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[macOS] Forward mouseDown/Up to view controller #40241

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Mar 11, 2023

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@cbracken cbracken commented Mar 11, 2023

This works around an AppKit bug in which mouseDown/mouseUp events are not correctly forwarded up the responder chain for views nested inside an NSPopover if (and only if) the macOS "Reduce Transparency" accessibility setting is enabled in the System Settings.

When the above conditions are satisfied, the nested NSView receives the mouseDown:/mouseUp: call but if it delegates to the default implementation (implemented in NSResponder) mouseDown:/mouseUp: calls are triggered on containing views (in our case FlutterViewWrapper) but not triggered on the view controller and other responders in the responder chain until we an _NSPopoverWindow class is hit.

A minimal AppKit-only (non-Flutter) repro shows this bug repros with even a minimal NSViewController implementation and an unmodified NSView. See: https://github.com/cbracken/PopoverRepro

A radar has been filed with Apple and a copy posted to OpenRadar. See: http://www.openradar.me/FB12050037

In order to work around this bug, we override mouseDown/mouseUp in the topmost containing view of FlutterView (in our case, FlutterViewWrapper) to have the behaviour documented as the default behaviour in NSResponder's mouseDown:/mouseUp: documentation. In other words, to simply forward the call to self.nextResponder.
See: https://developer.apple.com/documentation/appkit/nsresponder/1524634-mousedown

Because replicating the exact configuration of a FlutterView contained in an NSPopover and System Settings that have been modified to enable the "Reduce Transparency" setting is difficult and likely error-prone in infra, we instead simulate the bug by testing that even if NSResponder's mouseDown/mouseUp method are swizzled to no-op, these calls are correctly forwarded to the next responder in the chain.

If, in the future Apple does fix this issue, this workaround can be removed once Flutter's minimum supported macOS SDK is at least the version that contains the fix.

Issue: flutter/flutter#115015

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This works around an AppKit bug in which mouseDown/mouseUp events are
not correctly forwarded up the responder chain for views nested inside
an NSPopover if (and only if) the macOS "Reduce Transparency"
accessibility setting is enabled in the System Settings.

When the above conditions are satisfied, the nested NSView receives the
mouseDown:/mouseUp: call but if it delegates to the default
implementation (implemented in NSResponder) mouseDown/mouseUp calls are
triggered on containing views (in our case FlutterViewWrapper) but not
triggered on the view controller and other responders in the responder
chain until we an _NSPopoverWindow class is hit.

A minimal AppKit-only (non-Flutter) repro shows this behaviour repros
with even a minimal NSViewController implementation and an unmodified NSView.
See: https://github.com/cbracken/PopoverRepro

A radar has been filed with Apple and a copy posted to OpenRadar.
See: http://www.openradar.me/FB12050037

In order to work around this bug, we override mouseDown/mouseUp in the
topmost containing view of FlutterView (in our case, FlutterViewWrapper)
to have the behaviour documented as the default behaviour in
NSResponder's mouseDown/mouseUp documentation. In otherwords, to simply
forward the call to self.nextResponder.
See: https://developer.apple.com/documentation/appkit/nsresponder/1524634-mousedown

Because replicating the exact configuration of a FlutterView contained
in an NSPopover and System Settings that have been modified to enable
the "Reduce Transparency" setting is difficult and likely error-prone in
infra, we instead simulate the bug by testing that even if NSResponder's
mouseDown/mouseUp method are swizzled to no-op, these calls are
correctly forwarded to the next responder in the chain.

If, in the future Apple does fix this issue, this workaround can be
removed once Flutter's minimum supported macOS SDK is at least the
version that contains the fix.

