Project 2

1. a procedure with two or more parameters
2. a procedure that calls another procedure of yours
3. a procedure that is called from at least five different places in your code
4. a function, i.e. a procedure that returns a value
5. at least one For-Next loop
6. at least one Select-Case statement

When a project begins executing, it should show an empty form to the user. The user then clicks on the form, causing the image to be drawn. You will not be using controls extensively. All of the graphics will be produced by program code, written by you as procedures. Of course, since the image is produced when the user clicks on the form, the you’ll start your programming effort with the Form_Click() event subroutine. The window can be closed to terminate its execution, i.e. you do not need to explicitly stop it.

In developing the image program, you should emphasize writing procedures. (One could easily imagine writing a dozen small procedures for this project.) First of all, writing procedures is the purpose of the project. Secondly, and more importantly, procedures allow you to organize the development, encapsulating effects that you can then compose into more complex images. Accordingly, the Form_Click() event procedure should not be a very long piece of code, but rather it should merely orchestrate the calling of procedures that do the work, probably by calling other procedures.

1. Recall from Lecture (11) that the size of the window that you have to work with is given by the ScaleWidth and ScaleHeight properties. See p. 396.
2. It is possible to "splash" the window across the whole display, i.e. maximize it, by setting the WindowState property of the form to 2, e.g.

    frmMain.WindowState = 2

After this, ScaleWidth and ScaleHeight will be huge. Find out by running this version of the Form_Click() procedure from a normal size window:

Sub Form_Click()
    MsgBox "The initial size is " & ScaleWidth & " x " & ScaleHeight
    frmMain.WindowState = 2
    MsgBox "The new size is " & ScaleWidth & " x " & ScaleHeight
End Sub

3. The QBColors mentioned in Lecture (11) are pretty basic. It is possible to create, using a combination of red, green and blue, any color that can be displayed. This is explained on pages 391-394. As an example of producing a color by the combination of red, green and blue, use the RGB(r,g,b) function which has the three obvious parameters. The numbers given for each of the parameters have to be between 0 and 255. Try it by writing in the Form_Click() procedure

    frmMain.BackColor = RGB(216,232,182)

which turns the background to an "olive green". Of course, it is possible to dynamically change these values.

4. It is possible to develop the code discussed in the book to find the proper R-G-B values for your desired colors, but that kind of code is already running in many applications. For example, in Microsoft Word, go to Format à Background à More Colors à Custom to get to one of the places where the color palette is available. Many other programs include this feature, including Windows Paint (Options à Edit Colors… à Define Custom Colors >>) and the Display Properties control panel. Click in the color square and adjust the brightness slider on the right until you find the color you want, and use the Red, Green, and Blue values in your program when calling the RGB() procedure.
5. As discussed in Lecture (11) to draw a box on frmMain, use the line drawing facilities as follows:

FillColor = RGB(_,_,_)   'set color for inside of rectangle
FillStyle = 0            'make shapes filled with solid color
frmMain.Line (boxLeft, boxTop)-(boxLeft + boxWidth, boxTop + boxHeight), RGB(_,_,_), B

where you must put everything after the first two lines on a single line in your program. Also, fill in the blank R-G-B values with numbers or variable values from 0 through 255. Remember the key points about this call, namely the facts that you are specifying two corners of a rectangle, the "—" is required between the two corners, and the "B" is required. If you don’t put in the second RGB() call shown, then the line around the rectangle is black.

Drawing a circle is even easier (p. 419):

FillColor = RGB(_,_,_)
FillStyle = 0
frmMain.Circle (centerLeft, centerTop), radius, RGB(_,_,_)

where, if the RGB() is omitted, the line around the circle is black. Of course, (centerLeft, centerTop) is the center point of the circle, and radius is the radius.

6. An interesting technique is shown by Wright on p. 413 of the book:



He calls it splatter painting, and you should read about how it works in the book. I used it in the following procedure to get the effect shown:

Private Sub Form_Click()
    Dim nIndex As Integer        'declare a loop index variable
    Dim nXCoord As Integer, nYCoord As Integer
    Dim nRed As Integer, nGreen As Integer, nBlue As Integer
    
    DrawMode = 9

    Randomize                   'Set up random number generator

    For nIndex = 1 To 32000
	nXCoord = Int(Rnd(1) * frmMain.ScaleWidth)
	nYCoord = Int(Rnd(1) * frmMain.ScaleHeight)
	nRed = Int(Rnd(1) * 255)
	nGreen = Int(Rnd(1) * 255)
	nBlue = Int(Rnd(1) * 255)
	PSet (nXCoord, nYCoord), RGB(nRed, nGreen, nBlue)
    Next nIndex
    
    DrawMode = 13
End Sub

Set up form so that it starts out with a white background (as described in lecture) and place a label with the words "Hi, Mom!" as its caption. The splatters will normally cover the form, including the letters. This looks kind of dumb, so the way to avoid this (on black letters) is to change the form property DrawMode to 9, Mask Pen. The DrawModes have different effects on how color appears when you draw, and you might want to experiment with them.

The loop goes through 32,000 iterations. (Wright used only 2,000.) It is not possible to go through more than 32,767 using a standard Integer. So, to do more iterations of splattering, you will need to enclose the "32000-loop" shown in another, outer loop.

A key idea in this example is random numbers. Computers cannot generate true random numbers, because they follow instructions faithfully. But, they can generate number sequences that "look" random and that can be verified scientifically to have random properties. To use random numbers, you need to do two things: First, you must put the Randomize command at the start of your program so the computer sets up the randomization. Second, when you want a random number, just write the function Rnd(1). The result is a random number between 0 and 1. So, the procedure above finds a random color value between 0 and 255 by the code

    Int(Rnd(1)*255)

Suppose the random number from Rnd(1) was 0.5 (which doesn’t seem too random, I suppose!), then the product would yield 127.5 Since this must be converted into a whole number, the Int function is applied to the result to throw away the fractional digits, giving 127.

7. Recall how we got the clock to "run" by redisplaying it whenever the time event went off? That same idea can be used for animations, too. Place a timer control on your form as we did before. (Don’t worry about where you place it, because it will disappear when the program starts running.) Next, declare a global variable at the top of your form code,

Dim tickTime As Integer

so that it is global to the timer routine. Next, initialize the tickTime variable in the Form_Load() event procedure

Private Sub Form_Load()
    TickTime = 0
End Sub

Finally, write some code to draw on each time tick:

Private Sub tmrMyClock()
    FillStyle = 0
    FillColor = RGB(200, 100, 50)
    frmMain.Line (200 + tickTime * 200, 200)-(400 + tickTime * 200, 400), RGB(200, 100, 50), B
    tickTime = tickTime + 1
End Sub

Remember the line drawing command must be on a single line. Then, whenever the timer goes off, the box is drawn in the next position. Run it. Nothing happen? Did you set the Interval on the timer? Experiment with different "speeds", smaller numbers make the timer go off more frequently, speeding up the image drawn. How do you stop it from running off the form? An If statement can be used to assure that tickTime isn’t allowed to get too large.

8. There’s a quick and easy way to clear your entire form window (set it back to its background color):