Transparent Tooltip Background [closed] - c

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Closed 10 years ago.
I have 2 regions in a window, each with their own tooltip.
these tooltips are custom drawn by handling the WM_PAINT message (to prevent flicker).
This is the creation of the tooltips:
tooltips[MAIN_GRAPH_TT].tthWnd = CreateWindowEx(WS_EX_TOPMOST,TOOLTIPS_CLASS,0,WS_POPUP | TTS_NOPREFIX | TTS_ALWAYSTIP | TTS_NOFADE,CW_USEDEFAULT, CW_USEDEFAULT,CW_USEDEFAULT,CW_USEDEFAULT,0,0,g_hInst,0);
tooltips[SECONDARY_GRAPH_TT].tthWnd = CreateWindowEx(WS_EX_TOPMOST,TOOLTIPS_CLASS,0,WS_POPUP | TTS_NOPREFIX | TTS_ALWAYSTIP | TTS_NOFADE,CW_USEDEFAULT, CW_USEDEFAULT,CW_USEDEFAULT,CW_USEDEFAULT,0,0,g_hInst,0);
This is initialisation of the tooltips:
if (tooltips[MAIN_GRAPH_TT].tthWnd)
{
lpfnOldTTProc = (WNDPROC)SetWindowLong(tooltips[MAIN_GRAPH_TT].tthWnd,
GWL_WNDPROC, (DWORD) TooltipProc);
SetWindowLong(tooltips[MAIN_GRAPH_TT].tthWnd, GWL_EXSTYLE, WS_EX_LAYERED|WS_EX_TOOLWINDOW);
SetLayeredWindowAttributes(tooltips[MAIN_GRAPH_TT].tthWnd,RGB(255,0,0),0,ULW_COLORKEY);
SendMessage(tooltips[MAIN_GRAPH_TT].tthWnd,CWM_SETWNDPROC,0,(LPARAM)new WNDPROC(lpfnOldTTProc));
}
if (tooltips[SECONDARY_GRAPH_TT].tthWnd)
{
lpfnOldTTProc = (WNDPROC)SetWindowLong(tooltips[SECONDARY_GRAPH_TT].tthWnd, GWL_WNDPROC, (DWORD) TooltipProc);
SetWindowLong(tooltips[SECONDARY_GRAPH_TT].tthWnd, GWL_EXSTYLE, WS_EX_LAYERED|WS_EX_TOOLWINDOW);
SetLayeredWindowAttributes(tooltips[SECONDARY_GRAPH_TT].tthWnd,RGB(255,0,0),0,ULW_COLORKEY);
SendMessage(tooltips[SECONDARY_GRAPH_TT].tthWnd,CWM_SETWNDPROC,0,(LPARAM)new WNDPROC(lpfnOldTTProc));
}
And this is the WM_PAINT of the custom tooltip WNDPROC:
case WM_PAINT:
{
const int FRAME_WIDTH = 1;
const int CORNER_DIAMETER = 10;
PAINTSTRUCT ps;
HDC hdc = BeginPaint(hWnd,&ps);
HDC hMemDC;
RECT cr;
GetClientRect(hWnd,&cr);
hMemDC = CreateCompatibleDC(hdc);
HBITMAP memBM = CreateCompatibleBitmap(hdc, cr.right-cr.left, cr.bottom-cr.top);
HBITMAP hOldBM = (HBITMAP) SelectObject(hMemDC,memBM);
//drawing start [draw to hMemDC]
{
FillSolidRect(hMemDC,0,0,cr.right-cr.left,cr.bottom-cr.top,RGB(255,0,0));
HPEN hFramePen = CreatePen(PS_SOLID,FRAME_WIDTH,BLACK);
HBRUSH hBGBrush = GetSysColorBrush(COLOR_INFOBK);
SetTextColor(hMemDC,GetSysColor(COLOR_INFOTEXT));
SetBkColor(hMemDC,WHITENESS);
SetBkMode(hMemDC,TRANSPARENT);
HBRUSH hOldBrush = (HBRUSH) SelectObject(hMemDC,hBGBrush);
HPEN hOldPen = (HPEN) SelectObject(hMemDC,hFramePen);
HFONT hOldFont = SelectFont(hMemDC,g_hFonts[FONT_TOOLTIP]);
RoundRect(hMemDC,cr.left,cr.top,cr.right,cr.bottom,CORNER_DIAMETER,CORNER_DIAMETER);
RECT textRec = cr;
textRec.left += FRAME_WIDTH*2;
textRec.right -= FRAME_WIDTH*2;
textRec.top += FRAME_WIDTH*2;
textRec.bottom -= FRAME_WIDTH*2;
if(hWnd == tooltips[MAIN_GRAPH_TT].tthWnd)
DrawText(hMemDC,tttBuffer[MAIN_GRAPH_TT],sizeof(tttBuffer),&textRec,DT_LEFT|DT_TOP);
else if(hWnd == tooltips[SECONDARY_GRAPH_TT].tthWnd)
DrawText(hMemDC,tttBuffer[SECONDARY_GRAPH_TT],sizeof(tttBuffer),&textRec,DT_LEFT|DT_TOP);
SelectObject(hMemDC,hOldBrush);
SelectObject(hMemDC,hOldPen);
SelectObject(hMemDC,hOldFont);
DeleteObject(hFramePen);
DeleteObject(hBGBrush);
}
//drawing end
BitBlt(hdc,
cr.left,
cr.top,
cr.right-cr.left, cr.bottom-cr.top,
hMemDC,
0,
0,
SRCCOPY);
SelectObject(hdc,hOldBM);
DeleteObject(memBM);
DeleteDC(hMemDC);
EndPaint(hWnd,&ps);
}
break;
The problem with these tooltips is, the corners (outside of the round rect) are supposed to be transparent, but i cant seem to get them to dissapear.
I have tried (naívely) to use HOLLOW_BRUSH to paint the background rect, but didnt work, and as you can see from the example i've tried using the layered window approach, again to no avail.
Can anyone help me get transparency for the background of my tooltips?
Here is a picture of the tooltip without transparency
[the corners have been recoloured white for visibility -- these are the parts that need to be transparent]
(Text blanked out)

Answer 1

When dealing with controls and transparency, I found that WS_EX_TRANSPARENT exStyle can save you some time. Also, you may want to check out if the tooltip sends a WM_CTLCOLORSTATIC message to the main window, if it does you may want to send back a hollow (null) brush handle in response. You may also need to set the background mode to transparent at that point in time, by calling SetBkMode on the hDC the WM_CTLCOLORSTATIC message provides.
Sorry for not testing any of this, but it works well with static and group controls. The only control up to now I evidenced is unresponsive to this method is the checkbox button, which I was unable to set background transparency for.
Regards.

Answer 2

You can use SetWindowRgn to make parts of a window transparent (create a region using CreateRoundRectRgn).
Alternatively, you can use SetLayeredWindowAttributes to use true alpha blending to make parts of the window transparent.