pattern: add gradient_is_solid function

It contains in a single place the logic needed to check if a gradient
pattern is solid (within a specified region).

2 files changed, 58 insertions, 0 deletions

diff --git a/src/cairo-pattern.c b/src/cairo-pattern.c
index 2aa80d5e..319101f6 100644
--- a/src/cairo-pattern.c
+++ b/src/cairo-pattern.c
@@ -1790,6 +1790,59 @@ _gradient_is_clear (const cairo_gradient_pattern_t *gradient,
 }
 
 /**
+ * _cairo_gradient_pattern_is_solid
+ *
+ * Convenience function to determine whether a gradient pattern is
+ * a solid color within the given extents. In this case the color
+ * argument is initialized to the color the pattern represents.
+ * This functions doesn't handle completely transparent gradients,
+ * thus it should be called only after _cairo_pattern_is_clear has
+ * returned FALSE.
+ *
+ * Return value: %TRUE if the pattern is a solid color.
+ **/
+cairo_bool_t
+_cairo_gradient_pattern_is_solid (const cairo_gradient_pattern_t *gradient,
+				  const cairo_rectangle_int_t *extents,
+				  cairo_color_t *color)
+{
+    unsigned int i;
+
+     /* TODO: radial, degenerate linear */
+    if (gradient->base.type == CAIRO_PATTERN_TYPE_LINEAR) {
+	if (gradient->base.extend == CAIRO_EXTEND_NONE) {
+	    cairo_linear_pattern_t *linear = (cairo_linear_pattern_t *) gradient;
+	    double t[2];
+
+	    /* We already know that the pattern is not clear, thus if some
+	     * part of it is clear, the whole is not solid.
+	     */
+
+	    if (extents == NULL)
+		return FALSE;
+
+	    _extents_to_linear_parameter (linear, extents, t);
+	    if (t[0] < 0.0 || t[1] > 1.0)
+		return FALSE;
+	}
+    } else
+	return FALSE;
+
+    for (i = 1; i < gradient->n_stops; i++)
+	if (! _cairo_color_stop_equal (&gradient->stops[0].color,
+				       &gradient->stops[i].color))
+	    return FALSE;
+
+    _cairo_color_init_rgba (color,
+			    gradient->stops[0].color.red,
+			    gradient->stops[0].color.green,
+			    gradient->stops[0].color.blue,
+			    gradient->stops[0].color.alpha);
+
+    return TRUE;
+}
+
+/**
  * _cairo_pattern_is_opaque_solid
  *
  * Convenience function to determine whether a pattern is an opaque
diff --git a/src/cairoint.h b/src/cairoint.h
index 59af6844..b7c072d2 100644
--- a/src/cairoint.h
+++ b/src/cairoint.h
@@ -2216,6 +2216,11 @@ _cairo_pattern_transform (cairo_pattern_t      *pattern,
 			  const cairo_matrix_t *ctm_inverse);
 
 cairo_private cairo_bool_t
+_cairo_gradient_pattern_is_solid (const cairo_gradient_pattern_t *gradient,
+				  const cairo_rectangle_int_t *extents,
+				  cairo_color_t *color);
+
+cairo_private cairo_bool_t
 _cairo_pattern_is_opaque_solid (const cairo_pattern_t *pattern);
 
 cairo_private cairo_bool_t