Preserve current position when new items are added to a buffer

tests/components/backlog.rs

@@ -31,6 +31,23 @@ fn rect(x: u16, y: u16, width: u16, height: u16) -> Rect {
   }
 }
 
+macro_rules! items_iter {
+  [ $($item: expr),* ] => {
+    || vec![
+      $(
+        {
+          let BufferItem { content, prerender, unique_id } = &$item;
+          BufferItem {
+            content: content.clone(),
+            prerender,
+            unique_id: *unique_id,
+          }
+        },
+      )*
+    ].into_iter()
+  }
+}
+
 #[test]
 fn test_single_item() {
   let mut bl = Backlog::default();
@@ -38,9 +55,10 @@ fn test_single_item() {
   let item = BufferItem {
     content: BufferItemContent::Text(Text::raw("hello")),
     prerender: &prerender,
+    unique_id: None,
   };
   let mut buf = Buffer::empty(rect(0, 0, 18, 8));
-  bl.draw_items(&mut buf, rect(3, 2, 12, 4), vec![item].into_iter())
+  bl.draw_items(&mut buf, rect(3, 2, 12, 4), items_iter![item])
     .context("Failed to draw")
     .unwrap();
 
@@ -64,10 +82,11 @@ fn test_single_item_cached() {
   let item = BufferItem {
     content: BufferItemContent::Text(Text::raw("hello")),
     prerender: &prerender,
+    unique_id: None,
   };
   let mut buf = Buffer::empty(rect(0, 0, 18, 8));
   let area = rect(3, 2, 12, 4);
-  bl.draw_items(&mut buf, area, vec![item].into_iter())
+  bl.draw_items(&mut buf, area, items_iter![item])
     .context("Failed to draw")
     .unwrap();
 
@@ -88,9 +107,10 @@ fn test_single_item_cached() {
   let item = BufferItem {
     content: BufferItemContent::Text(Text::raw("hello")),
     prerender: &prerender,
+    unique_id: None,
   };
   let mut buf = Buffer::empty(rect(0, 0, 18, 8));
-  bl.draw_items(&mut buf, area, vec![item].into_iter())
+  bl.draw_items(&mut buf, area, items_iter![item])
     .context("Failed to draw")
     .unwrap();
   assert_eq!(buf, expected);
@@ -105,16 +125,18 @@ fn test_only_necessary_width() {
   let item1 = BufferItem {
     content: BufferItemContent::Text(Text::raw("hi\nworld")),
     prerender: &prerender1,
+    unique_id: None,
   };
   let item2 = BufferItem {
     content: BufferItemContent::Text(Text::raw(":)")),
     prerender: &prerender2,
+    unique_id: None,
   };
   let mut cell = ratatui::buffer::Cell::default();
   cell.set_char('.');
   let mut buf = Buffer::filled(rect(0, 0, 18, 7), &cell); // poisoned buffer
   let area = rect(3, 1, 12, 5);
-  bl.draw_items(&mut buf, area, vec![item2, item1].into_iter())
+  bl.draw_items(&mut buf, area, items_iter![item2, item1])
     .context("Failed to draw")
     .unwrap();
 
@@ -134,13 +156,15 @@ fn test_only_necessary_width() {
   let item1 = BufferItem {
     content: BufferItemContent::Text(Text::raw("hi\nworld")),
     prerender: &prerender1,
+    unique_id: None,
   };
   let item2 = BufferItem {
     content: BufferItemContent::Text(Text::raw(":)")),
     prerender: &prerender2,
+    unique_id: None,
   };
   let mut buf = Buffer::empty(rect(0, 0, 18, 7));
-  bl.draw_items(&mut buf, area, vec![item2, item1].into_iter())
+  bl.draw_items(&mut buf, area, items_iter![item2, item1])
     .context("Failed to draw")
     .unwrap();
   let expected = Buffer::with_lines(vec![
@@ -162,9 +186,10 @@ fn test_single_item_tight() {
   let item = BufferItem {
     content: BufferItemContent::Text(Text::raw("hello")),
     prerender: &prerender,
+    unique_id: None,
   };
   let mut buf = Buffer::empty(rect(0, 0, 13, 7));
-  bl.draw_items(&mut buf, rect(3, 2, 7, 3), vec![item].into_iter())
+  bl.draw_items(&mut buf, rect(3, 2, 7, 3), items_iter![item])
     .context("Failed to draw")
     .unwrap();
 
