How to not discard a CDC path?

Question

I draw some symbols, that belong to certain objects, into a device context and now want to be able to later test if the mouse cursor is above such a symbol.

To do this, my plan was to first create a CDC path and use that to create a CRgn region object.

pDC->BeginPath();
pDC->Ellipse(ellipse[0], ellipse[1], ellipse[2], ellipse[3]); // Create path only
pDC->EndPath();

// Actually draw the ellipse
pDC->StrokeAndFillPath(); // Apparently removes the path from the DC

CRgn region;
if (region.CreateFromPath(pDC)) // Would also remove the path from the DC
{
    // We never get here :-/

    // Here I would copy the region's data,
    // attach it to the object being drawn and
    // destroy the region.
    // That way I can create a region later on and do the hit-testing.
}

How can I use the path for both, drawing and creating the region, without having to draw twice? Drawing twice pretty much doubles the time spent in my drawing method, which is something I'd like to avoid.

Answer 1

region.CreateFromPath before calling StrokeAndFillPath. That saves the path as a region -- then you can StrokeAndFillPath, and after that use the region.

Edit: Oops, quite right. Fortunately, there seems to be a way around that problem too though: although the documentation doesn't directly say so, it appears that SaveDC/RestoreDC saves and restores the path along with the other "stuff", so you can do something like:

pDC->BeginPath();
pDC->Ellipse(ellipse[0], ellipse[1], ellipse[2], ellipse[3]);
pDC->EndPath();

int dc_id = pDC->SaveDC();

pDC->StrokeAndFillPath();

pDC->RestoreDC(dc_id);

CRgn region;
if (region.CreateFromPath(pDC))
{
            // Now we do get here...
 MessageBox(L"Region Created");
}