TweetFollow Us on Twitter

Foundation Of Quickdraw
Volume Number:1
Issue Number:2
Column Tag:features of Mac Pascal

QuickDraw Graphics

By Chris Derossi

One of the most valuable features of Mac Pascal is it ability to take advantage of the Macintosh’s powerful ROM capabilities. To do this, Mac Pascal must be able to access the various routines that are contained within the Mac Toolbox. In this month’s column, we will examine the interface between Mac Pascal and the ROM, and the necessary data structures for accessing quickdraw. Finally, a sample program is included which makes use of quickdraw’s graphics routines.

In order to communicate to the Toolbox, several data structures have to be defined. These data structures are all presented in Pascal format because the routines contained in the Mac ROM are constructed for a Pascal environment. Unlike other programming languages, this makes data compatiblitly pretty much straight forward for Mac Pascal users. But before we get into the details, let’s briefly describe some of the theory behind QuickDraw.

FOUNDATION OF QUICKDRAW

QuickDraw graphics exist in cartesian coordinate planes. What this means is that graphics may be present on any portion of a continuous surface. The QuickDraw planes are finite, and extend from values -32768 to 32767 in both the vertical and horizontal directions. The smallest unit of distance that QuickDraw can work with is 1. An area of 1 by 1 is, therefore, a point. The boundary separating two points at sequential locations of the plane is of size zero. This means that two points placed next to each other are continuous, and have no space between them. Keep in mind that these are theoretical concepts, not screen bit-map specifications.

QUICKDRAW DATA STRUCTURES

In Mac Pascal, the data structure ‘Point’ is a record with two components representing the coordinates of the upper left corner of a point. The two fields of Point are Point.h and Point.v which are the horizontal and vertical coordinates respectively. Each value is of type Integer.

The rectangle is a common object found in QuickDraw. Rectangles are frequently used to create windows, define drawing areas, and to provide parameters for manipualting other objects. A rectangle has four parameters. These are: Top, Left, Bottom, and Right. These parameters may be thought of as four integers, or as the two points TopLeft and BottomRight. In actuality, the second method is used, and the type ‘Rect’ is defined as a record with the two fields Rect.TopLeft and Rect.BotRight. Each of the fields is of type point.

Another object defined with points is the line. Although there is no Mac Pascal data type for this object, it can be characterized by two points, for the beginning and ending positions of the line.

The final data type we will examine this month is the pattern. QuickDraw allows regions to be filled with patterns, as is done with the paint bucket in MacPaint. A pattern is a set of sixty-four points either on or off, arranged in an eight by eight square. To fill an area larger than eight by eight, the Macintosh repeats the pattern both vertically and horizontally as many times as neccessary. The upper left corner of the pattern is aligned with the coordinate (0,0), and is independent of the coordinates of the area being filled.

Since a byte is eight bits, and a bit represents one point, patterns can be represented as a series of eight bytes. In Mac Pascal, the type ‘Pattern’ is an array [0..7] of 0..255, which is effectively eight sequential bytes. There are some predefined patterns including White, Black, and Grey.

DRAWING IN QUICKDRAW

The drawing mechanism in QuickDraw is the Pen. The pen has modifyable properties which include location, width, height, and pattern. There are further properties which will be covered in a later column. A pen of width and height of one, and a pattern of black will always draw with one-point wide, black lines.

In addition to the many objects of QuickDraw, many actions are available to be performed on or with them. Most objects may be Framed, Painted, Filled, and Erased. The QuickDraw actions are called QuickDraw verbs, and they are applied to objects. The verb Frame specifies that the outline of the given object should be drawn. The verb Paint means that the object is drawn completely filled. Each of these actions use the pen for drawing, and as such use the current pen pattern. The verb Erase does not use the pen pattern, but instead uses the pattern currently set for the background. Fill allows you to specify a pattern to use, and is therefore a little bit more versatile than Paint.

For example, FrameRect will draw the outline of a rectangle, while PaintRect will draw a solid rectangle. FillRect will draw a solid rectangle in the given pattern. EraseRect clears the given rectangle to the current background pattern.

