From 670b496a824b91d6dd331d61355042b10420dcf9 Mon Sep 17 00:00:00 2001
From: Stephan Dilly <dilly.stephan@gmail.com>
Date: Fri, 30 Oct 2020 02:34:23 +0100
Subject: [PATCH] fix scrollbar (#350)

---
 src/components/commit_details/details.rs |  3 +--
 src/components/diff.rs                   |  2 +-
 src/ui/scrollbar.rs                      | 23 +++++++++++++----------
 3 files changed, 15 insertions(+), 13 deletions(-)

diff --git a/src/components/commit_details/details.rs b/src/components/commit_details/details.rs
index 6bcc66a01a..f11cd914b3 100644
--- a/src/components/commit_details/details.rs
+++ b/src/components/commit_details/details.rs
@@ -359,8 +359,7 @@ impl DrawableComponent for DetailsComponent {
                 f,
                 chunks[1],
                 &self.theme,
-                self.get_number_of_lines(width as usize)
-                    .saturating_sub(height as usize),
+                self.get_number_of_lines(width as usize),
                 self.scroll_top.get(),
             )
         }
diff --git a/src/components/diff.rs b/src/components/diff.rs
index d38c0eb35d..cf6e3a05f7 100644
--- a/src/components/diff.rs
+++ b/src/components/diff.rs
@@ -591,7 +591,7 @@ impl DrawableComponent for DiffComponent {
                 r,
                 &self.theme,
                 self.lines_count(),
-                self.selection.get_end(),
+                self.scroll_top.get(),
             );
         }
 
diff --git a/src/ui/scrollbar.rs b/src/ui/scrollbar.rs
index 673c3ceadf..5cd63bd472 100644
--- a/src/ui/scrollbar.rs
+++ b/src/ui/scrollbar.rs
@@ -12,16 +12,16 @@ use tui::{
 
 ///
 struct Scrollbar {
-    max: u16,
+    lines: u16,
     pos: u16,
     style_bar: Style,
     style_pos: Style,
 }
 
 impl Scrollbar {
-    fn new(max: usize, pos: usize) -> Self {
+    fn new(lines: usize, pos: usize) -> Self {
         Self {
-            max: u16::try_from(max).unwrap_or_default(),
+            lines: u16::try_from(lines).unwrap_or_default(),
             pos: u16::try_from(pos).unwrap_or_default(),
             style_pos: Style::default(),
             style_bar: Style::default(),
@@ -41,11 +41,11 @@ impl Widget for Scrollbar {
             vertical: 1,
         });
 
-        if area.height < 4 {
+        if area.height == 0 {
             return;
         }
 
-        if area.height > self.max {
+        if area.height >= self.lines {
             return;
         }
 
@@ -53,12 +53,15 @@ impl Widget for Scrollbar {
             buf.set_string(right, y, THICK_VERTICAL, self.style_bar);
         }
 
-        let progress = f32::from(self.pos) / f32::from(self.max);
-        let pos = f32::from(area.height.saturating_sub(1)) * progress;
+        let max_pos = self.lines.saturating_sub(area.height);
+        let progress = f32::from(self.pos) / f32::from(max_pos);
+        let progress = if progress > 1.0 { 1.0 } else { progress };
+        let pos = f32::from(area.height) * progress;
+
         //TODO: any better way for this?
         #[allow(clippy::cast_sign_loss)]
         #[allow(clippy::cast_possible_truncation)]
-        let pos = pos as u16;
+        let pos = (pos as u16).saturating_sub(1);
 
         buf.set_string(right, area.top() + pos, FULL, self.style_pos);
     }
@@ -68,10 +71,10 @@ pub fn draw_scrollbar<B: Backend>(
     f: &mut Frame<B>,
     r: Rect,
     theme: &SharedTheme,
-    max: usize,
+    lines: usize,
     pos: usize,
 ) {
-    let mut widget = Scrollbar::new(max, pos);
+    let mut widget = Scrollbar::new(lines, pos);
     widget.style_pos = theme.scroll_bar_pos();
     f.render_widget(widget, r)
 }