[Drawkit] Converting units

[Brad Larson]

I'm still working on the file import and am able to programmatically  
add paths and shapes now, but I'm not able to define shapes in terms  
of the proper units.  First, I initialize the drawing document with

DKDrawing *currentDrawing = [[DKDrawing alloc]  
initWithSize:NSMakeSize(1000, 1000)];
[currentDrawing setDrawingUnits:@"Microns"  
unitToPointsConversionFactor:(kGCGridDrawingLayerMetricInterval /  
10000)];

DKObjectDrawingLayer* currentLayer = [[DKObjectDrawingLayer alloc]  
init];
[currentDrawing addLayer:currentLayer];
[currentDrawing setActiveLayer:currentLayer];

DKGuideLayer* guides = [[DKGuideLayer alloc] init];
[currentDrawing addLayer:guides];
[guides release];

I'm starting with our application-specific XML format for our  
dispenser, which specifies everything in terms of microns (1 cm =  
10000 microns), so I set the drawing units to that.  I then set up the  
layers that I saw were initialized for a blank document in DrawDemo.

I parse the XML document being loaded, and, as an example, for adding  
a drawn line to the drawing I do the following (code is not efficient,  
due to debugging):

NSBezierPath* currentBezierPath = [NSBezierPath bezierPath];
NSPoint pointToConvert = NSMakePoint([[xmlPatternItemAttributes  
valueForKey:@"x"] doubleValue], [[xmlPatternItemAttributes  
valueForKey:@"y"] doubleValue]);
NSLog(@"Before: (%f,%f)",pointToConvert.x, pointToConvert.y);
DKGridLayer *testLayer = [currentDrawing gridLayer];
NSPoint convertedPoint = [testLayer  
pointForGridLocation:pointToConvert];
NSLog(@"After: (%f,%f)",pointToConvert.x, pointToConvert.y);
[currentBezierPath moveToPoint:convertedPoint];

pointToConvert = NSMakePoint([[xmlPatternItemAttributes  
valueForKey:@"x2"] doubleValue], [[xmlPatternItemAttributes  
valueForKey:@"y2"] doubleValue]);
NSLog(@"Before: (%f,%f)",pointToConvert.x, pointToConvert.y);
convertedPoint = [testLayer pointForGridLocation:pointToConvert];
NSLog(@"After: (%f,%f)",pointToConvert.x, pointToConvert.y);
[currentBezierPath lineToPoint:[[currentDrawing gridLayer]  
pointForGridLocation:pointToConvert]];
					
DKDrawablePath* currentPath = [[DKDrawablePath alloc]  
initWithBezierPath:currentBezierPath];
[currentPath setPathEditingMode:kGCPathCreateModeLineCreate];	
[currentLayer addObject:currentPath];
[currentPath release];

xmlPatternAttributes is an NSDictionary containing the parsed  
attributes of an imported drawing object, such as the starting x and y  
coordinates ("x" and "y") and ending x and y coordinates ("x2", "y2")  
of a line.  It looked to me like DKGridLayer was the repository of  
methods that would convert from realspace coordinates (x and y in  
microns) to Quartz coordinates (what's needed for the NSBezierPath)  
and back.  First, am I right in doing it this way or is there an  
easier way to create objects starting from realspace coordinates?   
Second, [currentDrawing gridLayer] is returning nil.  Is there  
something in the initialization that I've missed?  I think I have  
everything that the DrawDemo application used for initializing the  
drawing.

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