Cocoa Drinking Fool

After spending most of my spare time building Web technologies lately, I’m finally going to switch gears to building a Cocoa application.

I can’t tell you much about the application — yet — but I do plan to present weekly status-like reports. For example, do you know that Quartz uses floating point coordinates? You probably did. But did you also know that the whole number coordinates represent the point immediately between two screen pixels? So in order to draw a single pixel line you actually have to offset your coordinates by 0.5.

Consider the following example:

- (void) drawRect: (NSRect) rect
{
    float cellWidth= rect.size.width/7.0;
    float cellHeight= rect.size.height/5.0;

    [[NSColor blackColor] set];

    [NSBezierPath strokeRect: rect];

    NSBezierPath* path= [[[NSBezierPath alloc] init] autorelease];

    int column;
    int row;

    for (column=1; column<7; ++column)
    {
        [path moveToPoint: NSMakePoint( cellWidth * column + 0.5,
                                        0.5 )];
        [path lineToPoint: NSMakePoint( cellWidth * column + 0.5,
                                        rect.size.height - 0.5 )];
    }

    for (row=1; row<5; ++row)
    {
        [path moveToPoint: NSMakePoint( 0.5, cellHeight * row + 0.5 )];
        [path lineToPoint: NSMakePoint( rect.size.width - 0.5,
                                        cellHeight * row + 0.5 )];
    }

    [path stroke];
}

Of course, I could make this considerably more efficient by only creating the NSBezierPath once and then just scaling it to match the view’s rectangle. And of course, there are probably a hundred other little things I could be doing to make this better.

That’s part of the exercise: I’d like to expose what I’m working on so I can learn from the feedback. I’ve learned a tremendous amount from the feedback on my Javascript posts; so I’m eager to see what I’ll learn now that I’m delving into Objective C and Cocoa.

My next post will be about mimicing the recurring event logic of iCal. I’ve built my own version of the NSRecurrenceRule class (which I’ve read will debut in Leopard). This comes complete with unit tests — well some, anyway.

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