TweetFollow Us on Twitter

About Color Animation
Volume Number:6
Issue Number:5
Column Tag:Pascal Procedures

Related Info: Vert. Retrace Mgr Event Manager Color Quickdraw

Color Animation

By Ajay Nath, Oakland Gardens, NY

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

[Ajay Nath has B.A. degrees in Mathematics and Chemistry from New York University and is currently a third year medical student at the Mount Sinai School of Medicine where he tries to find the time to program and to learn medicine.]

It all started when I started playing with a shareware breakout game. Paul, a friend of mine who saw me playing it, thought it was neat and liked playing it but there were a few problems with the game. It was an old game and didn’t use the larger screen of my Mac IIcx or color and it had other annoying things about it. Well I’ve been much too busy to write a new game for my friend, but I was able to discover a method for doing simple animation that will work well on a Mac II or better machine.

When I first sat down and thought about the problem I thought, well I’ll simply use a vbl task to set a global variable and my program’s main loop will examine that variable and know when to draw. To do this I declared a variable of the following simple type:

{1}

 XVBLRec= RECORD
 xVBLTask : VBLTask;
 xDoTask: INTEGER;
 END;

The first field of the record (xVBLTask) is used in the calls to install and remove the vbl task, the second field xDoTask is an integer which the vbl task I use will set to 1 when it runs. My programs main loop just has to examine the xDoTask field and draw when it is non-zero.

This technique is not very different from the method which involves examining the current value of the Mac global variable TickCount and drawing when it changes, i.e. (in pseudocode):

{2}

 count = TickCount;
 while count = TickCount do nothing;
 { start drawing real fast! }.

On older Macs the TickCount was changed when vbl tasks were run so the above method was really very similar to using a vbl task to set a global variable.

I took a quick look in Inside Mac Vol. V (pp. 566-567) before I started writing my vbl task and found some interesting information there. The new Macs have vertical retrace interrupts which can vary according to their video card and we can create vbl tasks which run at the ‘heart rate’ of the whichever video card we want. Well, the obvious thing to do is to run our vbl task at the rate of the video card of our main screen, and we then should be able to do simple animation easily! The new calls are called SlotVInstall and SlotVRemove and just like the old calls need a pointer to a vbltask record but in addition, need a slot number so they know which slot to attach the vbl task to. All we need to know then is the slot number of the video card which drives our main screen. After a quick five minute search through IM V I found a call, “GetVideoDefault”, which would give me the slot number of the default video card and I was on my way.

I used TML Pascal II to write my main program and used MPW Assembler to write the vbl task. I’ll explain the vbl tasks code first since its so simple (only three lines). When the task runs, register A0 is a ptr to our vbltask record and this allows us to reset our tasks vblcount. Since we defined an integer that comes right after this record in our XVBLRec type (see above), we can change its value to 1 at this point since A0 points to our record. The three lines of the vbl task do the following (in pseudocode):

1) reset the vblcount

2) set the xDoTask variable to 1

3) return (exit) from the vbl task.

All the main program loop has to do is (in pseudocode):

 repeat
 if (xDoTask <> 0) begin
 DrawStuff;
 set xDoTask to 0
 endif
 until done

The following MPW commands will build and run the example program (you may need to change the paths to build it on your hard disk):

# 3

####
Asm vbltask.a
TMLPascal slotvbltaskdemo.p
Link -w -t ‘APPL’ -c ‘????’ 
 slotvbltaskdemo.p.o vbltask.a.o 
 “HD-80:MPW:Libraries:Libraries:”Runtime.o 
 “HD-80:MPW:Libraries:Libraries:”Interface.o 
 “HD-80:MPW:Libraries:TMLPLibraries:”TMLPasLib.o 
 “HD-80:MPW:Libraries:TMLPLibraries:”SANELib.o 
 -o SlotVBLTaskDemo
Rez -append -o SlotVBLTaskDemo slotvbltaskdemo.r
SlotVBLTaskDemo
####

Note that the code does check to make sure that the machine its running on is a Mac II or better before running, since the new calls are not available on lower end machines. On lower machines using regular vbl tasks is probably sufficient to do simple animation. That’s about all the explanation the code needs other than to say that it ‘bounces’ a red string vertically in its draggable window and can run in the background.