@@ -187,14 +212,16 @@ fn test_two_items() {
   let item1 = BufferItem {
     content: BufferItemContent::Text(Text::raw("hi")),
     prerender: &prerender1,
+    unique_id: None,
   };
   let prerender2 = Prerender::new();
   let item2 = BufferItem {
     content: BufferItemContent::Text(Text::raw("world")),
     prerender: &prerender2,
+    unique_id: None,
   };
   let mut buf = Buffer::empty(rect(0, 0, 14, 7));
-  bl.draw_items(&mut buf, rect(1, 1, 12, 5), vec![item2, item1].into_iter())
+  bl.draw_items(&mut buf, rect(1, 1, 12, 5), items_iter![item2, item1])
     .context("Failed to draw")
     .unwrap();
 
@@ -219,13 +246,15 @@ fn test_two_items_scroll() {
   let item1 = BufferItem {
     content: BufferItemContent::Text(Text::raw("hi")),
     prerender: &prerender1,
+    unique_id: Some(123),
   };
   let item2 = BufferItem {
     content: BufferItemContent::Text(Text::raw("world")),
     prerender: &prerender2,
+    unique_id: Some(456),
   };
   let mut buf = Buffer::empty(rect(0, 0, 14, 7));
-  bl.draw_items(&mut buf, rect(1, 1, 12, 5), vec![item2, item1].into_iter())
+  bl.draw_items(&mut buf, rect(1, 1, 12, 5), items_iter![item2, item1])
     .context("Failed to draw")
     .unwrap();
 
@@ -245,13 +274,15 @@ fn test_two_items_scroll() {
   let item1 = BufferItem {
     content: BufferItemContent::Text(Text::raw("hi")),
     prerender: &prerender1,
+    unique_id: Some(123),
   };
   let item2 = BufferItem {
     content: BufferItemContent::Text(Text::raw("world")),
     prerender: &prerender2,
+    unique_id: Some(456),
   };
   let mut buf = Buffer::empty(rect(0, 0, 14, 7));
-  bl.draw_items(&mut buf, rect(1, 1, 12, 5), vec![item2, item1].into_iter())
+  bl.draw_items(&mut buf, rect(1, 1, 12, 5), items_iter![item2, item1])
     .context("Failed to draw")
     .unwrap();
 
@@ -271,13 +302,15 @@ fn test_two_items_scroll() {
   let item1 = BufferItem {
     content: BufferItemContent::Text(Text::raw("hi")),
     prerender: &prerender1,
+    unique_id: Some(123),
   };
   let item2 = BufferItem {
     content: BufferItemContent::Text(Text::raw("world")),
     prerender: &prerender2,
+    unique_id: Some(456),
   };
   let mut buf = Buffer::empty(rect(0, 0, 14, 7));
-  bl.draw_items(&mut buf, rect(1, 1, 12, 5), vec![item2, item1].into_iter())
+  bl.draw_items(&mut buf, rect(1, 1, 12, 5), items_iter![item2, item1])
     .context("Failed to draw")
     .unwrap();
 
@@ -300,14 +333,16 @@ fn test_two_items_multiline() {
   let item1 = BufferItem {
     content: BufferItemContent::Text(Text::raw("hi")),
     prerender: &prerender1,
+    unique_id: None,
   };
   let prerender2 = Prerender::new();
   let item2 = BufferItem {
     content: BufferItemContent::Text(Text::raw("world\n!")),
     prerender: &prerender2,
+    unique_id: None,
   };
   let mut buf = Buffer::empty(rect(0, 0, 14, 7));
-  bl.draw_items(&mut buf, rect(1, 1, 12, 5), vec![item2, item1].into_iter())
+  bl.draw_items(&mut buf, rect(1, 1, 12, 5), items_iter![item2, item1])
     .context("Failed to draw")
     .unwrap();
 
