patch 8.2.3204: display garbled when 'cursorline' is set and lines wrap

Problem:    Display garbled when 'cursorline' is set and lines wrap. (Gabriel
            Dupras)
Solution:   Avoid inserting lines twice.

src/drawscreen.c

@@ -2249,9 +2249,11 @@ win_update(win_T *wp)
 	    // up or down to minimize redrawing.
 	    // Don't do this when the change continues until the end.
 	    // Don't scroll when dollar_vcol >= 0, keep the "$".
+	    // Don't scroll when redrawing the top, scrolled already above.
 	    if (lnum == mod_top
 		    && mod_bot != MAXLNUM
-		    && !(dollar_vcol >= 0 && mod_bot == mod_top + 1))
+		    && !(dollar_vcol >= 0 && mod_bot == mod_top + 1)
+		    && row >= top_end)
 	    {
 		int		old_rows = 0;
 		int		new_rows = 0;

src/testdir/dumps/Test_cursorline_redraw_1.dump

@@ -0,0 +1,20 @@
+| +0&#ffffff0@23|o|n|e| |b|y| |o|n|e| |t|o| |a|v
+|o|i|d| |p|r|o|b|l|e|m|s|.| @26
+@24|A|l|s|o| |s|e@1| |||:|s|e|t|-|a
+|r|g|s||| |a|b|o|v|e|.| @28
+@40
+|T|h|e| |{|o|p|t|i|o|n|}| |a|r|g|u|m|e|n|t|s| |t|o| |"|:|s|e|t|"| |m|a|y| |b|e| 
+|r|e|p|e|a|t|e|d|.| @1|F|o|r| |e|x|a|m|p|l|e|:| |>| @14
+@8|:|s|e|t| |a|i| |n|o|s|i| |s|w|=|3| |t|s|=|3| @9
+|I|f| |y|o|u| |m|a|k|e| |a|n| |e|r@1|o|r| |i|n| |o|n|e| |o|f| |t|h|e| |a|r|g|u|m
+|e|n|t|s|,| |a|n| |e|r@1|o|r| |m|e|s@1|a|g|e| |w|i|l@1| |b|e| |g|i|v|e|n| @3
+|a|n|d| |t|h|e| |f|o|l@1|o|w|i|n|g| |a|r|g|u|m|e|n|t|s| |w|i|l@1| |b|e| |i|g|n|o
+|r|e|d|.| @35
+@40
+@40
+@16|*|:|s|e|t|-|v|e|r|b|o|s|e|*| @9
+>W+8&&|h|e|n| |'|v|e|r|b|o|s|e|'| |i|s| |n|o|n|-|z|e|r|o|,| |d|i|s|p|l|a|y|i|n|g| |a
+|n| |o|p|t|i|o|n| |v|a|l|u|e| |w|i|l@1| |a|l|s|o| |t|e|l@1| |w|h|e|r|e| |i|t| @1
+|w+0&&|a|s| |l|a|s|t| |s|e|t|.| @1|E|x|a|m|p|l|e|:| |>| @14
+@8|:|v|e|r|b|o|s|e| |s|e|t| |s|h|i|f|t|w|i|d|t|h| |c|i|n|d|e|n|t|?
+|<| |2@1|L|,| |9|4|2|B| @10|1|2|,|1| @9|2|0|%| 

