Drawing on a RichEdit?

i'm 'drawing' a colored rectangle on a subclassed Richedit control using InvertRect, but everytime the region gets covered by another control it reverts to the background color.

this is the code i'm using:

Code:

---

void PaintSelection()
{
               
                // hdcMem is memory device context that i'm blitting from
                // to avoid flicker.
                // hDC is the device context of the RichEdit
                // rectClient is the rectangular region of the RichEdit
                // rectPrev is the previously highlighted region
                // rectCurr is the currently highlighted region
                BitBlt(hdcMem, 0, 0, rectClient.right - rectClient.left,
                        rectClient.bottom - rectClient.top, hDC, 0, 0, SRCCOPY);
                InvertRect(hdcMem, &rectPrev);
                InvertRect(hdcMem, &rectCurr);

                BitBlt(hDC, 0, 0, rectClient.right - rectClient.left,
                        rectClient.bottom - rectClient.top, hdcMem, 0, 0, SRCCOPY);
                rectPrev = rectCurr;
}
// WM_PAINT handler
.....
case WM_PAINT:
                        PAINTSTRUCT ps;
                        // This calls the Default Handler to paint the screen
                        ::CallWindowProc(m_oldProc, this->m_hWnd, uMsg, wParam, lParam);
                       
                        // Now it calls PaintSelection
                        BeginPaint(m_hWnd, &ps);
                        PaintSelection();
                        EndPaint(m_hWnd, &ps);
                       
                        return false;
.....

---

Perhaps you need to intercept WM_ERASEBKGND as well?

gg

I think I've found the problem. InvertRect doesn't use a Brush to color the rect, so it seems like the output only gets reflected on the monitor. If I use FillRect with an alternating Black and White brush like this:

Code:

---

FillRect(hdcMem, &rectPrev, (HBRUSH)GetStockObject(WHITE_BRUSH));
FillRect(hdcMem, &rectCurr, (HBRUSH)GetStockObject(BLACK_BRUSH));

---

then Windows remembers the colors of the rectangular regions. The only problem is that everything (text) in the rectangle gets colored black or white, which is not what I want.

So I guess I need to find out how to invert the colors of a rectangular region using a brush or how to capture the text inside a RECT and invert its color.

to invert colors you could use SRCINVERT constant with BitBlt.

Hope that helps!

Quote:

---

Originally posted by Benzakhar
to invert colors you could use SRCINVERT constant with BitBlt.

Hope that helps!

---

Actually InvertRect calls BitBlt with those arguments anyway so it basically boils down to the same thing. I did however find out what the problem was and how to fix it.

Because BitBlt doesn't use a Brush to paint the screen, Windows doesn't really 'know' about the color change, so every time WM_PAINT gets called, it reverts back to the color of the Brush associated with the Device Context. IOW, I should only invert the rect ONCE when I call the function from WM_PAINT because windows already set it back to it's original color.

I fixed it by adding a Boolean parameter to the PaintSelection function which specifies whether or not it was being called from WM_PAINT. If it was, then there is no need to invert the previous rect because the default handler (::CallWindowProc(m_oldProc.....) set it back already.

Thanks for the help anway.

Haha, it's usually something simple....

gg