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BitmapScreen Class Reference

A VScreen implemented as a bitmap. More...

#include <BitmapScreen.h>

Inherits VScreen.

List of all members.

Public Methods
DIBitmap *	getWriteBuffer ()
bool	DoneWriting ()
const DIBitmap *	getReadBuffer ()
void	DoneReading ()
void	paint (HDC)
	BitmapScreen (const int, const int, const int, const int)
Private Attributes
DIBitmap	buffer [2]
	Two DIBitmaps forming a double buffer.
HANDLE	writeMutex
	A Handle to a Mutex used for serialising calls to getWriteBuffer().
CSWMRG	currentBufferLock
	A single writer multiple reader guard protecting the switch between buffers.
volatile int	currentBuffer
	An index into the array of DIBitmaps.

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Detailed Description

Provides a double buffered di bitmap 'screen' with read and write locks. The bitmap being read is the 'currentBuffer', many simultaneous reads can be carried out. Writes are performed on the other buffer, writes are serialised and requests are blocking until reads have completed.

Definition at line 25 of file BitmapScreen.h.

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Constructor & Destructor Documentation

BitmapScreen::BitmapScreen (  const int    tlX, const int    tlY, const int    w, const int    h )

Constructor - Takes the same parameters as VScreen Definition at line 16 of file BitmapScreen.cpp. References buffer, DIBitmap::createCompatible(), currentBuffer, and writeMutex. : VScreen(tlX, tlY, w, h) { currentBuffer = 0; buffer[0].createCompatible(w, h, 8); buffer[1].createCompatible(w, h, 8); writeMutex = CreateMutex(NULL, false, NULL); }

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Member Function Documentation

void BitmapScreen::DoneReading (    )

Releases the read lock. This most be called for each read lock obtained or a write lock will never suceed and block any other lock attempts. Definition at line 70 of file BitmapScreen.cpp. References currentBufferLock, and CSWMRG::Done(). Referenced by Cls_OnCommand(), Cls_OnCreate(), and UpdateHandler::update(). { currentBufferLock.Done(); }

bool BitmapScreen::DoneWriting (    )

After checking the validity of the updated buffer a write lock is obtained the buffers are switched and the lock released. The Mutex serialising writes is also released. Returns: bool : true iff the buffer written to is a bitmap compatible with this screen Definition at line 94 of file BitmapScreen.cpp. References buffer, currentBuffer, currentBufferLock, CSWMRG::Done(), VScreen::getHeight(), DIBitmap::getPBITMAPINFOHEADER(), VScreen::getWidth(), CSWMRG::WaitToWrite(), and writeMutex. Referenced by Cls_OnCreate(), and UpdateHandler::update(). { int otherBuffer = 0 == currentBuffer ? 1 : 0; if( abs(buffer[otherBuffer].getPBITMAPINFOHEADER()->biHeight) != abs(VScreen::getHeight()) || buffer[otherBuffer].getPBITMAPINFOHEADER()->biWidth != VScreen::getWidth() ){ assert( ReleaseMutex(writeMutex) ); return false; } currentBufferLock.WaitToWrite(); currentBuffer = otherBuffer; currentBufferLock.Done(); assert( ReleaseMutex(writeMutex) ); return true; }

const DIBitmap * BitmapScreen::getReadBuffer (    )

Obtains a read lock and returns a pointer to a const DIBitmap. The pointer should be considered invalid after calling DoneReading. Definition at line 60 of file BitmapScreen.cpp. References buffer, currentBuffer, currentBufferLock, and CSWMRG::WaitToRead(). Referenced by Cls_OnCommand(), Cls_OnCreate(), and UpdateHandler::update(). { currentBufferLock.WaitToRead(); return &buffer[currentBuffer]; }

DIBitmap * BitmapScreen::getWriteBuffer (    )

Returns a pointer to a writable DIBitmap. This function is serialised using the writeMutex. The pointer should be considered invalid after calling DoneWriting. Definition at line 80 of file BitmapScreen.cpp. References buffer, currentBuffer, and writeMutex. Referenced by Cls_OnCreate(), and UpdateHandler::update(). { WaitForSingleObject(writeMutex, INFINITE); return &buffer[0 == currentBuffer ? 1 : 0]; }

void BitmapScreen::paint (  HDC    hDC )  [virtual]

Requests a read lock and then sets the dibs bits to the specified DC. Releases the read lock before returning. Parameters: hDC  : Handle to a device context. Reimplemented from VScreen. Definition at line 35 of file BitmapScreen.cpp. References buffer, currentBuffer, currentBufferLock, CSWMRG::Done(), VScreen::getRgnRect(), and CSWMRG::WaitToRead(). Referenced by Cls_OnPaint(). { currentBufferLock.WaitToRead(); RECT regionR = VScreen::getRgnRect(); SetDIBitsToDevice( hDC, regionR.left, regionR.top, buffer[currentBuffer].getPBITMAPINFOHEADER()->biWidth, abs(buffer[currentBuffer].getPBITMAPINFOHEADER()->biHeight), 0, 0, 0, abs(buffer[currentBuffer].getPBITMAPINFOHEADER()->biHeight), buffer[currentBuffer].getPBytes(), buffer[currentBuffer].getPBITMAPINFO(), DIB_RGB_COLORS); currentBufferLock.Done(); }

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The documentation for this class was generated from the following files:

• BitmapScreen.h
• BitmapScreen.cpp

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