TweetFollow Us on Twitter

Drawers and Disclosure

Volume Number: 16 (2000)
Issue Number: 9
Column Tag: OS X

More or Less: Drawers and Disclosure Views for Cocoa

by Andrew C. Stone

In designing an intuitive interface for users, the great French architect Le Corbusier's adage still rings true: less is more. The less user interface you have visible, the more likely the user will be able to understand your program's feature set. But applications without depth and functionality are boring and leave the user feeling "if only the application could do X or Y". There are several ways to hide complexity and still have the features available for expert users. Along with the ubiquitous tabview, two major techniques are the drawer and the disclosure view.

Mac OS X introduces the concept of the drawer - a Daliesque subwindow which expands from under the parent window in a smooth opening animation, remaining attached to the window until no longer needed when it animates smoothly closed. An example of a good use of drawers is Mail.app's "Mailboxes". Drawers have certain limitations however - for instance, you cannot pull out a bottom-mounted drawer with a depth greater than the height of the window since this would violate the physical reality being emulated. Moreover, there were no drawers in Mac OS 9 or Mac OS X Server, so another technique, disclosure views must be used. The disclosure view, the little blue triangle that "shows more" by expanding the window to reveal more user interface, is one excellent technique. You can see this button in the standard Save Panel - which expands to show the file browser or collapses to present a very simple save interface. In this article, you will learn how to implement drawers and two types of disclosure views: one that expands the window to the right, and one that expands the window below.

<<ClosedDrawer.tiff This window presents a simplified interface for the user, with the drawer closed.>> <<ExpandedDrawer.tiff When the drawer is pulled out, additional options become available>>

Drawing Upon Drawers

The drawer is an instance of the NSDrawer object, a simple non-visual controller type object that acts as a coordinator. NSDrawer has a simple application programmer's interface (API) which allows you to specify the parent window, the content or container view which gets inserted into the drawer, the preferred edge from which the drawer expands, methods to programmatically open and close it, and a method to determine whether the drawer is open, closed, opening or closing. Moreover, there are optional delegate methods sent to the drawer's delegate and objects which register for drawer notifications before and after closing and opening and before resizing of the drawer. The full API is presented in /System/Library/Frameworks/AppKit.framework/Headers/NSDrawer.h.

InterfaceBuilder - the application to build graphical user interfaces via drag and drop of components - now has two ways to create drawers without writing a single line of code. From IB's Windows Palette, you can either drag out an NSDrawer object, and hook up the parent and content view yourself, or drag out a window with the drawer window already attached. The first method is excellent if you are modifying an existing interface, and the latter when you are designing from scratch.<<DrawersPalette.tiff: You can create completely functional drawers just by drag and drop from InterfaceBuilder>>.

I recommend that you create a new IB document and add a drawer/window combination to see how easy it is, and to learn a trick of the trade: the invisible box grouping technique. All visible objects in Cocoa are NSView subclasses, and they form a hierarchy that is rooted in the window's content view, the root enclosing view which contains everything in the window except the window controls and shadows. Because you cannot use IB to connect to this content view directly, you'll need to explicitly create a view which contains all of the user interface items that belong in the drawer. Select all the items and choose Layout -> Group in Box. Bring up the Inspector, and choose the Attributes pop-up menu item. Click on "No Title" and the no border icon - now you have an invisible containing view. If you click on the smaller drawer window created when you added the drawer/window combination, you see just such an invisible NSBox. Be sure to add your drawer components inside of this box by double-clicking it before dragging on new user interface elements.

Interface Builder allows you to specify the preferred edge from which the drawer should expand with the NSDrawer Inspector's Attributes sub-panel. For full control of the drawer's appearance and position, you may have to actually write a few lines of code, because some functionality is not yet fully exposed in Interface Builder. As of DP4, you need to set the drawer's delegate and size constraints programmatically. You can control the maximum and minimum size of the drawer, as well as the leading and trailing offsets. On a side mounted window, the leading offset is the height difference between the top of the drawer, and the top of the parent window's content view. Likewise, the trailing offset is the difference between the bottom of the drawer and the bottom of the parent window. All of the size constraints are mostly hints because there may be conflicting parameters.

Now that the drawer is configured, all that is required is to provide the user a means of opening and closing it. You need to have a button on the main window or a menu item which will expand the drawer when closed, and close it when open, simultaneously adjusting the text and/or icon on the button to synchronize with the drawer's state. Because the drawer can be in the act of opening or closing, you might want your button to do something only if it is actually closed or open, and just ignore clicks if the drawer is still animating between the open and closed state.

