TweetFollow Us on Twitter

Splitting Windows
Volume Number:11
Issue Number:1
Column Tag:Improving The Framework

Splitting Windows in MacApp

You know, programming in MacApp is a lot like playing golf.

By Tom Otvos, EveryWare Development Corp.

Note: Source code files accompanying article are located on MacTech CD-ROM or source code disks.

You know, programming in MacApp is a lot like playing golf. With a little bit of practice, you can become fairly competent and hit a respectable score, and with about the same amount of practice, you can write a respectable, Mac-looking application. There will come a time, however, when you want to stretch the bounds a little bit, and add some cool user interface gadget that will differentiate your application from another. You want to hit a birdie on that par four 15th. To make that kind of advance, you need a little bit more than practice; you need a deeper understanding of the game, and the ability ”to read the greens”. You need to understand how some of these disparate parts of a rather complicated application framework come together, so you can not only make it do what you want, but do it the right way.

Before I lead you too far along, I should say at this point that I am not a very good golfer. I have not yet made that transition to really knowing what I am doing, and then merely applying that knowledge to the situation at hand. Okay, let’s cut to the chase. I am struggling. I have been doing MacApp a bit longer, however, and so I can generally get it to do what I want in the way that I want it with relative ease. Along the way, I have picked up a few tricks that, in the end, are really very simple, but they achieve a neat effect that has a lot of application. In this article, I want to talk about a useful trick that, amazingly, I was not able to find documented anywhere else, namely splitting windows. I really needed to split windows for an app that I am working on, so I created the following two classes to do it. Since it was really very simple and a trivial amount of code, I figured that sharing it would be the right thing to do. I hope you find it useful.

Splitting components

So that we have a clear picture in our heads during the following discussion, let’s look at the geometry a bit. Splitting windows, in MacApp terms, really reduces to taking two TView objects and adjusting their sizes inversely relative to each other. In the simplest case, picture two views joined along one edge, and then dragging that edge so that as one view grows in size, the other shrinks. If the two view objects are the same class, then you can easily implement the classic word processing implementation of splitting, where you are looking at the same document in two or more panes, each displaying a different region of the document. Or, the two views can be from very different classes that display some common data in different ways. An example might be a view editor that shows the view hierarchy as it would appear on screen in one area, and a list representation of the hierarchy in another area.

To split a window, I have created two classes: TSplitterControl and TSplitterTracker. The TSplitterControl class does two very simple things. First, it provides a user interface to the splitting action, giving the user a “knob” to direct the split. Second, it is responsible, at the programmatic level, for initiating the splitting by instantiating the splitter tracker. The TSplitterTracker class is the workhorse of the pair, as it tracks the mouse during splitting, providing continual user feedback and, ultimately, reconfiguring the views after the splitting is done. [Because the code for these classes is so simple, I will include it in the text of this article. Some code polish that I have added to my classes will be omitted, but I assure you that nothing important will be left out.]

TSplitterControl

The class definition for the TSplitterControl is reproduced below.

class TSplitterControl : public TControl
{
private:
 TView* fFirstView;
 TView* fSecondView;
public:
 virtual pascal void Initialize();
 virtual pascal void DoMouseCommand(
 VPoint&    theMouse, 
 TToolboxEvent*  event, 
 CPoint   hysteresis);
 virtual pascal void Draw(const VRect& area); 
 // override
 virtual pascal void SuperViewChangedFrame(
 const VRect&  oldFrame,  
 const VRect&  newFrame,  
 Boolean  invalidate);
 virtual pascal void SetSplitViews(
 TView* firstView, 
 TView* secondView);
};

The only method that is of any real consequence is DoMouseCommand():

pascal void TSplitterControl::DoMouseCommand(
 VPoint&    theMouse, 
 TToolboxEvent*  event, 
 CPoint   hysteresis)
 // override
{
    // mouse hits in our control will immediately post a splitter
    // tracker command
 TSplitterTracker* splitter = new TSplitterTracker;
 splitter->ISplitterTracker(fFirstView, 
 fSecondView, this, theMouse);
 this->PostCommand(splitter);
 
 inherited::DoMouseCommand(theMouse, event, hysteresis);
}

The only function of this method is to detect mouse hits in our control and post an instance of our splitter tracker. Note that in MacApp a TTracker is a TCommand subclass and needs to be posted in the command queue to get executed. Also note that the control passes to the tracker two views as part of its initialization. These two views are the views that are going to be adjusted at the end of the splitting process.

