updated for version 7.3.1164

Problem:    Can't test what is actually displayed on screen.
Solution:   Add the screenchar() and screenattr() functions.

runtime/doc/eval.txt

@@ -1906,6 +1906,8 @@ repeat( {expr}, {count})	String	repeat {expr} {count} times
 resolve( {filename})		String	get filename a shortcut points to
 reverse( {list})		List	reverse {list} in-place
 round( {expr})			Float	round off {expr}
+screenattr( {row}, {col})	Number	attribute at screen position
+screenchar( {row}, {col})	Number	character at screen position
 screencol()			Number	current cursor column
 screenrow()			Number	current cursor row
 search( {pattern} [, {flags} [, {stopline} [, {timeout}]]])
@@ -4890,6 +4892,21 @@ round({expr})							*round()*
 <			-5.0
 		{only available when compiled with the |+float| feature}
 
+screenattr(row, col)						*screenattr()*
+		Like screenchar(), but return the attribute.  This is a rather
+		arbitrary number that can only be used to compare to the
+		attribute at other positions.
+
+screenchar(row, col)						*screenchar()*
+		The result is a Number, which is the character at position
+		[row, col] on the screen.  This works for every possible
+		screen position, also status lines, window separators and the
+		command line.  The top left position is row one, column one
+		The character excludes composing characters.  For double-byte
+		encodings it may only be the first byte.
+		This is mainly to be used for testing.
+		Returns -1 when row or col is out of range.
+
 screencol()							*screencol()*
 		The result is a Number, which is the current screen column of
 		the cursor. The leftmost column has number 1.

src/eval.c

@@ -654,6 +654,8 @@ static void f_reverse __ARGS((typval_T *argvars, typval_T *rettv));
 #ifdef FEAT_FLOAT
 static void f_round __ARGS((typval_T *argvars, typval_T *rettv));
 #endif
+static void f_screenattr __ARGS((typval_T *argvars, typval_T *rettv));
+static void f_screenchar __ARGS((typval_T *argvars, typval_T *rettv));
 static void f_screencol __ARGS((typval_T *argvars, typval_T *rettv));
 static void f_screenrow __ARGS((typval_T *argvars, typval_T *rettv));
 static void f_search __ARGS((typval_T *argvars, typval_T *rettv));
@@ -8037,6 +8039,8 @@ static struct fst
 #ifdef FEAT_FLOAT
     {"round",		1, 1, f_round},
 #endif
+    {"screenattr",	2, 2, f_screenattr},
+    {"screenchar",	2, 2, f_screenchar},
     {"screencol",	0, 0, f_screencol},
     {"screenrow",	0, 0, f_screenrow},
     {"search",		1, 4, f_search},
@@ -15803,6 +15807,59 @@ f_round(argvars, rettv)
 }
 #endif
+/*
+ * "screenattr()" function
+ */
+    static void
+f_screenattr(argvars, rettv)
+    typval_T	*argvars UNUSED;
+    typval_T	*rettv;
+{
+    int		row;
+    int		col;
+    int		c;
+
+    row = get_tv_number_chk(&argvars[0], NULL) - 1;
+    col = get_tv_number_chk(&argvars[1], NULL) - 1;
+    if (row < 0 || row >= screen_Rows
+	    || col < 0 || col >= screen_Columns)
+	c = -1;
+    else
+	c = ScreenAttrs[LineOffset[row] + col];
+    rettv->vval.v_number = c;
+}
+
+/*
+ * "screenchar()" function
+ */
+    static void
+f_screenchar(argvars, rettv)
+    typval_T	*argvars UNUSED;
+    typval_T	*rettv;
+{
+    int		row;
+    int		col;
+    int		off;
+    int		c;
+
+    row = get_tv_number_chk(&argvars[0], NULL) - 1;
+    col = get_tv_number_chk(&argvars[1], NULL) - 1;
+    if (row < 0 || row >= screen_Rows
+	    || col < 0 || col >= screen_Columns)
+	c = -1;
+    else
+    {
+	off = LineOffset[row] + col;
+#ifdef FEAT_MBYTE
+	if (enc_utf8 && ScreenLinesUC[off] != 0)
+	    c = ScreenLinesUC[off];
+	else
+#endif
+	    c = ScreenLines[off];
+    }
+    rettv->vval.v_number = c;
+}
+
 /*
  * "screencol()" function
  *

src/version.c

@@ -728,6 +728,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1164,
 /**/
     1163,
 /**/