Advanced MFC Programming

Chapter 4. Button
Chapter 4
Buttons
Button is one of the most commonly used controls, almost every application needs to include one or
more buttons. It seems that it is very easy to implement a standard button in a dialog box: all we
need to do is adding a button resource to the dialog template, then using Class Wizard to generate
message handlers. However, it is not very easy to further customize button’s default properties.
In this chapter, we will discuss how to implement different type of customized buttons. At the end of
this chapter, we will be able to include some eye-catching buttons in our applications.
4.1 Bitmap Button: Automatic Method
Generally, buttons display plain text on its interface. Sometimes it is more desirable to let them have
graphic user interface. A typical application that uses this type of buttons would be a CD player, everyone
would like the play button to have a graphic interface instead of just displaying text such as “play”, “stop”
(so that it looks like a real “play” button).
Button States
Before customizing button’s default feature, it is important for us to understand some basics of buttons.
Every button has four states. When a button is not clicked, is in “up” state (the most common state). When
it is pressed down, it is in “down” state. To emphasis a button’s 3D effect, a default button will recess when
it is pressed by the mouse. Also, a button could be disabled, in this state, the button will not respond to any
mouse clicking (As the default implementation, when a button is disabled, it will be drawn with “grayed”
effect). Finally, a button has a “focused” or “unfocused” state. In the “focused” state, the button is an active
window, and is accessible through using keyboard (ENTER or downward ARROW key). For the default
implementation, a rectangle with dashed border will be drawn over a button’s face when it has the current
focus.
Owner-Draw Bitmap Button
We can use owner draw bitmap button to add graphics to the button. To distinguish among different
states, we need to associate different states with different images if necessary.
The simplest way to create this type of button is to implement bitmap button using class
CBitmapButton. To create a bitmap button, first we must set its “Owner Draw” style. This can be
implemented by checking “Owner Draw” check box in the “Push Button Properties” property sheet when
creating the button resource (We need to add button resource in order to create button, this is the same with
a normal button. See Figure 4-1). For an owner-draw button, message WM_DRAWITEM will be sent to the
button when it needs to be painted (remember, a button is also a window that can receive message). Upon
receiving this message, the button will be drawn by the overridden function. For non-owner-draw button,
its interface is implemented by the default method, and will display a plain text on the button’s face.
Class CBitmapButton handles message trapping and processing; also, it contains member functions
that can be used to paint the button. If we use this class to implement bitmaps buttons, all we need to do is
preparing some bitmap resources, declaring variables using class CBitmapButton, and associating bitmap
resources with the corresponding buttons.
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