patch 8.1.0675: text property column in screen columns is not practical

Problem:    Text property column is screen columns is not practical.
Solution:   Use byte values for the column.
diff --git a/src/testdir/dumps/Test_textprop_01.dump b/src/testdir/dumps/Test_textprop_01.dump
index e6e756d..f78c447 100644
--- a/src/testdir/dumps/Test_textprop_01.dump
+++ b/src/testdir/dumps/Test_textprop_01.dump
@@ -1,20 +1,6 @@
 | +0#af5f00255#ffffff0@1|1| >O+0#0000000&|n|e| +0&#ffff4012|t|w|o| +0&#ffffff0@63
-| +0#af5f00255&@1|2| |N+0#0000000#ffff4012|u|m|b|e|r| |1+0#4040ff13&|2|3| +0#0000000&|a|n|d| |t|h|e|n| |4+0#4040ff13&|5|6|7|.+0#0000000&| +0&#ffffff0@45
-| +0#af5f00255&@1|3| |T+0#0000000#ffff4012|h|r|e+0&#ffffff0@1| @65
+| +0#af5f00255&@1|2| |N+0#0000000#ffff4012|u|m|b|é|r| |1+0#4040ff13&|2|3| +0#0000000&|ä|n|d| |t|h|œ|n| |4+0#4040ff13&|¾|7|.+0#0000000&| +0&#ffffff0@46
+| +0#af5f00255&@1|3| |T+0#0000000#ffff4012|h|r+0&#ffffff0|e@1| @65
 |~+0#4040ff13&| @73
 |~| @73
-|~| @73
-|~| @73
-|~| @73
-|~| @73
-|~| @73
-|~| @73
-|~| @73
-|~| @73
-|~| @73
-|~| @73
-|~| @73
-|~| @73
-|~| @73
-|~| @73
 | +0#0000000&@56|1|,|1| @10|A|l@1| 
diff --git a/src/testdir/test_textprop.vim b/src/testdir/test_textprop.vim
index ad6fd09..fdf6045 100644
--- a/src/testdir/test_textprop.vim
+++ b/src/testdir/test_textprop.vim
@@ -7,6 +7,8 @@
 
 source screendump.vim
 
+" test length zero
+
 func Test_proptype_global()
   call prop_type_add('comment', {'highlight': 'Directory', 'priority': 123, 'start_incl': 1, 'end_incl': 1})
   let proptypes = prop_type_list()
@@ -112,6 +114,12 @@
   1del
   call assert_equal(s:expected_props, prop_list(1))
 
+  " Prop without length or end column is zero length
+  call prop_clear(1)
+  call prop_add(1, 5, {'type': 'two'})
+  let expected = [{'col': 5, 'length': 0, 'type': 'two', 'id': 0, 'start': 1, 'end': 1}]
+  call assert_equal(expected, prop_list(1))
+
   call DeletePropTypes()
   bwipe!
 endfunc
@@ -220,7 +228,7 @@
   call assert_equal([expect1], prop_list(1))
   let expect2 = {'col': 1, 'length': 10, 'type': 'comment', 'start': 0, 'end': 0, 'id': 0}
   call assert_equal([expect2], prop_list(2))
-  let expect3 = {'col': 1, 'length': 5, 'type': 'comment', 'start': 0, 'end': 1, 'id': 0}
+  let expect3 = {'col': 1, 'length': 4, 'type': 'comment', 'start': 0, 'end': 1, 'id': 0}
   call assert_equal([expect3], prop_list(3))
   call prop_clear(1, 3)
 
@@ -236,30 +244,31 @@
 
   bwipe!
 
-  " Test deleting the first line with a prop.
+  " Test deleting the first line of a multi-line prop.
   call Setup_three_line_prop()
+  let expect_short = {'col': 2, 'length': 1, 'type': 'comment', 'start': 1, 'end': 1, 'id': 0}
+  call assert_equal([expect_short], prop_list(1))
   let expect2 = {'col': 4, 'length': 4, 'type': 'comment', 'start': 1, 'end': 0, 'id': 0}
   call assert_equal([expect2], prop_list(2))
   2del
-  let expect_short = {'col': 2, 'length': 1, 'type': 'comment', 'start': 1, 'end': 1, 'id': 0}
   call assert_equal([expect_short], prop_list(1))
   let expect2 = {'col': 1, 'length': 6, 'type': 'comment', 'start': 1, 'end': 0, 'id': 0}
   call assert_equal([expect2], prop_list(2))
   bwipe!
 
-  " Test deleting the last line with a prop.
+  " Test deleting the last line of a multi-line prop.
   call Setup_three_line_prop()
   let expect3 = {'col': 1, 'length': 6, 'type': 'comment', 'start': 0, 'end': 0, 'id': 0}
   call assert_equal([expect3], prop_list(3))
-  let expect4 = {'col': 1, 'length': 5, 'type': 'comment', 'start': 0, 'end': 1, 'id': 0}
+  let expect4 = {'col': 1, 'length': 4, 'type': 'comment', 'start': 0, 'end': 1, 'id': 0}
   call assert_equal([expect4], prop_list(4))
   4del
-  let expect3 = {'col': 1, 'length': 6, 'type': 'comment', 'start': 0, 'end': 1, 'id': 0}
+  let expect3.end = 1
   call assert_equal([expect3], prop_list(3))
   call assert_equal([expect_short], prop_list(4))
   bwipe!
 
-  " Test appending a line below the text prop start.
+  " Test appending a line below the multi-line text prop start.
   call Setup_three_line_prop()
   let expect2 = {'col': 4, 'length': 4, 'type': 'comment', 'start': 1, 'end': 0, 'id': 0}
   call assert_equal([expect2], prop_list(2))
@@ -287,22 +296,23 @@
 
 " screenshot test with textprop highlighting
 funct Test_textprop_screenshots()
-  if !CanRunVimInTerminal()
+  if !CanRunVimInTerminal() || &encoding != 'utf-8'
     return
   endif
   call writefile([
-	\ "call setline(1, ['One two', 'Number 123 and then 4567.', 'Three'])",
+	\ "call setline(1, ['One two', 'Numbér 123 änd thœn 4¾7.', 'Three'])",
 	\ "hi NumberProp ctermfg=blue",
 	\ "hi LongProp ctermbg=yellow",
 	\ "call prop_type_add('number', {'highlight': 'NumberProp'})",
 	\ "call prop_type_add('long', {'highlight': 'LongProp'})",
 	\ "call prop_add(1, 4, {'end_lnum': 3, 'end_col': 3, 'type': 'long'})",
-	\ "call prop_add(2, 8, {'length': 3, 'type': 'number'})",
-	\ "call prop_add(2, 21, {'length': 4, 'type': 'number'})",
+	\ "call prop_add(2, 9, {'length': 3, 'type': 'number'})",
+	\ "call prop_add(2, 24, {'length': 4, 'type': 'number'})",
 	\ "set number",
+	\ "hi clear SpellBad",
 	\ "set spell",
 	\], 'XtestProp')
-  let buf = RunVimInTerminal('-S XtestProp', {})
+  let buf = RunVimInTerminal('-S XtestProp', {'rows': 6})
   call VerifyScreenDump(buf, 'Test_textprop_01', {})
 
   " clean up