fix branchlist scrollbr

Author: Stephan Dilly

Cargo.lock

@@ -41,6 +41,7 @@ anyhow = "1.0"
 unicode-width = "0.1"
 textwrap = "0.13"
 unicode-truncate = "0.2.0"
+easy-cast = "0.4"
 
 [target.'cfg(all(target_family="unix",not(target_os="macos")))'.dependencies]
 which = "4.1"

Cargo.toml

@@ -505,6 +505,7 @@ impl BranchListComponent {
         r: Rect,
     ) -> Result<()> {
         let height_in_lines = r.height as usize;
+        self.current_height.set(height_in_lines.try_into()?);
 
         self.scroll_top.set(calc_scroll_top(
             self.scroll_top.get(),
@@ -524,17 +525,17 @@ impl BranchListComponent {
 
         let mut r = r;
         r.width += 1;
+        r.height += 2;
+        r.y = r.y.saturating_sub(1);
 
         ui::draw_scrollbar(
             f,
             r,
             &self.theme,
-            self.branches.len(),
+            self.branches.len().saturating_sub(height_in_lines),
             self.scroll_top.get(),
         );
 
-        self.current_height.set(height_in_lines.try_into()?);
-
         Ok(())
     }
 }

src/components/branchlist.rs

@@ -237,16 +237,12 @@ impl DiffComponent {
     }
 
     fn lines_count(&self) -> usize {
-        self.diff
-            .as_ref()
-            .map_or(0, |diff| diff.lines.saturating_sub(1))
+        self.diff.as_ref().map_or(0, |diff| diff.lines)
     }
 
     fn modify_selection(&mut self, direction: Direction) {
-        if let Some(diff) = &self.diff {
-            let max = diff.lines.saturating_sub(1);
-
-            self.selection.modify(direction, max);
+        if self.diff.is_some() {
+            self.selection.modify(direction, self.lines_count());
         }
     }
 
@@ -610,9 +606,11 @@ impl DrawableComponent for DiffComponent {
             r.height.saturating_sub(2),
         ));
 
+        let current_height = self.current_size.get().1;
+
         self.scroll_top.set(calc_scroll_top(
             self.scroll_top.get(),
-            self.current_size.get().1 as usize,
+            current_height as usize,
             self.selection.get_end(),
         ));
 
@@ -628,7 +626,7 @@ impl DrawableComponent for DiffComponent {
                 self.theme.text(false, false),
             )])]
         } else {
-            self.get_text(r.width, self.current_size.get().1)
+            self.get_text(r.width, current_height)
         };
 
         f.render_widget(
@@ -648,7 +646,8 @@ impl DrawableComponent for DiffComponent {
                 f,
                 r,
                 &self.theme,
-                self.lines_count(),
+                self.lines_count()
+                    .saturating_sub(usize::from(current_height)),
                 self.scroll_top.get(),
             );
         }

src/components/diff.rs

@@ -1,4 +1,5 @@
 use super::style::SharedTheme;
+use easy_cast::CastFloat;
 use std::convert::TryFrom;
 use tui::{
     backend::Backend,
@@ -12,16 +13,16 @@ use tui::{
 
 ///
 struct Scrollbar {
-    lines: u16,
+    max: u16,
     pos: u16,
     style_bar: Style,
     style_pos: Style,
 }
 
 impl Scrollbar {
-    fn new(lines: usize, pos: usize) -> Self {
+    fn new(max: usize, pos: usize) -> Self {
         Self {
-            lines: u16::try_from(lines).unwrap_or_default(),
+            max: u16::try_from(max).unwrap_or_default(),
             pos: u16::try_from(pos).unwrap_or_default(),
             style_pos: Style::default(),
             style_bar: Style::default(),
@@ -31,50 +32,51 @@ impl Scrollbar {
 
 impl Widget for Scrollbar {
     fn render(self, area: Rect, buf: &mut Buffer) {
-        let right = area.right().saturating_sub(1);
-        if right <= area.left() {
+        if area.height <= 2 {
             return;
-        };
-
-        let area = area.inner(&Margin {
-            horizontal: 0,
-            vertical: 1,
-        });
+        }
 
-        if area.height == 0 {
+        if self.max == 0 {
             return;
         }
 
-        if area.height >= self.lines {
+        let right = area.right().saturating_sub(1);
+        if right <= area.left() {
             return;
-        }
+        };
+
+        let (bar_top, bar_height) = {
+            let scrollbar_area = area.inner(&Margin {
+                horizontal: 0,
+                vertical: 1,
+            });
+
+            (scrollbar_area.top(), scrollbar_area.height)
+        };
 
-        for y in area.top()..area.bottom() {
+        for y in bar_top..(bar_top + bar_height) {
             buf.set_string(right, y, DOUBLE_VERTICAL, self.style_bar);
         }
 
-        let max_pos = self.lines.saturating_sub(area.height);
-        let progress = f32::from(self.pos) / f32::from(max_pos);
+        let progress = f32::from(self.pos) / f32::from(self.max);
         let progress = if progress > 1.0 { 1.0 } else { progress };
-        let pos = f32::from(area.height) * progress;
+        let pos = f32::from(bar_height) * progress;
 
-        //TODO: any better way for this?
-        #[allow(clippy::cast_sign_loss)]
-        #[allow(clippy::cast_possible_truncation)]
-        let pos = (pos as u16).saturating_sub(1);
+        let pos: u16 = pos.cast_nearest();
+        let pos = pos.saturating_sub(1);
 
-        buf.set_string(right, area.top() + pos, FULL, self.style_pos);
+        buf.set_string(right, bar_top + pos, FULL, self.style_pos);
     }
 }
 
 pub fn draw_scrollbar<B: Backend>(
     f: &mut Frame<B>,
     r: Rect,
     theme: &SharedTheme,
-    lines: usize,
+    max: usize,
     pos: usize,
 ) {
-    let mut widget = Scrollbar::new(lines, pos);
+    let mut widget = Scrollbar::new(max, pos);
     widget.style_pos = theme.scroll_bar_pos();
     f.render_widget(widget, r)
 }