Objective-C/XCode measurement question

I am building an app (desktop) that is an ad layout manager. The measurements from the Indesign template I am working with is in inches. For example, the magazine is 8x10.5 inches. So to give the user a view of the mag page I place a NSScrollView, on the main window and was using a conversion of 72 (pixels per inch) and then displaying the rulers, like so:

displayPageRect=NSMakeRect(400.0, 70.0,72*8.125,72*10.5);
displayPage = [[NSScrollView alloc] initWithFrame:displayPageRect];

//set up the rulers display
[displayPage setRulersVisible:YES];
[displayPage setHasVerticalRuler:YES];
[displayPage setHasHorizontalRuler:YES];

 //set up border color and width
 [displayPage setBorderType:NSLineBorder];

 //display the displayPage on the screen
 [[mainWin contentView] addSubview:displayPage];

this works fine but the rulers comes out in inches and is a wee bit off.

Also, notice in the image there's a purple rect that starts off screen top and is off center on the view. This is a subview of the NSScroll and is suppose to represent the margins of the page. This is also off.

    //make a new page element for page border开发者_开发百科s
PageElements* pageBorders = [PageElements new];
NSColor* borderColor = [NSColor purpleColor];
[pageBorders setColor:borderColor];
[pageBorders initWithFrame:NSMakeRect(72*.313, 72*.375, 72*7.499, 72*9.875)];
[[displayPage contentView] addSubview:pageBorders];

Obviously I am doing something wrong in my conversion/placements. Can someone correct me on this? Also, is there anyway to get the 0,0 of the ruler to line up with the x=0, y=0, coordinates of the view?

Try experimenting with the appropriate properties of the associated NSRulerView:

NSRulerView *hRuler = [displayPage horizontalRulerView];
[hRuler setMeasurementUnits:@"Points"]; // User whatever registered units you want here
[hRuler setOriginOffset:5.0]; // Experiment with this number to see way works for you

Note that the units you use when setting measurement units must be registered. There are a few defaults registered or you can use your own. See the documentation of the NSRulerView class documentation for more info on the various ways you can configure ruler views.