W3C home > Mailing lists > Public > www-style@w3.org > April 2011

Re: ISSUE-136 (getCoordsAt): Consider adding MouseEvent.getCoordsAt(element)

From: Simon Fraser <smfr@me.com>
Date: Fri, 08 Apr 2011 17:22:23 -0700
Cc: "www-dom@w3.org" <www-dom@w3.org>, "www-style@w3.org" <www-style@w3.org>
Message-id: <FC59DF98-4300-4A46-B53F-7B692A1DC113@me.com>
To: Jacob Rossi <jrossi@microsoft.com>
I agree that this belongs in CSSOM-View.

An issue in CSS is what the "local coordinate system" is for an inline element that is split over lines. What is the origin of that coordinate space?

Simon

On Apr 8, 2011, at 4:39 PM, Jacob Rossi wrote:

> Hi folks,
>  
> Per our resolution on our resolution on 2010-10-13, I have resolved this issue for D3E. Our recommendation is that this proposal be made to CSSOM-View since it is not necessarily specific to mouse events.
>  
> Thanks,
>  
> Jacob
>  
> [1] http://lists.w3.org/Archives/Public/www-dom/2010OctDec/0062.html
>  
>  
> From: Jonathan Watt <jwatt@jwatt.org>
> Date: Wed, 06 Oct 2010 23:02:27 +0100
> Message-ID: <4CACF1F3.9090601@jwatt.org>
> To: Jonas Sicking <jonas@sicking.cc>
> CC: www-dom@w3.org
> On 06/10/2010 05:29, Jonas Sicking wrote:
> > This would this also take account for things like parent plain HTML
> > elements being scrolled and things like that right?
>  
> Yes. It wouldn't be much use if it didn't.
>  
> > What happens if you pass in an element which the mouse isn't actually
> > over? Would it be possible to transform the coordinates to that
> > elements coordinate space anyway?
>  
> Yes. I don't see any reason why the pointer should be over the specified
> element. The function just transforms the pointer's x/y by the transform from
> the pointer event's coordinate system (the window coordinate system) to the
> specified element's coordinate system. It's just a transform after all.
>  
> Jonathan
>  
> From: Jonas Sicking <jonas@sicking.cc>
> Date: Tue, 5 Oct 2010 21:29:45 -0700
> Message-ID: <AANLkTinaoyv90tYuPovk8eZL76Nz1RzZUsQ1WSnJHgxg@mail.gmail.com>
> To: Jonathan Watt <jwatt@jwatt.org>
> Cc: www-dom@w3.org
> On Tue, Oct 5, 2010 at 3:06 AM, Jonathan Watt <jwatt@jwatt.org> wrote:
> > Hi WG,
> > 
> > Background:
> > 
> > Positioning elements based off the position of a pointer event is regularly
> > tripping people up in SVG, and with the advent of CSS-transforms, I imagine also
> > in HTML.
> > 
> > To position an element based off the position of a pointer event you need to get
> > the coordinates of the event in the local coordinate system of the element. To
> > do that currently authors have to get the *correct* element-to-root transform,
> > invert it, create an SVGPoint, copy the event coordinates to the SVGPoint, then
> > use the inverted transform to transform the point and read back the coordinates.
> > For something so simple, it's not obvious that this is what you need to do, or
> > even how to do it.
> > 
> > Proposal:
> > 
> > To make life easier for authors I'd like to propose the addition of a
> > 'getCoordsAt' method to the MouseEvent interface. This method would be passed
> > the element at which the local coordinates of the event are required, and return
> > an object implementing the SVGPoint interface[1] (or a new interface
> > implementing 'x' and 'y' properties).
> > 
> > I've uploaded a JavaScript implemented demo of this method here:
> > 
> >  http://jwatt.org/svg/tmp/mouse-relative-positioning.svg
> > 
> > See also the comments in the source code.
> > 
> > Regards,
> > Jonathan
> > 
> > [1] http://www.w3.org/TR/SVG11/coords.html#InterfaceSVGPoint
>  
> This would this also take account for things like parent plain HTML
> elements being scrolled and things like that right?
>  
> What happens if you pass in an element which the mouse isn't actually
> over? Would it be possible to transform the coordinates to that
> elements coordinate space anyway? Or would it simply return a
> null-like value? I would hope for the former.
>  
> / Jonas
>  
> From: Jonathan Watt <jwatt@jwatt.org>
> Date: Tue, 05 Oct 2010 11:06:04 +0100
> Message-ID: <4CAAF88C.6000307@jwatt.org>
> To: www-dom@w3.org
> Hi WG,
>  
> Background:
>  
> Positioning elements based off the position of a pointer event is regularly
> tripping people up in SVG, and with the advent of CSS-transforms, I imagine also
> in HTML.
>  
> To position an element based off the position of a pointer event you need to get
> the coordinates of the event in the local coordinate system of the element. To
> do that currently authors have to get the *correct* element-to-root transform,
> invert it, create an SVGPoint, copy the event coordinates to the SVGPoint, then
> use the inverted transform to transform the point and read back the coordinates.
> For something so simple, it's not obvious that this is what you need to do, or
> even how to do it.
>  
> Proposal:
>  
> To make life easier for authors I'd like to propose the addition of a
> 'getCoordsAt' method to the MouseEvent interface. This method would be passed
> the element at which the local coordinates of the event are required, and return
> an object implementing the SVGPoint interface[1] (or a new interface
> implementing 'x' and 'y' properties).
>  
> I've uploaded a JavaScript implemented demo of this method here:
>  
>   http://jwatt.org/svg/tmp/mouse-relative-positioning.svg
>  
> See also the comments in the source code.
>  
> Regards,
> Jonathan
>  
> [1] http://www.w3.org/TR/SVG11/coords.html#InterfaceSVGPoint
>  
Received on Saturday, 9 April 2011 00:23:07 GMT

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