[Drawkit] Questions on control knobs

[Brad Larson]

On Jun 26, 2008, at 7:43 PM, Graham Cox wrote:
>
>> There's just one issue I have with the current implementation, and  
>> that's when you are drawing the arc it currently uses a stroke  
>> width of 2.0 for the initial radius line.  At the high  
>> magnifications that we're dealing with, that becomes enormous.  For  
>> someone who is zoomed out, it might also present a problem.  This  
>> could be fixed by copying the current style and changing its color  
>> to make the temporary stroke style used at the beginning of  
>> DKArcPath's  arcCreateLoop: method, rather than generating it from  
>> scratch using the styleWithFillColour:strokeColour:strokeWidth:  
>> method as is done now.  This should be simple, but I can't figure  
>> out an easy way to reach into a DKStyle and address its DKStroke so  
>> that I can set the DKStroke's properties.
>
> I agree the 2.0 stroke is way too heavy, but in fact I've addressed  
> it by losing it altogether. Now that the shape uses the normal  
> selection highlighting and DKKnob to do its thing, during the  
> creation phase that serves perfectly fine, with no need to hack the  
> style about as previously. It also means that the arcCreateLoop  
> function is a lot simpler and more straightforward (I do love it  
> when that happens - cut out lots of code and it works *better*!).
>
> If you'd like the final source for DKArcPath I'll post it, otherwise  
> it'll be in the next drop.
>

I can wait for the next release.  It won't be too hard for me to  
adjust the code I have to fit the minor namespace and API changes.

>> Additionally, I have one last shape (source attached) that is  
>> simply a point.  We use it to represent a single droplet put down  
>> by our dispenser, so it's a very simple object that can't be  
>> resized, only placed on the drawing and moved.  Internally, its  
>> path just consists of a MoveTo the center of the point and a LineTo  
>> the same center point.  We use a feature style that has rounded  
>> endcaps and is as wide as the droplet would be.  I cribbed most of  
>> its code from the DKArcPath example you provided.  I can load and  
>> save the object using our XML file handling routines that  
>> programmatically create it, drag on its center to move it around,  
>> and delete it, but when I go to draw it, I click on the drawing and  
>> see it appear, then immediately disappear as I lift up the mouse.   
>> There didn't seem to be a path drawing routine that handled  
>> stamping an object onto the drawing, so I repurposed  
>> lineCreateLoop:, but nothing leaps out at me as to what's going  
>> wrong.  I'll keep digging, but any suggestions as to what I might  
>> be missing would be greatly appreciated.
>
> The short answer:
>
> add this overridden method to your point class:
>
> - (BOOL)  objectIsValid
> {
> 	return YES;
> }
>
>
> The long(er) answer:
>
> When DKObjectCreationTool is creating a shape or path, it starts off  
> with a size of zero. For most objects, a size of zero at the end of  
> the creation operation (mouse up) would mean that a useless object  
> was created, so rather than pollute the drawing with such objects  
> (which would usually be invisible), it discards it. Whether the  
> object is really OK to be added depends on the result from - 
> objectIsValid, so the object can determine for itself what it  
> considers to be "valid". Check out the implementation in  
> DKDrawablePath and DKDrawableShape for examples. For a naked  
> DKDrawableObject, this returns NO by default.
>
> So your point object gets temporarily added by the creation tool,  
> then because it thinks it isn't valid at mouse up, it is then  
> discarded. That's why it appears then disappears. You can just  
> return YES as suggested or figure out a better test.


I figured that it was related to some sort of culling, but didn't know  
where.  Thanks again, this works well.

______________________
Brad Larson
SonoPlot, Inc.
3030 Laura Lane, Suite 120
Middleton, WI 53562