patch 9.1.0917: various vartabstop and shiftround bugs when shifting lines

Problem:  various vartabstop and shiftround bugs when shifting lines
Solution: Fix the bugs, add new tests for shifting lines in various ways
          (Gary Johnson)

fixes: #14891
closes: #16193

Signed-off-by: Gary Johnson <garyjohn@spocom.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>

src/ops.c

@@ -218,25 +218,57 @@ op_shift(oparg_T *oap, int curs_top, int amount)
     }
 }
 
+#ifdef FEAT_VARTABS
 /*
- * Shift the current line one shiftwidth left (if left != 0) or right
- * leaves cursor on first blank in the line.
+ * Return the tabstop width at the index of the variable tabstop array.  If an
+ * index greater than the length of the array is given, the last tabstop width
+ * in the array is returned.
  */
-    void
-shift_line(
-    int	left,
-    int	round,
-    int	amount,
-    int call_changed_bytes)	// call changed_bytes()
+    static int
+get_vts(int *vts_array, int index)
 {
-    vimlong_T	count;
-    int		i, j;
-    int		sw_val = trim_to_int(get_sw_value_indent(curbuf, left));
+    int	ts;
 
-    if (sw_val == 0)
-	sw_val = 1;		// shouldn't happen, just in case
+    if (index < 1)
+	ts = 0;
+    else if (index <= vts_array[0])
+	ts = vts_array[index];
+    else
+	ts = vts_array[vts_array[0]];
 
-    count = get_indent();	// get current indent
+    return ts;
+}
+
+/*
+ * Return the sum of all the tabstops through the index-th.
+ */
+    static int
+get_vts_sum(int *vts_array, int index)
+{
+    int	sum = 0;
+    int	i;
+
+    // Perform the summation for indeces within the actual array.
+    for (i = 1; i <= index && i <= vts_array[0]; i++)
+	sum += vts_array[i];
+
+    // Add topstops whose indeces exceed the actual array.
+    if (i <= index)
+	sum += vts_array[vts_array[0]] * (index - vts_array[0]);
+
+    return sum;
+}
+#endif
+
+    static vimlong_T
+get_new_sw_indent(
+    int		left,		// TRUE if shift is to the left
+    int		round,		// TRUE if new indent is to be to a tabstop
+    vimlong_T	amount,		// Number of shifts
+    vimlong_T	sw_val)
+{
+    vimlong_T	count = get_indent();
+    vimlong_T	i, j;
 
     if (round)			// round off indent
     {
@@ -252,20 +284,124 @@ shift_line(
 	}
 	else
 	    i += amount;
-	count = (vimlong_T)i * (vimlong_T)sw_val;
+	count = i * sw_val;
     }
-    else		// original vi indent
+    else			// original vi indent
     {
 	if (left)
 	{
-	    count -= (vimlong_T)sw_val * (vimlong_T)amount;
+	    count -= sw_val * amount;
 	    if (count < 0)
 		count = 0;
 	}
 	else
-	    count += (vimlong_T)sw_val * (vimlong_T)amount;
+	    count += sw_val * amount;
     }
 
+    return count;
+}
+
+#ifdef FEAT_VARTABS
+    static vimlong_T
+get_new_vts_indent(
+    int	left,			// TRUE if shift is to the left
+    int	round,			// TRUE if new indent is to be to a tabstop
+    int	amount,			// Number of shifts
+    int	*vts_array)
+{
+    vimlong_T	indent = get_indent();
+    int		vtsi = 0;
+    int		vts_indent = 0;
+    int		ts = 0;		// Silence uninitialized variable warning.
+    int		offset;		// Extra indent spaces to the right of the
+				// tabstop
+
+    // Find the tabstop at or to the left of the current indent.
+    while (vts_indent <= indent)
+    {
+	vtsi++;
+	ts = get_vts(vts_array, vtsi);
+	vts_indent += ts;
+    }
+    vts_indent -= ts;
+    vtsi--;
+
+    offset = indent - vts_indent;
+
+    if (round)
+    {
+	if (left)
+	{
+	    if (offset == 0)
+		indent = get_vts_sum(vts_array, vtsi - amount);
+	    else
+		indent = get_vts_sum(vts_array, vtsi - (amount - 1));
+	}
+	else
+	    indent = get_vts_sum(vts_array, vtsi + amount);
+    }
+    else
+    {
+	if (left)
+	{
+	    if (amount > vtsi)
+		indent = 0;
+	    else
+		indent = get_vts_sum(vts_array, vtsi - amount) + offset;
+	}
+	else
+	    indent = get_vts_sum(vts_array, vtsi + amount) + offset;
+    }
+
+    return indent;
+}
+#endif
+
+/*
+ * Shift the current line 'amount' shiftwidth(s) left (if 'left' is TRUE) or
+ * right.
+ *
+ * The rules for choosing a shiftwidth are:  If 'shiftwidth' is non-zero, use
+ * 'shiftwidth'; else if 'vartabstop' is not empty, use 'vartabstop'; else use
+ * 'tabstop'.  The Vim documentation says nothing about 'softtabstop' or
+ * 'varsofttabstop' affecting the shiftwidth, and neither affects the
+ * shiftwidth in current versions of Vim, so they are not considered here.
+ */
+    void
+shift_line(
+    int	left,			// TRUE if shift is to the left
+    int	round,			// TRUE if new indent is to be to a tabstop
+    int	amount,			// Number of shifts
+    int	call_changed_bytes)	// call changed_bytes()
+{
+    vimlong_T	count;
+    long	sw_val = curbuf->b_p_sw;
+    long	ts_val = curbuf->b_p_ts;
+#ifdef FEAT_VARTABS
+    int		*vts_array = curbuf->b_p_vts_array;
+#endif
+
+    if (sw_val != 0)
+	// 'shiftwidth' is not zero; use it as the shift size.
+	count = get_new_sw_indent(left, round, amount, sw_val);
+    else
+#ifdef FEAT_VARTABS
+	if ((vts_array == NULL) || (vts_array[0] == 0))
+#endif
+    {
+	// 'shiftwidth is zero and 'vartabstop' is empty; use 'tabstop' as the
+	// shift size.
+	count = get_new_sw_indent(left, round, amount, ts_val);
+    }
+#ifdef FEAT_VARTABS
+    else
+    {
+	// 'shiftwidth is zero and 'vartabstop' is defined; use 'vartabstop'
+	// to determine the new indent.
+	count = get_new_vts_indent(left, round, amount, vts_array);
+    }
+#endif
+
     // Set new indent
     if (State & VREPLACE_FLAG)
 	change_indent(INDENT_SET, trim_to_int(count), FALSE, NUL, call_changed_bytes);