There is a bug which occurs when things are being drawn at the top of the screen and when you use the simple method of ‘erase old stuff then draw new stuff’ as I do in this example. You may see things start to flicker when drawing at the top of the screen. The problem I think is in the way the screen is drawn which is left to right and from top to bottom. I haven’t thought of a solution for this problem yet other than to use a call to CopyBits to blast in whatever your drawing, rather then to use straight QuickDraw calls. If anyone can think of a good explanation of this problem and how to solve it I’d like to hear about it.

Much love and thanks to the boys of ‘9A’ and of course, to K.S.

Listing:  vbltask.a

 INCLUDE‘SysEqu.a’
 EXPORT MyVBLTask

MyVBLTask PROC
;
; On entry A0 is a ptr to our XVBLRec which was defined
; as follows:
;
;XVBLRec= RECORD
;xVBLTask : VBLTask;
;xDoTask: INTEGER;
;END;
;
; We can use MPW RECORDs to define it in assembly as follows:
;
XVBLRec RECORD 0
xVBLTaskDS.BvblPhase+2
xDoTask DS.W1
 ENDR

kVBLCount EQU    1

 WITH XVBLRec
 ; Reset the vblCount
 MOVE.W #kVBLCount,XVBLRec+xVBLTask+vblCount(A0)

 ; Make xDoTask non-zero
 MOVE.W #1,XVBLRec+xDoTask(A0)

 ; Exit Task
 RTS

ENDWITH
ENDP
 END  ; For Assembler
Listing:  slotvbltaskdemo.p

PROGRAM SlotVBLTaskDemo;

USES
 MemTypes, QuickDraw, OSIntf, ToolIntf;

{ Declare our external vbl task }
PROCEDURE MyVBLTask; EXTERNAL;

CONST
 F =  False;
 T =  True;
 kBallSpeed =  4;

TYPE
 XVBLRec= RECORD
 xVBLTask : VBLTask;
 xDoTask: INTEGER;
 END;

VAR
 gDone  : BOOLEAN;
 gVideoInfoRec : DefVideoRec;
 gEvt : EventRecord;
 gFontInfo: FontInfo;
 gBoxDir: INTEGER;
 gBoxRect : Rect;
 gBoxColor: RGBColor;
 gBoxString :  Str255;

 gDragRect,
 gRect  : Rect;
 gMainWindow:  WindowPtr;
 gWRec  : WindowRecord;

 gXVBLRec : XVBLRec;

{ Proc to run if a crash occurs }
PROCEDURE Crash;
BEGIN
 ExitToShell;
END;

{ Proc that does MacInits }
PROCEDURE MacInits;
BEGIN
 MaxApplZone;

 MoreMasters;
 MoreMasters;
 MoreMasters;
 MoreMasters;

 InitGraf (@thePort);
 InitFonts;
 InitWindows;
 InitMenus;
 TEInit;
 InitDialogs (@Crash);
 InitCursor;
END;

{ Proc that sets up our window }
PROCEDURE SetUpWindows;
BEGIN
 gRect := ScreenBits.bounds;
 WITH gRect DO BEGIN
 left := left + 20;
 right := left + 400;
 top := top + 40;
 bottom := bottom - 20;
 END;

 gMainWindow := NewCWindow (@gWRec, gRect,
 ‘SlotVBLTaskDemo - Click in this window to Exit’,
 T, noGrowDocProc, WindowPtr (-1), F, 0);
 SetPort (gMainWindow);
END;

{ Proc that sets up the box for our ball }
PROCEDURE SetUpBox;
VAR
 width  : INTEGER;
BEGIN
 gBoxDir := kBallSpeed;

 gBoxString := ‘I love you Manu’;

 width := StringWidth (gBoxString);

 GetFontInfo (gFontInfo);

 WITH gBoxRect DO BEGIN
 top := 10;
 bottom := top + gFontInfo.ascent + gFontInfo.descent;
 left := ((gRect.right - gRect.left) DIV 2) - (width DIV 2);
 right := left + width;
 END;

 WITH gBoxColor DO BEGIN
 red := -1;
 green := 0;
 blue := 0;
 END;

