Drawing shapes and lines

[qedusa]

Hi, I can draw the shapes and lines, etc OK but I want to know if there's a way I can draw these offscreen and then copy them instantaneously to the screen so the drawing process appears smooth and instant just like drawing a bitmap using BitBlt() function.

As an example, say I want to draw a graph or pie chart and want to update it every so often. I would like the updated graph to appear instant rather then the user seeing the entire graph being built up from scratch again every time.

Is there a way I can do this and, if so, how?

Thanks

 

[Triac]

...just like drawing a bitmap using BitBlt() function.

That's the way!
Here's an example. It's quite simple, I guess there's no need to further explanations.

CClientDC clientDC(this);
CDC memDC;
CBitmap memBitmap;
CRect rect;

memDC.CreateCompatibleDC(&clientDC);
GetClientRect(&rect);
memBitmap.CreateCompatibleBitmap(&clientDC,rect.Width(),rect.Height());
memDC.SelectObject(&memBitmap);

// Here goes your drawing code
for (int i=0; i<rect.Width(); i++) {
for (int j=0; j<rect.Height(); j++) {
memDC.SetPixel(i,j,RGB(i%255,j%255,(i*j)%255));
}
}
// end drawing code

clientDC.BitBlt(0,0,rect.Width(),rect.Height(),&memDC,0,0,SRCCOPY);


I hope this is what you were looking for.

 

[qedusa]

Thanks!! I'll give it a blast!