The remaining methods of this class are what I lump into “polish”, and you can provide your own variations as you see fit. Specifically, the Draw() method can be overridden, as I originally did, to draw a filled rectangle as the splitting knob. Users of Microsoft Word or MPW will find this type of splitter familiar. Ultimately, I opted for a splitting more like Object Master or MacBrowse, in which window panes are dragged by their edges to reconfigure their sizes. In this case, the Draw() method is superfluous, and the default MacApp drawing with appropriate adornment suits me just fine. The override to SuperViewChangedFrame() is necessary if you position your control such that its location needs to be modified when the window is zoomed or otherwise resized. I can never understand why MacApp views do not have a position determiner instance variable, with values like posRelRightEdge, so that I do not always have to override this method.

In my implementation, I always had two views defined in my window and so effectively, my window was already split. The splitter was merely adjusting the relative sizes of these views. However, you could easily envision a case where you would want to do true splitting, and every time you dragged down on the splitter control, you would split off a new pane of the existing view. I haven’t tried this, but I would guess that the best way to do this would be to clone the view you wish to split in the DoMouseCommand() method, insert it into the superview at an appropriate location, set its initial size to zero, and then pass it into the TSplitterTracker as one of the views.

One other user interface tip: You can have MacApp automatically change the cursor when it tracks over your control without writing a single line of code. Just use your favorite view editor to tell MacApp that the control is going to handle the cursor (fHandlesCursor), and specify a cursor resource ID (fCursorID) that should be used. I use a neat double-headed arrow

TSplitterTracker

The tracker does most of the work required for splitting, and MacApp handles most of the work required for tracking. Typically, you only need to override methods of TTracker to provide specific user feedback, to constrain tracking in a particular direction, and to “do something” when the tracking is done. The class definition of TSplitterTracker is shown below:

class TSplitterTracker : public TTracker
{
private:
 VCoordinate fDelta;
 TView* fFirstView;
 TView* fSecondView;
 TView* fSplitter;
public:
 virtual pascal void ISplitterTracker(
 TView* firstView, 
 TView* secondView, 
 TView* splitter, 
 VPoint&  itsMouse);
 virtual pascal void TrackConstrain(
 TrackPhase aTrackPhase, 
 const VPoint&   anchorPoint, 
 const VPoint&   previousPoint,
 VPoint&  nextPoint, 
 Boolean  mouseDidMove); 
 // override
 virtual pascal void TrackFeedback(
 TrackPhase aTrackPhase, 
 const VPoint&   anchorPoint, 
 const VPoint&   previousPoint,
 const VPoint&   nextPoint, 
 Boolean  mouseDidMove, 
 Boolean  turnItOn); 
 // override
 virtual pascal void DoIt(); // override
};

I always found trackers a rather mystifying element of the MacApp architecture, until I sat down and actually wrote a couple. They turn out to be quite simple largely because MacApp handles a lot of the gory details for you. For example, if you want to limit tracking in a single direction, the only thing you have to do is override TrackConstrain() and do something like this:

 inherited::TrackConstrain(aTrackPhase, anchorPoint, 
 previousPoint, nextPoint, 
 mouseDidMove);
 if (mouseDidMove)
    // limit tracking to one direction only
 nextPoint.h = previousPoint.h;

Basically, this method gives you a chance to recalculate the position of the mouse, so that MacApp thinks that it only moved in one direction. In the example above, I am forcing the tracker to only track in the vertical direction.

Initializing the tracker includes one important detail that you must pay attention to. When you call ITracker, you must provide a view with which the tracker is associated. One of the side effects of this is that tracking will be clipped to this view, so typically you would specify an enclosing view that will contain all of the tracking, such as, in our case, the window being split.