// given an instance variable "drawer" for the NSDrawer  and the sender is the button:

- (void)openOrCloseDrawer:(id)sender {
     if ([drawer state] == NSDrawerClosedState) {
	// tell the drawer to begin the opening animation:
		[drawer open:sender];
	// remember, not everyone speaks English! Code internationally:
		[sender setTitle:NSLocalizedStringFromTable(@"Less Options",@"CoolApp",
		@"title of drawer open and close button when the drawer is open")];
		[sender setImage:[NSImage imageNamed:@"OpenDrawer"];
    } else if ([drawer state] == NSDrawerOpenState) {
		[drawer close:sender];
		[sender setTitle:NSLocalizedStringFromTable(@"More Options",@"CoolApp",
		@"title of drawer open and close button when the drawer is closed")];
		[sender setImage:[NSImage imageNamed:@"CloseDrawer"];
    }
    // if it's in an opening or closing state, we'll ignore the click
}

As for initializing the drawer, you might want to do some of the following in the method that gets called by any object in an IB nib file after all the outlets are initialized, awakeFromNib:

- (void)awakeFromNib
{
  [drawer setLeadingOffset:10.];
  [drawer setTrailingOffset:40.];
  [drawer setContentSize:[rightBox frame].size];
  [drawer close:self];
  [drawer setDelegate:self];
  ...

Secret Disclosures

When a drawer is inappropriate because of size, backwards compatibility, or design issues, the classic disclosure view comes in handy. When disclosing additional user interface elements, the programmer is responsible for resizing the window and making sure everything fits correctly. All of this can be done easily using the technique of the invisible box as the top level container of the items in the standard window, and another invisible box as the top level container of the additional items which are presented when the window is expanded. The two most typical configurations are windows which expand to the right, and windows which expand below. We'll look at the expand to the right case first since it is simpler, because it does not involve moving the origin of the window. The underlying window display mechanism in the AppKit will automatically handle the cases where expanding the window would place part of the window off screen.

To understand the automatic resizing behavior of views (autosizing), it is helpful to look at InterfaceBuilder's Autosizing interface element of the Size Inspector. Each of the 6 possible stretch behaviors are represented graphically with rods and springs. A rod means "leave this dimension static" and a spring means "let this dimension fluctuate with the changing size of the window". <<StretchTheObject.tiff In this case, the object stretches and shrinks to fit into its containing view>> <<LeaveObjectRelativeToLowerRight.tiff Here, the object will remain in relative position to the lower right of its containing view.>>

Of course, you can set these all programmatically using NSView's -setAutosizing:(int)mask method by or'ing together the vertical and horizontal stretching behaviors: NSViewNotSizable, NSViewMinXMargin, NSViewWidthSizable, NSViewMaxXMargin, NSViewMinYMargin, NSViewHeightSizable andNSViewMaxYMargin.

Usually, you want the main items in the window to be resized when the user resizes the window - for example, a scrollable text view. In order that the disclosure view maintains the correct size whether it's showing or not, we'll approach the problem by always leaving the extra box in the window. When the extra box is hidden, the window will clip the box, when it's revealed, the window will be resized to contain it. This solves two problems: one, the extra items will be correctly freed when the window is released regardless of whether the extra items are showing, and two, the extra items will be correctly resized when the window is resized, even if they are not currently exposed.

In the following example, we have subclassed NSWindowController and placed the logic of resizing in the subclass controller. In InterfaceBuilder, the autosizing of the elements has been established, and we honor these settings by noting them at the beginning, and resetting them after resizing the window.

The button is set to be a two state "toggle" button, and we assign the images inside InterfaceBuilder in the Icon and Alternate Icon fields. By changing the state of the button, the icon automatically changes. This works with text as well by assigning an alternate title to the button, however, a down facing triangle image when the window is collapsed but can be expanded downward and an upward facing triangle image when it is expanded but can be collapsed works well.

// given: the controls to be displayed when the window expands are all inside
// an invisible NSBox named rightBox. The main controls are all inside a box named
// leftBox. The two boxes are laid out side by side in the window to fill the window's 
// contentView. Inside the left box, near the upper right is the two-state button whose
// target is the window controller with the action moreOrLessToTheRightAction:.