Issue: flutter/flutter#115015
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LGTM

@cbracken cbracken merged commit 04e8d54 into flutter:main Mar 11, 2023
@cbracken cbracken deleted the reduced-transparency branch March 11, 2023 20:50
engine-flutter-autoroll added a commit to engine-flutter-autoroll/flutter that referenced this pull request Mar 11, 2023
auto-submit bot pushed a commit to flutter/flutter that referenced this pull request Mar 11, 2023
…gine#40241) (#122472)

Roll Flutter Engine from c7894a662ae1 to 04e8d5431203 (1 revision)
sourcegraph-bot pushed a commit to sgtest/megarepo that referenced this pull request Mar 11, 2023
…lutter/engine#40241) (#122472)

Commit: 5887b430c815a7802935511120f23db7c3aa3986
jonahwilliams added a commit to jonahwilliams/engine that referenced this pull request Mar 13, 2023
commit db8dfbe
Author: jonahwilliams <jonahwilliams@google.com>
Date:   Mon Mar 13 10:44:36 2023 -0700

    update malioc diff

commit 0877a53
Merge: 04e8d80 7c5a9d5
Author: jonahwilliams <jonahwilliams@google.com>
Date:   Mon Mar 13 10:40:07 2023 -0700

    Merge branch 'master' of github.com:flutter/engine into uv_computation

commit 7c5a9d5
Author: Jackson Gardner <jacksongardner@google.com>
Date:   Mon Mar 13 09:54:22 2023 -0700

    Use plain Uint32List objects with the fragmenter APIs. (flutter#40239)

    Use plain Uint32List objects with the fragmenter APIs.

commit 04e8d80
Author: jonahwilliams <jonahwilliams@google.com>
Date:   Mon Mar 13 09:50:23 2023 -0700

    fix double divide and add test

commit 9b42cbc
Author: jonahwilliams <jonahwilliams@google.com>
Date:   Mon Mar 13 09:32:48 2023 -0700

    [impeller] implement GetPositionUVBuffer

commit 3d545ad
Author: Dan Field <dnfield@google.com>
Date:   Mon Mar 13 09:22:28 2023 -0700

    [Impeller][Compute] Fix visual issues with heart (flutter#40240)

commit 650c6e3
Author: Zachary Anderson <zanderso@users.noreply.github.com>
Date:   Mon Mar 13 08:45:38 2023 -0700

    Revert "[Impeller] More sundry fixes to the Vulkan backend. (flutter#40244)" (flutter#40247)

    Revert "[Impeller] More sundry fixes to the Vulkan backend."

commit 3ac895e
Author: Jonah Williams <jonahwilliams@google.com>
Date:   Mon Mar 13 08:42:13 2023 -0700

    [Impeller] support for foreground shaders on text (flutter#40193)

    [Impeller] support for foreground shaders on text

commit bb1ca8f
Author: Lasse R.H. Nielsen <lrn@google.com>
Date:   Mon Mar 13 13:43:04 2023 +0100

    Change `extends Iterator` to using `implements` (flutter#40175)

    The Dart 3.0 libraries will mark Iterator with the interface class modifier, which prevents extends. It will do so because the class has no implementation to inherit, and is only intended as an interface, which it is now possible to express.

    This should unblock relanding https://dart-review.googlesource.com/c/sdk/+/287760
    (Also working on disabling the class-modifiers experiment for Flutter dart: libraries, which was enabled along with the Dart SDK libraries, until the experiment can be intentionally turned back on.)

commit 24afaf9
Author: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Date:   Mon Mar 13 09:44:31 2023 +0000

    Bump github/codeql-action from 2.2.5 to 2.2.6 (flutter#40246)

    Bump github/codeql-action from 2.2.5 to 2.2.6

commit ae979a8
Author: Chinmay Garde <chinmaygarde@google.com>
Date:   Sun Mar 12 23:49:22 2023 -0700

    [Impeller] More sundry fixes to the Vulkan backend. (flutter#40244)

    [Impeller] More sundry fixes to the Vulkan backend.

commit 57f7120
Author: Zachary Anderson <zanderso@users.noreply.github.com>
Date:   Sat Mar 11 19:38:43 2023 -0800

    Add GN arguments that disable building host artifacts (flutter#40242)

commit 04e8d54
Author: Chris Bracken <chris@bracken.jp>
Date:   Sat Mar 11 12:49:59 2023 -0800

    [macOS] Forward mouseDown/Up to view controller (flutter#40241)

    This works around an AppKit bug in which mouseDown/mouseUp events are
    not correctly forwarded up the responder chain for views nested inside
    an NSPopover if (and only if) the macOS "Reduce Transparency"
    accessibility setting is enabled in the System Settings.

