Custom color shape on a WIN32 dialogbox - c++

Question

My dialog box displays the current selected audio input in the manner that Sound manager does in Windows Vista:
Here's my WIN32 dialogbox. The desired location of the shape is pointed at with an arrow:
What is the best strategy for painting this shape. Custom drawn control? GDI?
Note that the application is practically done (So no WPF nor Direct2D) and that the color is given in COLORREF so there's no option to prepare a list of icons to choose from.
\\\\\\\\\\ EDIT[1] \\\\\\\\\\\\\\
I've made some additional investigations. It seems like GDI was replaced by GDI+ which is simpler to use and has antialiasing and Alpha which are important to me.
If you take a closer look at the image they use in the Sound Manager you'll see for yourself:
So I've written GDI+ code and it works OK. That is, the image is reasonable but I create the whole bitmap it with every WM_PAINT, which is ugly.
I did not find a way (In GDI+) to create a bitmap in memory (Equivalent of CreateCompatibleDC) then to copy it to target (Equivalent of BitBlt). I've seen examples that mix GDI and GDI+. Is it the correct way to go?

Answer 1

The best strategy is draw using GDI an HBITMAP that will act as buffer, every time the color changed just recreate that bitmap. Then in WndProc of shape when WM_PAINT of controls is made just draw it:
case WM_PAINT:
PAINTSTRUCT ps;
HDC hdc;
BITMAP bitmap;
HDC hdcMem;
HGDIOBJ oldBitmap;
hdc = BeginPaint(hWnd, &ps);
hdcMem = CreateCompatibleDC(hdc);
oldBitmap = SelectObject(hdcMem, hBitmap);
GetObject(hBitmap, sizeof(bitmap), &bitmap);
BitBlt(hdc, 0, 0, bitmap.bmWidth, bitmap.bmHeight, hdcMem, 0, 0, SRCCOPY);
SelectObject(hdcMem, oldBitmap);
DeleteDC(hdcMem);
EndPaint(hWnd, &ps);
break;
For the simplicity of desired drawing (a circle inside a circle) you could draw it all in WM_PAINT, but it's a good practice to create a buffer as suggested that is faster and will avoid flickering and also will allow you to draw parts and not entire image. To create the buffer use: CreateCompatibleBitmap create a memory DC:
HDC hDC;
int width = 16;
int height= 16;
HDC hMemDC = ::CreateCompatibleDC(NULL);
HBITMAP hBmp = ::CreateCompatibleBitmap(hDC, width, height);
::SelectObject(hMemDC, hBmp);
And draw using WINAPI, take a look at Win32 GDI Drawing a circle
If you want to draw from a resource, in WM_CREATE load the bitmap:
HBITMAP g_hbmBall = NULL;
case WM_CREATE:
g_hbmBall = LoadBitmap(GetModuleHandle(NULL), MAKEINTRESOURCE(IDB_BALL));
if(g_hbmBall == NULL)
MessageBox(hwnd, "Could not load IDB_BALL!", "Error", MB_OK | MB_ICONEXCLAMATION);
break;
Then just draw on WM_PAINT:
case WM_PAINT:
{
BITMAP bm;
PAINTSTRUCT ps;
HDC hdc = BeginPaint(hwnd, &ps);
HDC hdcMem = CreateCompatibleDC(hdc);
HBITMAP hbmOld = SelectObject(hdcMem, g_hbmBall);
GetObject(g_hbmBall, sizeof(bm), &bm);
BitBlt(hdc, 0, 0, bm.bmWidth, bm.bmHeight, hdcMem, 0, 0, SRCCOPY);
SelectObject(hdcMem, hbmOld);
DeleteDC(hdcMem);
EndPaint(hwnd, &ps);
}
break;
Just because its a small icon you can do all drawing on WM_PAINT of window's WndProc... but just to avoid to create another control and because it's a small bitmap.
Hope It Helps!
EDIT
If you plan to use GDI+ (I though you weren't interested on it... i'm sorry). Sure, you can draw a bitmap using GDI+. All the things change to draw you only need to create a Graphics and make drawings. Also, you can load a Bitmap and draw it using `DrawImage', example taken from MSDN:
Image image(L"Grapes.jpg");
graphics.DrawImage(&image, 60, 10);
When you are on WinProc you can create a Graphics from hDC and then paint. Remember to dispose the Graphics and don't make call to base WinProc.
MSDN Reference