- (void)moreOrLessToTheRightAction:(id)sender
{
   NSWindow *win = [self window];
   NSRect winFrame = [win frame];
   NSRect rightFrame = [rightBox frame];

// get the original settings for reestablishing later:
   int leftMask = [leftBox autoresizingMask];
   int rightMask = [rightBox autoresizingMask];
   
// toggle the state
   int stateToSet = 1 - [sender tag];

// set the boxes to not automatically resize when the window resizes:
   [leftBox setAutoresizingMask:NSViewNotSizable];
   [rightBox setAutoresizingMask:NSViewNotSizable];

   // if the button's state is 1, then stateToSet == 0, let's collapse:
   if (stateToSet == 0) {
	    // reduce the desired size by the width of the right box:
        winFrame.size.width -= NSWidth(rightFrame);
   } else {
	   // increase the desired width by the width of the right box:
       winFrame.size.width += NSWidth(rightFrame);
    }

   // change the state of the button
   [sender setState:stateToSet];
   [sender setTag:stateToSet];

   // resize the window and display:
   [win setFrame:winFrame display:YES];

   // reset the boxes to their original autosize masks:
   [leftBox setAutoresizingMask:leftMask];
   [rightBox setAutoresizingMask:rightMask];
}

Adding a disclosure view which expands the window below is slightly more tricky because we'll have to move the origin of the window as we increase or decrease the height of the window so that the window keeps the title bar in the same location. Moreover, since origins begin at the bottom and move to positive Y upwards, we'll have to move the origins of the boxes as well.

- (IBAction)moreOrLessDownAction:(id)sender {
   NSWindow *win = [self window];
   NSRect winFrame = [win frame];

// we'll need to know the size of both boxes in this case:
   NSRect topFrame = [topBox frame];
   NSRect bottomFrame = [bottomBox frame];

// get the original settings for reestablishing later:
   int topMask = [topBox autoresizingMask];
   int bottomMask = [bottomBox autoresizingMask];
   
// toggle the state
   int stateToSet = 1 - [sender tag];

// set the boxes to not automatically resize when the window resizes:
   [topBox setAutoresizingMask:NSViewNotSizable];
   [bottomBox setAutoresizingMask:NSViewNotSizable];

   // if the button's state is 1, then stateToSet == 0, collapse it:
   if (stateToSet == 0) {
       // adjust the desired height and origin of the window:
        winFrame.size.height -= NSHeight(bottomFrame);
        winFrame.origin.y += NSHeight(bottomFrame);
	    // adjust the origin of the bottom box well below the window:
        bottomFrame.origin.y = -NSHeight(bottomFrame);
		// begin the top box at the bottom of the window
        topFrame.origin.y = 0.0;
   } else {
	   // stack the boxes one on top of the other:
       bottomFrame.origin.y = 0.0;
       topFrame.origin.y = NSHeight(bottomFrame);

       // adjust the desired height and origin of the window:
       winFrame.size.height += NSHeight(bottomFrame);
       winFrame.origin.y -= NSHeight(bottomFrame);
   }

   // adjust locations of the boxes:
   [topBox setFrame:topFrame];
   [bottomBox setFrame:bottomFrame];

   // change the state of the button to reflect new arrangement:
   [sender setState:stateToSet];
   [sender setTag:stateToSet];

  // resize the window and display:
   [win setFrame:winFrame display:YES];

   // reset the boxes to their original autosize masks:
   [topBox setAutoresizingMask:topMask];
   [bottomBox setAutoresizingMask:bottomMask];
}

Conclusion

With drawers and disclosure views, you have the tools and techniques to present simple and elegant interfaces, with more features available at the click of a button. InterfaceBuilder can provide almost all of the support necessary to fully implement drawers, and with just a few lines of code, your applications can take advantage of the powerful new features of Cocoa.


Andrew Stone <andrew@stone.com> is the chief executive haquer at Stone Design Corp <http://www.stone.com/> and divides his time between raising children, llamas & cane and writing applications for Mac OS X and playing with Darwin.

