patch 9.0.1770: lines disappear when modifying chars before virt text

Problem:  lines disappear when modifying chars before virt text
Solution: take virtual text property length into account

closes: #12558
closes: #12244

Signed-off-by: Christian Brabandt <cb@256bit.org>
Co-authored-by: Ibby <33922797+SleepySwords@users.noreply.github.com>

src/charset.c

@@ -808,16 +808,14 @@ win_linetabsize_cts(chartabsize_T *cts, colnr_T len)
 						      MB_PTR_ADV(cts->cts_ptr))
 	cts->cts_vcol += win_lbr_chartabsize(cts, NULL);
 #ifdef FEAT_PROP_POPUP
-    // check for a virtual text on an empty line
+    // check for a virtual text at the end of a line or on an empty line
-    if (cts->cts_has_prop_with_text && *cts->cts_ptr == NUL
+    if (cts->cts_has_prop_with_text && *cts->cts_ptr == NUL)
-					      && cts->cts_ptr == cts->cts_line)
     {
 	(void)win_lbr_chartabsize(cts, NULL);
 	cts->cts_vcol += cts->cts_cur_text_width;
-
 	// when properties are above or below the empty line must also be
 	// counted
-	if (cts->cts_prop_lines > 0)
+	if (cts->cts_ptr == cts->cts_line && cts->cts_prop_lines > 0)
 	    ++cts->cts_vcol;
     }
 #endif
@@ -1190,7 +1188,7 @@ win_lbr_chartabsize(
 		       || (tp->tp_col == MAXCOL
 			   && ((tp->tp_flags & TP_FLAG_ALIGN_ABOVE)
 				? col == 0
-				: (s[0] == NUL || s[charlen] == NUL)
+				: s[0] == NUL
 						  && cts->cts_with_trailing)))
 		    && -tp->tp_id - 1 < gap->ga_len)
 	    {

src/testdir/dumps/Test_modify_text_before_prop_1.dump

@@ -0,0 +1,5 @@
+| +0#af5f00255#ffffff0@1|1| >t+0#0000000&|e|s|t|_|w|o|r|d|s|a+0&#ffd7ff255@45
+| +0#af5f00255#ffffff0@3|a+0#0000000#ffd7ff255@18| +0&#ffffff0@36
+| +0#af5f00255&@3|a+0#4040ff13&@54|…
+| +0#af5f00255&@1|2| |s+0#0000000&|e|c|o|n|d| |l|i|n|e| @44
+@42|1|,|1| @10|T|o|p| 

src/testdir/dumps/Test_modify_text_before_prop_2.dump

@@ -0,0 +1,5 @@
+| +0#af5f00255#ffffff0@1|1| >a+0#0000000&|s|t|_|w|o|r|d|s|a+0&#ffd7ff255@46
+| +0#af5f00255#ffffff0@3|a+0#0000000#ffd7ff255@17| +0&#ffffff0@37
+| +0#af5f00255&@3|a+0#4040ff13&@54|…
+| +0#af5f00255&@1|2| |s+0#0000000&|e|c|o|n|d| |l|i|n|e| @44
+@42|1|,|1| @10|T|o|p| 

src/testdir/test_textprop.vim

@@ -3979,6 +3979,28 @@ func Test_error_after_using_negative_id()
   call StopVimInTerminal(buf)
 endfunc
 
+func Test_modify_text_before_prop()
+  CheckRunVimInTerminal
+
+  let lines =<< trim END
+      vim9script
+      setline(1, ['test_words', 'second line', 'third line', 'fourth line'])
+      set number
+      prop_type_add('text', {highlight: 'DiffChange'})
+      prop_type_add('below', {highlight: 'NonText'})
+      prop_add(1, 11, {type: 'text', text: repeat('a', 65)})
+      prop_add(1, 0, {type: 'below', text: repeat('a', 65), text_align: 'below'})
+  END
+  call writefile(lines, 'XtextPropModifyBefore', 'D')
+  let buf = RunVimInTerminal('-S XtextPropModifyBefore', #{rows: 5, cols: 60})
+  call VerifyScreenDump(buf, 'Test_modify_text_before_prop_1', {})
+
+  call term_sendkeys(buf, "xxia\<Esc>")
+  call VerifyScreenDump(buf, 'Test_modify_text_before_prop_2', {})
+
+  call StopVimInTerminal(buf)
+endfunc
+
 func Test_overlong_textprop_above_crash()
   CheckRunVimInTerminal
 

src/version.c

@@ -695,6 +695,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1770,
 /**/
     1769,
 /**/