 RGBForeColor (gBoxColor);
END;

{ Proc that inits our globals }
PROCEDURE GlobalInits;
BEGIN
 SetUpWindows;
 SetUpBox;
 gDragRect := ScreenBits.bounds;
 InsetRect (gDragRect, 4, 4);

 gDone := F;
END;

{ Proc that cleans up before we exit }
PROCEDURE CleanUps;
BEGIN
 CloseWindow (gMainWindow);
END;

{ Func that makes sure we run in the currect environment }
FUNCTION EnvironmentOK : BOOLEAN;
VAR
 err  : OSErr;
 theWorld : SysEnvRec;
BEGIN
 EnvironmentOK := F; { Assume env is bad }

 err := SysEnvirons (curSysEnvVers, theWorld);

 IF (err = noErr) THEN BEGIN
 IF (theWorld.machineType >= envMacII) THEN
 EnvironmentOK := T;
 END; { IF }
END;

{ Func that sets up our vbl task }
FUNCTION VBLTaskSetUp : BOOLEAN;
VAR
 err  : OSErr;
BEGIN
 VBLTaskSetUp := F; { Assume we fail }

 GetVideoDefault (@gVideoInfoRec);

 WITH gXVBLRec DO BEGIN
 xDoTask := 0;

 WITH xVBLTask DO BEGIN
 qType := ORD (vType);
 vblAddr := @MyVBLTask;
 vblCount := 1;
 vblPhase := 0;
 END;

 err := SlotVInstall (@xVBLTask, gVideoInfoRec.sdSlot);
 IF (err = noErr) THEN
 VBLTaskSetUp := T; { We succeeded! }
 END;
END;

{ Proc that removes our vbl task }
PROCEDURE RemoveVBLTask;
VAR
 err  : OSErr;
BEGIN
 err := SlotVRemove (@gXVBLRec.xVBLTask, gVideoInfoRec.sdSlot);
END;

{ Proc that draws our window }
PROCEDURE DrawStuff;
VAR
 oldPort: GrafPtr;
BEGIN
 GetPort (oldPort);
 SetPort (gMainWindow);
 EraseRect (gBoxRect);

 WITH gBoxRect DO BEGIN
 top := top + gBoxDir;
 bottom := bottom + gBoxDir;
 END;

 IF (gBoxRect.bottom >= gWRec.port.portRect.bottom) THEN
 gBoxDir := -kBallSpeed
 ELSE BEGIN
 IF (gBoxRect.top <= gWRec.port.portRect.top) THEN
 gBoxDir := kBallSpeed;
 END;

 MoveTo (gBoxRect.left, gBoxRect.bottom - gFontInfo.descent);
 DrawString (gBoxString);

 SetPort (oldPort);
END;

{ Proc that handles mouse downs }
PROCEDURE DoMouseDown;
VAR
 result : INTEGER;
 whichWindow:  WindowPtr;
BEGIN
 result := FindWindow (gEvt.where, whichWindow);

 CASE result OF
 inContent:
 gDone := T;
 inDrag:
 DragWindow (whichWindow, gEvt.where, gDragRect);
 OTHERWISE
 END;
END;

{ Main }
BEGIN
 MacInits;

 IF (EnvironmentOK) THEN BEGIN
 GlobalInits;

 IF (VBLTaskSetUp) THEN BEGIN

 REPEAT
 IF NOT (WaitNextEvent (mDownMask, gEvt, 0, NIL)) THEN BEGIN
 IF (gXVBLRec.xDoTask <> 0) THEN BEGIN
 DrawStuff;
 gXVBLRec.xDoTask := 0;
 END;
 END
 ELSE
 DoMouseDown;
 UNTIL (gDone);
 RemoveVBLTask;
 END;
 CleanUps;
 END;

 ExitToShell; { Back to the Finder! (or MultiFinder) }
END.
Listing:  slotvbltaskdemo.r

