[pitivi] guidelines: Pixel perfect lines

[Alexandru Băluț <alexbalut src gnome org>]

commit a8bb1603073e87733e770307bc05f46e92a8938a
Author: Alexandru Băluț <alexandru balut gmail com>
Date:   Fri May 8 22:19:01 2020 +0200

    guidelines: Pixel perfect lines

 pitivi/utils/misc.py        |  9 +++++++--
 pitivi/viewer/guidelines.py | 23 +++++++++++++++--------
 tests/test_utils_misc.py    | 31 +++++++++++++++++++++++++++++++
 3 files changed, 53 insertions(+), 10 deletions(-)
---
diff --git a/pitivi/utils/misc.py b/pitivi/utils/misc.py
index 84e29a50..27b875f6 100644
--- a/pitivi/utils/misc.py
+++ b/pitivi/utils/misc.py
@@ -25,8 +25,8 @@ from urllib.parse import urlparse
 from urllib.parse import urlsplit
 
 from gi.repository import GdkPixbuf
-from gi.repository import GLib
 from gi.repository import GES
+from gi.repository import GLib
 from gi.repository import Gst
 from gi.repository import Gtk
 
@@ -230,6 +230,10 @@ def quantize(value, interval):
     return (value // interval) * interval
 
 
+def round05(value):
+    return (2 * value) // 2 + 0.5
+
+
 def show_user_manual(page=None):
     """Displays the user manual.
 
@@ -460,6 +464,7 @@ def video_info_get_natural_height(video_info):
 
     return video_info.get_height()
 
+
 def asset_get_duration(asset):
     assert isinstance(asset, GES.UriClipAsset)
 
@@ -470,4 +475,4 @@ def asset_get_duration(asset):
     if res:
         return duration
 
-    return asset.get_duration()
\ No newline at end of file
+    return asset.get_duration()
diff --git a/pitivi/viewer/guidelines.py b/pitivi/viewer/guidelines.py
index f5dcefd3..bb5ef409 100644
--- a/pitivi/viewer/guidelines.py
+++ b/pitivi/viewer/guidelines.py
@@ -21,6 +21,7 @@ from gettext import gettext as _
 
 from gi.repository import Gtk
 
+from pitivi.utils.misc import round05
 from pitivi.utils.ui import SPACING
 
 
@@ -30,17 +31,23 @@ class Guideline(Enum):
     @staticmethod
     def __three_by_three_draw_func(cr, width, height):
         for i in range(1, 3):
-            cr.move_to(i * width / 3, 0)
-            cr.line_to(i * width / 3, height)
-            cr.move_to(0, i * height / 3)
-            cr.line_to(width, i * height / 3)
+            x = round05(i * width / 3)
+            cr.move_to(x, 0)
+            cr.line_to(x, height)
+
+            y = round05(i * height / 3)
+            cr.move_to(0, y)
+            cr.line_to(width, y)
 
     @staticmethod
     def __vertical_horizontal_center_draw_func(cr, width, height):
-        cr.move_to(width / 2, 0)
-        cr.line_to(width / 2, height)
-        cr.move_to(0, height / 2)
-        cr.line_to(width, height / 2)
+        x = round05(width / 2)
+        cr.move_to(x, 0)
+        cr.line_to(x, height)
+
+        y = round05(height / 2)
+        cr.move_to(0, y)
+        cr.line_to(width, y)
 
     @staticmethod
     def __diagonals_draw_func(cr, width, height):
diff --git a/tests/test_utils_misc.py b/tests/test_utils_misc.py
new file mode 100644
index 00000000..99a19a1b
--- /dev/null
+++ b/tests/test_utils_misc.py
@@ -0,0 +1,31 @@
+# -*- coding: utf-8 -*-
+# Pitivi video editor
+# Copyright (c) 2020, Alexandru Băluț <alexandru balut gmail com>
+#
+# This program is free software; you can redistribute it and/or
+# modify it under the terms of the GNU Lesser General Public
+# License as published by the Free Software Foundation; either
+# version 2.1 of the License, or (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public
+# License along with this program; if not, see <http://www.gnu.org/licenses/>.
+from pitivi.utils.misc import round05
+from tests import common
+
+
+class TestMisc(common.TestCase):
+
+    def test_round05(self):
+        self.assertEqual(round05(0), 0.5)
+        self.assertEqual(round05(0.999), 0.5)
+
+        self.assertEqual(round05(1), 1.5)
+        self.assertEqual(round05(1.999), 1.5)
+
+        self.assertEqual(round05(2), 2.5)
+        self.assertEqual(round05(2.999), 2.5)