Each verb-object combination is a procedure, and takes applicable parameters. The Rect procedures take a rectangle as their only parameter. The FillRect procedure needs a Rect first, and a Pattern second. The rectangle is drawn as a solid with the pattern.

A frequently encountered situation is one where the Macintosh needs to know if a given point is inside a particular rectangle. (i.e. is the mouse’s position inside a certain window?) To satisfy this need, a function titled PtInRect returns a boolean of True if the point is inside the rectangle, and False if not. The parameters of this function are a point first, and then a rectangle.

PROGRAMMING EXAMPLE

Now let us examine the example program that makes use of these data structures, procedures, and functions. The operation of the program is fairly simple and straight forward. The user is presented with a blank background and the mouse pointer. The user forms rectangles by pressing the mouse button when the pointer is at one of the rectangle’s corners, and holds the button down while dragging the mouse to the opposite diagonal corner. In order to provide some feedback about the shape of the rectangle, a ‘rubber banding’ diagonal line follows the mouse until the button is released. When the button is released, the rubber band line is removed, and the rectangle is drawn.

WHERE’S THE MOUSE?

After the rectangle is drawn, the user may place the mouse pointer inside the rectangle, and press the button. As long as the button is held, the Mac continually fills the rectangle with random, changing patterns. Once the mouse button is pressed outside of the rectangle, the pattern is frozen, and a new rectangle is begun. (Please see the sample output in fig. 1.)

The construction of the program is not complex. The variable declarations for the main program consist of three points and one rectangle. The points are used as work variables for reading the mouse location, and the rectangle is the one currently being drawn or filled.

The main program calls two procedures. The first one allows the user to create the rectangle, and provides the rubberbanding effect. The second one creates random patterns and fills the rectangle.

Since the value of a rectangle’s Top must be less than or equal to that of its bottom, two procedures called ‘Min’ and ‘Max’ help keep the points in the right order. The same holds true for the Left and Right values.

The key procedure calls in the Make_Rect procedure are Button, GetMouse, DrawLine, PenPat, FrameRect, and InsetRect. The function Button returns True if the mouse button is pressed, and False if not. GetMouse uses two VAR parameters for obtaining the current horizontal and vertical position of the mouse pointer.

Since we need to draw and erase the rubberbanding line, we use the two pen patterns of Black and White. This has the disadvantage of erasing whatever the line passes over, but you can’t have everything in a simple little program. The procedure PenPat sets the working pen pattern to the passed value.

DrawLine uses two points, this time in the form of four coordinates, to designate the starting and ending points of the line. DrawLine, of course, uses the current pen pattern.

Finally, after the mouse button is released, the rectangle is drawn with FrameRect. This is done with the pen pattern set to black. Since we don’t want to draw over the outline with subsequent FillRect calls, the procedure InsetRect is called to change the coordinates of the rectangle by one on each side, making it slightly smaller.

After the rectangle is drawn, the Fill_Rect procedure is called to fill it in. Note, please, that Fill_Rect is distinct from FillRect. Fill_Rect uses the calls Button, GetMouse, PtInRect, Random, and FillRect to perform its task. Button and GetMouse are used as before. PtInRect determines if the mouse is inside the new rectangle when the button is depressed.

A new pattern is created by calling the function Random eight times within a loop. Random returns a value from -32768 and 32767. Abs and Mod are used to bring the random number in the range 0..255. After the random pattern is created, FillRect is called to draw the pattern into the rectangle.

MODIFYING THE PROGRAM

The program runs forever, and the menu option Halt must be chosen to exit. In order to overcome this, you might want to modify the program to present you with a Black or Grey box (read rectangle) where you’d click the mouse to quit. Where in the program would you draw the rectangle? At what point or points would you have to check to see if it has been clicked? How will you handle rectangles that overlap your ‘exit’ box? These exercises are left to the student!