src/testdir/dumps/Test_cursorline_redraw_2.dump

@@ -0,0 +1,20 @@
+| +0&#ffffff0@39
+|T|h|e| |{|o|p|t|i|o|n|}| |a|r|g|u|m|e|n|t|s| |t|o| |"|:|s|e|t|"| |m|a|y| |b|e| 
+|r|e|p|e|a|t|e|d|.| @1|F|o|r| |e|x|a|m|p|l|e|:| |>| @14
+| +8&&@7>:|s|e|t| |a|i| |n|o|s|i| |s|w|=|3| |t|s|=|3| @9
+|I+0&&|f| |y|o|u| |m|a|k|e| |a|n| |e|r@1|o|r| |i|n| |o|n|e| |o|f| |t|h|e| |a|r|g|u|m
+|e|n|t|s|,| |a|n| |e|r@1|o|r| |m|e|s@1|a|g|e| |w|i|l@1| |b|e| |g|i|v|e|n| @3
+|a|n|d| |t|h|e| |f|o|l@1|o|w|i|n|g| |a|r|g|u|m|e|n|t|s| |w|i|l@1| |b|e| |i|g|n|o
+|r|e|d|.| @35
+@40
+@40
+@16|*|:|s|e|t|-|v|e|r|b|o|s|e|*| @9
+|W|h|e|n| |'|v|e|r|b|o|s|e|'| |i|s| |n|o|n|-|z|e|r|o|,| |d|i|s|p|l|a|y|i|n|g| |a
+|n| |o|p|t|i|o|n| |v|a|l|u|e| |w|i|l@1| |a|l|s|o| |t|e|l@1| |w|h|e|r|e| |i|t| @1
+|w|a|s| |l|a|s|t| |s|e|t|.| @1|E|x|a|m|p|l|e|:| |>| @14
+@8|:|v|e|r|b|o|s|e| |s|e|t| |s|h|i|f|t|w|i|d|t|h| |c|i|n|d|e|n|t|?
+|<| @1|s|h|i|f|t|w|i|d|t|h|=|4| |~| @22
+@10|L|a|s|t| |s|e|t| |f|r|o|m| |m|o|d|e|l|i|n|e| |l|i|n|e| |1| 
+|~| @38
+@2|c|i|n|d|e|n|t| |~| @28
+@22|7|,|2|-|9| @8|4@1|%| 

src/testdir/test_cursorline.vim

@@ -110,6 +110,7 @@ endfunc
 func Test_cursorline_screenline()
   CheckScreendump
   CheckOption cursorlineopt
+
   let filename='Xcursorline'
   let lines = []
 
@@ -197,4 +198,52 @@ func Test_cursorline_screenline()
   call delete(filename)
 endfunc
 
+func Test_cursorline_redraw()
+  CheckScreendump
+  CheckOption cursorlineopt
+
+  let textlines =<< END
+			When the option is a list of flags, {value} must be
+			exactly as they appear in the option.  Remove flags
+			one by one to avoid problems.
+			Also see |:set-args| above.
+
+The {option} arguments to ":set" may be repeated.  For example: >
+	:set ai nosi sw=3 ts=3
+If you make an error in one of the arguments, an error message will be given
+and the following arguments will be ignored.
+
+							*:set-verbose*
+When 'verbose' is non-zero, displaying an option value will also tell where it
+was last set.  Example: >
+	:verbose set shiftwidth cindent?
+<  shiftwidth=4 ~
+	  Last set from modeline line 1 ~
+  cindent ~
+	  Last set from /usr/local/share/vim/vim60/ftplugin/c.vim line 30 ~
+This is only done when specific option values are requested, not for ":verbose
+set all" or ":verbose set" without an argument.
+When the option was set by hand there is no "Last set" message.
+When the option was set while executing a function, user command or
+END
+  call writefile(textlines, 'Xtextfile')
+
+  let script =<< trim END
+      set cursorline scrolloff=2
+      normal 12G
+  END
+  call writefile(script, 'Xscript')
+
+  let buf = RunVimInTerminal('-S Xscript Xtextfile', #{rows: 20, cols: 40})
+  call VerifyScreenDump(buf, 'Test_cursorline_redraw_1', {})
+  call term_sendkeys(buf, "zt")
+  call TermWait(buf)
+  call term_sendkeys(buf, "\<C-U>")
+  call VerifyScreenDump(buf, 'Test_cursorline_redraw_2', {})
+
+  call StopVimInTerminal(buf)
+  call delete('Xscript')
+  call delete('Xtextfile')
+endfunc
+
 " vim: shiftwidth=2 sts=2 expandtab

src/version.c

@@ -755,6 +755,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    3204,
 /**/
     3203,
 /**/