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Screensaver is a
program that is used primarily to safeguard your computer monitor
from phosphorus burn. If you keep your computer idle for few
minutes, the static picture on your monitor may be harmful for the
health of your monitor. The fixed pattern of pixels will induce the
electron gun to hit the same area on your monitor with the same
intensity. This can permanently damage your monitor. To avoid such
situation, people keep screensavers in to their computers. The duty
of these screensavers is to save your computer screen from this
situation. After a certain predefined idle time, the screensaver
activates itself and envelop the complete screen. The characteristic
of good screensaver is that it should cover the entire screen and
colors, picture, geometry etc. should have some motion in to it. You
might have seen that most of the time the background of the
screensavers is kept black. This is a good practice to relax the
computer monitor.
In this article, I will tell you how to write your own screensaver
program using Visual C++. The prerequisite to learn this is that you
must have programming knowledge in Visual C++. The very first thing
you must know that screensavers are also executable files with
extension “.scr”. If you can write a program to create some
animation in a window, you can easily build a screensaver too. A
screensaver also draw the animation in side a window only. But this
window is little different from the conventional one. In a
screensaver, we create a window without any caption bar, menu bar,
toolbar, status bar. The size of the window is equal to the display
size of your monitor. Once you have created this window, keep the
background color black (or any other color of your choice). Now draw
some picture, geometry inside the window and animate it. That’s it.
Your screensaver is ready. But still few things are missing. You
know that on some user input action like button press or mouse move
etc. the screensaver must disappear. You must catch these user input
signals and destroy the screensaver window to finish it. This way
you can create a screensaver of your own design. Once you have
created the screensaver, change its extension from .exe to .scr and
copy it to C:/Windows/system32 directory. It will automatically be
listed in the screensaver list.
Now, let me tell you how you can do all this using Visual C++
programs.
1. You must register a new class of window with no cursor.
m_lpszClassName = AfxRegisterWndClass(CS_HREDRAW|CS_VREDRAW,
::LoadCursor(AfxGetResourceHandle(),
MAKEINTRESOURCE(IDC_NULLCURSOR)));
2. Get the extent of your computer monitor
CRect rect(0, 0, ::GetSystemMetrics(SM_CXSCREEN),
::GetSystemMetrics(SM_CYSCREEN));
3. Now create a window
CreateEx(WS_EX_TOPMOST, m_lpszClassName, _T(""),WS_VISIBLE|WS_POPUP,
rect.left, rect.top, rect.right - rect.left, rect.bottom - rect.top,
pParentWnd->GetSafeHwnd(), NULL, NULL );
Now with these three steps, you can create a rectangular window of
full screen size without a cursor.
4. Use WM_TIMER event to create a time loop.
During the creation of the window, set the time loop parameter as
shown below.
SetTimer(1, 50, NULL);
This function ensures that the WM_TIMER event will be generated
every 1/20 sec. This will be helpful in creation and updation of
your animation.
5. Write a function OnTimer( ) to handle WM_TIMER event.
Here, you must update the animation variables etc. Always send an
invalidate message from this function call. This will call the
OnPaint( ) message. This way, you can update your drawing on the
screen.
6. Write drawing code inside the OnPaint( ) function.
Keep all your drawing code inside this function. This is the heart
of the screensaver. The content of this function actually governs
the screensaver.
7. Write callback functions to handle user inputs
Add these callback functions in to your application –
OnMouseMove ( )
OnLButtonDown( )
OnMButtonDown( )
OnRButtonDown( )
OnKeyDown( )
OnSysKeyDown( )
All these callback functions must have the following line inside
them –
PostMessage(WM_CLOSE);
So, this is all about how you can write your own screensaver. So do
not wait START WRITING.
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