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Fix compute physicalX/Y for TalkBack events.
Extracted compute function to a helper file.
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113 changes: 113 additions & 0 deletions
113
lib/web_ui/lib/src/engine/pointer_binding/event_position_helper.dart
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,113 @@ | ||
| // Copyright 2013 The Flutter Authors. All rights reserved. | ||
| // Use of this source code is governed by a BSD-style license that can be | ||
| // found in the LICENSE file. | ||
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| import 'package:ui/ui.dart' as ui show Offset; | ||
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| import '../dom.dart'; | ||
| import '../semantics.dart' show EngineSemanticsOwner; | ||
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| /// Returns an [ui.Offset] of the position of [event], relative to the position of [actualTarget]. | ||
| /// | ||
| /// The offset is *not* multiplied by DPR or anything else, it's the closest | ||
| /// to what the DOM would return if we had currentTarget readily available. | ||
| /// | ||
| /// This needs an `actualTarget`, because the `event.currentTarget` (which is what | ||
| /// this would really need to use) gets lost when the `event` comes from a "coalesced" | ||
| /// event. | ||
| /// | ||
| /// It also takes into account semantics being enabled to fix the case where | ||
| /// offsetX, offsetY == 0 (TalkBack events). | ||
| // | ||
| // TODO(dit): Make this understand 3D transforms in the platform view case, https://github.com/flutter/flutter/issues/117091 | ||
| ui.Offset computeEventOffsetToTarget(DomMouseEvent event, DomElement actualTarget) { | ||
| // On top of a platform view | ||
| if (event.target != actualTarget) { | ||
| return _computeOffsetOnPlatformView(event, actualTarget); | ||
| } | ||
| // On a TalkBack event | ||
| if (EngineSemanticsOwner.instance.semanticsEnabled && event.offsetX == 0 && event.offsetY == 0) { | ||
| return _computeOffsetForTalkbackEvent(event, actualTarget); | ||
| } | ||
| // Return the offsetX/Y in the normal case. | ||
| return ui.Offset(event.offsetX, event.offsetY); | ||
| } | ||
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| /// Computes the event offset when hovering over a platformView. | ||
| /// | ||
| /// This still uses offsetX/Y, but adds the offset from the top/left corner of the | ||
| /// platform view to the glass pane (`actualTarget`). | ||
| /// | ||
| /// ×--FlutterView(actualTarget)--------------+ | ||
| /// |\ | | ||
| /// | x1,y1 | | ||
| /// | | | ||
| /// | | | ||
| /// | ×-PlatformView(target)---------+ | | ||
| /// | |\ | | | ||
| /// | | x2,y2 | | | ||
| /// | | | | | ||
| /// | | × (event) | | | ||
| /// | | \ | | | ||
| /// | | offsetX, offsetY | | | ||
| /// | | (Relative to PlatformView) | | | ||
| /// | +------------------------------+ | | ||
| /// +-----------------------------------------+ | ||
| /// | ||
| /// Offset between PlatformView and FlutterView (xP, yP) = (x2 - x1, y2 - y1) | ||
| /// | ||
| /// Event offset relative to FlutterView = (offsetX + xP, offsetY + yP) | ||
| ui.Offset _computeOffsetOnPlatformView(DomMouseEvent event, DomElement actualTarget) { | ||
| final DomElement target = event.target! as DomElement; | ||
| final DomRect targetRect = target.getBoundingClientRect(); | ||
| final DomRect actualTargetRect = actualTarget.getBoundingClientRect(); | ||
| final double offsetTop = targetRect.y - actualTargetRect.y; | ||
| final double offsetLeft = targetRect.x - actualTargetRect.x; | ||
| return ui.Offset(event.offsetX + offsetLeft, event.offsetY + offsetTop); | ||
| } | ||
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| /// Computes the event offset when TalkBack is firing the event. | ||
| /// | ||
| /// In this case, we need to use the clientX/Y position of the event (which are | ||
| /// relative to the absolute top-left corner of the page, including scroll), then | ||
| /// deduct the offsetLeft/Top from every offsetParent of the `actualTarget`. | ||
| /// | ||
| /// ×-Page----║-------------------------------+ | ||
| /// | ║ | | ||
| /// | ×-------║--------offsetParent(s)-----+ | | ||
| /// | |\ | | | ||
| /// | | offsetLeft, offsetTop | | | ||
| /// | | | | | ||
| /// | | | | | ||
| /// | | ×-----║-------------actualTarget-+ | | | ||
| /// | | | | | | | ||
| /// ═════ × ─ (scrollLeft, scrollTop)═ ═ ═ | ||
| /// | | | | | | | ||
| /// | | | × | | | | ||
| /// | | | \ | | | | ||
| /// | | | clientX, clientY | | | | ||
| /// | | | (Relative to Page + Scroll) | | | | ||
| /// | | +-----║--------------------------+ | | | ||
| /// | +-------║----------------------------+ | | ||
| /// +---------║-------------------------------+ | ||
| /// | ||
| /// Computing the offset of the event relative to the actualTarget requires to | ||
| /// compute the clientX, clientY of the actualTarget. To do that, we iterate | ||
| /// up the offsetParent elements of actualTarget adding their offset and scroll | ||
| /// positions. Finally, we deduct that from clientX, clientY of the event. | ||
| ui.Offset _computeOffsetForTalkbackEvent(DomMouseEvent event, DomElement actualTarget) { | ||
| assert(EngineSemanticsOwner.instance.semanticsEnabled); | ||
| // Use clientX/clientY as the position of the event (this is relative to | ||
| // the top left of the page, including scroll) | ||
| double offsetX = event.clientX; | ||
| double offsetY = event.clientY; | ||
| // Compute the scroll offset of actualTarget | ||
| DomHTMLElement parent = actualTarget as DomHTMLElement; | ||
| while(parent.offsetParent != null){ | ||
| offsetX -= parent.offsetLeft - parent.scrollLeft; | ||
| offsetY -= parent.offsetTop - parent.scrollTop; | ||
| parent = parent.offsetParent!; | ||
| } | ||
| return ui.Offset(offsetX, offsetY); | ||
| } |