@@ -330,14 +365,16 @@ fn test_two_items_tight() {
   let item1 = BufferItem {
     content: BufferItemContent::Text(Text::raw("hi")),
     prerender: &prerender1,
+    unique_id: None,
   };
   let prerender2 = Prerender::new();
   let item2 = BufferItem {
     content: BufferItemContent::Text(Text::raw("world")),
     prerender: &prerender2,
+    unique_id: None,
   };
   let mut buf = Buffer::empty(rect(0, 0, 9, 6));
-  bl.draw_items(&mut buf, rect(1, 1, 7, 4), vec![item2, item1].into_iter())
+  bl.draw_items(&mut buf, rect(1, 1, 7, 4), items_iter![item2, item1])
     .context("Failed to draw")
     .unwrap();
 
@@ -359,11 +396,12 @@ fn test_cache_moved() {
   let item1 = BufferItem {
     content: BufferItemContent::Text(Text::raw("hi")),
     prerender: &prerender1,
+    unique_id: None,
   };
 
   // Draw once
   let mut buf = Buffer::empty(rect(0, 0, 14, 7));
-  bl.draw_items(&mut buf, rect(1, 1, 12, 5), vec![item1].into_iter())
+  bl.draw_items(&mut buf, rect(1, 1, 12, 5), items_iter![item1])
     .context("Failed to draw")
     .unwrap();
   let expected = Buffer::with_lines(vec![
@@ -381,14 +419,16 @@ fn test_cache_moved() {
   let item1 = BufferItem {
     content: BufferItemContent::Text(Text::raw("hi")),
     prerender: &prerender1,
+    unique_id: None,
   };
   let prerender2 = Prerender::new();
   let item2 = BufferItem {
     content: BufferItemContent::Text(Text::raw("world")),
     prerender: &prerender2,
+    unique_id: None,
   };
   let mut buf = Buffer::empty(rect(0, 0, 14, 7));
-  bl.draw_items(&mut buf, rect(1, 1, 12, 5), vec![item2, item1].into_iter())
+  bl.draw_items(&mut buf, rect(1, 1, 12, 5), items_iter![item2, item1])
     .context("Failed to draw")
     .unwrap();
   let expected = Buffer::with_lines(vec![
@@ -413,20 +453,23 @@ fn test_overflow_and_scroll() {
   let item1 = BufferItem {
     content: BufferItemContent::Text(Text::raw("line1 x")),
     prerender: &prerender1,
+    unique_id: None,
   };
   let item2 = BufferItem {
     content: BufferItemContent::Text(Text::raw("line2  y\nline3  y\nline4  y")),
     prerender: &prerender2,
+    unique_id: None,
   };
   let item3 = BufferItem {
     content: BufferItemContent::Text(Text::raw("line5   z")),
     prerender: &prerender3,
+    unique_id: None,
   };
   let mut buf = Buffer::empty(rect(0, 0, 14, 7));
   bl.draw_items(
     &mut buf,
     rect(1, 1, 12, 5),
-    vec![item3, item2, item1].into_iter(),
+    items_iter![item3, item2, item1],
   )
   .context("Failed to draw")
   .unwrap();
@@ -446,20 +489,23 @@ fn test_overflow_and_scroll() {
   let item1 = BufferItem {
     content: BufferItemContent::Text(Text::raw("line1 x")),
     prerender: &prerender1,
+    unique_id: None,
   };
   let item2 = BufferItem {
     content: BufferItemContent::Text(Text::raw("line2  y\nline3  y\nline4  y")),
     prerender: &prerender2,
+    unique_id: None,
   };
   let item3 = BufferItem {
     content: BufferItemContent::Text(Text::raw("line5   z")),
     prerender: &prerender3,
+    unique_id: None,
   };
   let mut buf = Buffer::empty(rect(0, 0, 14, 7));
   bl.draw_items(
     &mut buf,
     rect(1, 1, 12, 5),
-    vec![item3, item2, item1].into_iter(),
+    items_iter![item3, item2, item1],
   )
   .context("Failed to draw")
   .unwrap();
@@ -479,20 +525,23 @@ fn test_overflow_and_scroll() {
   let item1 = BufferItem {
     content: BufferItemContent::Text(Text::raw("line1 x")),
     prerender: &prerender1,
+    unique_id: None,
   };
   let item2 = BufferItem {
