Our plug-in has existed since the heyday of CS6 for both WIN and MAC platforms. Adding XCODE tooltips to the controls on our panels for the MAC flavor was easy, and we've had that since the early days. But, having now spent many days of trial and error at various times over the last three years, I'm close to giving up trying to figure out the intricacies of adding tooltips to the Windows version of the panels.
It appears to me that after creating each control using CreateWindowEx I then need to create a tooltip for that control, also using CreateWindowEx, and link that to the control using TTM_ADDTOOL using a TOOLINFO structure. Do I also need a handler in the message pump to make the tooltip show? I'm basing what I have on the Microsoft CppWindowsCommonControls sample project.
Bottom line, does anyone have a working windows based Illustrator plug-in that puts tooltips onto their panels? It seems like the answer must be yes, but I'm wondering how it's done!
Sounds like you are doing the right thing:
I have never used tooltips, but I would suggest you create a standalone windows application (just create new win32 project in Visual Studio) and then use your code to try and add a tool tip. If the code works in a standalone application, but not in an Illustrator plugin, then it is because Illustrator is intercepting some windows message before it gets to your plugin.