Render only visible rows in the transcript pager

codex-rs/tui/src/pager_overlay.rs

@@ -15,13 +15,14 @@
 //! recomputed. `ChatWidget` is responsible for producing a key that changes when the active cell
 //! mutates in place or when its transcript output is time-dependent.
 
+mod scrolling;
+
 use std::io::Result;
 use std::sync::Arc;
 
 use crate::chatwidget::ActiveCellTranscriptKey;
 use crate::history_cell::HistoryCell;
 use crate::history_cell::SessionInfoCell;
-use crate::history_cell::UserHistoryCell;
 use crate::key_hint;
 use crate::key_hint::KeyBinding;
 use crate::key_hint::KeyBindingListExt;
@@ -30,18 +31,14 @@ use crate::keymap::PagerKeymap;
 use crate::render::Insets;
 use crate::render::renderable::InsetRenderable;
 use crate::render::renderable::Renderable;
-use crate::style::user_message_style;
 use crate::terminal_hyperlinks::HyperlinkLine;
-use crate::terminal_hyperlinks::mark_buffer_hyperlinks;
-use crate::terminal_hyperlinks::visible_lines_ref;
 use crate::tui;
 use crate::tui::TuiEvent;
 use crossterm::event::KeyCode;
 use crossterm::event::KeyEvent;
 use ratatui::buffer::Buffer;
 use ratatui::buffer::Cell;
 use ratatui::layout::Rect;
-use ratatui::style::Style;
 use ratatui::style::Stylize;
 use ratatui::text::Line;
 use ratatui::text::Span;
@@ -50,6 +47,9 @@ use ratatui::widgets::Clear;
 use ratatui::widgets::Paragraph;
 use ratatui::widgets::Widget;
 use ratatui::widgets::Wrap;
+use scrolling::CellRenderable;
+use scrolling::HyperlinkLinesRenderable;
+use scrolling::render_offset_content;
 
 pub(crate) enum Overlay {
     Transcript(TranscriptOverlay),
@@ -417,6 +417,11 @@ impl Renderable for CachedRenderable {
     fn render(&self, area: Rect, buf: &mut Buffer) {
         self.renderable.render(area, buf);
     }
+
+    fn render_scrolled(&self, area: Rect, buf: &mut Buffer, scroll_offset: u16) -> bool {
+        self.renderable.render_scrolled(area, buf, scroll_offset)
+    }
+
     fn desired_height(&self, width: u16) -> u16 {
         if self.last_width.get() != Some(width) {
             let height = self.renderable.desired_height(width);
@@ -427,56 +432,6 @@ impl Renderable for CachedRenderable {
     }
 }
 
-struct CellRenderable {
-    cell: Arc<dyn HistoryCell>,
-    highlighted: bool,
-}
-
-impl Renderable for CellRenderable {
-    fn render(&self, area: Rect, buf: &mut Buffer) {
-        let hyperlink_lines = self.cell.transcript_hyperlink_lines(area.width);
-        let style = if self.cell.as_any().is::<UserHistoryCell>() {
-            if self.highlighted {
-                user_message_style().reversed()
-            } else {
-                user_message_style()
-            }
-        } else {
-            Style::default()
-        };
-        let p = Paragraph::new(Text::from(visible_lines_ref(&hyperlink_lines)))
-            .style(style)
-            .wrap(Wrap { trim: false });
-        p.render(area, buf);
-        mark_buffer_hyperlinks(buf, area, &hyperlink_lines, /*scroll_rows*/ 0);
-    }
-
-    fn desired_height(&self, width: u16) -> u16 {
-        self.cell.desired_transcript_height(width)
-    }
-}
-
-struct HyperlinkLinesRenderable {
-    lines: Vec<HyperlinkLine>,
-}
-
-impl Renderable for HyperlinkLinesRenderable {
-    fn render(&self, area: Rect, buf: &mut Buffer) {
-        Paragraph::new(Text::from(visible_lines_ref(&self.lines)))
-            .wrap(Wrap { trim: false })
-            .render(area, buf);
-        mark_buffer_hyperlinks(buf, area, &self.lines, /*scroll_rows*/ 0);
-    }
-
-    fn desired_height(&self, width: u16) -> u16 {
-        Paragraph::new(Text::from(visible_lines_ref(&self.lines)))
-            .wrap(Wrap { trim: false })
-            .line_count(width)
-            .try_into()
-            .unwrap_or(/*default*/ 0)
-    }
-}
-
 #[derive(Clone, Copy, Debug, Default, Eq, PartialEq)]
 pub(crate) enum TranscriptHistoryState {
     #[default]
@@ -1055,33 +1010,6 @@ impl StaticOverlay {
     }
 }
 
