From 3a836aaa922dae723908803854b09605db115df1 Mon Sep 17 00:00:00 2001
From: Alexandre Bury <alexandre.bury@gmail.com>
Date: Thu, 12 Oct 2017 12:30:00 -0700
Subject: [PATCH] Fixes drag scroll position

---
 src/div.rs         | 29 +++++++++++++++--------------
 src/view/scroll.rs | 11 ++++++-----
 2 files changed, 21 insertions(+), 19 deletions(-)

diff --git a/src/div.rs b/src/div.rs
index faddc8b..f8d581b 100644
--- a/src/div.rs
+++ b/src/div.rs
@@ -1,15 +1,16 @@
+use num::Num;
 
-// Integer division that rounds up.
-// pub fn div_up_usize(p: usize, q: usize) -> usize {
-// div_up(p as u32, q as u32) as usize
-// }
-//
-// Integer division that rounds up.
-// pub fn div_up(p: u32, q: u32) -> u32 {
-// if p % q == 0 {
-// p / q
-// } else {
-// 1 + p / q
-// }
-// }
-//
+/// Integer division that rounds up.
+#[allow(dead_code)]
+pub fn div_up<T>(p: T, q: T) -> T
+where
+    T: Num + Clone,
+{
+    let d = p.clone() / q.clone();
+
+    if p % q == T::zero() {
+        d
+    } else {
+        T::one() + d
+    }
+}
diff --git a/src/view/scroll.rs b/src/view/scroll.rs
index 7799f79..70430e0 100644
--- a/src/view/scroll.rs
+++ b/src/view/scroll.rs
@@ -2,6 +2,7 @@ use Printer;
 use std::cmp::{max, min};
 use theme::ColorStyle;
 use vec::Vec2;
+use div::div_up;
 
 /// Provide scrolling functionalities to a view.
 ///
@@ -146,9 +147,10 @@ impl ScrollBase {
     pub fn scroll_to_thumb(&mut self, thumb_y: usize, thumb_height: usize) {
         // The min() is there to stop at the bottom of the content.
         // The saturating_sub is there to stop at the bottom of the content.
+        eprintln!("Scrolling to {}", thumb_y);
         self.start_line = min(
-            (1 + self.content_height - self.view_height) * thumb_y
-                / (self.view_height - thumb_height + 1),
+            div_up((1 + self.content_height - self.view_height) * thumb_y
+                , (self.view_height - thumb_height + 1)),
             self.content_height - self.view_height,
         );
     }
@@ -180,11 +182,9 @@ impl ScrollBase {
         } else {
             // Just jump a bit...
             self.thumb_grab = height / 2;
+            self.drag(position);
         }
 
-        self.drag(position);
-
-
         true
     }
 
@@ -192,6 +192,7 @@ impl ScrollBase {
     pub fn drag(&mut self, position: Vec2) {
         // Our goal is self.scrollbar_thumb_y()+thumb_grab == position.y
         // Which means that position.y is the middle of the scrollbar.
+        eprintln!("Dragged: {:?}", position);
         let height = self.scrollbar_thumb_height();
         let grab = self.thumb_grab;
         self.scroll_to_thumb(position.y.saturating_sub(grab), height);