Introduction to QuickDraw Graphics

Code Warrior has a suite of predefined functions for graphics that we will be using in future programs. It is important to note that these functions are not part of standard C++ but are specific only to Code Warrior are are only for the Mac. The prototypes for these QuickDraw functions are automatically included and do not need #include statements. There are however some functions in macStuff.h that will be needed. To do this we add the following statement to our programs:

  #include "macStuff.h" //  Quotes mean get the file from our files, 
                        //  not Code Warrior's!!

The Screen

The screen is composed of pixels. The term comes from "picture element".

To Draw Lines

The easiest way to do this is imagine that you have a pen. QuickDraw provides functions to allow your pen to do certain things:

• Move it to a location without drawing:
  • MoveTo(h, v);
    • Lets you move to an absolute location with horizontal location of h and a vertical location of v.
  • Move(dh, dv);
    • Lets you move relative to where the pen is currently by moving dh pixels horizontally and dv pixels vertically.
• Draw a line, leaving the pen at the end:
  • LineTo(h, v);
    • Lets you draw a line beginning where the pen currently is and ending at the absolute location of (h, v).
  • Line( dh, dv );
    • Lets you draw a line beginning where the pen currently is and ending at dh pixels horizontally and dv pixels vertically from the beginning of the line.
• Change width and height of the pen in pixels.
  • PenSize(w, h);
    • Changes the size of the pen stroke by width w and height h.

Note: All the above parameters are of type short. So when programming declare these of type short and you will make your friend the compiler much happier!!

Rectangles and Ovals

Code Warrior has predefined types Rect and Point. Notice the case!!! If the wrong case is used you will find yourself in heaps of trouble. Also keep in mind that there is no notion of a pen here. We will be using boundary frames instead.

To set up a Rect:

    Rect r;
    ...    
    SetRect(&r, left, top, right, bottom);

Notice the "&" before the first argument. It may look quite mysterious at first but it is quite common. We will be getting to it later, but for now humor the function and put it in. The types are also all short so please declare them as such. This call just sets up the frame for the rectangle. It actually doesn't draw it. To do this we need more function calls.

• To draw the outline of the rectangle:
  • FrameRect(&r);
• To draw the rectangle and fill it with current foreground color:
  • PaintRect(&r);
• To change the foreground color to red:
  • ForeColor(redColor);
  • Other colors would be:
    • blueColor
    • greenColor
    • yellowColor
    • cyanColor
    • magentaColor
• To erase a Rect:
  • EraseRect(&r);
• To fill the Rect with a black pattern:
  • FillRect(&r, &qd.black);
  • Other patterns:
    • &qd.white
    • &qd.gray
    • &qd.dkGray
    • &qd.ltGray

There are other functions for ovals, rectangles with rounded corners, strings, arcs, etc.

Some Bookkeeping

1. Rect actually includes pixels with:
   • left <= h < right
   • top <= v < bottom
2. There must be a call

   openDrawing();

   before you use any of the graphics!! This function call will open a graphics window for you where your graphics will be displayed.
3. It is also important to read your QuickDraw handout for more information on these graphic capabilities.
4. Make sure you go to PUBLIC and run the following demos. They are there so that you can become comfortable with some graphics code and are quite a lot of fun!!
   • graphDemo.cpp
   • boxes.cpp
   • invertOvals.cpp
   • psychBoxes.cpp
   • DrawAMac.cpp