Search Tools Links Login

Changing the Shapes of Your Forms


Learn how to change your form's shapes!

Original Author: Campbell Productions Software

Code

Changing
    the Shapes of Your Forms

  

Are you tired
    of your square or rectangle forms? Would you like to create a splash screen
    that actually looks like a splash? Would you like to create an About Us
    screen in the shape of a circle or a star? Well, this is the tutorial
    for you. In this tutorial, you will learn how to use the Win32 API to
    change the shapes of your forms.


  

Only one
    pre-requisite is required for this tutorial. You must know the 2D cartesian
    coordinate system. To plot a shape like a star or a triangle, you must
    know the coordinates of the points of the star or the three vertexes of
    the triangle. Other than the knowledge of cartesian plotting, you will
    need nothing more than a VB compiler and some time.


  

Let's get
    started, shall we? To begin, create a new Standard EXE project and add
    a Module (right-click on the Project Explorer, select "New"
    and select "Module.") Save your project right off the bat. You
    can name the form, project, and module files anything you want.


  

Double-click
    on the module in the Project Explorer window. Add in the following code.
    We shall explain what it does in more detail a little later in the tutorial:


  

    

Public Declare Function
     CreatePolygonRgn Lib "gdi32" (lpPoint As POINTAPI, ByVal nCount
     As Long, ByVal_ nPolyFillMode As Long) As Long


    

Public Declare Function
     SetWindowRgn Lib "user32" _

     (ByVal hWnd As Long, ByVal hRgn As Long, _

     ByVal bRedraw As Boolean) As Long


    

Public Type POINTAPI

     x As Long

     y As Long

     End Type


  

  

Now let's
    take a closer look at the functions. The first API function, CreatePolygonRgn()
    creates a region or a set of points that describes a
    separate entity. SetWindowRgn() sets your form to abide by the shape and
    characteristics of a certain region. In other words, you would use CreatePolygonRgn()
    to create a star shape and then use SetWindowRgn() to make your form's
    shape a star. The declaration of the type POINTAPI simply allows you to
    declare a variable that can hold the set of points that will define the
    region created with the CreatePolygonRgn() function.


  

Note, though,
    that creating a perfect circle using the CreatePolygonRgn() function is
    completely impossible. Therefore, to create a circle, we declare a second
    region-creating function called CreateEllipticRgn(). The code for a circle-shaped
    form will be shown later in the tutorial.


  

Now that
    you have your functions, it is time to create a star out of your form.
    In the Options Explicit section of your form, we must create a variable
    of type POINTAPI. Note that a POINTAPI variable can hold two values: x
    and y. To create a star, therefore, we must make an array with type POINTAPI
    to hold the x and y coordinates for multiple points. To do this, we declare
    the variable p (for points) in the Options Explicit section of form1:


  

    

Dim p(20) As POINTAPI


  

  

A star only
    requires 14 unique points, but we shall declare 20 in case you want to
    mess around with the points and turn your form into a deformed star or
    a triangle, etc. Now that we have a variable, it is time to declare the
    points (I.E. give p(20) values.) It is difficult to explain in text why
    the following points are why they are, but if you were to plot them on
    a 2D cartesian graph, they would form a star. When you create your own
    shapes, you must first lay out all of your points. The following code
    must be put in the _Load() event of Form1.


  

    

p(1).x = 100

     p(1).y = 0

    

     p(2).x = 120

     p(2).y = 40

    

     p(3).x = 180

     p(3).y = 40

    

     p(4).x = 140

     p(4).y = 80

    

     p(5).x = 180

     p(5).y = 120

    

     p(6).x = 120

     p(6).y = 120

    

     p(7).x = 100

     p(7).y = 160

    

     p(8).x = 80

     p(8).y = 120

    

     p(9).x = 20

     p(9).y = 120

    

     p(10).x = 60

     p(10).y = 80

    

     p(11).x = 20

     p(11).y = 40

    

     p(12).x = 80

     p(12).y = 40

    

     p(13).x = 100

     p(13).y = 0


  

  

Now, create a command
    button, named cmdChangeShape, and in its _Click() event, put the following
    code:


  

    

SetWindowRgn hWnd,
     CreatePolygonRgn(p(1), 13, 1), True


  

  

The SetWindowRgn()
    function is used to set the window's shape to the region created with
    the function CreatePolygonRgn(). Let's look at the two function's arguments.
    SetWindowRgn takes the handle of the window whose shape it will change,
    i.e. form1. hWnd, therefore, represents form1's handle as a long value.
    After the window handle, the function takes the long value of the region
    by which it shall change the window's shape. This value is determined
    in this example by the function CreatePolygonRgn(). After the region,
    it takes a boolean (true, false,) value of fwhether it should refresh
    the window. If this is false, then the window shall do nothing until it
    is unloaded and reloaded. When set to true, the window will instantaneously
    change shape.


  

The CreatePolygonRgn()
    function takes first the POINTAPI variable that holds the points for the
    region. In this example, it is p(). Since p is an array, we must tell
    it which array entry to start with, hence the p(1). After the POINTAPI
    variable, it takes the number of entries of the array to consider. Since
    we only give values to entries less than p(13), we put a "13"
    for this argument. Finally, the CreatePolygonRgn function takes a fillmode.
    The fillmode tells the SetWindowRgn() function what to put in the shaped
    form once the shaped form is shaped. 1 tells the function to add the contents
    of the window before it was shaped. It is recommended that you use either
    1 or 2 as a default for this argument.


  

Now, run
    the program. Click on the command button and watch your form turn into
    a star.


  

 


  

As promised
    above, we shall take a look at the CreateEllipticRgn() function. The declaration
    syntax is below. Put this in the module along with the CreatePolygonRgn()
    and the SetWindowrgn():


  

    

Declare Function CreateEllipticRgn
     lib "gdi32.dll" (ByVal X1 as long, ByVal Y1 as Long, _


    

ByVal X2 as Long,
     ByVal Y2 as Long)


  

  

X1 and Y1
    are the coordinates for the upper-left hand corner of the square that
    contains the circle. X2 and Y2 are the coordinates for the lower-right
    hand corner of the square that contains the circle. To create a circle,
    simply replace the CreatePolygonRgn(p(1), 13, 1) in the SetWindowRgn()
    function to: CreateEllipticRgn(-1, 1, 1, -1) With this change, the line
    in cmdChangeShape_Click() event would be:


  

    

SetWindowRgn hWnd,
     CreateEllipticRgn(-1, 1, 1, -1), True


  

  

WHERE
    TO GO FROM HERE

    


  

Now, all
    you can do is simply try different sets of points for CreatePolygonRgn()
    and see what shapes you can make!

About this post

Posted: 2003-06-01
By: ArchiveBot
Viewed: 136 times

Categories

Visual Basic 6

Attachments

No attachments for this post


Loading Comments ...

Comments

No comments have been added for this post.

You must be logged in to make a comment.