Bypassing WS_CLIPCHILDREN - c++

Question

I have create a custom scroll bar with transparency option. The way this transparency works is very simple, I invalidate the required region and let the parent to erase and paint itself, after that I repaint the scroll bar itself. Here's some piece of code:
void Refresh(bool bForceOwnerRedraw)
{
if (Gui.OwnerRedraw || bForceOwnerRedraw)
InvalidateBackgroundRegion(State.CurrentState);
RedrawWindow(Gui.OwnerWindow, &Gui.DrawingRectangle, NULL, RDW_INVALIDATE | RDW_NOERASE | RDW_INTERNALPAINT);
}
void InvalidateBackgroundRegion(DWORD State)
{
HWND hWndParent = GetParent(Gui.OwnerWindow);
POINT p = {0};
MapWindowPoints(Gui.OwnerWindow, hWndParent, &p, 1);
HRGN BackGroundRegion = CreateRectRgn(Gui.DrawingRectangle.left + p.x, Gui.DrawingRectangle.top + p.y, Gui.DrawingRectangle.right + p.x, Gui.DrawingRectangle.bottom + p.y);
HRGN MainRegion = NULL;
if (State & SELECTED || State & SELECTED_HOVER)
{
int Width = Gui.DrawingRectangle.left + Position.SelectedState.MainDrawing.right + p.x + 1,
Height = Gui.DrawingRectangle.top + Position.SelectedState.MainDrawing.bottom + p.y + 1;
MainRegion = CreateRoundRectRgn(Position.SelectedState.MainDrawing.left + Gui.DrawingRectangle.left + p.x, Position.SelectedState.MainDrawing.top + Gui.DrawingRectangle.top + p.y, Width, Height, Gui.uiCornerRoundness, Gui.uiCornerRoundness);
}
else if (State & UNSELECTED || State & UNSELECTED_HOVER)
{
int Width = Gui.DrawingRectangle.left + Position.UnselectedState.MainDrawing.right + p.x + 1,
Height = Gui.DrawingRectangle.top + Position.UnselectedState.MainDrawing.bottom + p.y + 1;
MainRegion = CreateRoundRectRgn(Position.UnselectedState.MainDrawing.left+Gui.DrawingRectangle.left+p.x, Position.UnselectedState.MainDrawing.top+Gui.DrawingRectangle.top+p.y, Width, Height, Gui.uiCornerRoundness, Gui.uiCornerRoundness);
}
else if (State & INTERMEDIATE || State & INTERMEDIATE_HOVER)
{
int Width = Gui.DrawingRectangle.left + Position.IntermediateState.MainDrawing.right + p.x + 1,
Height = Gui.DrawingRectangle.top + Position.IntermediateState.MainDrawing.bottom + p.y + 1;
MainRegion = CreateRoundRectRgn(Position.IntermediateState.MainDrawing.left + Gui.DrawingRectangle.left + p.x, Position.IntermediateState.MainDrawing.top + Gui.DrawingRectangle.top + p.y, Width, Height, Gui.uiCornerRoundness, Gui.uiCornerRoundness);
}
CombineRgn(BackGroundRegion, BackGroundRegion, MainRegion, RGN_DIFF);
RedrawWindow(hWndParent, NULL, BackGroundRegion, RDW_INVALIDATE | RDW_ERASE | RDW_INTERNALPAINT);
DeleteObject(MainRegion);
DeleteObject(BackGroundRegion);
}
The problem occurs when I resize the main window, everything flickers. However I can prevent that by using WS_CLIPCHILDREN flag on main window, but then my scroll bar looses it's transparency, because I no longer can't invalidate parts, that are owned by child windows.
What I have tried so far:
Before invalidating parent, I removed WS_CLIPCHILDREN flag, repainted, and then set WS_CLIPCHILDREN flag back. [Result: It worked, however my CPU usage went over 30%, so it's a no no.]
Tried validating child windows (without WS_CLIPCHILDREN), before erasing and repainting.
[Result: didn't work, don't know why... maybe I... nope no idea.]
Completely disabled all repainting in my scroll bar (without WS_CLIPCHILDREN) [Result: didn't work, still flickers.]
What I would like to achieve here is to find a way to to bypass WS_CLIPCHILDREN by invalidating window manually (maybe somehow invalidating using SendMessage() to bypass it). Any other suggestion are also welcome. Thanks
EDIT:
Some more information about how I create my scroll bar. In the code below you can see that my scroll bar is just an empty child window with WS_VISIBLE and WS_CHILD flags, all of the painting is done using good old gdi.
void RegisterScrollbarClass()
{
if (RegisteredClasses.bCustomScrollBar)
return;
WNDCLASSEX wc;
wc.cbSize = sizeof(WNDCLASSEX);
wc.style = CS_HREDRAW | CS_VREDRAW;
wc.lpfnWndProc = BaseWindow::stWinMsgHandler;
wc.cbClsExtra = 0;
wc.cbWndExtra = 0;
wc.hInstance = NULL;
wc.hIcon = NULL;
wc.hCursor = NULL;
wc.hbrBackground = NULL;
wc.lpszMenuName = NULL;
wc.lpszClassName = TEXT("CUSTOM_SCROLLBAR");
wc.hIconSm = NULL;
if (!RegisterClassEx(&wc))
{
MessageBox(NULL, TEXT("Button Class Registration Failed!"), TEXT("ERROR!"), MB_ICONERROR);
exit(EXIT_FAILURE);
}
RegisteredClasses.bCustomScrollBar = true;
}
HWND CreateScrollbar(DWORD dwExStyle, LPCTSTR lpClassName, LPCTSTR lpWindowName, DWORD dwStyle, int x, int y, int nWidth, int nHeight, HWND hWndParent, HMENU hMenu, HINSTANCE hInstance, LPVOID lpParam)
{
DWORD ScrollbarStyle = NULL, Child = NULL;
if ((dwStyle & SB_VERT) == SB_VERT)
ScrollbarStyle = SB_VERT;
else if ((dwStyle & SB_HORZ) == SB_HORZ)
ScrollbarStyle = SB_HORZ;
else
return NULL;
if ((dwStyle & WS_CHILD) == WS_CHILD)
Child = WS_CHILD;
if ((dwStyle & WS_VISIBLE) == WS_VISIBLE)
Child |= WS_VISIBLE;
RegisterScrollbarClass();
Scrollbar.push_back(CustomScrollbar(ScrollbarStyle, x, y, nWidth, nHeight, (int)hMenu));
for(unsigned int i = 0; i < Scrollbar.size(); i++)
Scrollbar.at(i).Create();
if (Scrollbar.at(Scrollbar.size()-1).Create(dwExStyle, lpClassName, NULL, Child, x, y, nWidth, nHeight, hWndParent, hMenu, hInstance, lpParam) != NULL)
{
if (Scrollbar.size() == 2)
Scrollbar.at(Scrollbar.size() - 1).EnableTransparent(true);
return Scrollbar.at(Scrollbar.size()-1).WindowHandle();
}
else
{
Scrollbar.pop_back();
return NULL;
}
}
Here you can download sample program: http://www.putlocker.com/file/B8704C613BC7EC96
SOLVED:
Thanks to Raymond Chen, I have removed CS_HREDRAW | CS_VREDRAW from my Scroll bar class and I works like a charm without WS_CLIPCHILDREN.