The TrackFeedback() method, not surprisingly, allows you a chance to provide whatever feedback you wish to the user, as well as hook in during the various track “phases” to extract whatever information you might think is necessary. For example, in the code below, I use my override to initialize an instance variable that will be used to determine how much tracking was done, and when the tracking is done, I calculate how far the mouse tracked in the vertical direction:

 switch (aTrackPhase) {
 case trackBegin:// initialize our track delta
 fDelta = 0;
 break;
 case trackEnd:  // how far did we go?
    // anchor point is always in splitter coordinates
 anchor = anchorPoint;
 fSplitter->LocalToWindow(anchor);
 next = nextPoint;
    // next point is always in view coordinates
 fView->LocalToWindow(next);
 fDelta = next.v - anchor.v;
 break;
 }
    // draw some nice feedback for the user  
 PenSize(2, 2);
 PenPat(&qd.gray);
 fView->GetQDExtent(qdExtent);
 MoveTo(qdExtent[topLeft].h, nextPoint.v);
 LineTo(qdExtent[botRight].h, nextPoint.v);

Additionally, regardless of the track phase, I draw a thick gray line across the width of the views being split, giving the user clear and easily understood feedback. MacApp provides some default feedback for you, if you wish to use it, in the form of a gray outline of the view to which the tracker is attached, but generally, I find that I have to provide my own feedback for one reason or another.

As mentioned earlier, the TTracker class descends from TCommand, and it uses the DoIt() method of TCommand to signal when tracking is complete and you need to react to it in some way. Here is the DoIt() method in its entirety:

pascal void TSplitterTracker::DoIt()
{
 VRect frame1, frame2;
    // adjust fDelta so neither view becomes invalid
 fFirstView->GetFrame(frame1);
 if (fDelta < frame1.top - frame1.bottom)
 fDelta = frame1.top - frame1.bottom;
 fSecondView->GetFrame(frame2);
 if (fDelta > frame2.bottom - frame2.top)
 fDelta = frame2.bottom - frame2.top;
    // adjust the first view from the bottom, the second from the top
 frame1.bottom += fDelta;
 fFirstView->SetFrame(frame1, kRedraw);
 frame2.top += fDelta;
 fSecondView->SetFrame(frame2, kRedraw);
}

In the code above, after some preflighting to ensure that neither view becomes negative in size, the views’ frames are adjusted in the vertical dimension by the delta amount tracked by the tracker. Note that one view has its bottom adjusted, and the other has its top adjusted. We could just as easily have tracked in the horizontal direction, and consequently adjusted the right and left edges. Or, a truly generic tracker could have been written that could track in either direction, or both. A simple call to SetFrame() was all that was needed to resize the two views. If your view hierarchy is set up correctly, then all relevant subviews will resize as necessary. Additionally, any overrides to SuperViewChangedFrame() in your subviews will also be called, in case you need to do dynamic repositioning of objects not done automatically by MacApp.

The Final Word

As I stated at the outset, there is not a lot of code required to achieve the view splitting effect in MacApp. I was actually amazed that there was not already some sample code out there that I could mooch from. Equally amazing was that cries for help on MacApp3Tech$ from others looking for similar code went unanswered. Well, someone was listening, and I hope that this article helps.

