[olilarkin]

I have experienced this myself on windows and here is how i fixed it. I can't say if this will work
without other modifications but you could try it

in IGraphicsWin::WndProc()

replace

if (pGraphics->IsDirty(&dirtyR)) {
  RECT r = { dirtyR.L, dirtyR.T, dirtyR.R, dirtyR.B };
  InvalidateRect(hWnd, &r, FALSE);
  UpdateWindow(hWnd);
  if (pGraphics->mParamEditWnd) {
	pGraphics->mParamEditMsg = kUpdate;
  }
}

with

if (pGraphics->IsDirty(&dirtyR)) {
  RECT r = { dirtyR.L, dirtyR.T, dirtyR.R, dirtyR.B };
  
  InvalidateRect(hWnd, &r, FALSE);
  
  if (pGraphics->mParamEditWnd) {
	IRECT* notDirtyR = pGraphics->mEdControl->GetRECT();
	RECT r2 = { notDirtyR->L, notDirtyR->T, notDirtyR->R, notDirtyR->B };
	ValidateRect(hWnd, &r2); // make sure we dont redraw the edit box area
	UpdateWindow(hWnd);
	pGraphics->mParamEditMsg = kUpdate;
  }
  else 
    UpdateWindow(hWnd);
}