From 580edb4f4b189ba7b4b5648aa7fb99b8a80efd7c Mon Sep 17 00:00:00 2001
From: Will McGugan <willmcgugan@gmail.com>
Date: Fri, 6 May 2022 16:39:03 +0100
Subject: [PATCH] comment and tests

---
 src/textual/widget.py  |  3 +++
 tests/test_geometry.py | 12 ++++++++++++
 2 files changed, 15 insertions(+)

diff --git a/src/textual/widget.py b/src/textual/widget.py
index 96b02a10c..ece019f25 100644
--- a/src/textual/widget.py
+++ b/src/textual/widget.py
@@ -423,8 +423,11 @@ class Widget(DOMNode):
         container_region = self.content_region + container_geometry.region.origin
 
         if widget_region in container_region:
+            # Widget is visible, nothing to do
             return False
 
+        # We can either scroll so the widget is at the top of the container, or so that
+        # it is at the bottom. We want to pick which has the shortest distance
         top_delta = widget_region.origin - container_region.origin
         bottom_delta = widget_region.origin - (
             container_region.origin
diff --git a/tests/test_geometry.py b/tests/test_geometry.py
index 72d5de462..26b7a330b 100644
--- a/tests/test_geometry.py
+++ b/tests/test_geometry.py
@@ -132,6 +132,18 @@ def test_region_origin():
     assert Region(1, 2, 3, 4).origin == Offset(1, 2)
 
 
+def test_region_bottom_left():
+    assert Region(1, 2, 3, 4).bottom_left == Offset(1, 6)
+
+
+def test_region_top_right():
+    assert Region(1, 2, 3, 4).top_right == Offset(4, 2)
+
+
+def test_region_bottom_right():
+    assert Region(1, 2, 3, 4).bottom_right == Offset(4, 6)
+
+
 def test_region_add():
     assert Region(1, 2, 3, 4) + (10, 20) == Region(11, 22, 3, 4)
     with pytest.raises(TypeError):