patch 9.1.1489: terminal: no visual highlight of empty cols with empty 'listchars'

Problem:  terminal: no visual highlight of empty cols when 'listchars'
          is empty (Yousef Mohammed)
Solution: reset wlv.win_attr when column is zero and we are drawing a
          terminal buffer

fixes: #17559
closes: #17618

Co-authored-by: Hirohito Higashi <h.east.727@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>

src/drawline.c

@@ -2772,6 +2772,13 @@ win_line(
 #endif
 		// no more cells to skip
 		skip_cells = 0;
+#ifdef FEAT_TERMINAL
+		if (term_show_buffer(wp->w_buffer)
+		    && wlv.col == 0
+		    && wlv.win_attr == term_get_attr(wp, lnum, -1))
+		    // reset highlighting attribute
+		    wlv.win_attr = 0;
+#endif
 	    }
 
 	    if (has_mbyte)

src/testdir/dumps/Test_terminal_empty_listchars.dump

@@ -0,0 +1,15 @@
+>h+0&#ffffff0|e+0#0000001#a8a8a8255|l@1|o| +0#0000000#ffffff0@69
+| +0#0000001#a8a8a8255| +0#0000000#ffffff0@73
+|h+0#0000001#a8a8a8255|e|l@1|o| +0#0000000#ffffff0@69
+|~+0#4040ff13&| @73
+|~| @73
+|~| @73
+|!+2#ffffff16#00e0003|s|h| |-|c| |"|p|r|i|n|t|f| |'|h|e|l@1|o|\@1|n|\@1|n|h|e|l@1|o|'|"| |[|f|i|n|i|s|h|e|d|]| @11|1|,|1| @11|A|l@1
+| +0#0000000#ffffff0@74
+|~+0#4040ff13&| @73
+|~| @73
+|~| @73
+|~| @73
+|~| @73
+|[+1#0000000&|N|o| |N|a|m|e|]| @47|0|,|0|-|1| @9|A|l@1
+|-+2&&@1| |V|I|S|U|A|L| |L|I|N|E| |-@1| +0&&@46|3| @9

src/testdir/test_terminal3.vim

@@ -1018,4 +1018,22 @@ func Test_autocmd_buffilepost_with_hidden_term()
   bw! XTestFile
 endfunc
 
+func Test_terminal_visual_empty_listchars()
+  CheckScreendump
+  CheckRunVimInTerminal
+  CheckUnix
+
+  let lines = [
+  \ 'set listchars=',
+  \ ':term sh -c "printf ''hello\\n\\nhello''"'
+  \ ]
+  call writefile(lines, 'XtermStart1', 'D')
+  let buf = RunVimInTerminal('-S XtermStart1', #{rows: 15})
+  call term_wait(buf)
+  call term_sendkeys(buf, "V2k")
+  call VerifyScreenDump(buf, 'Test_terminal_empty_listchars', {})
+
+  call StopVimInTerminal(buf)
+endfunc
+
 " vim: shiftwidth=2 sts=2 expandtab

src/version.c

@@ -719,6 +719,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1489,
 /**/
     1488,
 /**/