    When the above conditions are satisfied, the nested NSView receives the
    mouseDown:/mouseUp: call but if it delegates to the default
    implementation (implemented in NSResponder) mouseDown/mouseUp calls are
    triggered on containing views (in our case FlutterViewWrapper) but not
    triggered on the view controller and other responders in the responder
    chain until we an _NSPopoverWindow class is hit.

    A minimal AppKit-only (non-Flutter) repro shows this behaviour repros
    with even a minimal NSViewController implementation and an unmodified NSView.
    See: https://github.com/cbracken/PopoverRepro

    A radar has been filed with Apple and a copy posted to OpenRadar.
    See: http://www.openradar.me/FB12050037

    In order to work around this bug, we override mouseDown/mouseUp in the
    topmost containing view of FlutterView (in our case, FlutterViewWrapper)
    to have the behaviour documented as the default behaviour in
    NSResponder's mouseDown/mouseUp documentation. In otherwords, to simply
    forward the call to self.nextResponder.
    See: https://developer.apple.com/documentation/appkit/nsresponder/1524634-mousedown

    Because replicating the exact configuration of a FlutterView contained
    in an NSPopover and System Settings that have been modified to enable
    the "Reduce Transparency" setting is difficult and likely error-prone in
    infra, we instead simulate the bug by testing that even if NSResponder's
    mouseDown/mouseUp method are swizzled to no-op, these calls are
    correctly forwarded to the next responder in the chain.

    If, in the future Apple does fix this issue, this workaround can be
    removed once Flutter's minimum supported macOS SDK is at least the
    version that contains the fix.

    Issue: flutter/flutter#115015

commit c7894a6
Author: Dan Field <dnfield@google.com>
Date:   Fri Mar 10 16:39:04 2023 -0800

    Make the context current before accessing GL in MakeSkiaGpuImage (flutter#40208)

    Make the context current before accessing GL in MakeSkiaGpuImage

commit 7f25023
Author: LongCatIsLooong <31859944+LongCatIsLooong@users.noreply.github.com>
Date:   Fri Mar 10 15:42:18 2023 -0800

    Revert "Make FlutterTest the default test font (flutter#40188)" (flutter#40237)

    This reverts commit 9270e3d.

commit 12f2fdf
Author: Yegor <yjbanov@google.com>
Date:   Fri Mar 10 14:46:06 2023 -0800

    Revert "[web] Access engine version to get correct gstatic URL (flutter#40194)" (flutter#40235)

    This reverts commit 161f759.

commit 3018843
Author: skia-flutter-autoroll <skia-flutter-autoroll@skia.org>
Date:   Fri Mar 10 17:44:48 2023 -0500

    Manual roll Dart SDK from 7240b35cc401 to c766fffb626e (9 revisions) (flutter#40233)

    Manual roll requested by asiva@google.com

    https://dart.googlesource.com/sdk.git/+log/7240b35cc401..c766fffb626e

    2023-03-10 dart-internal-merge@dart-ci-internal.iam.gserviceaccount.com Version 3.0.0-322.0.dev
    2023-03-10 dart-internal-merge@dart-ci-internal.iam.gserviceaccount.com Version 3.0.0-321.0.dev
    2023-03-10 dart-internal-merge@dart-ci-internal.iam.gserviceaccount.com Version 3.0.0-320.0.dev
    2023-03-10 dart-internal-merge@dart-ci-internal.iam.gserviceaccount.com Version 3.0.0-319.0.dev
    2023-03-09 dart-internal-merge@dart-ci-internal.iam.gserviceaccount.com Version 3.0.0-318.0.dev
    2023-03-09 dart-internal-merge@dart-ci-internal.iam.gserviceaccount.com Version 3.0.0-317.0.dev
    2023-03-09 dart-internal-merge@dart-ci-internal.iam.gserviceaccount.com Version 3.0.0-316.0.dev
    2023-03-09 dart-internal-merge@dart-ci-internal.iam.gserviceaccount.com Version 3.0.0-315.0.dev
    2023-03-09 dart-internal-merge@dart-ci-internal.iam.gserviceaccount.com Version 3.0.0-314.0.dev

    If this roll has caused a breakage, revert this CL and stop the roller
    using the controls here:
    https://autoroll.skia.org/r/dart-sdk-flutter-engine
    Please CC aam@google.com,asiva@google.com,dart-vm-team@google.com,jimgraham@google.com,rmistry@google.com on the revert to ensure that a human
    is aware of the problem.

