Open your GraphPaper project in Project Builder and the MainMenu.nib file in Interface Builder.

Resize the TrackingGraphView in the GraphPaper window so that it’s smaller, and put it somewhere in the window that is out of the way.

Don’t worry about the size or position of the TrackingGraphView — it will automatically be resized and placed in the proper position when GraphPaper runs.

Subclass the NSScrollView class and rename the new subclass “ZoomScrollView”.

Add the subView and zoomButton outlets and the changeZoom: action method to the new ZoomScrollView class.

Drag a CustomView icon from IB’s Cocoa-Containers palette and drop it in the GraphPaper window. Change its class to ZoomScrollView.

Resize the on-screen ZoomScrollView instance to be as large as the previous TrackingGraphView instance. Note that the TrackingGraphView instance shows through the ZoomScrollView a bit.

Choose IB’s Layout → Send To Back menu command to put the ZoomScrollView instance “behind” the TrackingGraphView instance, as shown in Figure 19-2.

The only reason to send the ZoomScrollView to the back is so we can easily see both NSViews at the same time; it won’t make a difference in the way GraphPaper runs.

Figure 19-2. ZoomScrollView in GraphPaper window

Drag a pop-up menu button from IB’s Cocoa-Other palette and place it below the ZoomScrollView, to the left of the x: field (see Figure 19-3). Do not place it on the ZoomScrollView.

Double-click the pop-up menu button.

One by one, drag three more menu items from the Cocoa-Menus palette and drop them in the pop-up menu. Make the width of the pop-up menu smaller.

Name the menu cells 100%, 125%, 150%, 175%, 200%, and 300%, and give them the tags 100, 125, 150, 175, 200, and 300, respectively (use the NSMenuCell Attributes Info dialog). When you’re done, the pop-up menu should look like the one shown here.

Connect the NSPopUpButton’s cover to the ZoomScrollView so that it sends the changeZoom: action message (see Figure 19-3).

Click the 100% item and close the pop-up menu by clicking somewhere else in the window. This ensures that the initial condition will be with the pop-up menu at 100%.

Connect the ZoomScrollView’s zoomButton outlet to the pop-up menu button. Note that this connection is in the opposite direction of the previous one.

Connect the ZoomScrollView’s subView outlet to the TrackingGraphView, as shown in Figure 19-4.

Create the class files for ZoomScrollView and insert them into the GraphPaper project.

Insert the lines shown here in bold into ZoomScrollView.h :

#import <Cocoa/Cocoa.h>

@interface ZoomScrollView : NSScrollView
{
    IBOutlet id subView;
    IBOutlet id zoomButton;    double scaleFactor;
}
- (IBAction)changeZoom:(id)sender;- (id)initWithFrame:(NSRect)theFrame;
                        - (void)awakeFromNib;
                        - (void)setScaleFactor:(float)aFloat;
                        - (void)tile;
@end

Insert the initWithFrame: method into ZoomScrollView.m:

                        - (id)initWithFrame:(NSRect)theFrame
                        {
                            [super initWithFrame:theFrame];
                            [self setBackgroundColor:[NSColor whiteColor]];
                            scaleFactor = 1.0;
                            return self;
                        }

Insert the following awakeFromNib method into ZoomScrollView.m:

                        -(void) awakeFromNib
                        {
                            [self setHasHorizontalScroller:YES];
                            [self setHasVerticalScroller:YES];
                            [self setBorderType:NSLineBorder];
                        
    // Set up the zoom button
                            [[zoomButton cell] setBordered:NO];
                            [[zoomButton cell] setBezeled:YES];
                            [[zoomButton cell] setFont:[NSFont labelFontOfSize:10.0]];
                            [self addSubview:zoomButton];
                        
    // The next two lines install the subView (TrackingGraphView)
                            // and set its size to be the same as the NSScrollView
                            [self setDocumentView:subView];
                            [subView setFrame:[[self contentView] frame]];
                        }

Insert the following setScaleFactor: method into ZoomScrollView.m:

                        - (void)setScaleFactor:(float)aFactor
                        {
                            NSAssert(aFactor!=0,@"Illegal scale factor. Set the tag!");
                        
    if (scaleFactor != aFactor) {
                                float delta = aFactor/scaleFactor;
                                scaleFactor = aFactor;
                                [[self contentView]
                                 scaleUnitSquareToSize:NSMakeSize(delta,delta)];
                            }
                        }

Insert the line shown here in bold into the changeZoom: method in ZoomScrollView.m :

- (IBAction)changeZoom:(id)sender
{    [self setScaleFactor:[[sender selectedCell] tag] / 100.0];
}

Insert the following tile method into ZoomScrollView.m:

                        - (void)tile
                        {
                            NSRect scrollerRect, buttonRect;
                        
    [super tile];
                        
    // Place the pop-up button next to the scroller
                            scrollerRect = [[self horizontalScroller] frame];
                            NSDivideRect(scrollerRect, &buttonRect, &scrollerRect, 50.0,
                                         NSMaxXEdge);
                            [[self horizontalScroller] setFrame: scrollerRect];
                            [zoomButton setFrame: NSInsetRect(buttonRect, 1.0, 1.0)];
                        }

Build and run GraphPaper, saving all files first.

You should get a magnification button in the lower-right corner of the ZoomScrollView, as shown in the window at the top of Figure 19-5. Enter a function and click the Graph button.

Press the pop-up menu button, drag to 175%, and release the mouse button. The zoom button’s title should change, as shown in the window at the bottom of Figure 19-5.

Resize the GraphPaper window — oops, we haven’t taken care of Autosizing yet! We’ll show you how to do that in the next section.

Resize the GraphPaper window anyway and drag the scroll knobs. The ZoomScrollView should stretch, making more of the graph visible, rather than changing its scale, as it did previously.

Quit GraphPaper.

Back in IB, select ZoomScrollView and type Command-3. Make ZoomScrollView’s Autosizing box look like the one on the left in Figure 19-6.

Then select the NSForm (xmin, xmax, etc.) and make its Autosizing box look like the one on the right in Figure 19-6.

Build and run GraphPaper, saving the nib file. Note how quickly the building process took this time — PB only had to stuff a new nib file in the .app directory, not much work.

Graph a function and resize GraphPaper. It works better but is still not perfect. See Section 19.6 at the end of this chapter for more.

Quit GraphPaper.