Advanced MFC Programming

Chapter 4. Button
Here, we use subclass instead of automatic method to load bitmaps. Also, we use
IDB_BITMAP_BTNUNCHECK and IDB_BITMAP_BTNCHECK to implement button’s normal and highlighted states
respectively.
Because mouse related messages are handled within the member functions of class MCSenButton, once
we declare variables within it, the buttons will automatically become mouse sensitive. There is no need for
us to write extra code for handling mouse messages outside the class.
Summary
1) We can use class CBitmapButton to implement bitmap buttons. To use this class, we need to prepare 1
to 4 bitmap resources indicating button’s different states, then use class CBitmapButton to declare
variables, and call either CBitmapButton::AutoLoad(…) or CBitmapButton::LoadBitmaps(…) to
associate the bitmap resources with the buttons.
2) To use function CBitmapButton::AutoLoad(…), the bitmap resources must have string IDs, and must
be created by suffixing ‘U’, ‘D’, ‘F’ or ‘X’ to the button’s caption text.
3) Buttons, check boxes and radio buttons implemented by class CButton can display user-provided
bitmaps by calling function CButton::LoadBitmap(…). With this method, the button could be
associated with only one image at any time. Also, its focused state will be indicated by drawing a dashbordered
rectangle over button’s face.
4) We can call function CBitmapButton::LoadBitmaps(…) at any time to change the associated bitmaps.
This provides us a way of implementing check box and radio button using push button.
5) Irregular shape button can be implemented by drawing images with transparency. We can prepare a
normal image and a black-and-white mask image. When drawing the button, only the unmasked region
of the normal image should be output to the target device.
6) A button can handle mouse-related messages. If we want to know the mouse position when a button is
being pressed, we can trap WM_LBUTTONUP message.
5) We can implement mouse sensitive button by handling WM_MOUSEMOVE message and setting window
capture.
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