C / C++ / MFC

17-Jul-02 0:08

I'm working on an application which has a CWnd descended window called CAnimateWnd.

CAnimateWnd uses SetWindowRgn(hClipRgn, TRUE) to change the shape of the window frequently. It then uses SetWindowPos() to change the location of the window.

Calling SetWindowRgn() with the second param (bRedraw) TRUE causes the window to be redrawn. Changing the position of the window with SetWindowPos() or MoveWindow() causes the window to be redrawn. However, since the new shape of the window may look wrong until the window is in its new position, I want the window to be redrawn only once.

If I call SetWindowRgn() with bRedraw as FALSE, the area beneath the window is filled back under the assumption of the new region shape rather than the old, leaving bits of the previous view behind.

Is there a way to set the window region and change the position in the same instant?

Joaquín M López Muñoz17-Jul-02 2:21

17-Jul-02 2:21

Hide the window before setting the new region and show it back after repositioning it.

Joaquín M López Muñoz
Telefónica, Investigación y Desarrollo

Dov Sherman17-Jul-02 2:47

17-Jul-02 2:47

That works but it also makes the window flicker. Is there any other way to do it?

Joaquín M López Muñoz17-Jul-02 2:58

17-Jul-02 2:58

Well, I haven't tried this, but it might help reduce the flickering. Before repositioning the window, save its original surrounding rectangle with GetWindowRect. After repositiong, invalidate the desktop window with InvalidateRect using the rectangle previously saved.

Joaquín M López Muñoz
Telefónica, Investigación y Desarrollo

Dov Sherman17-Jul-02 4:58

17-Jul-02 4:58

That'sa good idea. I tried it but it didn't seem to have any effect at all. Maybe I'm doing it wrong. Do you see any obvious problems with this code?

<br />
void CAnimateWnd::ChangeAppearanceAndPosition(HRGN hNewRgn, int iPosX, int iPosY)<br />
{<br />
CRect oldRect;<br />
GetWindowRect(&oldRect);<br />
<br />
SetWindowRgn(hNewRgn, FALSE); // change shape without redrawing<br />
SetWindowPos(&wndTopMost, iPosX, iPosY, 100, 100, SWP_NOACTIVATE);<br />
<br />
::InvalidateRect( GetDesktopWindow()->GetSafeHwnd(), &oldRect, TRUE);<br />
}<br />

Joaquín M López Muñoz17-Jul-02 5:09

17-Jul-02 5:09

The code seems OK to me Frown | :(

There are a couple of things you might want to try:

Do a ScreenToClient of the rectangle for the desktop window prior to using it in InvalidateRect.
Force the repainting of the desktop window with UpdateWindow after invalidating.

Other than these, I cannot come out with any other possible reason for this failing.

Joaquín M López Muñoz
Telefónica, Investigación y Desarrollo

Dov Sherman17-Jul-02 5:47

17-Jul-02 5:47

I tried each of those but there was no change. My guess is that, since I did not repaint during my SetWindowRgn() call, the desktop thinks it is intended to leave the bits of previous regions behind.

If I have to I can live with the flicker but I'd much rather have a perfectly smooth animation display.

Joaquín M López Muñoz17-Jul-02 6:54

17-Jul-02 6:54

What about this?

void CAnimateWnd::ChangeAppearanceAndPosition(HRGN hNewRgn, int iPosX, int iPosY)
{
CRgn oldRgn;
oldRgn.CreateRectRgn(0,0,0,0);
GetWindowRgn(oldRgn);
SetWindowRgn(hNewRgn, FALSE); // change shape without redrawing
GetDesktopWindow()->InvalidateRect(&oldRgn);
SetWindowPos(&wndTopMost, iPosX, iPosY, 100, 100, SWP_NOACTIVATE);
}

Joaquín M López Muñoz
Telefónica, Investigación y Desarrollo

Dov Sherman17-Jul-02 7:10

17-Jul-02 7:10

Ah, you mean InvalidateRgn(), right? Hrmm... still no visible effect. I wonder if we're misinterpreting the expected behavior for the Desktop Window. Maybe it doesn't know how to update but, rather, is simply storing an image of the desktop in its current state, in which case that current state would include the broken bits of previous animation frames.

Joaquín M López Muñoz17-Jul-02 7:47

17-Jul-02 7:47

Ummm. One more try:

void CAnimateWnd::ChangeAppearanceAndPosition(HRGN hNewRgn, int iPosX, int iPosY)
{
  CRgn oldRgn;
  oldRgn.CreateRectRgn(0,0,0,0);
  GetWindowRgn(oldRgn);
  SetWindowRgn(hNewRgn, FALSE); // change shape without edrawing
  InvalidateRect(&oldRgn);
  SetWindowPos(&wndTopMost, iPosX, iPosY, 100, 100, SWP_NOACTIVATE);
}

Would you care to tell me the result now?

Joaquín M López Muñoz
Telefónica, Investigación y Desarrollo

Dov Sherman17-Jul-02 8:24

17-Jul-02 8:24

Same as before. No visible change. Frown | :(

Dov Sherman19-Jul-02 2:17

19-Jul-02 2:17

I found a solution. For the curious, I will post it here:

The main problem is that the window needs to change its HRGN shape and its position at the same time. Since the new shape will not be correct until the window is in the new position, I needed the window to redrawn only when both the new HRGN and the new position have been set but I still needed to restore the background in areas of the old shape which were not part of the new shape.

<br />
void CAnimateWnd::UpdateRgnAndPos(HRGN hNewRgn, int iPosX, int iPosY)<br />
{<br />
HRGN hOldRgn = CreateRectRgn(0, 0, 0, 0); // make blank region<br />
GetWindowRgn(hOldRgn);<br />
<br />
HRGN hOffRgn = CreateRectRgn(0, 0, 0, 0); // make blank region<br />
CombineRgn(hOffRgn, hNewRgn, NULL, RGN_COPY); // make a copy<br />
OffsetRgn(hOffRgn, iPosX - m_iOldPosX, iPosY - m_iOldPosY); // compensate for later movment<br />
<br />
HRGN hCombinedRgn = CreateRectRgn(0, 0, 0, 0); // make blank region<br />
CombineRgn(hCombineRgn, hOffRgn, hOldRgn, RGN_OR); // combine region so that lost area gets deleted<br />
<br />
SetWindowRgn(hCombinedRgn, FALSE); // don't redraw yet<br />
<br />
SetWindowPos(iPosX, iPosY, 100, 100, SWP_NOACTIVATE); // change position<br />
<br />
SetWindowRgn(hNewRgn, TRUE); // redraw now so that lost areas of combined region are restored<br />
<br />
Invalidate(TRUE); // make it pretty<br />
<br />
m_iOldPosX = iPosX; // remember old position for next time<br />
m_iOldPosY = iPosY;<br />
}<br />