I'm trying to display images with overlays in a 'CListCtrl' within an MFC dialog box. The list control is in report/details mode.
I cannot find good documentation for showing overlays on some of my item images.
The code that is failing is shown below. I have a 64x32 bitmap with a folder icon in the first 32x32 pixels, and an overlay image in the second 32x32 pixels (IDB_FOLDERS32_OVERLAY). The bitmap has transparencies that seem to work fine.
CBitmap bm;
bm.LoadBitmap(IDB_FOLDERS32_OVERLAY);
m_ImageList.Create(32, 32, ILC_COLOR32, 2, 1);
int index = m_ImageList.Add(&bm, RGB(0, 0, 0));
ASSERT(index >= 0);
m_ImageList.SetOverlayImage(index, 2);
The last line returns 0, which indicates an error. GetLastError() returns 6 (ERROR_INVALID_HANDLE).
I can't for the life of me find reasonable documentation for how to do this anywhere on the web. Can anyone see what I'm missing?
Jonathan Potter was correct that I needed to include the ILC_MASK flag in order for SetOverlayImage() to returns a value that indicates success.
However, of all the documentation I could find online, nothing provided a complete description of how to do this. I didn't find a single source, for example, that showed what my bitmap should look like.
To make it more complicated, I am using ILC_COLOR32 to signify a 32-bit color bitmap with alpha (transparency) channel. So I don't have a mask and a mask does not appear compatible with alpha channels.
So in the end, I just created a bitmap with two images: The first is a folder, and the second is a folder with my overlay image on top of it. Problem solved.
At this point, it seems pointless to try and figure out if, or how, masks can be created with 32-bit alpha channel bitmaps.