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/proto/textprop.pro b/src/proto/textprop.pro
index 52bb6bc..5a648c4 100644
--- a/src/proto/textprop.pro
+++ b/src/proto/textprop.pro
@@ -13,4 +13,5 @@
 void f_prop_type_list(typval_T *argvars, typval_T *rettv);
 void clear_global_prop_types(void);
 void clear_buf_prop_types(buf_T *buf);
+void adjust_prop_columns(linenr_T lnum, colnr_T col, int bytes_added);
 /* vim: set ft=c : */
diff --git a/src/structs.h b/src/structs.h
index 4ac98b1..5b8c80b 100644
--- a/src/structs.h
+++ b/src/structs.h
@@ -705,7 +705,7 @@
  */
 typedef struct textprop_S
 {
-    colnr_T	tp_col;		// start column (one based)
+    colnr_T	tp_col;		// start column (one based, in bytes)
     colnr_T	tp_len;		// length in bytes
     int		tp_id;		// identifier
     int		tp_type;	// property type
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
diff --git a/src/textprop.c b/src/textprop.c
index 016298b..ce6b66c 100644
--- a/src/textprop.c
+++ b/src/textprop.c
@@ -17,8 +17,8 @@
  * Text properties have a type, which can be used to specify highlighting.
  *
  * TODO:
- * - Perhaps we only need TP_FLAG_CONT_NEXT ?
- * - Adjust text property column and length when text is inserted/deleted
+ * - Adjust text property column and length when text is inserted/deleted.
+ * - Perhaps we only need TP_FLAG_CONT_NEXT and can drop TP_FLAG_CONT_PREV?
  * - Add an arrray for global_proptypes, to quickly lookup a prop type by ID
  * - Add an arrray for b_proptypes, to quickly lookup a prop type by ID
  * - Checking the text length to detect text properties is slow.  Use a flag in
@@ -198,12 +198,12 @@
     {
 	long length = dict_get_number(dict, (char_u *)"length");
 
-	if (length < 1 || end_lnum > start_lnum)
+	if (length < 0 || end_lnum > start_lnum)
 	{
 	    EMSG2(_(e_invargval), "length");
 	    return;
 	}
-	end_col = start_col + length - 1;
+	end_col = start_col + length;
     }
     else if (dict_find(dict, (char_u *)"end_col", -1) != NULL)
     {
@@ -260,13 +260,13 @@
 	}
 
 	if (lnum == end_lnum)
-	    length = end_col - col + 1;
+	    length = end_col - col;
 	else
 	    length = textlen - col + 1;
 	if (length > (long)textlen)
-	    length = textlen;  // can include the end-of-line
-	if (length < 1)
-	    length = 1;
+	    length = textlen;	// can include the end-of-line
+	if (length < 0)
+	    length = 0;		// zero-width property
 
 	// Allocate the new line with space for the new proprety.
 	newtext = alloc(buf->b_ml.ml_line_len + sizeof(textprop_T));
@@ -912,4 +912,14 @@
     buf->b_proptypes = NULL;
 }
 
+/*
+ * Adjust the columns of text properties in line "lnum" after position "col" to
+ * shift by "bytes_added" (can be negative).
+ */
+    void
+adjust_prop_columns(linenr_T lnum UNUSED, colnr_T col UNUSED, int bytes_added UNUSED)
+{
+    // TODO
+}
+
 #endif // FEAT_TEXT_PROP
diff --git a/src/version.c b/src/version.c
index 17f7733..e3db6e5 100644
--- a/src/version.c
+++ b/src/version.c
@@ -800,6 +800,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    675,
+/**/
     674,
 /**/
     673,