Don't test PDF tests known to fail due to poppler limitations

The following four tests are disabled:

	gradient-alpha, linear-gradient, text-pattern, trap-clip

We don't use XFAIL as that would disable all backends, (but
we can still usefully use these tests on backends other than
PDF).

boilerplate/cairo-boilerplate-pdf.c

@@ -42,6 +42,14 @@ typedef struct _pdf_target_closure
     cairo_surface_t	*target;
 } pdf_target_closure_t;
 
+#define ARRAY_LENGTH(__array) ((int) (sizeof (__array) / sizeof (__array[0])))
+static const char *pdf_ignored_tests[] = {
+    "gradient-alpha",
+    "linear-gradient",
+    "text-pattern",
+    "trap-clip"
+};
+
 cairo_surface_t *
 _cairo_boilerplate_pdf_create_surface (const char		 *name,
 				       cairo_content_t		  content,
@@ -53,6 +61,13 @@ _cairo_boilerplate_pdf_create_surface (const char		 *name,
     pdf_target_closure_t *ptc;
     cairo_surface_t *surface;
 
+    if (mode == CAIRO_BOILERPLATE_MODE_TEST) {
+	int i;
+	for (i = 0; i < ARRAY_LENGTH (pdf_ignored_tests); i++)
+	    if (strcmp (name, pdf_ignored_tests[i]) == 0)
+		return NULL;
+    }
+
     /* Sanitize back to a real cairo_content_t value. */
     if (content == CAIRO_TEST_CONTENT_COLOR_ALPHA_FLATTENED)
 	content = CAIRO_CONTENT_COLOR_ALPHA;

test/gradient-alpha.c

@@ -29,7 +29,8 @@ static cairo_test_draw_function_t draw;
 
 cairo_test_t test = {
     "gradient-alpha",
-    "Tests drawing of a gradient with various alpha values in the color stops",
+    "Tests drawing of a gradient with various alpha values in the color stops\n"
+    "PDF backend will not be tested due to limitations in poppler.",
     10, 10,
     draw
 };

test/linear-gradient.c

@@ -58,7 +58,8 @@ static cairo_test_draw_function_t draw;
 
 cairo_test_t test = {
     "linear-gradient",
-    "Tests the drawing of linear gradients",
+    "Tests the drawing of linear gradients\n"
+    "PDF backend will not be tested due to limitations in poppler.",
     WIDTH, HEIGHT,
     draw
 };

test/text-pattern.c

@@ -32,7 +32,8 @@ static cairo_test_draw_function_t draw;
 
 cairo_test_t test = {
     "text-pattern",
-    "Patterned Text",
+    "Patterned Text\n"
+    "PDF backend will not be tested due to limitations in poppler.",
     IMAGE_WIDTH, IMAGE_HEIGHT,
     draw
 };

test/trap-clip.c

@@ -168,7 +168,8 @@ static cairo_test_draw_function_t draw;
 
 cairo_test_t test = {
     "trap-clip",
-    "Trapezoid clipping",
+    "Trapezoid clipping\n"
+    "PDF backend will not be tested due to limitations in poppler.",
     IMAGE_WIDTH, IMAGE_HEIGHT,
     draw
 };