Core Fruition

Custom Drawing Using drawRect, Part 1

One of the more advanced techniques for creating custom user interfaces on the Mac is the use of NSView’s drawRect method.  Many answers to questions on StackOverflow and Apple’s mailing lists include recommendations to “just override drawRect and do the drawing yourself”.  Some folks see this recommendation and their eyes glaze over, thinking that it’s too advanced of a technique for them to wrap their heads around.  Over the next few days I’m going to go over some basic techniques that can yield powerful results.

Let’s start by setting up the Xcode project that will be the basis of the rest of these posts.

  • Open Xcode and create a new Cocoa Application project called DrawingSample.

  • Create a new NSView subclass called CustomDrawingView.

  • Open MainMenu.xib, add a new Custom View to the Main Window, set its class to be CustomDrawingView, and set it’s autosizing flags as seen here:

DrawingSample IB Layout

Save and Quit Interface Builder and switch back to Xcode.  Open CustomDrawingView.m, it should look like so:

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@implementation CustomDrawingView

- (id)initWithFrame:(NSRect)frame {
    self = [super initWithFrame:frame];
    if (self) {
        // Initialization code here.
    }
    return self;
}

- (void)drawRect:(NSRect)dirtyRect {
    // Drawing code here.
}

@end

We’re going to start (and finish) today with just a simple concept and some basic drawing that will set the stage for the future posts. All drawing in Cocoa is done by first setting up the environment in which you want to draw, and then doing the actual drawing. For instance, if we want to draw a blue box, we first have to setup the color blue, define the bounds of the box, and then draw it.  In this case we are using the NSRect that is passed to the drawRect method as the box we want to draw, and we setup the color blue by calling [[NSColor blueColor] set].  We then use the convenience method NSRectFill to fill the dirtyRect with the color blue.  Notice that we didn’t pass the color to NSRectFill, we set it, and from then on anything we draw will be blue until we change the color.

You can think of drawing in Cocoa much the same way as you would think of painting with a brush.  You dip your brush in a certain paint color, paint the shape you want to paint, and then dip your brush in a new color and paint some more.

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- (void)drawRect:(NSRect)dirtyRect {
  [[NSColor blueColor] set];
  NSRectFill(dirtyRect);
}

The preceding code, when run, will generate a view that looks like this:

NSRectFillNow, this may not look like much, but in future posts we will build on these concepts and, hopefully, by the end have drawn some pretty cool and useful things.

iLife 09 Won’t Install When the iPhone Simulator Is Running

This post is a bit of a deviation from my usual posts, but it falls into the something-that-bit-me-that-might-bite-you-too-so-here’s-how-to-fix-it category.

I recently upgraded to Snow Leopard by doing an erase and install. After getting everything back up and running I realized that I still needed to install iLife. I popped in disc 2 of my MacBook Pro install DVDs and proceeded to open the Install Bundled Software installer. After customizing my options I hit the install button and waited. And waited. And waited. The installer never got past the Preparing Bundled Applications stage.

I checked out the console and saw a series of messages that ended with: 10/17/09 4:23:10 PM Installer[8135] *** -[NSMachPort handlePortMessage:]: dropping incoming DO message because the connection or ports are invalid

I decided to try a restart to see if that would fix my problem but shortly after restarting and before I could try my install again I cranked open Xcode and the iPhone simulator to check out something in my latest project. Remember this part of the story, because it’s important.

A few days later I remembered that I still needed to install iLife and grabbed my MacBook Pro installation discs again. I kicked off the installation and instantly hit the same issue. The installer never got past the Preparing Application Bundles stage. I opened Console.app again and saw the same message: 10/20/09 7:39:40 PM Installer[9025] *** -[NSMachPort handlePortMessage:]: dropping incoming DO message because the connection or ports are invalid

I decided to turn to Google and happily came across this gem of a radar filing: Installer hanging for any installer after uptime of X hours. If you read through the comments on that bug you will find that the installer hang isn’t based on uptime, but rather on the iPhone Simulator running. I had been working on an iPhone project both times I tried to install iLife and it was causing the installer to hang (for some inexplicable reason).

I quit the simulator and Installer.app immediately stopped trying to prepare the bundled applications and displayed an error. I quit the installer, tried again, and voila, everything worked as it should.