Thread: autoredraw

Hard to tell without code. Too many options.

Post your OnPaint() handler as I think this is where the solution lies.


I suggest you look at DC's.
DC = Device Context. (MFC class CDC)
A DC contains a bitmap and the current font, brush, pen ect. The bitmap will retain the last image until you 'draw' on it.
You can dynamically create DC's and their contents (bmp, font ect). Using SelectObject() you 'push' the old object out (with the newly created one).

GetDC()
CreateCompatibleDC()
CreateCompatibleBitmap()
ReleaseDC()
DeleteDC()

well here is my paint code anyway

Code:

void CblaDlg::OnPaint() 
{
	if (IsIconic())
	{
		CPaintDC dc(this); // device context for painting

		SendMessage(WM_ICONERASEBKGND, (WPARAM) dc.GetSafeHdc(), 0);

		// Center icon in client rectangle
		int cxIcon = GetSystemMetrics(SM_CXICON);
		int cyIcon = GetSystemMetrics(SM_CYICON);
		CRect rect;
		GetClientRect(&rect);
		int x = (rect.Width() - cxIcon + 1) / 2;
		int y = (rect.Height() - cyIcon + 1) / 2;

		// Draw the icon
		dc.DrawIcon(x, y, m_hIcon);
	}
	CPaintDC dc(this);
	CBitmap Bitmap;
	CDC MemDC;

	Bitmap.LoadBitmap(IDB_BITMAP1);
	MemDC.CreateCompatibleDC(&dc);
	MemDC.SelectObject(&Bitmap);

	//Draw sides
	dc.StretchBlt(16,0,m_CX-32,16,&MemDC,16,0,16,16,SRCCOPY);
	dc.StretchBlt(0,16,16,m_CY-32,&MemDC,0,16,16,16,SRCCOPY);
	dc.StretchBlt(m_CX-16,16,16,m_CY-32,&MemDC,32,16,16,16,SRCCOPY);
	dc.StretchBlt(16,m_CY-16,m_CX-32,16,&MemDC,16,32,16,16,SRCCOPY);

	//Draw corners
	dc.StretchBlt(0,0,16,16,&MemDC,0,0,16,16,SRCCOPY);
	dc.StretchBlt(m_CX-16,0,16,16,&MemDC,32,0,16,16,SRCCOPY);
	dc.StretchBlt(0,m_CY-16,16,16,&MemDC,0,32,16,16,SRCCOPY);
	dc.StretchBlt(m_CX-16,m_CY-16,16,16,&MemDC,32,32,16,16,SRCCOPY);

	//Draw center
	dc.StretchBlt(16,16,m_CX-32,m_CY-32,&MemDC,16,16,16,16,SRCCOPY);
	MemDC.DeleteDC();
	Bitmap.DeleteObject();
}

hope you can understand what it does

ah btw m_CY is the dlg window height and m_CX is the dlg window width i got these in the onsize event is there a way to get them like in visual basic if you know Me.width Me.height i dunno how to get this in c++ im just starting to learn it

OK, some code.....

I'm not surprised thats slow! StretchBlt() is terrible, avoid its use. Better to draw to a full screen sized BMP then stretch back to the current size.

For what you want this will come close. I suggest you look at CDC's MoveTo(), LineTo, CreatePatternBrush(). Also LoadImage()
try

Code:

CBrush              BlackBrush,GreenBrush;
CRect                Rect;
CPaintDC          dc(this); // device context for painting

//find where to draw
GetUpdateRect(&Rect,0);
if(IsRectEmpty(&Rect))
     GetClientRect(&Rect);

//create the brushes
BlackBrush.CreateSolidBrush(RGB(0,0,0));
GreenBrush.CreateSolidBrush(RGB(0,255,0));
//erase background and fill with green
dc.FillRect(Rect,&GreenBrush);
//draw black edge
dc.FrameRect(Rect,&BlackBrush);

//clean up
//not selected into a DC so can just delete
BlackBrush.DeleteObject();
GreenBrush.DeleteObject();

Resize the image once after loading and hold it in memory. That suffices.

As for resizing this kind of image, take the center vertical and horizontal rows and duplicated them as necessary.

No, StretchBlt is the only resizing blitting function Windows has. You could write your own, but it wouldn't be faster. StretchBlt is fast at what it does, but what it does is slow by nature.

OK, to use StretchBlt(), but IMHO not OK to use it in a paint handler more than once.

Break the drawing into smaller parts. One DC for the frame and one DC for the text.
When the app inits create a compatible DC and compatible bmp (to the max screen size) then draw the 'frame' on it. When you need the frame 'stretch' this DC to the paint one.

Same for the text.

Return them to default and delete them when the app closes.

This will not be 100% as StretchBlt() works best when the two sizes are int multiples of one another ie 320x240 -> 640x480

Look at 'double buffering', you WILL need it to get the best results. Particularly if the update area is not the entire client area.

or

Load the bmp and use it to create a pattern brush.

or

Use two different green pens / brushes.
Draw the dark green, then the light edges.

EDIT:
Depending on the version of MSVC (pre .NET).

You CAN NOT delete a bmp that is currently selected into a DC. A DC MAY not delete if it contains non default GDI objects. That is you must put the DC back the way you created / got it.

Code:

HBITMAP    hOldBmp = SelectObject(hdc, hNewBmp);
//use

//set back to default GDI objects
SelectObject(hdc, hOldBmp);
//now can delete the BMP and hdc.

In the task manager you can watch the count of GDI objects your app is using. Watch for leaks.