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migrate web engine implementation to null-safe Dart #19172

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yjbanov merged 25 commits into from
Jun 26, 2020
Merged

migrate web engine implementation to null-safe Dart #19172

yjbanov merged 25 commits into from
Jun 26, 2020

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@yjbanov yjbanov commented Jun 19, 2020 •
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Description

This upgrades the dart:_engine code to null-safe Dart.

Notable changes:

  • Apply the new syntax (?, !, etc)
  • Implicit downcasts become explicit (required by the new language)
  • Disable dart2js inlining for tests for better stack traces
  • CSS attributes are no longer nullable => changed to assigning empty string instead of null
  • Changed html.window.navigator.clipboard?.writeText != null and html.window.navigator.clipboard?.readText != null to just html.window.navigator.clipboard != null because the tear-offs are never null.
  • Unimplemented non-null API that used to return null now throws UnsupportedError.
  • PathMetrics iterators throw RangeError instead of returning null (matches mobile behavior).
  • Refactor compositor/rasterizer.dart and compositor/surface.dart to initialize HtmlViewEmbedder upon construction so that it can be final and non-null.
  • Throw errors when CanvasKit fails to construct a GL surface, instead of just printing to window.console (this removes many null situations).
  • Replace List<Conic> with _ConicPair as temporary storage of results (NNBD does not support fixed-capacity lists).
  • Converted some constructors to factories so that final fields can be immediately initialized to non-null values as opposed to lazy initializing them (e.g. WriteBuffer, SurfaceCanvas)
  • EngineLineMetrics.withText uses bogus values for unsupported fields
  • Factories no longer return null (e.g. factory AutofillInfo.fromFrameworkMessage). This is a new language requirement.
  • Fixes an issue with getBoxesForRange in RTL mode (see paragraph_test.dart)

How to review this PR

  • This PR touches every file in the dart:_engine. It is not practical for one person to carefully review all of it. Instead, each reviewer is assigned a subset of files (although do feel free to comment on anything). The assignments are tracked in this spreadsheet: https://docs.google.com/spreadsheets/d/1Efar1J6eDARoeDlDI4qXdoldJuxUcMUeLpXpu3gQDMA/edit?pli=1#gid=180643056
  • The PR does not fix all nullability issues. It is not practical to address them all in a PR of this size. If you see places where something should be non-null but isn't, please file an issue so we remember to fix this in a smaller follow-up PR. The reverse is not true, however. If something has been make non-null where it should be nullable could lead to a bug, so please comment on that.

Related Issues

Fixes flutter/flutter#58811

@yjbanov yjbanov force-pushed the nnbd-migrate-web-engine branch from 74a6197 to def757f Compare June 20, 2020 00:12
ferhatb
ferhatb reviewed Jun 20, 2020
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First batch of comments.

ferhatb
ferhatb reviewed Jun 21, 2020
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Comments Batch2

lib/web_ui/lib/src/engine/houdini_canvas.dart
///
/// Painting outside the bounds of this rectangle is cropped.
final ui.Rect bounds;
final ui.Rect? bounds;
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@ferhatb ferhatb Jun 21, 2020

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why nullable?

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@yjbanov yjbanov Jun 23, 2020

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Should we kill HoudiniCanvas until we're ready for a proper investigation? Not sure if it's worth maintaining it with no tests and users.

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@ferhatb ferhatb Jun 24, 2020

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Please go ahead.

mdebbar
mdebbar reviewed Jun 22, 2020
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This is a great effort! Thank you so much for working on it.

I'm still not done with the review, but wanted to submit the comments I have so far. All my comments are things we can iterate on later, not blockers.

lib/web_ui/lib/src/engine/browser_detection.dart Outdated
/// This is used to implement operating system specific behavior such as
/// soft keyboards.
OperatingSystem get operatingSystem {
OperatingSystem? get operatingSystem {
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@mdebbar mdebbar Jun 22, 2020

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IIUC, this should never return null. debugOperatingSystemOverride is returned only if it's non-null. And _detectOperatingSystem() returns a non-nullable.

