Performance Question

[zenox0]

I have a program that has to draw the mouse whenever it is moved.. as the mouse is snaped to a grid. I hide the mouse cursor by setting it to be a transparent .cur file. Then for my mouse move code I have the following:

private void Map_MouseMove ( object sender, MouseEventArgs e )
{
	if ( drawCursor )
	{
		// First thing we need to do, is snap the cursor to the grid (ScaledRoomSize is the size of a block on my backbuffer)
		PointF cursorSnappedPosition = new PointF ( e.X - e.X % ScaledRoomSize, e.Y - e.Y % ScaledRoomSize );

		// Now if this changed
		if ( cursorSnappedPosition != lastSnappedPosition )
		{
			Graphics graphics = CreateGraphics ( );

			Bitmap backBufferBmp = new Bitmap ( mainBmp );
			Graphics backBufferDC = Graphics.FromImage ( backBufferDC );

			// Draw our cursor
			DrawCursor ( backBufferDC, cursorSnappedPosition, new PointF ( e.X, e.Y ) );

			// Finally draw the image
			graphics.DrawImage ( backBufferDC, 0, 0 );

			// Free our memory
			backBufferBmp.Dispose ( );
			backBufferDC.Dispose ( );
			graphics.Dispose ( );
			
			lastSnappedPosition = cursorSnappedPosition;

		} // End if changed
	}
} // End of MouseMove function

The DrawCursor function looks like this:

private void DrawCursor ( Graphics graphics, PointF cursorSnappedPosition, PointF cursorPosition )
{
	// Create our new solidBrush
	solidBrush = new SolidBrush ( Color.FromArgb ( 20, 20, 20, 20 ) );
	pen = new Pen ( Color.DarkBlue, 3 );

	// highlight the corisponding column
	graphics.FillRectangle ( solidBrush,
		cursorSnappedPosition.X, 0, ScaledRoomSize, this.Height );

	// highlight the corisponding row
	graphics.FillRectangle ( solidBrush,
		0, cursorSnappedPosition.Y, this.Width, ScaledRoomSize );

	// It has changed so we draw our snapped position
	graphics.DrawRectangle ( pen, cursorSnappedPosition.X, 
	cursorSnappedPosition.Y, ScaledRoomSize, ScaledRoomSize );
}

Now everything here works great.. Except one thing. When I move my mouse I get 70-100% processer used. (on a 2.2 ghz with a gig memory) When I try to move the cursor on a 1.5ghz computer it slows down and "skips".

The part of my code that takes most of the performance is the:

Bitmap backBufferBmp = new Bitmap ( mainBmp );
Graphics backBufferDC = Graphics.FromImage ( backBufferDC );

That exists in the MouseMove function.
What this is doing is taking a copy of my backround image, so that I can draw dynamically on top of it. Anyone know of a better way to do this? Do you think using something other than GDI+ would be better? (Like directx?) Thanks.

 

[zenox0]

Note:

Bitmap backBufferBmp = new Bitmap ( mainBmp );
Graphics backBufferDC = Graphics.FromImage ( backBufferDC );

Is actually:
Bitmap backBufferBmp = new Bitmap ( mainBmp );
Graphics backBufferDC = Graphics.FromImage ( backBufferBmp );

Sorry for confusion

 

[JurkMonkey]

Using mouse move logic sucks. It is always slow.

I read a few articles on "Selection" where you can create a selection similar to that on the desktop (highlite a few icons at once) and determine what is under the selection once the selection has finished.

I don't have any code samples right now but try searching msdn for "selection