Fix scroll limitation #41

CHANGELOG.md

@@ -1,6 +1,11 @@
 CHANGELOG
 =========
 
+0.1.1
+-----
+
+- Fix scroll limitation in source view #41
+
 0.1.0
 -----
 

src/app.rs

@@ -637,8 +637,9 @@ impl App {
                 context,
             });
         }
-        self.history.push(entry);
         self.session_view.reset();
+        self.session_view.scroll_to_line(entry.source(0).line_no);
+        self.history.push(entry);
         Ok(())
     }
 

src/view/session.rs

@@ -1,3 +1,5 @@
+use std::cell::Cell;
+
 use super::context::ContextComponent;
 use super::source::SourceComponent;
 use super::stack::StackComponent;
@@ -184,6 +186,7 @@ fn build_pane_widget(frame: &mut Frame, app: &App, pane: &Pane, area: Rect, inde
     };
 }
 
+#[derive(Default)]
 pub struct SearchState {
     pub show: bool,
     pub search: String,
@@ -196,9 +199,11 @@ impl SearchState {
     }
 }
 
+#[derive(Default)]
 pub struct SessionViewState {
     pub full_screen: bool,
     pub source_scroll: (u16, u16),
+    pub source_area: Cell<Rect>,
     pub context_scroll: (u16, u16),
     pub context_filter: SearchState,
     pub stack_scroll: (u16, u16),
@@ -207,17 +212,12 @@ pub struct SessionViewState {
     pub current_pane: usize,
 }
 
-impl Default for SessionViewState {
-    fn default() -> Self {
-        Self::new()
-    }
-}
-
 impl SessionViewState {
     pub fn new() -> Self {
         Self {
             full_screen: false,
             source_scroll: (0, 0),
+            source_area: Cell::new(Rect::new(0, 0, 0, 0)),
             context_scroll: (0, 0),
             context_filter: SearchState {
                 show: false,
@@ -271,10 +271,56 @@ impl SessionViewState {
     pub(crate) fn stack_depth(&self) -> u16 {
         self.stack_scroll.0
     }
+
+    pub(crate) fn scroll_to_line(&mut self, line_no: u32) -> () {
+        let area = self.source_area.get();
+        let mid_point = (area.height as u32).div_ceil(2);
+        let offset = if line_no > mid_point {
+            line_no - mid_point
+        } else {
+            0
+        };
+        self.source_scroll.0 = offset as u16;
+    }
 }
 
-#[derive(Debug, Clone)]
+#[derive(Debug, Clone, Default)]
 pub enum SessionViewMode {
+    #[default]
     Current,
     History,
 }
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    pub fn scroll_to_line() -> () {
+        let mut view = SessionViewState::default();
+        view.source_area = Cell::new(Rect{
+            x: 0,
+            y: 0,
+            width: 0,
+            height: 10, 
+        });
+        view.scroll_to_line(0);
+
+        assert_eq!(0, view.source_scroll.0);
+
+        view.scroll_to_line(5);
+        assert_eq!(0, view.source_scroll.0);
+
+        view.scroll_to_line(6);
+        assert_eq!(1, view.source_scroll.0);
+
+        view.scroll_to_line(10);
+        assert_eq!(5, view.source_scroll.0);
+
+        view.scroll_to_line(20);
+        assert_eq!(15, view.source_scroll.0);
+
+        view.scroll_to_line(100);
+        assert_eq!(95, view.source_scroll.0);
+    }
+}

src/view/source.rs

@@ -34,6 +34,11 @@ impl View for SourceComponent {
             .constraints(constraints)
             .split(area);
 
+        // make the app aware of the source area so we can
+        // center the source code on the releant line when
+        // setpping into code
+        app.session_view.source_area.set(rows[0]);
+
         let mut annotations = vec![];
         let mut lines: Vec<Line> = Vec::new();
 
@@ -86,23 +91,16 @@ impl View for SourceComponent {
             }
         }
 
-        let scroll: u16 = if stack.source.line_no as u16 > area.height {
-            let center = (stack.source.line_no as u16)
-                .saturating_sub(area.height.div_ceil(2)) as i16;
-            center
-                .saturating_add(app.session_view.source_scroll.0 as i16)
-                .max(0) as u16
-        } else {
-            app.session_view.source_scroll.0
-        };
-
-        frame.render_widget(Paragraph::new(lines.clone()).scroll((scroll, app.session_view.source_scroll.1)), rows[0]);
+        frame.render_widget(
+            Paragraph::new(lines.clone()).scroll(app.session_view.source_scroll),
+            rows[0],
+        );
 
         for (line_no, line_length, line) in annotations {
             let x_offset =  rows[0].x + (line_length as u16).saturating_sub(app.session_view.source_scroll.1);
             let area = Rect {
                 x: x_offset,
-                y: (line_no as u32).saturating_sub(scroll as u32) as u16 + 1,
+                y: (line_no as u32).saturating_sub(app.session_view.source_scroll.0 as u32) as u16 + 1,
                 width: rows[0].width.saturating_sub(x_offset),
                 height: 1,
             };