nesquena-hermes
fe40912eb9
iOS Safari portrait resolves its dynamic toolbar height after first paint; when the toolbar collapses the #messages scroller grows (clientHeight up), firing a scroll event with decreased scrollTop that was misread as an upward user scroll -> falsely set _messageUserUnpinned, and the ResizeObserver settle then self-cancelled, leaving the reader stranded at the TOP of a freshly-opened conversation (landscape unaffected since it doesn't resize late). Sibling of #4701. Fix (touch-safe, no-op on desktop/landscape where clientHeight is stable): - Track _lastMessageClientHeight; gate movedUp on !grew so a container-height INCREASE can't be read as an upward scroll. Reset on session switch. - For explicit (open) settles, also observe the scroller itself so a late portrait toolbar collapse re-anchors the bottom. Independent of #4818 (overflow-anchor paint-gap) — different mechanism, coexists. Diagnosis credit: investigation. Co-authored-by: reinocheong <reporter>
48 lines
2.4 KiB
Python
48 lines
2.4 KiB
Python
"""Regression test for #4702 (sibling #4701).
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iOS Safari in PORTRAIT resolves its dynamic toolbar height *after* first paint.
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When the toolbar collapses, the #messages scroller grows (clientHeight increases),
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which fires a native scroll event with a DECREASED scrollTop even though the user
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never scrolled. Before the fix that reflow was misread as an upward scroll
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(`movedUp`), which falsely set `_messageUserUnpinned=true; _scrollPinned=false` on
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a freshly-opened session — stranding portrait readers at the top, and the late
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ResizeObserver settle then self-cancelled because of the false unpin.
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These are source-level guards (the runtime behavior is iOS-Safari-specific and not
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reproducible in CI), mirroring the static-assertion style of
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test_issue1360_streaming_scroll_hardening.py.
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"""
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import pathlib
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REPO = pathlib.Path(__file__).resolve().parent.parent
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UI_JS = (REPO / "static" / "ui.js").read_text(encoding="utf-8")
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def test_client_height_growth_guard_declared():
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"""The scroller-height tracker must be declared so a toolbar-settle reflow can
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be distinguished from a real user scroll."""
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assert "let _lastMessageClientHeight=null;" in UI_JS
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def test_moved_up_ignores_container_growth():
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"""`movedUp` must be gated on `!grew` so a clientHeight increase (toolbar
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collapse) can't be misread as an upward user scroll (#4702)."""
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assert "const grew=_lastMessageClientHeight!==null&&el.clientHeight>_lastMessageClientHeight+1;" in UI_JS
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assert "const movedUp=!grew&&_lastScrollTop!==null&&top<_lastScrollTop-2;" in UI_JS
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# The height must be sampled every scroll event (so the next delta compares fresh).
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assert "_lastMessageClientHeight=el.clientHeight;" in UI_JS
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def test_client_height_tracker_reset_on_session_switch():
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"""A genuine session switch must reset the tracker so a stale cross-session
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height comparison can't suppress a real first scroll."""
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reset_idx = UI_JS.index("function _resetScrollDirectionTracker(){")
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body = UI_JS[reset_idx: reset_idx + 600]
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assert "_lastMessageClientHeight=null;" in body
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def test_explicit_settle_observes_scroller_for_portrait_toolbar():
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"""An explicit (open/user) settle must also observe the scroller itself, so a
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late portrait toolbar collapse re-anchors the bottom (#4702 defense-in-depth)."""
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assert "if(explicit&&observed!==el){ try{ ro.observe(el); }catch(_){ } }" in UI_JS
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