[Android] CarouselView: Remove rounding from SizedItemContentView that results in off-by-one pixel error

[filipnavara]

Description of Change

CarouselViewHandler on Android has a measurement logic that converts back and forth between sizes in different units (Context.FromPixels/Context.ToPixels). The logic in SizedItemContentView was inadvertently rounding the values, resulting in some size measurement having an off-by-one width on certain devices and emulators (eg. 1079 instead of 1080). This in turn resulted in the carousel being scrolled to incorrect item on re-measurement triggered from closing a modal page.

Before	After

Issues Fixed

[rmarinho]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 3 pipeline(s).

[jsuarezruiz]

The AddItemsToCarouselViewWorks UITest is failing on Android. In the test we add a new item and try to scroll to it.

This are the differences:

The scroll seems to not be working, the CurrentItem keeps the first item.

[filipnavara]

The AddItemsToCarouselViewWorks UITest is failing on Android.

I am not surprised it fails. I'm surprised it ever worked...

The item is added, which triggers MauiCarouselRecyclerView.CollectionItemsSourceChanged. This schedules the following code block to the dispatcher:

maui/src/Controls/src/Core/Handlers/Items/Android/MauiCarouselRecyclerView.cs

Lines 270 to 288 in c21b518

	Carousel.
	Handler.
	MauiContext.
	GetDispatcher()
	.Dispatch(() =>
	{
	SetCurrentItem(carouselPosition);
	UpdatePosition(carouselPosition);
	//If we are adding or removing the last item we need to update
	//the inset that we give to items so they are centered
	if (e.NewStartingIndex == count - 1 || removingLastElement)
	{
	UpdateItemDecoration();
	}
	UpdateVisualStates();
	});

Next, TestCarouselView.ScrollTo(5, animate: false); correctly scrolls the carousel to 5th item...
... which is then reset back by the dispatched code above.

Removing the delayed dispatch fixes this particular test. I'm not sure what was it supposed to handle. Unfortunately, this breaks this part of the logic:

maui/src/Controls/src/Core/Handlers/Items/Android/MauiCarouselRecyclerView.cs

Line 263 in c21b518

// Queue the rest up for later after the Adapter has finished processing item change notifications

[filipnavara]

I made a pragmatic change that should fix the test.

[rmarinho]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 3 pipeline(s).

[filipnavara]

Seems like there was a lot of timeouts ... and a diff for the test above, which actually shows the fixed size:

[filipnavara]

Was there a specific reason why this got closed?

[rmarinho]

@filipnavara sorry it was my fault I screwed up the force push I think . Can you reopen with your local copy ? Thanks

[filipnavara]

@filipnavara sorry it was my fault I screwed up the force push I think . Can you reopen with your local copy ? Thanks

Gotcha. I'll reopen and force push a rebased version.

[rmarinho]

We need to update images tests for CarouselView

[filipnavara]

Is it possible to rebase and also add a UI test that replicates the issue?

I can rebase it but it will likely fail the UI tests again because of the changed baseline and the images will need to be updated. Frankly, it's becoming quite cumbersome doing this for several months now.

Replicating the issue with wrong scrolling may be a bit tricky. Replicating the wrong rounding resulting in wrongly sized items is already covered by existing tests.

[rmarinho]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 3 pipeline(s).

[rmarinho]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 3 pipeline(s).

[rmarinho]

/azp run MAUI-DeviceTests-public

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[rmarinho]

/azp run MAUI-public

[rmarinho]

/azp run MAUI-UITests-public

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[filipnavara]

@rmarinho Thanks!