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

Dashlane 4.8.4 - Password manager and se...
Dashlane is an award-winning service that revolutionizes the online experience by replacing the drudgery of everyday transactional processes with convenient, automated simplicity - in other words,... Read more
FileZilla 3.27.1 - Fast and reliable FTP...
FileZilla (ported from Windows) is a fast and reliable FTP client and server with lots of useful features and an intuitive interface. Version 3.27.1: Fixed Vulnerabilities: Change client... Read more
f.lux 39.984 - Adjusts the color of your...
f.lux makes the color of your computer's display adapt to the time of day, warm at night and like sunlight during the day. Ever notice how people texting at night have that eerie blue glow? Or wake... Read more
Merlin Project 4.2.7 - $289.00
Merlin Project is the leading professional project management software for OS X. If you plan complex projects on your Mac, you won’t get far with a simple list of tasks. Good planning raises... Read more
Sound Studio 4.8.10 - Robust audio recor...
Sound Studio lets you easily record and professionally edit audio on your Mac. Easily rip vinyls and digitize cassette tapes, or record lectures and voice memos. Prepare for live shows with live... Read more
Google Chrome 60.0.3112.101 - Modern and...
Google Chrome is a Web browser by Google, created to be a modern platform for Web pages and applications. It utilizes very fast loading of Web pages and has a V8 engine, which is a custom built... Read more
Microsoft Office 2016 15.37 - Popular pr...
Microsoft Office 2016 - Unmistakably Office, designed for Mac. The new versions of Word, Excel, PowerPoint, Outlook and OneNote provide the best of both worlds for Mac users - the familiar Office... Read more
Sketch 46.2 - Design app for UX/UI for i...
Sketch is an innovative and fresh look at vector drawing. Its intentionally minimalist design is based upon a drawing space of unlimited size and layers, free of palettes, panels, menus, windows, and... Read more
beaTunes 5.0.4 - Organize your music col...
beaTunes is a full-featured music player and organizational tool for music collections. How well organized is your music library? Are your artists always spelled the same way? Any R.E.M. vs REM?... Read more
Yasu 4.0.4 - System maintenance app.
Yasu was created with system administrators who service large groups of workstations in mind, Yasu (Yet Another System Utility) was made to do a specific group of maintenance tasks quickly within a... Read more

Portal Walk (Games)
Portal Walk 1.0 Device: iOS Universal Category: Games Price: $1.99, Version: 1.0 (iTunes) Description: Portal Walk is adventure and relaxing platform game about Eugene. Eugene stuck between worlds and trying to find way back home.... | Read more »
Technobabylon (Games)
Technobabylon 1.0 Device: iOS Universal Category: Games Price: $4.99, Version: 1.0 (iTunes) Description: City of Newton, 2087. Genetic engineering is the norm, the addictive Trance has replaced almost any need for human interaction,... | Read more »
5 reasons why 2v2 is the best mode in Cl...
Supercell has been teasing fans with 2v2 windows that allow players to team up for limited periods of time. The Summer of 2v2 was just this past July, but players are already clamoring for more of that sweet, sweet team-based action. The fans have... | Read more »
The best deals on the App Store this wee...
It seems like the week's only just started, and yet here we are with a huge pile of discounted games to sort through. There are some real doozies on sale this week. We're talking some truly stellar titles. Let's take a look at four of the best... | Read more »
Cat Quest Guide - How to become a purrfe...
Cat Quest is an absolutely charming open-world RPG that's taken the gaming world quite by storm. This game about a world populated by furry kitty warriors is actually a full-length RPG with sturdy mechanics and a lovely little story. It's certainly... | Read more »
Silly Walks Guide - How to strut your st...
Silly Walks is an all new adventure game that lives up to its name. It sees you playing as a variety of snack foods as you teeter-totter your way to rescue your friends from the evil blender and his villainous minions. It's all very . . . well... | Read more »
The best mobile point-and-click adventur...
Nostalgia for classic point-and-click adventure games has reached an all-time high in recent years, and the rise of mobile games have provided a perfect platform for this old-school genre. This week we're going to take a look at some of the best... | Read more »
Titanfall: Assault Beginner's Guide...
Respawn's dazzling mech battler Titanfall has gotten its first mobile game at long last -- Titanfall: Assault. Assault transforms that parkour FPS action into a card battler not dissimilar to Clash Royale. Titanfall: Assault isn't just another... | Read more »
Unobstruct (Utilities)
Unobstruct 1.0 Device: iOS Universal Category: Utilities Price: $.99, Version: 1.0 (iTunes) Description: You’re already reading web pages on a pretty small screen. Don’t let floating social media sharing toolbars and the like get in... | Read more »
Burgle Bros (Games)
Burgle Bros 1.0 Device: iOS Universal Category: Games Price: $4.99, Version: 1.0 (iTunes) Description: Burgle Bros requires stealth, planning and a little bit of luck. In the tradition of classic heist movies like Ocean's 11 and The... | Read more »