Maybe we need the same trick you did in line 45?

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@yjbanov yjbanov Jun 23, 2020

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Done.

lib/web_ui/lib/src/engine/browser_detection.dart Outdated
return debugBrowserEngineOverride;
}
return _browserEngine ??= _detectBrowserEngine();
return debugBrowserEngineOverride ?? (_browserEngine ??= _detectBrowserEngine());
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@mdebbar mdebbar Jun 22, 2020

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Is this required to make the analyzer happy? I think it's possible to infer from the old code that the result is always non-nullable. Is this a known issue or should we file one?

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@yjbanov yjbanov Jun 23, 2020

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Yes, this is to satisfy the type inference. It's a known issue, but not easily solvable. Maybe sealed classes will help one day.

lib/web_ui/lib/src/engine/browser_location.dart Outdated

/// The active path in the browser history.
String get path;
String? get path;
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@mdebbar mdebbar Jun 22, 2020

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Is there a reason this is nullable? In the HashLocationStrategy it always returns a string.

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@yjbanov yjbanov Jun 23, 2020

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Done.

lib/web_ui/lib/src/engine/test_embedding.dart Outdated

@override
void pushState(dynamic state, String title, String url) {
void pushState(dynamic state, String title, String? url) {
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@mdebbar mdebbar Jun 22, 2020

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The nullable url here is probably what's causing multiple other things to be nullable (e.g. String? get path, etc). Let's make it non-nullable?

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@yjbanov yjbanov Jun 23, 2020

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Done.

lib/web_ui/lib/src/engine/test_embedding.dart

@override
void replaceState(dynamic state, String title, String url) {
void replaceState(dynamic state, String title, String? url) {
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@mdebbar mdebbar Jun 22, 2020

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ditto

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@yjbanov yjbanov Jun 23, 2020

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Done.

lib/web_ui/lib/src/engine/pointer_binding.dart Outdated
static PointerBinding? _instance;

static void initInstance(html.Element glassPaneElement) {
static void initInstance(html.Element? glassPaneElement) {
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@mdebbar mdebbar Jun 22, 2020

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glassPaneElement should never be null.

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@yjbanov yjbanov Jun 23, 2020

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Done.

lib/web_ui/lib/src/engine/pointer_binding.dart Outdated
final html.Element? glassPaneElement;
_PointerDataCallback _callback;
PointerDataConverter _pointerDataConverter;
PointerDataConverter? _pointerDataConverter;
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@mdebbar mdebbar Jun 22, 2020

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I couldn't find a situation where this can be null. It's always initialized in the constructor.

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@yjbanov yjbanov Jun 23, 2020

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Done.

lib/web_ui/lib/src/engine/profiler.dart Outdated
}

static Profiler get instance {
static Profiler? get instance {
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@mdebbar mdebbar Jun 22, 2020

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This never returns null. If _instance is null, it throws.

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@yjbanov yjbanov Jun 23, 2020

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Done.

lib/web_ui/lib/src/engine/text/measurement.dart Outdated
@visibleForTesting
ParagraphRuler findOrCreateRuler(ParagraphGeometricStyle style) {
ParagraphRuler ruler = _rulers[style];
ParagraphRuler? findOrCreateRuler(ParagraphGeometricStyle style) {
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@mdebbar mdebbar Jun 22, 2020

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In all cases, this function returns a ruler.

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@yjbanov yjbanov Jun 23, 2020

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Done.

lib/web_ui/lib/src/engine/text/paragraph.dart Outdated
final String? _ellipsis;
final ui.Locale? _locale;

String? get _effectiveFontFamily {
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@mdebbar mdebbar Jun 22, 2020

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This is never null.

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@yjbanov yjbanov Jun 23, 2020

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Done.

@yjbanov yjbanov force-pushed the nnbd-migrate-web-engine branch from d9771b6 to 56ea6bb Compare June 22, 2020 16:56
nturgut
nturgut reviewed Jun 22, 2020
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lib/web_ui/lib/src/engine/text_editing/input_type.dart Outdated

/// Given a [domElement], set attributes that are specific to this input type.
void configureInputMode(html.HtmlElement domElement) {
void configureInputMode(html.HtmlElement? domElement) {
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@nturgut nturgut Jun 22, 2020

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When calling this method, dom_element should not be null.

