From b85de9a2d017b52c392fac1b5bcf8d6407da39cf Mon Sep 17 00:00:00 2001
From: Ian Gulliver <git@flamingcow.io>
Date: Sat, 17 Oct 2026 10:52:39 -0700
Subject: [PATCH] jumpy scroll 2

---
 mac/Sources/Byre/Chat.swift         | 15 ++++++++++++---
 mac/Sources/Byre/MarkdownView.swift |  4 ++++
 2 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/mac/Sources/Byre/Chat.swift b/mac/Sources/Byre/Chat.swift
index d6ff725..669285e 100644
--- a/mac/Sources/Byre/Chat.swift
+++ b/mac/Sources/Byre/Chat.swift
@@ -1,5 +1,6 @@
 import AppKit
 import ByreAPI
+import os
 import SwiftUI
 
 enum ChatKind: Equatable {
@@ -484,10 +485,13 @@ struct CompactButton: View {
     }
 }
 
+let scrollLog = Logger(subsystem: "run.fc.byre.mac", category: "scroll")
+
 private struct ScrollMetrics: Equatable {
     let content: CGFloat
     let visible: CGFloat
     let distance: CGFloat
+    let offset: CGFloat
 }
 
 private struct TranscriptScroll: View {
@@ -535,25 +539,30 @@ private struct TranscriptScroll: View {
         .scrollPosition($position)
         .defaultScrollAnchor(.bottom)
         .onScrollGeometryChange(for: ScrollMetrics.self) { g in
-            ScrollMetrics(content: g.contentSize.height, visible: g.visibleRect.height, distance: g.contentSize.height - g.visibleRect.maxY)
+            ScrollMetrics(content: g.contentSize.height, visible: g.visibleRect.height, distance: g.contentSize.height - g.visibleRect.maxY, offset: g.contentOffset.y)
         } action: { old, new in
+            let snap = !scrolling && model.stuck && new.distance > 1 && (new.content != old.content || new.visible != old.visible)
+            scrollLog.notice("geom rows=\(model.builder.root.rows.count) content=\(new.content) dContent=\(new.content - old.content) offset=\(new.offset) dOffset=\(new.offset - old.offset) visible=\(new.visible) distance=\(new.distance) scrolling=\(scrolling) stuck=\(model.stuck) snap=\(snap)")
             if scrolling {
                 model.stuck = new.distance < 80
                 return
             }
-            if model.stuck && new.distance > 1 && (new.content != old.content || new.visible != old.visible) {
+            if snap {
                 position.scrollTo(edge: .bottom)
             }
         }
-        .onScrollPhaseChange { _, phase in
+        .onScrollPhaseChange { old, phase in
+            scrollLog.notice("phase \(String(describing: old), privacy: .public) -> \(String(describing: phase), privacy: .public)")
             scrolling = phase.isScrolling
         }
         .onChange(of: model.builder.pending.count) {
+            scrollLog.notice("pending scrollTo bottom")
             model.stuck = true
             position.scrollTo(edge: .bottom)
         }
         .onChange(of: model.scrollRequest?.seq, initial: true) {
             if let r = model.scrollRequest {
+                scrollLog.notice("request scrollTo \(String(describing: r.id), privacy: .public)")
                 position.scrollTo(id: r.id, anchor: r.anchor)
             }
         }
diff --git a/mac/Sources/Byre/MarkdownView.swift b/mac/Sources/Byre/MarkdownView.swift
index bb85016..5544840 100644
--- a/mac/Sources/Byre/MarkdownView.swift
+++ b/mac/Sources/Byre/MarkdownView.swift
@@ -1,3 +1,4 @@
+import os
 import SwiftUI
 
 enum MDSegment {
@@ -449,8 +450,10 @@ private struct FlowText: NSViewRepresentable {
         func size(_ text: NSAttributedString, _ width: CGFloat?) -> CGSize {
             let same = measured.map { $0.text === text || $0.text.isEqual(to: text) } ?? false
             if same, let m = measured, m.width == width {
+                scrollLog.notice("measure hit len=\(text.length) width=\(width ?? -1) height=\(m.size.height)")
                 return m.size
             }
+            let start = ContinuousClock.now
             if !same {
                 storage.setAttributedString(text)
             }
@@ -458,6 +461,7 @@ private struct FlowText: NSViewRepresentable {
             layout.ensureLayout(for: container)
             let used = layout.usedRect(for: container)
             let size = CGSize(width: width ?? ceil(used.width), height: ceil(used.height))
+            scrollLog.notice("measure miss len=\(text.length) width=\(width ?? -1) oldWidth=\(self.measured?.width ?? -1) newText=\(!same) height=\(size.height) ms=\((ContinuousClock.now - start) / .milliseconds(1))")
             measured = (text, width, size)
             return size
         }