That’s it for this month. In the next column, we’ll further explore the powerful features of QuickDraw, and find out what makes it so unique and wonderful among graphic tools. We’ll also have another program that utilizes these terrific features. If you like our Pascal column or have programming ideas of your own to contribute, please feel free to write me care of MacTech. Ciao.

program MacTutor_QD_Demo;

{ This program will use the standard features of } {QuickDraw to introduce 
use of QuickDraw data} {structures and routine calls from MacPascal.} 

{ -- By Chris Derossi}

 var
  P1, P2, P3 : Point;
  WorkingRect : Rect;

 function Min (Num1, Num2 : integer) : integer;

{ return the minimum of the two numbers passed.}

 begin
  if Num1 < Num2 then
   Min := Num1
  else
    Min := Num2;
 end;

 function Max (Num1, Num2 : integer) : integer;

{ returns the maximum of two numbers passed.}

 begin
  if Num1 > Num2 then
  Max := Num1
  else
    Max := Num2;
 end;

 procedure Make_Rect (var theRect : Rect);

{ This is the first of the two main procedure. It} 
{allows the user to select diagonal corners of the} 
{rectangle to be drawn, using a ‘rubber band’ line.} 
{When the button is released, the recatangle is} 
{drawn.}

 begin
  repeat
   until Button;  {Wait till the button is pressed}
  GetMouse(P1.h, P1.v); {Where was the mouse?}
  P2 := P1;
  P3 := P1;
  while Button do  {update while button is down.}
   begin
      GetMouse(P3.h, P3.v);
    if (P2.h <> P3.h) or (P2.v <> p3.v) then  
 {the mouse has moved}
    begin
        PenPat(White);
      DrawLine(P1.h, P1.v, P2.h, P2.v);  
 {Erase the old line}
      PenPat(Black);
    DrawLine(P1.h, P1.v, P3.h, P3.v);  
 {Draw the new line}
    P2 := P3;
    end;
   end;

  PenPat(White);  {Erase line for the last time.}
  DrawLine(P1.h, P1.v, P2.h, P2.v);
  PenPat(Black);
  theRect.TopLeft.v := Min(P1.v, P2.v); 
  
{Set the rectangle, making sure}
  theRect.TopLeft.h := Min(P1.h, P2.h);   
{that the top is above the bottom}
  theRect.BotRight.v := Max(P1.v, P2.v); 
{and the left is less than the}
  theRect.BotRight.h := Max(P1.h, P2.h); {right.}

  FrameRect(theRect);   {Draw the rectangle}
  InsetRect(theRect, 1, 1);  
{Shrink it so that the pattern does not draw}
 {over the rectangle frame.}
 end;

 procedure Fill_Rect (theRect : Rect);

  var
   myPat : Pattern;
   Index : Integer;
   Done : Boolean;

 begin
  Done := False;
  while not Done do  
{continue until the mouse is outside of the}
   {new rectangle.}
   begin
    repeat
      until Button;   {Wait for the button}
    GetMouse(P1.h, P1.v);
    if PtInRect(P1, theRect) then  
{is the mouse in the rectangle?}
    begin
    for Index := 0 to 7 do
     myPat[Index] := Abs(Random) mod 256; {make a random pattern}
     FillRect(theRect, myPat);  {Fill the rectangle}
    end
    else
    Done := True;
   end; {While}
 end; {Fill_Rect}


begin  {Main Program}
 while true do
  begin
    Make_Rect(WorkingRect);
    Fill_Rect(WorkingRect);
  end;
end.   {Main}

