[tor-commits] [nyx/master] Fix slider math

[atagar at torproject.org]

commit dabcc36baab06598fa4baa76bb779f09d82814cc
Author: Damian Johnson <atagar at torproject.org>
Date:   Wed Nov 16 09:52:35 2016 -0800

    Fix slider math
    
    Damn this scrollbar method has given me a lot of headaches. Correcting an
    off-by-one error that caused the tests to fail on my netbook but pass on my
    pc.
    
    I really hope this is the last time I need to weed one of these out. For my
    personal reference here's the numbers when working through the test...
    
      top = 15
      top_index = 21
      size = 30
      self.height = 25
    
      scrollbar_height = self.height - top - 1 = 25 - 15 - 1 = 9
    
      bottom_index = top_index + scrollbar_height = 21 + 9 = 30
    
      slider_top = (scrollbar_height * top_index) // size = (9 * 21) // 30 = 6
      slider_size = (scrollbar_height * (bottom_index - top_index + 1)) // size = (9 * (30 - 21 + 1)) // 30 = 3
---
 nyx/curses.py     | 9 +++++++--
 test/subwindow.py | 6 +++---
 2 files changed, 10 insertions(+), 5 deletions(-)

diff --git a/nyx/curses.py b/nyx/curses.py
index b733449..4396ab4 100644
--- a/nyx/curses.py
+++ b/nyx/curses.py
@@ -885,9 +885,14 @@ class _Subwindow(object):
     # determines scrollbar dimensions
 
     scrollbar_height = self.height - top - 1  # -1 is for the bottom border
-    bottom_index = top_index + scrollbar_height + 1
+
+    # Bottom index of the scroll bar. We show (scrollbar_height + 1) items at a
+    # time but have -1 to make the bottom bound inclusive.
+
+    bottom_index = top_index + scrollbar_height
+
     slider_top = (scrollbar_height * top_index) // size
-    slider_size = (scrollbar_height * (bottom_index - top_index)) // size
+    slider_size = (scrollbar_height * (bottom_index - top_index + 1)) // size
     max_slider_top = scrollbar_height - slider_size - 1
 
     # ensures slider isn't at top or bottom unless really at those extreme bounds
diff --git a/test/subwindow.py b/test/subwindow.py
index db97970..61246d2 100644
--- a/test/subwindow.py
+++ b/test/subwindow.py
@@ -34,7 +34,7 @@ EXPECTED_SCROLLBAR_TOP = """
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- |
+*|
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@@ -48,7 +48,7 @@ EXPECTED_SCROLLBAR_MIDDLE = """
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- |
+*|
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@@ -62,7 +62,7 @@ EXPECTED_SCROLLBAR_BOTTOM = """
  |
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- |
+*|
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