From e1704d198b8c1320c5d608d83971c354d9bd9da1 Mon Sep 17 00:00:00 2001
From: Matthias Clasen <mclasen@redhat.com>
Date: Thu, 30 Sep 2021 17:08:29 -0400
Subject: 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
---
 pango/pangocairo-fcfont.c | 14 +++++++++++++-
 tests/testmisc.c          | 41 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 54 insertions(+), 1 deletion(-)

diff --git a/pango/pangocairo-fcfont.c b/pango/pangocairo-fcfont.c
index 0019f83a..85cc45c8 100644
--- a/pango/pangocairo-fcfont.c
+++ b/pango/pangocairo-fcfont.c
@@ -76,8 +76,20 @@ pango_cairo_fc_font_create_base_metrics_for_context (PangoCairoFont *cfont,
 						     PangoContext   *context)
 {
   PangoFcFont *fcfont = (PangoFcFont *) (cfont);
+  PangoFontMetrics *metrics;
+  const cairo_font_options_t *options;
 
-  return pango_fc_font_create_base_metrics_for_context (fcfont, context);
+  metrics = pango_fc_font_create_base_metrics_for_context (fcfont, context);
+
+  options = pango_cairo_context_get_font_options (context);
+  if (cairo_font_options_get_hint_metrics (options) == CAIRO_HINT_METRICS_ON)
+    {
+      metrics->ascent = PANGO_PIXELS_CEIL (metrics->ascent) * PANGO_SCALE;
+      metrics->descent = PANGO_PIXELS_CEIL (metrics->descent) * PANGO_SCALE;
+      metrics->height = PANGO_PIXELS_CEIL (metrics->height) * PANGO_SCALE;
+    }
+
+  return metrics;
 }
 
 static void
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 ();
 }
-- 
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