#include “Types.r”
#define kMinSize 25/* application’s minimum size (in K) */
#define kPrefSize50/* application’s preferred size (in K) */

resource ‘SIZE’ (-1) {
 dontSaveScreen,
 acceptSuspendResumeEvents,
 enableOptionSwitch,
 canBackground,  /* we can background  */
 multiFinderAware,
 backgroundAndForeground,
 dontGetFrontClicks,
 ignoreChildDiedEvents,
 not32BitCompatible,
 reserved,
 reserved,
 reserved,
 reserved,
 reserved,
 reserved,
 reserved,
 kPrefSize * 1024,
 kMinSize * 1024 
};

 
AAPL
$102.50
Apple Inc.
+0.25
MSFT
$45.43
Microsoft Corpora
+0.55
GOOG
$571.60
Google Inc.
+2.40

MacTech Search:
Community Search:

Software Updates via MacUpdate

Skype 6.19.0.450 - Voice-over-internet p...
Skype allows you to talk to friends, family and co-workers across the Internet without the inconvenience of long distance telephone charges. Using peer-to-peer data transmission technology, Skype... Read more
VueScan 9.4.41 - Scanner software with a...
VueScan is a scanning program that works with most high-quality flatbed and film scanners to produce scans that have excellent color fidelity and color balance. VueScan is easy to use, and has... Read more
Cloud 3.0.0 - File sharing from your men...
Cloud is simple file sharing for the Mac. Drag a file from your Mac to the CloudApp icon in the menubar and we take care of the rest. A link to the file will automatically be copied to your clipboard... Read more
LibreOffice 4.3.1.2 - Free Open Source o...
LibreOffice is an office suite (word processor, spreadsheet, presentations, drawing tool) compatible with other major office suites. The Document Foundation is coordinating development and... Read more
SlingPlayer Plugin 3.3.20.505 - Browser...
SlingPlayer is the screen interface software that works hand-in-hand with the hardware inside the Slingbox to make your TV viewing experience just like that at home. It features an array of... Read more
Get Lyrical 3.8 - Auto-magically adds ly...
Get Lyrical auto-magically add lyrics to songs in iTunes. You can choose either a selection of tracks, or the current track. Or turn on "Active Tagging" to get lyrics for songs as you play them.... Read more
Viber 4.2.2 - Send messages and make cal...
Viber lets you send free messages and make free calls to other Viber users, on any device and network, in any country! Viber syncs your contacts, messages and call history with your mobile device,... Read more
Cocktail 7.6 - General maintenance and o...
Cocktail is a general purpose utility for OS X that lets you clean, repair and optimize your Mac. It is a powerful digital toolset that helps hundreds of thousands of Mac users around the world get... Read more
LaunchBar 6.1 - Powerful file/URL/email...
LaunchBar is an award-winning productivity utility that offers an amazingly intuitive and efficient way to search and access any kind of information stored on your computer or on the Web. It provides... Read more
Maya 2015 - Professional 3D modeling and...
Maya is an award-winning software and powerful, integrated 3D modeling, animation, visual effects, and rendering solution. Because Maya is based on an open architecture, all your work can be scripted... Read more

Latest Forum Discussions

See All

Rhonna Designs Magic (Photography)
Rhonna Designs Magic 1.0 Device: iOS Universal Category: Photography Price: $1.99, Version: 1.0 (iTunes) Description: Want to sprinkle *magic* on your photos? With RD Magic, you can add colors, filters, light leaks, bokeh, edges,... | Read more »
This Week at 148Apps: August 25-29, 2014
Shiny Happy App Reviews   | Read more »
Qube Kingdom – Tips, Tricks, Strategies,...
Qube Kingdom is a tower defense game from DeNA. You rally your troops – magicians, archers, knights, barbarians, and others – and fight against an evil menace looking to dominate your kingdom of tiny squares. Planning a war isn’t easy, so here are a... | Read more »
Qube Kingdom Review
Qube Kingdom Review By Nadia Oxford on August 29th, 2014 Our Rating: :: KIND OF A SQUARE KINGDOMUniversal App - Designed for iPhone and iPad Qube Kingdom has cute visuals, but it’s a pretty basic tower defense game at heart.   | Read more »
Fire in the Hole Review
Fire in the Hole Review By Rob Thomas on August 29th, 2014 Our Rating: :: WALK THE PLANKUniversal App - Designed for iPhone and iPad Seafoam’s Fire in the Hole looks like a bright, 8-bit throwback, but there’s not enough booty to... | Read more »
Alien Creeps TD is Now Available Worldwi...
Alien Creeps TD is Now Available Worldwide Posted by Ellis Spice on August 29th, 2014 [ permalink ] Universal App - Designed for iPhone and iPad | Read more »
Dodo Master Review
Dodo Master Review By Jordan Minor on August 29th, 2014 Our Rating: :: NEST EGGiPad Only App - Designed for the iPad Dodo Master is tough but fair, and that’s what makes it a joy to play.   | Read more »
Motorsport Manager Review
Motorsport Manager Review By Lee Hamlet on August 29th, 2014 Our Rating: :: MARVELOUS MANAGEMENTUniversal App - Designed for iPhone and iPad Despite its depth and sense of tactical freedom, Motorsport Manager is one of the most... | Read more »
Motorsport Manager – Beginner Tips, Tric...
The world of Motorsport management can be an unforgiving and merciless one, so to help with some of the stress that comes with running a successful race team, here are a few hints and tips to leave your opponents in the dust. | Read more »
CalPal Update Brings the App to 2.0, Add...
CalPal Update Brings the App to 2.0, Adds Lots of New Stuff Posted by Ellis Spice on August 29th, 2014 [ permalink ] | Read more »