-fn render_offset_content(
-    area: Rect,
-    buf: &mut Buffer,
-    renderable: &dyn Renderable,
-    scroll_offset: u16,
-) -> u16 {
-    let height = renderable.desired_height(area.width);
-    let mut tall_buf = Buffer::empty(Rect::new(
-        0,
-        0,
-        area.width,
-        height.min(area.height + scroll_offset),
-    ));
-    renderable.render(*tall_buf.area(), &mut tall_buf);
-    let copy_height = area
-        .height
-        .min(tall_buf.area().height.saturating_sub(scroll_offset));
-    for y in 0..copy_height {
-        let src_y = y + scroll_offset;
-        for x in 0..area.width {
-            buf[(area.x + x, area.y + y)] = tall_buf[(x, src_y)].clone();
-        }
-    }
-
-    copy_height
-}
-
 #[cfg(test)]
 mod tests {
     use super::*;

codex-rs/tui/src/pager_overlay/scrolling.rs

@@ -0,0 +1,123 @@
+//! Viewport-aware transcript rendering and the fallback for generic pager content.
+
+use std::sync::Arc;
+
+use crate::history_cell::HistoryCell;
+use crate::history_cell::UserHistoryCell;
+use crate::render::renderable::Renderable;
+use crate::style::user_message_style;
+use crate::terminal_hyperlinks::HyperlinkLine;
+use crate::terminal_hyperlinks::mark_buffer_hyperlinks;
+use crate::terminal_hyperlinks::visible_lines_ref;
+use ratatui::buffer::Buffer;
+use ratatui::layout::Rect;
+use ratatui::style::Style;
+use ratatui::text::Text;
+use ratatui::widgets::Paragraph;
+use ratatui::widgets::Widget;
+use ratatui::widgets::Wrap;
+
+/// Renders a committed history cell directly into the visible transcript viewport.
+pub(super) struct CellRenderable {
+    pub(super) cell: Arc<dyn HistoryCell>,
+    pub(super) highlighted: bool,
+}
+
+impl Renderable for CellRenderable {
+    fn render(&self, area: Rect, buf: &mut Buffer) {
+        self.render_scrolled(area, buf, /*scroll_offset*/ 0);
+    }
+
+    /// Scroll visible text and hyperlink metadata together without rendering hidden rows.
+    fn render_scrolled(&self, area: Rect, buf: &mut Buffer, scroll_offset: u16) -> bool {
+        let hyperlink_lines = self.cell.transcript_hyperlink_lines(area.width);
+        let style = if self.cell.as_any().is::<UserHistoryCell>() {
+            if self.highlighted {
+                user_message_style().reversed()
+            } else {
+                user_message_style()
+            }
+        } else {
+            Style::default()
+        };
+        let p = Paragraph::new(Text::from(visible_lines_ref(&hyperlink_lines)))
+            .style(style)
+            .wrap(Wrap { trim: false })
+            .scroll((scroll_offset, 0));
+        p.render(area, buf);
+        mark_buffer_hyperlinks(buf, area, &hyperlink_lines, usize::from(scroll_offset));
+        true
+    }
+
+    fn desired_height(&self, width: u16) -> u16 {
+        self.cell.desired_transcript_height(width)
+    }
+}
+
+/// Renders the optional in-flight transcript tail without allocating hidden rows.
+pub(super) struct HyperlinkLinesRenderable {
+    pub(super) lines: Vec<HyperlinkLine>,
+}
+
+impl Renderable for HyperlinkLinesRenderable {
+    fn render(&self, area: Rect, buf: &mut Buffer) {
+        self.render_scrolled(area, buf, /*scroll_offset*/ 0);
+    }
+
+    /// Keep live-tail hyperlinks aligned with the same visible rows as their text.
+    fn render_scrolled(&self, area: Rect, buf: &mut Buffer, scroll_offset: u16) -> bool {
+        Paragraph::new(Text::from(visible_lines_ref(&self.lines)))
+            .wrap(Wrap { trim: false })
+            .scroll((scroll_offset, 0))
+            .render(area, buf);
+        mark_buffer_hyperlinks(buf, area, &self.lines, usize::from(scroll_offset));
+        true
+    }
+
+    fn desired_height(&self, width: u16) -> u16 {
+        Paragraph::new(Text::from(visible_lines_ref(&self.lines)))
+            .wrap(Wrap { trim: false })
+            .line_count(width)
+            .try_into()
+            .unwrap_or(/*default*/ 0)
+    }
+}
+
+/// Render visible rows directly when supported, preserving the legacy scratch-buffer fallback.
+pub(super) fn render_offset_content(
+    area: Rect,
+    buf: &mut Buffer,
+    renderable: &dyn Renderable,
+    scroll_offset: u16,
+) -> u16 {
+    let height = renderable.desired_height(area.width);
+    let copy_height = area.height.min(height.saturating_sub(scroll_offset));
+    if copy_height == 0 {
+        return 0;
+    }
+
+    let visible_area = Rect::new(area.x, area.y, area.width, copy_height);
+    if renderable.render_scrolled(visible_area, buf, scroll_offset) {
+        return copy_height;
+    }
+
+    let mut tall_buf = Buffer::empty(Rect::new(
+        /*x*/ 0,
+        /*y*/ 0,
+        area.width,
+        scroll_offset + copy_height,
+    ));
+    renderable.render(*tall_buf.area(), &mut tall_buf);
+    for y in 0..copy_height {
+        let src_y = y + scroll_offset;
+        for x in 0..area.width {
+            buf[(area.x + x, area.y + y)] = tall_buf[(x, src_y)].clone();
+        }
+    }
+
+    copy_height
+}
+
+#[cfg(test)]
+#[path = "scrolling_tests.rs"]
+mod tests;