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

Latest Forum Discussions

See All

Top Mobile Game Discounts
Every day, we pick out a curated list of the best mobile discounts on the App Store and post them here. This list won't be comprehensive, but it every game on it is recommended. Feel free to check out the coverage we did on them in the links... | Read more »
Price of Glory unleashes its 1.4 Alpha u...
As much as we all probably dislike Maths as a subject, we do have to hand it to geometry for giving us the good old Hexgrid, home of some of the best strategy games. One such example, Price of Glory, has dropped its 1.4 Alpha update, stocked full... | Read more »
The SLC 2025 kicks off this month to cro...
Ever since the Solo Leveling: Arise Championship 2025 was announced, I have been looking forward to it. The promotional clip they released a month or two back showed crowds going absolutely nuts for the previous competitions, so imagine the... | Read more »
Dive into some early Magicpunk fun as Cr...
Excellent news for fans of steampunk and magic; the Precursor Test for Magicpunk MMORPG Crystal of Atlan opens today. This rather fancy way of saying beta test will remain open until March 5th and is available for PC - boo - and Android devices -... | Read more »
Prepare to get your mind melted as Evang...
If you are a fan of sci-fi shooters and incredibly weird, mind-bending anime series, then you are in for a treat, as Goddess of Victory: Nikke is gearing up for its second collaboration with Evangelion. We were also treated to an upcoming... | Read more »
Square Enix gives with one hand and slap...
We have something of a mixed bag coming over from Square Enix HQ today. Two of their mobile games are revelling in life with new events keeping them alive, whilst another has been thrown onto the ever-growing discard pile Square is building. I... | Read more »
Let the world burn as you have some fest...
It is time to leave the world burning once again as you take a much-needed break from that whole “hero” lark and enjoy some celebrations in Genshin Impact. Version 5.4, Moonlight Amidst Dreams, will see you in Inazuma to attend the Mikawa Flower... | Read more »
Full Moon Over the Abyssal Sea lands on...
Aether Gazer has announced its latest major update, and it is one of the loveliest event names I have ever heard. Full Moon Over the Abyssal Sea is an amazing name, and it comes loaded with two side stories, a new S-grade Modifier, and some fancy... | Read more »
Open your own eatery for all the forest...
Very important question; when you read the title Zoo Restaurant, do you also immediately think of running a restaurant in which you cook Zoo animals as the course? I will just assume yes. Anyway, come June 23rd we will all be able to start up our... | Read more »
Crystal of Atlan opens registration for...
Nuverse was prominently featured in the last month for all the wrong reasons with the USA TikTok debacle, but now it is putting all that behind it and preparing for the Crystal of Atlan beta test. Taking place between February 18th and March 5th,... | Read more »

Price Scanner via MacPrices.net

AT&T is offering a 65% discount on the ne...
AT&T is offering the new iPhone 16e for up to 65% off their monthly finance fee with 36-months of service. No trade-in is required. Discount is applied via monthly bill credits over the 36 month... Read more
Use this code to get a free iPhone 13 at Visi...
For a limited time, use code SWEETDEAL to get a free 128GB iPhone 13 Visible, Verizon’s low-cost wireless cell service, Visible. Deal is valid when you purchase the Visible+ annual plan. Free... Read more
M4 Mac minis on sale for $50-$80 off MSRP at...
B&H Photo has M4 Mac minis in stock and on sale right now for $50 to $80 off Apple’s MSRP, each including free 1-2 day shipping to most US addresses: – M4 Mac mini (16GB/256GB): $549, $50 off... Read more
Buy an iPhone 16 at Boost Mobile and get one...
Boost Mobile, an MVNO using AT&T and T-Mobile’s networks, is offering one year of free Unlimited service with the purchase of any iPhone 16. Purchase the iPhone at standard MSRP, and then choose... Read more
Get an iPhone 15 for only $299 at Boost Mobil...
Boost Mobile, an MVNO using AT&T and T-Mobile’s networks, is offering the 128GB iPhone 15 for $299.99 including service with their Unlimited Premium plan (50GB of premium data, $60/month), or $20... Read more
Unreal Mobile is offering $100 off any new iP...
Unreal Mobile, an MVNO using AT&T and T-Mobile’s networks, is offering a $100 discount on any new iPhone with service. This includes new iPhone 16 models as well as iPhone 15, 14, 13, and SE... Read more
Apple drops prices on clearance iPhone 14 mod...
With today’s introduction of the new iPhone 16e, Apple has discontinued the iPhone 14, 14 Pro, and SE. In response, Apple has dropped prices on unlocked, Certified Refurbished, iPhone 14 models to a... Read more
B&H has 16-inch M4 Max MacBook Pros on sa...
B&H Photo is offering a $360-$410 discount on new 16-inch MacBook Pros with M4 Max CPUs right now. B&H offers free 1-2 day shipping to most US addresses: – 16″ M4 Max MacBook Pro (36GB/1TB/... Read more
Amazon is offering a $100 discount on the M4...
Amazon has the M4 Pro Mac mini discounted $100 off MSRP right now. Shipping is free. Their price is the lowest currently available for this popular mini: – Mac mini M4 Pro (24GB/512GB): $1299, $100... Read more
B&H continues to offer $150-$220 discount...
B&H Photo has 14-inch M4 MacBook Pros on sale for $150-$220 off MSRP. B&H offers free 1-2 day shipping to most US addresses: – 14″ M4 MacBook Pro (16GB/512GB): $1449, $150 off MSRP – 14″ M4... Read more

Jobs Board

All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.