How do I ask Windows for the size of system tray icons?

Question

I noticed that my app sends icons to the Windows tray with a size of 16x16 pixels--and my Vista PC I've got a doublewide taskbar that appears to show icons at 18x18. The resizing artifacts on my app's icon look awful. How can I ask Windows what size the icons should be?

Edit

I'm generating the icon dynamically, with a pixel font text overlay. It seems wasteful to generate a bunch of icon sizes dynamically, so it would be nice to avoid building an icon with all the "possible" sizes (not that I'm even sure what those are).

• GetSystemMetrics(SM_CXSMICON) returns 16--the incorrect value.
• GetThemeBackgroundContentRect didn't help, either.

Answer 1

Create your icons in multiple formats, and let Windows select the one it wants.

Here's the Wikipedia article on the .ico format.

If you really need to know, GetSystemMetrics with a parameter of SM_CXICON or SM_CYICON will tell you the width and height that Windows wants to load.