    To file a bug in Flutter Engine: https://github.com/flutter/flutter/issues/new/choose

    To report a problem with the AutoRoller itself, please file a bug:
    https://bugs.chromium.org/p/skia/issues/entry?template=Autoroller+Bug

    Documentation for the AutoRoller is here:
    https://skia.googlesource.com/buildbot/+doc/main/autoroll/README.md

commit 220e867
Author: Zachary Anderson <zanderso@users.noreply.github.com>
Date:   Fri Mar 10 14:38:58 2023 -0800

    Roll buildroot to 287917d (flutter#40232)

    To pick up flutter/buildroot#691

commit c99baf2
Author: Jim Graham <flar@google.com>
Date:   Fri Mar 10 14:32:52 2023 -0800

    Roll Fuchsia Linux SDK to 12.20230309.0.1 (flutter#40231)

    Roll Fuchsia Linux SDK to 12.20230309.0.1

commit 3b07c4c
Author: Jonah Williams <jonahwilliams@google.com>
Date:   Fri Mar 10 14:24:45 2023 -0800

    [Impeller] remove unused shader, format malioc diff (flutter#40230)

    [Impeller] remove unused shader, format malioc diff
cbracken added a commit to cbracken/flutter_engine that referenced this pull request Aug 25, 2024
In flutter#40241, I added a workaround for an
AppKit bug wherein mouseDown/Up events were ignored when the *Reduced
Transparency* accessibility setting was enabled, and the view was hosted in an
`NSPopover`.

I filed a Radar and Apple reported the bug fixed in macOS 13.3.1.

When we drop support for macOS 12 in Flutter, we should remove the workaround in
FlutterViewController, here:
https://github.com/flutter/engine/blob/3ce6c4bf17534fddb07ea98df035d33243d9fd7a/shell/platform/darwin/macos/framework/Source/FlutterViewController.mm#L289-L316

So long as nothing else has been added to these methods at that time, the method
overrides themselves should be removed, so that we fall back to the default
behaviour.

See: http://www.openradar.me/FB12050037
See: https://developer.apple.com/documentation/appkit/nsresponder/1535349-mouseup

Issue: flutter/flutter#154063
Issue: flutter/flutter#115015
cbracken added a commit to cbracken/flutter_engine that referenced this pull request Aug 25, 2024
In flutter#40241, I added a workaround for an
AppKit bug wherein mouseDown/Up events were ignored when the *Reduced
Transparency* accessibility setting was enabled, and the view was hosted in an
`NSPopover`.

I filed a Radar and Apple reported the bug fixed in macOS 13.3.1.

When we drop support for macOS 12 in Flutter, we should remove the workaround in
FlutterViewController, here:
https://github.com/flutter/engine/blob/3ce6c4bf17534fddb07ea98df035d33243d9fd7a/shell/platform/darwin/macos/framework/Source/FlutterViewController.mm#L289-L316

So long as nothing else has been added to these methods at that time, the method
overrides themselves should be removed, so that we fall back to the default
behaviour.

See: http://www.openradar.me/FB12050037
See: https://developer.apple.com/documentation/appkit/nsresponder/1535349-mouseup

Issue: flutter/flutter#154063
Issue: flutter/flutter#115015
auto-submit bot pushed a commit that referenced this pull request Aug 25, 2024
In #40241, I added a workaround for an AppKit bug wherein mouseDown/Up events were ignored when the *Reduced Transparency* accessibility setting was enabled, and the view was hosted in an `NSPopover`.

I filed a Radar and Apple reported the bug fixed in macOS 13.3.1.

When we drop support for macOS 12 in Flutter, we should remove the workaround.

So long as nothing else has been added to these methods at that time, the method overrides themselves should be removed, so that we fall back to the default behaviour.

See: http://www.openradar.me/FB12050037
See: https://developer.apple.com/documentation/appkit/nsresponder/1535349-mouseup

Issue: flutter/flutter#154063
Issue: flutter/flutter#115015

No tests modified since this only adds a comment.

[C++, Objective-C, Java style guides]: https://github.com/flutter/engine/blob/main/CONTRIBUTING.md#style
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