Now, if someone can only help me cure my slice

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

Latest Forum Discussions

See All

Combo Quest (Games)
Combo Quest 1.0 Device: iOS Universal Category: Games Price: $.99, Version: 1.0 (iTunes) Description: Combo Quest is an epic, time tap role-playing adventure. In this unique masterpiece, you are a knight on a heroic quest to retrieve... | Read more »
Hero Emblems (Games)
Hero Emblems 1.0 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0 (iTunes) Description: ** 25% OFF for a limited time to celebrate the release ** ** Note for iPhone 6 user: If it doesn't run fullscreen on your device... | Read more »
Puzzle Blitz (Games)
Puzzle Blitz 1.0 Device: iOS Universal Category: Games Price: $1.99, Version: 1.0 (iTunes) Description: Puzzle Blitz is a frantic puzzle solving race against the clock! Solve as many puzzles as you can, before time runs out! You have... | Read more »
Sky Patrol (Games)
Sky Patrol 1.0.1 Device: iOS Universal Category: Games Price: $1.99, Version: 1.0.1 (iTunes) Description: 'Strategic Twist On The Classic Shooter Genre' - Indie Game Mag... | Read more »
The Princess Bride - The Official Game...
The Princess Bride - The Official Game 1.1 Device: iOS Universal Category: Games Price: $3.99, Version: 1.1 (iTunes) Description: An epic game based on the beloved classic movie? Inconceivable! Play the world of The Princess Bride... | Read more »
Frozen Synapse (Games)
Frozen Synapse 1.0 Device: iOS iPhone Category: Games Price: $2.99, Version: 1.0 (iTunes) Description: Frozen Synapse is a multi-award-winning tactical game. (Full cross-play with desktop and tablet versions) 9/10 Edge 9/10 Eurogamer... | Read more »
Space Marshals (Games)
Space Marshals 1.0.1 Device: iOS Universal Category: Games Price: $4.99, Version: 1.0.1 (iTunes) Description: ### IMPORTANT ### Please note that iPhone 4 is not supported. Space Marshals is a Sci-fi Wild West adventure taking place... | Read more »
Battle Slimes (Games)
Battle Slimes 1.0 Device: iOS Universal Category: Games Price: $1.99, Version: 1.0 (iTunes) Description: BATTLE SLIMES is a fun local multiplayer game. Control speedy & bouncy slime blobs as you compete with friends and family.... | Read more »
Spectrum - 3D Avenue (Games)
Spectrum - 3D Avenue 1.0 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0 (iTunes) Description: "Spectrum is a pretty cool take on twitchy/reaction-based gameplay with enough complexity and style to stand out from the... | Read more »
Drop Wizard (Games)
Drop Wizard 1.0 Device: iOS Universal Category: Games Price: $1.99, Version: 1.0 (iTunes) Description: Bring back the joy of arcade games! Drop Wizard is an action arcade game where you play as Teo, a wizard on a quest to save his... | Read more »

Price Scanner via MacPrices.net

13-inch M4 MacBook Airs on sale for $150 off...
Amazon has new 13″ M4 MacBook Airs on sale for $150 off MSRP right now, starting at $849. Sale prices apply to most colors and configurations. Be sure to select Amazon as the seller, rather than a... Read more
15-inch M4 MacBook Airs on sale for $150 off...
Amazon has new 15″ M4 MacBook Airs on sale for $150 off Apple’s MSRP, starting at $1049. Be sure to select Amazon as the seller, rather than a third-party: – 15″ M4 MacBook Air (16GB/256GB): $1049, $... Read more
Amazon is offering a $50 discount on Apple’s...
Amazon has Apple’s 11th-generation A16 iPads in stock on sale for $50 (or a little more) off MSRP this week. Shipping is free: – 11″ 11th-generation 128GB WiFi iPads: $299 $50 off MSRP – 11″ 11th-... Read more
Clearance 13-inch M1 MacBook Airs available f...
Walmart has clearance, but new, Apple 13″ M1 MacBook Airs (8GB RAM, 256GB SSD) available online for $649, $360 off original MSRP, in Space Gray, Silver, and Gold colors. These are new MacBooks for... Read more
iPad minis on sale for $100 off Apple’s MSRP...
Amazon is offering $100 discounts (up to 20% off) on Apple’s newest 2024 WiFi iPad minis, each with free shipping. These are the lowest prices available for new minis among the Apple retailers we... Read more
AirPods Max headphones on sale for $479, $70...
Amazon has AirPods Max with USB-C on sale for $479.99 in all colors. Shipping is free. Their price is $70 off Apple’s MSRP, and it’s the lowest price available today for AirPods Max. Keep an eye on... Read more
14-inch M4 Pro/M4 Max MacBook Pros on sale th...
Don’t pay full price! Get a new 14″ MacBook Pro with an M4 Pro or M4 Max CPU for up to $320 off Apple’s MSRP this weekend at these retailers…they are the lowest prices available for these MacBook... Read more
Get a 15-inch M4 MacBook Air for $150 off App...
A couple of Apple retailers are offering $150 discounts on new 15″ M4 MacBook Airs this weekend. Prices at these retailers start at $1049: (1): Amazon has new 15″ M4 MacBook Airs on sale for $150 off... Read more
Unreal Mobile is offering a $100 discount on...
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, 13, and SE phones... Read more
16-inch M4 Pro MacBook Pros on sale for $250-...
Don’t pay full price! Amazon has 16-inch M4 Pro MacBook Pros (Silver or Black colors) on sale right now for up to $300 off Apple’s MSRP. Shipping is free. These are the lowest prices currently... Read more

Jobs Board

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