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

GarageSale 7.0.7 - Create outstanding eB...
GarageSale is a slick, full-featured client application for the eBay online auction system. Create and manage your auctions with ease. With GarageSale, you can create, edit, track, and manage... Read more
SpamSieve 2.9.28 - Robust spam filter fo...
SpamSieve is a robust spam filter for major email clients that uses powerful Bayesian spam filtering. SpamSieve understands what your spam looks like in order to block it all, but also learns what... Read more
Thunderbird 45.7.1 - Email client from M...
As of July 2012, Thunderbird has transitioned to a new governance model, with new features being developed by the broader free software and open source community, and security fixes and improvements... Read more
Opera 43.0.2442.991 - High-performance W...
Opera is a fast and secure browser trusted by millions of users. With the intuitive interface, Speed Dial and visual bookmarks for organizing favorite sites, news feature with fresh, relevant content... Read more
OnyX 3.2.4 - Maintenance and optimizatio...
OnyX is a multifunction utility that you can use to verify the startup disk and the structure of its system files, to run miscellaneous maintenance and cleaning tasks, to configure parameters in the... Read more
VueScan 9.5.71 - 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
Slack 2.5.1 - Collaborative communicatio...
Slack is a collaborative communication app that simplifies real-time messaging, archiving, and search for modern working teams. Version 2.5.1: New The way we load teams you don't view often has been... Read more
HandBrake 1.0.3 - Versatile video encode...
HandBrake is a tool for converting video from nearly any format to a selection of modern, widely supported codecs. Features Supported Sources VIDEO_TS folder, DVD image or real DVD (unencrypted... Read more
Vivaldi 1.7.735.46 - An advanced browser...
Vivaldi is a browser for our friends. In 1994, two programmers started working on a web browser. Our idea was to make a really fast browser, capable of running on limited hardware, keeping in mind... Read more
Vivaldi 1.7.735.46 - An advanced browser...
Vivaldi is a browser for our friends. In 1994, two programmers started working on a web browser. Our idea was to make a really fast browser, capable of running on limited hardware, keeping in mind... Read more

Last week on Pocket Gamer
If you’re wondering what’s going on in the wider world of portable gaming, our sister site PocketGamer has you covered. Each week we like to check in on the PG team and see what they’ve been preoccupied with. From the latest on the Nintendo Switch... | Read more »
Mudd Masher arrives this week
Atooi Games, the minds behind Totes the Goat and Mutant Mudds, have a new game in the works -- Mudd Masher. The game, a hybrid of the independent studio's first two titles, is expected to launch this week on March 2. [Read more] | Read more »
The best sales on the App Store this wee...
The App Store has quite an exciting lineup of discount games this week that range across a variety of genres. It's a great opportunity to catch up on some of the premium games you may have been holding off on -- and some you can even grab for free... | Read more »
The best new games we played this week
Ah, here we are again at the close of another busy week. Don't rest too easy, though. We had a lot of great new releases in mobile games this week, and now you're going to have to spend all weekend playing them. That shouldn't be too much of a... | Read more »
Rollercoaster Tycoon Touch Guide: How to...
| Read more »
Rabbids Crazy Rush Guide: How to unlock...
The Rabbids are back in a new endless running adventure, Rabbids Crazy Rush. It's more ridiculous cartoon craziness as you help the little furballs gather enough fuel (soda) to get to the moon. Sure, it's a silly idea, but everyone has dreams --... | Read more »
Tavern Guardians (Games)
Tavern Guardians 1.0 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0 (iTunes) Description: Tavern Guardians is a Hack-and-Slash action game played in the style of a match-three. You can experience high pace action... | Read more »
Slay your way to glory in idle RPG Endle...
It’s a golden age for idle games on the mobile market, and those addictive little clickers have a new best friend. South Korean developer Ekkorr released Endless Frontier last year, and players have been idling away the hours in the company of its... | Read more »
Tiny Striker: World Football Guide - How...
| Read more »
Good news everyone! Futurama: Worlds of...
Futurama is finding a new home on mobile in TinyCo and Fox Interactive's new game, Futurama: Worlds of Tomorrow. They're really doing it up, bringing on board Futurama creator Matt Groening along with the original cast and writers. TinyCo wants... | Read more »

