patch 9.1.0163: Calling STRLEN() to compute ml_line_textlen when not needed

Problem:  Calling STRLEN() to compute ml_line_textlen when not needed.
Solution: Use 0 when STRLEN() will be required and call STRLEN() later.
          (zeertzjq)

closes: #14155

Signed-off-by: zeertzjq <zeertzjq@outlook.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/change.c b/src/change.c
index 847c187..3af19b6 100644
--- a/src/change.c
+++ b/src/change.c
@@ -1364,7 +1364,7 @@
 	    mch_memmove(newp + newlen + 1, oldp + oldlen + 1,
 			       (size_t)curbuf->b_ml.ml_line_len - oldlen - 1);
 	curbuf->b_ml.ml_line_len -= count;
-	curbuf->b_ml.ml_line_textlen = (int)STRLEN(newp) + 1;
+	curbuf->b_ml.ml_line_textlen = 0;
     }
 #endif
 
diff --git a/src/edit.c b/src/edit.c
index 998647c..26853dc 100644
--- a/src/edit.c
+++ b/src/edit.c
@@ -5088,7 +5088,7 @@
 			vim_free(curbuf->b_ml.ml_line_ptr);
 		    curbuf->b_ml.ml_line_ptr = newp;
 		    curbuf->b_ml.ml_line_len -= i;
-		    curbuf->b_ml.ml_line_textlen = (int)STRLEN(newp) + 1;
+		    curbuf->b_ml.ml_line_textlen = 0;
 		    curbuf->b_ml.ml_flags =
 			   (curbuf->b_ml.ml_flags | ML_LINE_DIRTY) & ~ML_EMPTY;
 		}
diff --git a/src/memline.c b/src/memline.c
index 19d037f..99b9e9f 100644
--- a/src/memline.c
+++ b/src/memline.c
@@ -2700,9 +2700,13 @@
     colnr_T
 ml_get_buf_len(buf_T *buf, linenr_T lnum)
 {
-    if (*ml_get_buf(buf, lnum, FALSE) == NUL)
+    char_u	*line;
+
+    if (*(line = ml_get_buf(buf, lnum, FALSE)) == NUL)
         return 0;
 
+    if (buf->b_ml.ml_line_textlen <= 0)
+	buf->b_ml.ml_line_textlen = (int)STRLEN(line) + 1;
     return buf->b_ml.ml_line_textlen - 1;
 }
 
@@ -2799,8 +2803,11 @@
 	buf->b_ml.ml_line_ptr = (char_u *)dp + start;
 	buf->b_ml.ml_line_len = end - start;
 #if defined(FEAT_BYTEOFF) && defined(FEAT_PROP_POPUP)
-	if (buf->b_has_textprop)
-	    buf->b_ml.ml_line_textlen = (int)STRLEN(buf->b_ml.ml_line_ptr) + 1;
+	// Text properties come after a NUL byte, so ml_line_len should be
+	// larger than the size of textprop_T if there is any.
+	if (buf->b_has_textprop
+			 && (size_t)buf->b_ml.ml_line_len > sizeof(textprop_T))
+	    buf->b_ml.ml_line_textlen = 0;  // call STRLEN() later when needed
 	else
 #endif
 	    buf->b_ml.ml_line_textlen = buf->b_ml.ml_line_len;
diff --git a/src/structs.h b/src/structs.h
index b3b3f6a..47a0050 100644
--- a/src/structs.h
+++ b/src/structs.h
@@ -802,8 +802,8 @@
 #define ML_ALLOCATED	0x10	// ml_line_ptr is an allocated copy
     int		ml_flags;
 
-    colnr_T	ml_line_len;	// length of the cached line + textproperties, including NUL
-    colnr_T	ml_line_textlen;// length of the cached line, including NUL
+    colnr_T	ml_line_len;	// length of the cached line + NUL + text properties
+    colnr_T	ml_line_textlen;// length of the cached line + NUL, 0 if not known yet
     linenr_T	ml_line_lnum;	// line number of cached line, 0 if not valid
     char_u	*ml_line_ptr;	// pointer to cached line
 
diff --git a/src/version.c b/src/version.c
index cc63356..d1ca31b 100644
--- a/src/version.c
+++ b/src/version.c
@@ -705,6 +705,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    163,
+/**/
     162,
 /**/
     161,