[Drawkit] warped/warpable grid?

[Graham Cox]

Hi James,

It's unlikely that a grid like this would be worth my while writing as  
a general DK class, is it sounds pretty unique to your situation. I  
could just about buy the need for logarithmic or polar grids but even  
then I doubt they'd be all that worthwhile for general-purpose use.

In terms of drawing the grid and snapping a point to a given grid  
position, DKGridLayer does already give you most of what you need. As  
long as you can actually come up with a way to reliably describe your  
grid, you can implement it. To draw the grid, override the - 
createGridCacheInRect: method and use it to set up the NSBezierPath  
objects that are drawn to display the grid. To snap a given point to  
the grid, override the -nearestGridIntersectionToPoint: method and do  
what you need to do to return the right point. The nudge feature is  
more difficult at present because it assumes that the grid has a  
constant linear increment - that's something I can change so it nudges  
to the next gridline from the current point (I think - I haven't  
looked at the code in detail or remember exactly how it's implemented).

You'll also find it won't be possible to synch up a non-linear grid to  
NSRulerView unless you also subclass it, but your timeline might  
already be providing that feature.

cheers, Graham




On 7 Jun 2008, at 2:07 am, James Maxwell wrote:

> Actually, I just realized that I'd also be talking about a grid  
> which is asymmetric along the x and y axes, which is probably kind  
> of unusual... It seems pretty clear that I'll need to make a fairly  
> complex subclass of DKGridLayer, if I want to take this route, but  
> any thoughts would still be appreciated. I'm thinking particularly  
> of whether this might be something worth including in the framework,  
> in general, Graham(??).
>
> cheers,
>
> J.
>
>
> On 6-Jun-08, at 8:54 AM, James Maxwell wrote:
>
>> Hello All,
>>
>> For the musical space I'm working on I need what could really be  
>> thought of as a "warped" grid. That is, a grid which is capable of  
>> having a changing spans, majors, and divisions - at least along the  
>> x-axis. A set division value for the y-axis would be fine (I don't  
>> even really need a y-axis grid, though it might provide a handy  
>> shortcut for some purposes). Also, the variable x-axis grid should  
>> be editable by the user (i.e., dynamically changing spans, majors,  
>> divisions).
>>
>> I've been looking over DKGridLayer.m, but there doesn't seem to be  
>> support for this kind of grid. Basically, I need to be able to mark  
>> an x-axis place on the grid as a new "origin", and change the grid  
>> spacing from that point "forward" (i.e., left-to-right in musical  
>> time). I have built a simple timeline object, which maintains  
>> something similar to a grid, which I could use for this purpose,  
>> but it would be more elegant to use a grid layer, to benefit from  
>> the integration with DK. In particular, it appears that the nudge  
>> amounts are dictated by the grid, so it would be nice to pick up  
>> the nudge functionality, without having to re-write it from scratch.
>>
>> I know this is not a function that many people would likely need,  
>> but it could still find uses in other types of applications, I  
>> think. Any thoughts on how to go about doing this would be  
>> appreciated.
>>
>> cheers,
>>
>> J.
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