http://developer.apple.com/documentation/Cocoa/Reference/ApplicationKit/ObjC_classic/Classes/NSTextTab.html
NSTextTab is a class used to define “Tabs” (right, left, center, decimal) for a NSParagraphStyle. This NSParagraphStyle can be applied to a number of different objects (see application to NSMutableAttributedString below).
I was disappointed to see that there wasn’t a description or useful example of NSTextTab. After hours of searching on the internet and tons of trial and error, I came up with a working NSTextTab example. This example sets up some Tabs for an NSMutableAttributedString to be used to set the “attributed” title of an NSMenuItem. There is an example of setting up a right tab, and a left tab.
NSMutableParagraphStyle *NPStyle = [[[NSMutableParagraphStyle alloc] init] autorelease]; NSFont *boldFont = [NSFont boldSystemFontOfSize:12];
[NPStyle setTabStops:[NSArray array]]; // delete default tabs
By default, a NSParagraphStyle has “12 left-aligned tabs, spaced at 28.0 points.” This threw me off the most because I didn’t realize that this code generate these defaults.
menuItemTitle = [NSString stringWithFormat:@”\t%@, %@: \t%@…%@ \t%@ \tprecip: %@”,dayName,date,low,high,shortFore,precip]; attrMenuItemTitle = [[[NSMutableAttributedString alloc] initWithString:menuItemTitle] autorelease];
// four tabs [NPStyle addTabStop:[[[NSTextTab alloc] initWithType:NSRightTabStopType location:headIndent+8] autorelease]]; [NPStyle addTabStop:[[[NSTextTab alloc] initWithType:NSLeftTabStopType location:headIndent+15] autorelease]]; [NPStyle addTabStop:[[[NSTextTab alloc] initWithType:NSLeftTabStopType location:headIndent+15+sndIndent+8] autorelease]]; [NPStyle addTabStop:[[[NSTextTab alloc] initWithType:NSLeftTabStopType location:headIndent+15+sndIndent+8+thdIndent+8] autorelease]];
The documentation for +[NSTextTab initWithType:location:] doesn’t mention what the units are for location, only that it is a float. After hours, I deduced (from above) that the units are “points” (1/72 inch). So we are setting the location of tabs based on points.
This code is used inside of a loop– I am aligning the elements of several different menuitems. headIndent is the max width of “%@, %@:” with the strings substituted in. Likewise, sndIndent is the max width of “%@…%@” and thdIndent is the max of “%@.”
In order to find the width of these various strings, I had to create intermediate strings. The code looks like this:
start loop: NSAttributedString *title = [[[NSAttributedString alloc] initWithString:[NSString stringWithFormat:@”%@, %@:\t”,date,dayName]] autorelease]; headIndent = MAX(headIndent, [title size].width); end loop;
Now we must attach attributes to the NSMutableAttributedString “attrMenuItemTitle”. To do this:
[attrMenuItemTitle addAttribute:NSFontAttributeName value:boldFont range:NSMakeRange(0,[dayName length] + [date length] + 4)]; [attrMenuItemTitle addAttribute:NSParagraphStyleAttributeName value:NPStyle range:NSMakeRange(0,[attrMenuItemTitle length])];
What does it look like? I thought a visual might help: http://www.cs.lafayette.edu/~crobakj/nstexttab_usage.jpg
-Joe
This is real nice work. Perhaps we could turn it into one of the RecentTutorials? – KritTer