Price Scanner via MacPrices.net

Apple now offering refurbished 21-inch 1.4GHz...
The Apple Store is now offering Apple Certified Refurbished 21″ 1.4GHz iMacs for $929 including free shipping plus Apple’s standard one-year warranty. Their price is $170 off the cost of new models,... Read more
Save $50 on the 2.5GHz Mac mini, on sale for...
B&H Photo has the 2.5GHz Mac mini on sale for $549.99 including free shipping. That’s $50 off MSRP, and B&H will also include a free copy of Parallels Desktop software. NY sales tax only. Read more
Save up to $300 on an iMac with Apple refurbi...
The Apple Store has Apple Certified Refurbished iMacs available for up to $300 off the cost of new models. Apple’s one-year warranty is standard, and shipping is free. These are the best prices on... Read more
The Rise of Phablets
Carlisle & Gallagher Consulting Group, a businesses and technology consulting firm focused solely on the financial services industry, has released an infographic depicting the convergence of... Read more
Bad Driver Database App Allows Good Drivers t...
Bad Driver Database 1.4 by Facile Group is a new iOS and Android app that lets users instantly input and see how many times a careless, reckless or just plain stupid driver has been added to the... Read more
Eddy – Cloud Music Player for iPhone/iPad Fre...
Ukraine based CapableBits announces the release of Eddy, its tiny, but smart and powerful cloud music player for iPhone and iPad that allows users to stream or download music directly from cloud... Read more
A&D Medical Launches Its WellnessConnecte...
For consumers and the healthcare providers and loved ones who care for them, A&D Medical, a leader in connected health and biometric measurement devices and services, has launched its... Read more
Anand Lal Shimpi Retires From AnandTech
Anand Lal Shimpi, whose AnandTech Website is famous for its meticulously detailed and thoroughgoing reviews and analysis, is packing it in. Lal Shimpi, who founded the tech site at age 14 in 1997,... Read more
2.5GHz Mac mini, Apple refurbished, in stock...
The Apple Store has Apple Certified Refurbished 2.5GHz Mac minis available for $509, $90 off MSRP. Apple’s one-year warranty is included, and shipping is free. Read more
13-inch 2.5GHz MacBook Pro on sale for $999,...
B&H Photo has the 13″ 2.5GHz MacBook Pro on sale for $999.99 including free shipping plus NY sales tax only. Their price is $100 off MSRP. Read more

Jobs Board

*Apple* Retail - Multiple Positions (US) - A...
Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, you're also the Read more
*Apple* Retail - Multiple Positions (US) - A...
Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, you're also the Read more
*Apple* Retail - Multiple Positions (US) - A...
Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, you're also the Read more
*Apple* Retail - Multiple Positions (US) - A...
Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, you're also the Read more
Senior Event Manager, *Apple* Retail Market...
…This senior level position is responsible for leading and imagining the Apple Retail Team's global event strategy. Delivering an overarching brand story; in-store, Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.