1 files changed, 10 insertions, 16 deletions

diff --git a/src/pdf_view.zig b/src/pdf_view.zig
index b2fd5866..13c02231 100644
--- a/src/pdf_view.zig
+++ b/src/pdf_view.zig
@@ -2542,11 +2542,13 @@ pub fn horizontalWheel(core: *pardes.Pardes, pane: *pardes.Pane, direction: i8)
 
 pub fn draw(
     core: *pardes.Pardes,
+    s: *pardes.Surface,
     pane: *pardes.Pane,
     rect: pardes.Rect,
     pane_id: usize,
     text_x: u16,
     text_width: u16,
+    rail: *pardes.Region,
 ) bool {
     if (comptime !enabled) return false;
     if (!core.native_images or rect.h <= pane.tag_rows) return false;
@@ -2616,16 +2618,12 @@ pub fn draw(
 
     // This frame has spent the motion used to choose its raster band.
     state.scroll_travel = 0;
-    const body_y = core.bodyTop(pane, rect);
-    const body_h = rect.h -| pane.tag_rows;
     const chrome = core.chromeTheme();
     const theme = core.theme();
     const pane_bg: pardes.Color = if (theme.bg) |color| .{ .rgb = color } else .default;
-    // The rail runs past the notice bands; only the thumb tracks the text.
-    core.surface.fill(rect.x, body_y, 1, body_h, .{ .bg = .{ .rgb = chrome.scroll_track } });
-    core.surface.fill(rect.x + 1, body_y, 1, body_h, .{ .bg = pane_bg });
-
-    const track_h: usize = body_h;
+    // The rail runs past the notice bands; only the thumb tracks the text,
+    // and it is measured here, in document pixels, for `place`'s region.
+    const track_h: usize = rail.rect.h;
     const total = @max(@as(u64, 1), state.document_height);
     const len = @max(
         @as(usize, 1),
@@ -2639,15 +2637,11 @@ pub fn draw(
         @as(u64, track_h -| 1),
         @as(u64, track_h) * offset / total,
     ));
-    var y = pos;
-    while (y < track_h and y < pos + len) : (y += 1)
-        core.surface.fill(
-            rect.x,
-            body_y + @as(u16, @intCast(y)),
-            1,
-            1,
-            .{ .bg = .{ .rgb = chrome.scroll_thumb } },
-        );
+    rail.thumb_y = @intCast(pos);
+    rail.thumb_h = @intCast(@min(len, track_h -| pos));
+    s.fill(rail.rect.x, rail.rect.y, 1, rail.rect.h, .{ .bg = .{ .rgb = chrome.scroll_track } });
+    s.fill(rail.rect.x + 1, rail.rect.y, 1, rail.rect.h, .{ .bg = pane_bg });
+    s.fill(rail.rect.x, rail.rect.y + rail.thumb_y, 1, rail.thumb_h, .{ .bg = .{ .rgb = chrome.scroll_thumb } });
     return true;
 }