" and "p2".  If they are equal (possibly
+// ignoring case) return true and set "len" to the number of bytes.
+static bool diff_equal_char(const char_u *const p1, const char_u *const p2,
+                            int *const len)
+{
+  const int l = utfc_ptr2len(p1);
+
+  if (l != utfc_ptr2len(p2)) {
+    return false;
+  }
+  if (l > 1) {
+    if (STRNCMP(p1, p2, l) != 0
+        && (!enc_utf8
+            || !(diff_flags & DIFF_ICASE)
+            || utf_fold(utf_ptr2char(p1)) != utf_fold(utf_ptr2char(p2)))) {
+      return false;
+    }
+    *len = l;
+  } else {
+    if ((*p1 != *p2)
+        && (!(diff_flags & DIFF_ICASE)
+            || TOLOWER_LOC(*p1) != TOLOWER_LOC(*p2))) {
+      return false;
+    }
+    *len = 1;
+  }
+  return true;
+}
+
 /// Find the difference within a changed line.
 ///
 /// @param  wp      window whose current buffer to check
@@ -1887,6 +1916,7 @@ bool diff_find_change(win_T *wp, linenr_T lnum, int *startp, int *endp)
   int ei_org;
   int ei_new;
   bool added = true;
+  int l;
 
   // Make a copy of the line, the next ml_get() will invalidate it.
   char_u *line_org = vim_strsave(ml_get_buf(wp->w_buffer, lnum, FALSE));
@@ -1933,11 +1963,11 @@ bool diff_find_change(win_T *wp, linenr_T lnum, int *startp, int *endp)
           si_org = (int)(skipwhite(line_org + si_org) - line_org);
           si_new = (int)(skipwhite(line_new + si_new) - line_new);
         } else {
-          if (line_org[si_org] != line_new[si_new]) {
+          if (!diff_equal_char(line_org + si_org, line_new + si_new, &l)) {
             break;
           }
-          ++si_org;
+          si_org += l;
-          ++si_new;
+          si_new += l;
         }
       }
 
@@ -1972,11 +2002,17 @@ bool diff_find_change(win_T *wp, linenr_T lnum, int *startp, int *endp)
               ei_new--;
             }
           } else {
-            if (line_org[ei_org] != line_new[ei_new]) {
+            const char_u *p1 = line_org + ei_org;
+            const char_u *p2 = line_new + ei_new;
+
+            p1 -= utf_head_off(line_org, p1);
+            p2 -= utf_head_off(line_new, p2);
+
+            if (!diff_equal_char(p1, p2, &l)) {
               break;
             }
-            ei_org--;
+            ei_org -= l;
-            ei_new--;
+            ei_new -= l;
           }
         }
 

src/nvim/testdir/test_diffmode.vim

@@ -279,13 +279,13 @@ func Test_diffopt_icase()
   set diffopt=icase,foldcolumn:0
 
   e one
-  call setline(1, ['One', 'Two', 'Three', 'Four'])
+  call setline(1, ['One', 'Two', 'Three', 'Four', 'Fi#ve'])
   redraw
   let normattr = screenattr(1, 1)
   diffthis
 
   botright vert new two
-  call setline(1, ['one', 'TWO', 'Three ', 'Four'])
+  call setline(1, ['one', 'TWO', 'Three ', 'Four', 'fI=VE'])
   diffthis
 
   redraw
@@ -294,6 +294,10 @@ func Test_diffopt_icase()
   call assert_notequal(normattr, screenattr(3, 1))
   call assert_equal(normattr, screenattr(4, 1))
 
+  let dtextattr = screenattr(5, 3)
+  call assert_notequal(dtextattr, screenattr(5, 1))
+  call assert_notequal(dtextattr, screenattr(5, 5))
+
   diffoff!
   %bwipe!
   set diffopt&