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@yjbanov yjbanov Jun 23, 2020

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Done

nturgut
nturgut reviewed Jun 22, 2020
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lib/web_ui/lib/src/engine/text_editing/input_type.dart Outdated
if (operatingSystem == OperatingSystem.iOs ||
operatingSystem == OperatingSystem.android) {
domElement.setAttribute('inputmode', inputmodeAttribute);
domElement!.setAttribute('inputmode', inputmodeAttribute!);
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@nturgut nturgut Jun 22, 2020

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dom_element should not be null

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@yjbanov yjbanov Jun 23, 2020

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Done

nturgut
nturgut reviewed Jun 22, 2020
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lib/web_ui/lib/src/engine/text_editing/input_type.dart Outdated
const EngineInputType();

static EngineInputType fromName(String name) {
static EngineInputType fromName(String? name) {
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@nturgut nturgut Jun 22, 2020

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name shouldn't be null. It always get defaulted to TextInputType.text on the framework side.

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@yjbanov yjbanov Jun 23, 2020

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Done.

@yjbanov yjbanov mentioned this pull request Jun 22, 2020
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@yjbanov yjbanov marked this pull request as ready for review June 22, 2020 19:29
ditman
ditman reviewed Jun 22, 2020
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yjbanov commented Jun 23, 2020

I think responded to all the comments (at least those I was able to find). PTAL! This is no longer a draft. While I'm still testing manually, this is good to go.

@yjbanov yjbanov force-pushed the nnbd-migrate-web-engine branch from 231bb98 to a21cf7e Compare June 23, 2020 23:52
nturgut
nturgut reviewed Jun 24, 2020
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lib/web_ui/lib/src/engine/semantics/semantics_helper.dart Outdated
}

html.Element prepareAccesibilityPlaceholder() {
html.Element? prepareAccesibilityPlaceholder() {
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@nturgut nturgut Jun 24, 2020

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prepareAccesibilityPlaceholder always returns a value so this is never null.

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@yjbanov yjbanov Jun 24, 2020

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Done.

nturgut
nturgut reviewed Jun 24, 2020
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lib/web_ui/lib/src/engine/semantics/semantics_helper.dart Outdated
@override
html.Element prepareAccesibilityPlaceholder() {
_semanticsPlaceholder = html.Element.tag('flt-semantics-placeholder');
html.Element? prepareAccesibilityPlaceholder() {
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@nturgut nturgut Jun 24, 2020

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this is never null (related to the previous comment)

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@yjbanov yjbanov Jun 24, 2020

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Done.

nturgut
nturgut reviewed Jun 24, 2020
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lib/web_ui/lib/src/engine/text_editing/text_editing.dart Outdated
AutofillInfo.fromFrameworkMessage(focusedElementAutofill);
final Map<String, html.HtmlElement> elements = <String, html.HtmlElement>{};
final Map<String, AutofillInfo> items = <String, AutofillInfo>{};
final Map<String?, html.HtmlElement> elements = <String?, html.HtmlElement>{};
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@nturgut nturgut Jun 24, 2020

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I might be missing something, I don't understand the usage of String? as a map key.

Does that mean the key is nullable?

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@yjbanov yjbanov Jun 24, 2020

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Done. Most of the conversion is syntactic. Prior to null safety everything was nullable. The goal of this PR is to convert to the new syntax (i.e. add ? to what's nullable). Converting to non-null is nice-to-have, but it's not realistic to clean up everything in one PR. I expect most of the actual refactoring will happen in many small PRs following this one.

nturgut
nturgut reviewed Jun 24, 2020
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lib/web_ui/lib/src/engine/text_editing/text_editing.dart Outdated
<StreamSubscription<html.Event>>[];
keys.forEach((String key) {
final html.Element element = elements[key];
keys.forEach((String? key) {
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@nturgut nturgut Jun 24, 2020

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same question. Why map can have null keys?