Price Scanner via MacPrices.net

13-inch 2.7GHz Retina MacBook Pro on sale for...
B&H Photo has the 2015 13″ 2.7GHz/128GB Retina Apple MacBook Pro on sale for $150 off MSRP. Shipping is free, and B&H charges NY tax only: - 13″ 2.7GHz/128GB Retina MacBook Pro (MF839LL/A): $... Read more
13-inch 1.6GHz/256GB MacBook Air on sale for...
Newegg has the 13″ 1.6GHz/256GB MacBook Air (MMGG2LL/A) on sale for $1029.99 including free shipping. Their price is $170 off MSRP, and it’s the lowest price available for this model. Choose Newegg... Read more
Apple refurbished Apple TVs available for up...
Apple has Certified Refurbished 32GB and 64GB Apple TVs available for up to $30 off the cost of new models. Apple’s standard one-year warranty is included with each model, and shipping is free: -... Read more
27-inch 3.3GHz 5K iMac on sale for $2099, sav...
B&H Photo has the 27″ 3.3GHz 5K Apple iMac on sale for $2099.99 including free shipping plus NY sales tax only. Their price is $200 off MSRP. Amazon also has the 27″ 3.3GHz 5K iMac on sale for $... Read more
21-inch iMacs on sale for up to $111 off MSRP
B&H Photo has select 21″ Apple iMacs on sale for up to $110 off MSRP, each including free shipping plus NY sales tax only: - 21″ 2.8GHz iMac: $1189 $110 off MSRP - 21″ 1.6GHz iMac: $999 $100 off... Read more
12-inch 1.2GHz Retina MacBooks on sale for $2...
Newegg has the 12″ 1.2GHz Space Gray Retina MacBook (sku MLH82LL/A) on sale for $1349.99 including free shipping. Their price is $250 off MSRP, and it’s the lowest price available for this model.... Read more
13-inch MacBook Airs on sale for $100 off MSR...
B&H Photo has 13″ MacBook Airs on sale for $100 off MSRP. Shipping is free, and B&H charges NY sales tax only: - 13″ 1.6GHz/128GB MacBook Air (MMGF2LL/A): $899 $100 off MSRP - 13″ 1.6GHz/... Read more
9-inch 32GB Silver iPad Pro on sale for $549,...
B&H Photo has the 9.7″ 32GB Silver Apple iPad Pro on sale for $549 for a limited time. Shipping is free, and B&H charges NY sales tax only. Their price is $50 off standard MSRP for this model... Read more
13-inch 2.0GHz Apple MacBook Pros on sale for...
B&H has the non-Touch Bar 13″ 2.0GHz MacBook Pros in stock today and on sale for $100 off MSRP. Shipping is free, and B&H charges NY sales tax only: - 13″ 2.0GHz MacBook Pro Space Gray (... Read more
15-inch Touch Bar MacBook Pros on sale for up...
B&H Photo has the new 2016 15″ Apple Touch Bar MacBook Pros in stock today and on sale for up to $150 off MSRP. Shipping is free, and B&H charges NY sales tax only: - 15″ 2.7GHz Touch Bar... Read more

Jobs Board

*Apple* Solutions Consultant - Apple (United...
# Apple Solutions Consultant Job Number: 55676865 Los Angeles, California, United States Posted: Feb. 22, 2017 Weekly Hours: 40.00 **Job Summary** As an Apple Read more
Programmer/Editor *Apple* Music Dance - App...
# Programmer/Editor Apple Music Dance Job Number: 55565967 Culver City, California, United States Posted: Feb. 23, 2017 Weekly Hours: **Job Summary** Apple Music Read more
Digital Marketing Specialist - *Apple* iClo...
# Digital Marketing Specialist - Apple iCloud Job Number: 54729233 Culver City, California, United States Posted: Feb. 22, 2017 Weekly Hours: 40.00 **Job Summary** Read more
Marketing Specialist, iTunes & *Apple*...
# Marketing Specialist, iTunes & Apple Music Job Number: 55704205 Culver City, California, United States Posted: Feb. 23, 2017 Weekly Hours: 40.00 **Job Summary** Read more
*Apple* Wireless Lead - T-ROC - The Retail O...
…of knowledge in wireless sales and activations to the Beautiful and NEW APPLE Experiencestore within MACYS. THIS role, APPLE Wireless Lead, isbrandnewas MACYS Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.