[OpenLayers-Dev] mouse cursors

[Tim Schaub]

Hey-

Disregard if this is not relevant here - only going a quick skim.

CSS class names that modify the cursor should be added and removed from 
existing element class names.

That is

class="olControlFoo someCursorClass"
class="olControlFoo someOtherCursorClass"

These class names can be managed (added, removed, existence tested) with 
simple utility methods.  I suggest the following

OpenLayers.Element.hasClassName
OpenLayers.Element.addClassName
OpenLayers.Element.removeClassName

I'll make a ticket and create a patch for these.  To see working code 
that does this, check out:

http://trac.openlayers.org/browser/sandbox/topp/almanac/lib/OpenLayers/BaseTypes/Element.js#L126

(and relevant tests in the tests dir)

All this assumes that you are reusing cursors for multiple controls.

Tim


bartvde at osgis.nl wrote:
> Hi list,
> 
> I've been working a bit on mouse cursors in OL, and would like to request
> some feedback on the current approach.
> 
> I've got an example up in my sandbox:
> http://dev.openlayers.org/sandbox/bartvde/cursor/examples/cursor.html
> 
> And I've added a very preliminary patch to ticket1484:
> http://trac.openlayers.org/attachment/ticket/1484/ticket1484.patch
> 
> I'll try and outline my approach a bit. The most difficult decision I found
> was whether or not to use css. I find it quite a bit of overhead to make
> css classes for all possible cursor combinations. In my case I would need
> the following classes (looks already quite cumbersome to me):
> 
> .olControlZoomBoxCursor
> .olControlZoomBoxOutCursor
> .olControlDragPanCursor
> .olControlDragPanMouseupCursor
> .olControlDragPanMousedownCursor
> 
> etc.? As you can see, even control properties (like the out property for
> ZoomBox) come into play, so we would need something like a cursorClass
> property for people to override the default class names. For the approach
> to work, we would need them to start their names with the 'olControl'
> prefix, otherwise we don't know which css classes are safe to remove from
> the map div when e.g. a different control is activated (we cannot just
> remove any css class from the map div, since people might have set stuff on
> it, so we should remove all classes that start with 'olControl' or some
> similar approach). This can be error-prone IMHO.
> 
> I did see there are some utility functions (like addClass, removeClass,
> toggleClass) in topp's almanac sandbox which could be used.
> 
> Disadvantage ofcourse of my approach is that the mouse cursors cannot
> easily be altered by non-programmers, but I wonder how often a chosen
> cursor approach will change in a project.
> 
> If people feel strongly that css is the way to go though, I can change the
> code to add and remove css classes on the map div.
> 
> What I've done is briefly:
> 
> * add a cursor property on the Control class, which is set on the map div
> when the control is activated
> * add a cursors property (array) on the Handler class, which makes it
> possible to set cursors on the map div in different functions of a Handler
> (like mousedown). For now I've only implemented mousedown and mouseup in
> the Drag Handler as an example.
> 
> I think the example and the patch tells the rest of the story best.
> 
> Feedback very much welcome. TIA.
> 
> Best regards,
> Bart
> 
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