As I noted in my earlier post, the method for selecting theme (‘accent’) colours in Windows ‘Blue’ build 9364 has changed from Windows 8 RTM. I’m not going to bother looking too closely at the updates to the functions in UxTheme.dll this early in the development process, but I did notice two new registry values in the key HKCUSoftwareMicrosoftWindowsCurrentVersionExplorerAccent: ‘AccentColor’ and ‘StartColor’. These are DWORD values that store the accent colour and background colour, respectively. The format is 0xAABBGGRR. The old ‘ColorSet_Version3’ value from Windows 8 is gone for obvious reasons. ‘AccentId_v8.00’ from Windows 8 is now ‘MotionAccentId_v1.00’, but it seems to serve the same purpose – indicating which background image is selected.
See also: Windows 8 Theme Colours Reference.
Windows 8 doesn’t offer developers access to system theme colours, unlike its cousin, Windows Phone. Even for a version 1 product, this seems like a strange omission. Then again, we still don’t have a working public API for retrieving the Aero glass colour (or whatever we call it now that Aero’s gone) 6 years after the release of Windows Vista.
The functions that the system uses to retrieve colours are defined in UxTheme.dll. In particular, we’re interested in GetImmersiveColorSetCount (export #94), GetImmersiveColorFromColorSetEx (export #95), GetImmersiveColorTypeFromName (export #96), GetImmersiveUserColorSetPreference (export #98) and GetImmersiveColorNamedTypeByIndex (export #100). Relying on undocumented functions is a bad idea, and will cause your program to fail certification, so you won’t be able to use them in apps distributed through the Windows Store anyway.
For desktop developers who still want to use these functions, read on. Just assume that they’ll break in future versions of Windows (or even with patches to Windows 8).