Question

I’m currently trying to write a program in VB.NET which fluidly changes the DWM window colorization colors in Windows 7.

I first tried to edit Registry values directly, but I had to restart the UXSMS service. This solution was unsatisfying, because of the toggle of the taskbar.

I’m now searching for a function in a DLL such as user32.dll or themecpl.dll which can reproduce the behaviour of control panel when setting the window color.

I’m now on IDA, searching for the adquate function (CColorCplPage::SetDwmColorizationColor seems good!). If anyone has one, please share it!

(If anyone need screens or code, please ask. Sorry for my poor English.)

Answer 1

Your first attempt failed because manually editing the Registry is never the correct way to change system settings. As you found out, lots of Windows components (and other applications!) read those configuration values once and cache them, preventing your changes from being propagated. Another problem (and you’d be surprised how often I see this) is applications that attempt to muck around in the Registry generally end up corrupting things.

Instead, you should call the documented API to change the settings. There’s almost always a documented way of doing this, and if there isn’t, well then you shouldn’t be doing it.

This appears to be one of those cases. There’s a documented DwmGetColorizationColor function, but there’s no corresponding DwmSetColorizationColor function, as one might expect.

The reason is that the user is supposed to be the only one who can change their colorization settings, not other applications. You might promise not to abuse this, and to only make such changes at the user’s explicit request, but not all applications can be trusted to do this. Lots of people would use it maliciously, so these functions have not been documented and exposed.

But as usual, if you press on, you can usually find an undocumented way of doing things. The problem with using undocumented functions is that there’s no guarantee they’ll work or continue to work. They’ve been intentionally left undocumented because they’re liable to change on new versions of Windows. You should only use them at your own risk.

In this case, if you use a program like DumpBin to obtain a list of all the exported functions from the DWM DLL (dwmapi.dll), you’ll see a number of undocumented exported functions.

The ones you’re interested in are DwmGetColorizationParameters and DwmSetColorizationParameters. Both of these functions take a COLORIZATIONPARAMS structure as an argument that contains the values they need.

So, you need to reverse engineer these functions and obtain the appropriate definitions. Then, you can call the DwmGetColorizationParameters function, passing in a COLORIZATIONPARAMS structure to obtain the current configuration settings; modify the member of the structure that contains the current colorization color; and then pass that modified version of the structure to the DwmSetColorizationParameters function.

Did I mention that I don’t recommend doing this?