test: Use a group to render PDF correctly using poppler.

In order to support blend modes, we need to use a clear background
whilst rendering the PDF, which inspired the use of DEST_OVER to avoid
having to render to an intermediate surface. However, the adjunct of
using subpixel text means that we cannot simply using the alpha channel
as the sole mask and so need to render to an intermediate and paint it
over an opaque background.

1 files changed, 6 insertions, 3 deletions

diff --git a/test/any2ppm.c b/test/any2ppm.c
index 55b4c7ec7..b4c9de6fe 100644
--- a/test/any2ppm.c
+++ b/test/any2ppm.c
@@ -357,14 +357,17 @@ _poppler_render_page (const char *filename,
 
     poppler_page_get_size (page, &width, &height);
 
-    surface = cairo_image_surface_create (CAIRO_FORMAT_ARGB32, width, height);
+    surface = cairo_image_surface_create (CAIRO_FORMAT_RGB24, width, height);
     cr = cairo_create (surface);
 
+    cairo_set_source_rgb (cr, 1., 1., 1.);
+    cairo_paint (cr);
+    cairo_push_group_with_content (cr, CAIRO_CONTENT_COLOR_ALPHA);
+
     poppler_page_render (page, cr);
     g_object_unref (page);
 
-    cairo_set_operator (cr, CAIRO_OPERATOR_DEST_OVER);
-    cairo_set_source_rgb (cr, 1., 1., 1.);
+    cairo_pop_group_to_source (cr);
     cairo_paint (cr);
 
     status = cairo_status (cr);