Open poke opened 4 years ago
@poke thanks for contacting us.
@poke what you are mentioning makes sense.
@SteveSandersonMS do you have any thoughts here?
@poke on a second look, I think the current behavior is actually fine.
I think that as a rule, for simplicity we want to keep the behavior where something:modifier
attributes to only apply if you also have a something
applied, like in this case mousedown
.
The reason is for simplicity and consistency within the language. If we were to do so, every time we introduce a new modifier we will have to think if it makes sense to apply it in isolation or not, and that will make the rule for modifiers very complicated (as it would depend on the modifier being applied).
The alternative, even though it requires a bit more code is simpler to understand and explain. If you want to apply some modifier something:modifier
you also need to apply something
, even if that doesn't cause any action.
/cc: @SteveSandersonMS in case he has other thoughts.
where
something:modifier
attributes to only apply if you also have asomething
applied
But that’s not what is the case here. Please note that in my example, I use @onmousedown:preventDefault
on a button element while I have to apply @onmousedown
on literally any other element.
Your statement makes it sound as if you would need to put both on the same element like this:
<button @onclick="Click"
@onmousedown="() => { }"
@onmousedown:preventDefault>Test</button>
If that was the case, I would probably accept this (although I would really dislike it). But the thing is that you do not need @onmousedown
on the element. You just need it somewhere throughout the whole app to make Blazor’s client side runtime register the event once on the document element.
The fact that this is so disconnected from the @onmousedown:preventDefault
makes this very confusing, and definitely not “simpler to understand and explain”. And considering that this is preventDefault
it is also very common to put this on events that you will usually not care about, so requiring an empty event handler just to make Blazor realize that the event handler is needed feels very redundant.
I understand the desire to keep the attribute:modifier
handling simple but it shouldn’t be too problematic to make @event:modifier
also trigger an empty registration of @event
.
There's been a bit of confusion here. I think there is a bug to be addressed here.
I think that as a rule, for simplicity we want to keep the behavior where something:modifier attributes to only apply if you also have a something applied, like in this case mousedown.
That's not how this was designed - see #14517:
For each @oneventname, there's also @oneventname:preventDefault and @oneventname:stopPropagation. These can be used either alongside @oneventname or independently of it.
I do agree there are valid use cases for using preventDefault/stopPropagation independently of handlers for the same event on the same element; that's something we always intended to support and in fact do support today. The bug is when you happen not to have any handlers for a given event type anywhere in the document.
@SteveSandersonMS Thanks a lot for the clarification :)
Thanks for contacting us.
We're moving this issue to the Next sprint planning
milestone for future evaluation / consideration. We will evaluate the request when we are planning the work for the next milestone. To learn more about what to expect next and how this issue will be handled you can read more about our triage process here.
We've moved this issue to the Backlog milestone. This means that it is not going to be worked on for the coming release. We will reassess the backlog following the current release and consider this item at that time. To learn more about our issue management process and to have better expectation regarding different types of issues you can read our Triage Process.
Facing the same issue )":
any updates?
It's been 2 years + 1 day
exactly now 😀
@SteveSandersonMS @javiercn Is this something we think we can still address for .NET 7? Or is the risk too high at this point?
@danroth27 Let's discuss it with the team. I don't think the risk is particularly high though if we implemented a fix we'd have a more precise sense of how disruptive the change is.
Thanks for contacting us.
We're moving this issue to the .NET 8 Planning
milestone for future evaluation / consideration. We would like to keep this around to collect more feedback, which can help us with prioritizing this work. We will re-evaluate this issue, during our next planning meeting(s).
If we later determine, that the issue has no community involvement, or it's very rare and low-impact issue, we will close it - so that the team can focus on more important and high impact issues.
To learn more about what to expect next and how this issue will be handled you can read more about our triage process here.
This is still the issue. I was trying to make sure that event is not propagated outside of some element, e.g. Google Maps, using the mouse scroll user can scale the map, but the page that contains this map should not scroll. In case of Blazor, everything is scrollable, no matter how I try to stop the propagation outside of the element.
<div class="canvas-chart"
@onwheel="OnWheelAction"
@onmousewheel="OnWheelAction"
@onmousemove="OnMouseMoveAction"
@onmouseout="OnMouseLeaveAction"
@onmousedown="OnMouseDownAction"
@ontouchmove:preventDefault
@ontouchcancel:preventDefault
@onwheel:preventDefault
@onmousewheel:preventDefault
@onmousemove:preventDefault
@onmouseout:preventDefault
@onmousedown:preventDefault
@ontouchcancel:stopPropagation
@ontouchmove:stopPropagation
@onwheel:stopPropagation
@onmousewheel:stopPropagation
@onmousemove:stopPropagation
@onmouseout:stopPropagation
@onmousedown:stopPropagation>
</div>
In JS, simple preventDefault
does the trick.
http://jsfiddle.net/eXQf3/371/
Thanks for contacting us.
We're moving this issue to the .NET 9 Planning
milestone for future evaluation / consideration. We would like to keep this around to collect more feedback, which can help us with prioritizing this work. We will re-evaluate this issue, during our next planning meeting(s).
If we later determine, that the issue has no community involvement, or it's very rare and low-impact issue, we will close it - so that the team can focus on more important and high impact issues.
To learn more about what to expect next and how this issue will be handled you can read more about our triage process here.
Thanks for contacting us.
We're moving this issue to the .NET 9 Planning
milestone for future evaluation / consideration. We would like to keep this around to collect more feedback, which can help us with prioritizing this work. We will re-evaluate this issue, during our next planning meeting(s).
If we later determine, that the issue has no community involvement, or it's very rare and low-impact issue, we will close it - so that the team can focus on more important and high impact issues.
To learn more about what to expect next and how this issue will be handled you can read more about our triage process here.
What is the status of this?
the new record: +4 years 😲
still no update for this issue?
the new record: +4 years
There's no need for this.
Mudblazor has a working solution for that:
https://mudblazor.com/components/swipearea#prevent-default-browser-behavior
Mudblazor has a working solution for that
It's an ugly workaround. We really hope that this issue will be addressed together with https://github.com/dotnet/aspnetcore/issues/24932
When using the new
@onevent:preventDefault
directive to prevent the default event behavior for events, I noticed that in order for this to work, there needs to be a@onevent
handler registered anywhere on the page.Apparently, server-side Blazor registers every event just once on the document instead of on individual elements. So e.g.
@onclick="…"
causes theclick
event to be subscribed on the document. Just using@onclick:preventDefault
on the page does not appear to register this global event handler on document, so thepreventDefault()
call is also never made in the handler.My use case for this is managing focus with buttons: When you click a button, then the button stays focused after clicking it, causing the focused style to be applied. In order to avoid this, you can subscribe to the
mousedown
event in JavaScript and just prevent the default behavior:Doing the same in Blazor would look like this:
This however does not work if there isn’t also some
mousedown
handler registered somewhere. As soon as you add one literally anywhere, it works:This is using server-side Blazor on ASP.NET Core 3.1.