pangocairo: Round font metrics when appropriate

When metrics hinting is on, we used to provide rounded
font metrics. We should keep doing that since otherwise
we end up with logical rects sometimes being rounded
and sometimes not, leading to jumping empty lines.

Test included.

Fixes: #421

1 files changed, 41 insertions, 0 deletions

diff --git a/tests/testmisc.c b/tests/testmisc.c
index 60694134..cf64e00f 100644
--- a/tests/testmisc.c
+++ b/tests/testmisc.c
@@ -489,6 +489,46 @@ test_extents (void)
   g_object_unref (context);
 }
 
+static void
+test_empty_line_height (void)
+{
+  PangoContext *context;
+  PangoLayout *layout;
+  PangoRectangle ext1, ext2, ext3;
+  cairo_font_options_t *options;
+  int hint;
+
+  context = pango_font_map_create_context (pango_cairo_font_map_get_default ());
+
+  for (hint = CAIRO_HINT_METRICS_OFF; hint <= CAIRO_HINT_METRICS_ON; hint++)
+    {
+      options = cairo_font_options_create ();
+      cairo_font_options_set_hint_metrics (options, hint);
+      pango_cairo_context_set_font_options (context, options);
+      cairo_font_options_destroy (options);
+
+      layout = pango_layout_new (context);
+
+      pango_layout_get_extents (layout, NULL, &ext1);
+
+      pango_layout_set_text (layout, "a", 1);
+
+      pango_layout_get_extents (layout, NULL, &ext2);
+
+      g_assert_cmpint (ext1.height, ==, ext2.height);
+
+      pango_layout_set_text (layout, "Pg", 1);
+
+      pango_layout_get_extents (layout, NULL, &ext3);
+
+      g_assert_cmpint (ext2.height, ==, ext3.height);
+
+      g_object_unref (layout);
+    }
+
+  g_object_unref (context);
+}
+
 int
 main (int argc, char *argv[])
 {
@@ -514,6 +554,7 @@ main (int argc, char *argv[])
   g_test_add_func ("/bidi/get-cursor", test_get_cursor);
   g_test_add_func ("/layout/index-to-x", test_index_to_x);
   g_test_add_func ("/layout/extents", test_extents);
+  g_test_add_func ("/layout/empty-line-height", test_empty_line_height);
 
   return g_test_run ();
 }