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@yjbanov yjbanov Jun 24, 2020

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Done.

nturgut
nturgut reviewed Jun 24, 2020
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lib/web_ui/lib/src/engine/text_editing/text_editing.dart Outdated
///
/// Used as id of the text field.
final String uniqueIdentifier;
final String? uniqueIdentifier;
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@nturgut nturgut Jun 24, 2020

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If there is autofill info, it means this value is always sent. Therefore this should not be null.

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@yjbanov yjbanov Jun 24, 2020

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Done.

nturgut
nturgut reviewed Jun 24, 2020
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lib/web_ui/lib/src/engine/text_editing/text_editing.dart Outdated
/// in the field.
/// See: https://developer.mozilla.org/en-US/docs/Web/HTML/Attributes/autocomplete
final String hint;
final String? hint;
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@nturgut nturgut Jun 24, 2020

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Same as above comment: "If there is autofill info, it means this value is always sent. Therefore this should not be null."

@yjbanov yjbanov force-pushed the nnbd-migrate-web-engine branch from a21cf7e to 8bb4e61 Compare June 24, 2020 18:11
ferhatb
ferhatb suggested changes Jun 24, 2020
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lib/web_ui/lib/src/engine/surface/painting.dart Outdated
@override
set strokeMiterLimit(double value) {
assert(value != null);
throw UnsupportedError('SurfacePaint.strokeMiterLimit');
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@ferhatb ferhatb Jun 24, 2020

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Please keeps assert and add TODO, there is already an issue i believe. Otherwise it would be breaking change (some apps using it today would start failing).

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@yjbanov yjbanov Jun 26, 2020

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Done.

lib/web_ui/lib/src/engine/surface/path.dart Outdated
(t1 * t1 * y2);
// Expand bounds.
minX = math.min(minX, extremaX);
minX = math.min(minX, extremaX as double);
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@ferhatb ferhatb Jun 24, 2020

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Suggestion change tprime/extremaX/Y to final double and remove as. Here and below.

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@yjbanov yjbanov Jun 26, 2020

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Done, although it seems as double is a noop in dart2js. It compiles to:

  extremaX = t13 * curX + t14 * cpX + t12 * x2;
  extremaY = t13 * curY + t14 * cpY + t12 * y2;
  minX = Math.min(minX, extremaX);
  maxX = Math.max(maxX, extremaX);
  minY = Math.min(minY, extremaY);
  maxY = Math.max(maxY, extremaY);

harryterkelsen
harryterkelsen suggested changes Jun 24, 2020
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lib/web_ui/lib/src/engine/compositor/rasterizer.dart
);

if (frameSize.isEmpty) {
if (layerTree.frameSize.isEmpty) {
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@harryterkelsen harryterkelsen Jun 24, 2020

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this never sets the frameSize on layerTree

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@yjbanov yjbanov Jun 24, 2020

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In order to de-null frameSize I changed the initialization sequence a little. frameSize is now final non-null field on LayerTree, so it's guaranteed to be available.

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@yjbanov yjbanov Jun 24, 2020

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I also removed frameSize from Rasterizer as it is available in the LayerTree, which Rasterizer has access to already.

harryterkelsen
harryterkelsen reviewed Jun 24, 2020
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lib/web_ui/lib/src/engine/window.dart Outdated
}

@override
double get devicePixelRatio => _debugDevicePixelRatio != null
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@harryterkelsen harryterkelsen Jun 24, 2020

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could this be double get devicePixelRatio => _debugDevicePixelRatio ?? browserDevicePixelRatio;

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Done.

@yjbanov yjbanov force-pushed the nnbd-migrate-web-engine branch from d78ee38 to 43882d0 Compare June 26, 2020 16:26
@yjbanov yjbanov mentioned this pull request Jun 26, 2020
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@yjbanov yjbanov merged commit de74f8a into flutter:master Jun 26, 2020
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@ditman ditman ditman approved these changes

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Make dart:_engine (web engine implementation) null safe

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