     content: BufferItemContent::Text(Text::raw("line2  y\nline3  y\nline4  y")),
     prerender: &prerender2,
+    unique_id: None,
   };
   let item3 = BufferItem {
     content: BufferItemContent::Text(Text::raw("line5   z")),
     prerender: &prerender3,
+    unique_id: None,
   };
   let mut buf = Buffer::empty(rect(0, 0, 14, 7));
   bl.draw_items(
     &mut buf,
     rect(1, 1, 12, 5),
-    vec![item3, item2, item1].into_iter(),
+    items_iter![item3, item2, item1],
   )
   .context("Failed to draw")
   .unwrap();
@@ -511,20 +560,23 @@ fn test_overflow_and_scroll() {
   let item1 = BufferItem {
     content: BufferItemContent::Text(Text::raw("line1 x")),
     prerender: &prerender1,
+    unique_id: None,
   };
   let item2 = BufferItem {
     content: BufferItemContent::Text(Text::raw("line2  y\nline3  y\nline4  y")),
     prerender: &prerender2,
+    unique_id: None,
   };
   let item3 = BufferItem {
     content: BufferItemContent::Text(Text::raw("line5   z")),
     prerender: &prerender3,
+    unique_id: None,
   };
   let mut buf = Buffer::empty(rect(0, 0, 14, 7));
   bl.draw_items(
     &mut buf,
     rect(1, 1, 12, 5),
-    vec![item3, item2, item1].into_iter(),
+    items_iter![item3, item2, item1],
   )
   .context("Failed to draw")
   .unwrap();
@@ -539,3 +591,79 @@ fn test_overflow_and_scroll() {
   ]);
   assert_eq!(buf, expected);
 }
+
+#[test]
+fn test_scrolledup_new_line() {
+  let mut bl = Backlog::default();
+  let prerender1 = Prerender::new();
+  let item1 = BufferItem {
+    content: BufferItemContent::Text(Text::raw("hi\nworld")),
+    prerender: &prerender1,
+    unique_id: Some(123),
+  };
+
+  // Draw once
+  let mut buf = Buffer::empty(rect(0, 0, 14, 7));
+  bl.draw_items(&mut buf, rect(1, 1, 12, 5), items_iter![item1])
+    .context("Failed to draw")
+    .unwrap();
+  let expected = Buffer::with_lines(vec![
+    "              ",
+    " ┌──────────┐ ",
+    " │          │ ",
+    " │hi        │ ",
+    " │world     │ ",
+    " └──────────┘ ",
+    "              ",
+  ]);
+  assert_eq!(buf, expected);
+
+  // Scroll up one line
+  bl.scroll_up(1);
+  let item1 = BufferItem {
+    content: BufferItemContent::Text(Text::raw("hi\nworld")),
+    prerender: &prerender1,
+    unique_id: Some(123),
+  };
+  let mut buf = Buffer::empty(rect(0, 0, 14, 7));
+  bl.draw_items(&mut buf, rect(1, 1, 12, 5), items_iter![item1])
+    .context("Failed to draw")
+    .unwrap();
+  let expected = Buffer::with_lines(vec![
+    "              ",
+    " ┌──────────┐ ",
+    " │          │ ",
+    " │          │ ",
+    " │hi        │ ",
+    " └──────────┘ ",
+    "              ",
+  ]);
+  assert_eq!(buf, expected);
+
+  // New item added at bottom, displayed paragraph should not move up
+  let item1 = BufferItem {
+    content: BufferItemContent::Text(Text::raw("hi\nworld")),
+    prerender: &prerender1,
+    unique_id: Some(123),
+  };
+  let prerender2 = Prerender::new();
+  let item2 = BufferItem {
+    content: BufferItemContent::Text(Text::raw("!")),
+    prerender: &prerender2,
+    unique_id: Some(456),
+  };
+  let mut buf = Buffer::empty(rect(0, 0, 14, 7));
+  bl.draw_items(&mut buf, rect(1, 1, 12, 5), items_iter![item2, item1])
+    .context("Failed to draw")
+    .unwrap();
+  let expected = Buffer::with_lines(vec![
+    "              ",
+    " ┌──────────┐ ",
+    " │          │ ",
+    " │          │ ",
+    " │hi        │ ",
+    " └──────────┘ ",
+    "              ",
+  ]);
+  assert_eq!(buf, expected);
+}