Price Scanner via MacPrices.net

New iOS 11 Productivity Features Welcome But...
The iOS community is in late summer holding mode awaiting the September arrival of the iPhone 8 and iOS 11. iOS 11 public betas have been available for months — number six was released this week —... Read more
Samsung Electronics Launches New Portable SSD...
Samsung Electronics America, Inc. has announced the launch of Samsung Portable SSD T5 – its newest portable solid state drive (PSSD) that raises the bar for the performance of external memory... Read more
TrendForce Reports YoY Gain of 3.6% for 2Q17...
Market research firm TrendForce reports that the global notebook shipments for this second quarter registered a sequential quarterly increase of 5.7% and a year-on-year increase of 3.6%, totaling 39.... Read more
Sale! 10-inch iPad Pros for $50 off MSRP, no...
B&H Photo has 10.5″ iPad Pros in stock today and on sale for $50 off MSRP. Each iPad includes free shipping, and B&H charges sales tax in NY & NJ only: – 10.5″ 64GB iPad Pro: $599, save $... Read more
Sale! 2017 13-inch Silver 2.3GHz MacBook Pro...
Amazon has new 2017 13″ 2.3GHz/128GB Silver MacBook Pro on sale today for $100 off MSRP including free shipping. Their price is the lowest available for this model from any reseller: – 13″ 2.3GHz/... Read more
WaterField Unveils Collaboratively-Designed,...
In collaboration with customers and seasoned travelers, San Francisco maker WaterField Designs set out to create the preeminent carry-on system to improve the experience of frequent fliers. The... Read more
Miya Notes Mac-Client for Google Keep (Launch...
MacPlus Software has announced te launch of Miya Notes for Google Keep 1.0, a powerful Mac-client for Google Keep. Millions of people use Google Keep on their phones and online, but a convenient Mac... Read more
Apple refurbished iMacs available starting at...
Apple has previous-generation Certified Refurbished 2015 21″ & 27″ iMacs available starting at $849. Apple’s one-year warranty is standard, and shipping is free. The following models are... Read more
2017 13-inch MacBook Airs on sale for $100 of...
B&H Photo new 2017 13″ MacBook Airs on sale today for $100 off MSRP, starting at $899: – 13″ 1.8GHz/128GB MacBook Air (MQD32LL/A): $899, $100 off MSRP – 13″ 1.8GHz/256GB MacBook Air (MQD42LL/A... Read more
12-inch MacBooks on sale for $100 off MSRP
Amazon has 2017 12″ Retina MacBooks on sale for $100 off MSRP. Shipping is free: 12″ 1.2GHz Space Gray MacBook: $1199.99 $100 off MSRP 12″ 1.2GHz Silver MacBook: $1198 $101 off MSRP 12″ 1.2GHz Gold... Read more

Jobs Board

SW Engineer *Apple* TV - Apple Inc. (United...
Job Summary The Apple TV team is looking for an experienced engineer with a passion for delivering first in class home entertainment solutions. The candidate will Read more
Development Operations and Site Reliability E...
Development Operations and Site Reliability Engineer, Apple Payment Gateway Job Number: 57572631 Santa Clara Valley, California, United States Posted: Jul. 27, 2017 Read more
Frameworks Engineering Manager, *Apple* Wat...
Frameworks Engineering Manager, Apple Watch Job Number: 41632321 Santa Clara Valley, California, United States Posted: Jun. 15, 2017 Weekly Hours: 40.00 Job Summary Read more
*Apple* Retail - Multiple Positions - Apple,...
Job Description: Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
*Apple* Solutions Consultant - Apple Inc. (U...
Job Summary As an Apple Solutions Consultant, you'll be the link between our future customers and our products. You'll showcase your entrepreneurial spirit as you Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.