Win32API Interview Questions and Answers

1 :: What is GDI object?

GDI object (is a graphical device object) used to write on a
device context for graphical output.
GDI objects are: Pen, Brush, Font,Line, Rectangle etc.
These objects are created using their corresponding win32
function. For eg, CreatePen, CreatePenIndirect are used to
create a pen object.
After these objects are created they would need to be
selected to the device context before processing using
"SelectObject" function.
GDI objects are not associated with any device context
during its creation. SelectObject function does that
assocaition.
Once an object is selected into the device context it would
be available until the object is destroyed through
DeleteObject or the program exits.

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2 :: Message to limit the size of window?

BOOL MoveWindow(
HWND hWnd, // handle to window
int X, // horizontal position
int Y, // vertical position
int nWidth, // width
int nHeight, // height
BOOL bRepaint // repaint option
);

This cud be used in the WM_PAINT event section and in
WM_INITDIALOG section.

WM_SIZE message is received by the window procedure when a
user resizes a window. In order to limite the size of a
window, you could handle the WM_SIZE message appropriately.

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3 :: What is the function to repaint a window immediately?

Invalidate() -- To repaint the entire client area
InvalidateRect() -- To repaint a specific portion of the
client area.

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4 :: Write About send message and post message?

SendMessage is a blocking call. ie., when a SendMessage()
API is called from an application, the lines written after
this API call cannot be executed until the message is
processed and returned by the window procedure.

Whereas PostMessage() just posts the message into the
windows corresponding message queue and returns immediately
irrespective of the message is processed or not.

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5 :: what Message displayed when a window is destroyed?

WM_QUIT message in the program message queue is posted.
This causes WinMain to drop out of message loop and exit
the runing application.

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