Fix vertical alignment of subtitles in some cases (#2569).

3 files changed, 57 insertions, 4 deletions

diff --git a/src/lib/render_text.cc b/src/lib/render_text.cc
index ddfccbde8..8e5acc0ff 100644
--- a/src/lib/render_text.cc
+++ b/src/lib/render_text.cc
@@ -287,8 +287,14 @@ y_position(dcp::SubtitleStandard standard, dcp::VAlign align, float position, in
 struct Layout
 {
 	Position<int> position;
+	int baseline_position;
 	dcp::Size size;
 	Glib::RefPtr<Pango::Layout> pango;
+
+	int baseline_to_bottom(int border_width)
+	{
+		return position.y + size.height - baseline_position - border_width;
+	}
 };
 
 
@@ -306,7 +312,22 @@ setup_layout(vector<StringText> subtitles, dcp::Size target, DCPTime time, int f
 	auto const markup = marked_up(subtitles, target.height, fade_factor, font_name);
 	auto layout = create_layout(font_name, markup);
 	auto ink = layout->get_ink_extents();
-	return { { ink.get_x() / Pango::SCALE, ink.get_y() / Pango::SCALE }, { ink.get_width() / Pango::SCALE, ink.get_height() / Pango::SCALE }, layout };
+
+	Layout description;
+	description.position = { ink.get_x() / Pango::SCALE, ink.get_y() / Pango::SCALE };
+	description.baseline_position = layout->get_baseline() / Pango::SCALE;
+	description.size = { ink.get_width() / Pango::SCALE, ink.get_height() / Pango::SCALE };
+	description.pango = layout;
+
+	return description;
+}
+
+
+static
+int
+border_width_for_subtitle(StringText const& subtitle, dcp::Size target)
+{
+	return subtitle.effect() == dcp::Effect::BORDER ? (subtitle.outline_width * target.width / 2048.0) : 0;
 }
 
 
@@ -341,7 +362,7 @@ render_line(vector<StringText> subtitles, dcp::Size target, DCPTime time, int fr
 		}
 	}
 
-	auto const border_width = first.effect() == dcp::Effect::BORDER ? (first.outline_width * target.width / 2048.0) : 0;
+	auto const border_width = border_width_for_subtitle(first, target);
 	layout.size.width += 2 * ceil (border_width);
 	layout.size.height += 2 * ceil (border_width);
 
@@ -392,7 +413,7 @@ render_line(vector<StringText> subtitles, dcp::Size target, DCPTime time, int fr
 	context->stroke ();
 
 	int const x = x_position(first.h_align(), first.h_position(), target.width, layout.size.width);
-	int const y = y_position(first.valign_standard, first.v_align(), first.v_position(), target.height, layout.position.y, layout.size.height);
+	int const y = y_position(first.valign_standard, first.v_align(), first.v_position(), target.height, layout.baseline_to_bottom(border_width), layout.size.height);
 	return PositionImage (image, Position<int>(max (0, x), max(0, y)));
 }
 
@@ -441,7 +462,8 @@ bounding_box(vector<StringText> subtitles, dcp::Size target, optional<dcp::Subti
 		/* We can provide dummy values for time and frame rate here as they are only used to calculate fades */
 		auto layout = setup_layout(pending, target, DCPTime(), 24);
 		int const x = x_position(subtitle.h_align(), subtitle.h_position(), target.width, layout.size.width);
-		int const y = y_position(standard, subtitle.v_align(), subtitle.v_position(), target.height, layout.position.y, layout.size.height);
+		auto const border_width = border_width_for_subtitle(subtitle, target);
+		int const y = y_position(standard, subtitle.v_align(), subtitle.v_position(), target.height, layout.baseline_to_bottom(border_width), layout.size.height);
 		rects.push_back({Position<int>(x, y), layout.size.width, layout.size.height});
 	};
 
diff --git a/test/burnt_subtitle_test.cc b/test/burnt_subtitle_test.cc
index 104cbe95c..734ac7148 100644
--- a/test/burnt_subtitle_test.cc
+++ b/test/burnt_subtitle_test.cc
@@ -149,3 +149,34 @@ BOOST_AUTO_TEST_CASE (burnt_subtitle_test_onto_dcp)
 	check_dcp("test/data/burnt_subtitle_test_onto_dcp2", film2);
 #endif
 }
+
+
+
+/** Check positioning of some burnt subtitles from XML files */
+BOOST_AUTO_TEST_CASE(burnt_subtitle_test_position)
+{
+	auto check = [](string alignment)
+	{
+		auto const name = String::compose("burnt_subtitle_test_position_%1", alignment);
+		auto subs = content_factory(String::compose("test/data/burn_%1.xml", alignment));
+		auto film = new_test_film2(name, subs);
+		subs[0]->text[0]->set_use(true);
+		subs[0]->text[0]->set_burn(true);
+		make_and_verify_dcp(
+			film,
+			{
+				dcp::VerificationNote::Code::MISSING_SUBTITLE_LANGUAGE,
+				dcp::VerificationNote::Code::INVALID_SUBTITLE_FIRST_TEXT_TIME,
+				dcp::VerificationNote::Code::MISSING_CPL_METADATA
+			});
+
+		check_dcp(String::compose("test/data/%1", name), film);
+	};
+
+	/* Should have a baseline 216 pixels from the top (0.2 * 1080) */
+	check("top");
+	/* Should have a baseline 756 pixels from the top ((0.5 + 0.2) * 1080) */
+	check("center");
+	/* Should have a baseline 864 pixels from the top ((1 - 0.2) * 1080) */
+	check("bottom");
+}
diff --git a/test/data b/test/data
-Subproject 068d944183876d7a323ef60f80bdd4deee8218e
+Subproject dab44217068e681f3bfded6a8d71a54867b1cf9