What does “Enable runtime themes” really mean, Windows tells “Enable visual styling” of applications through the following manifest entry
<dependentAssembly> <assemblyIdentity type="win32" name="Microsoft.Windows.Common-Controls" version="6.0.0.0" processorArchitecture="*" publicKeyToken="6595b64144ccf1df" language="*" /> </dependentAssembly>
In older versions of Delphi, you can also use runtime themes using different methods. Delphi 7 included the TXPManifest component, which had the same effect as “Enable Runtime Theme”.
Enabling runtime affects part of the application GUI. Obviously, drawing a Win 95-style flat button should be more impressive so that the drawing gradient is rounded off using the Win XP / Vista / Win7 button, but as @DavidHeffernan and @TLama note, this may be so. One of the issues here also measures actual performance, as it can depend on many factors. That way, even if you do some actual performance profiling results, you can skew a lot. The real question here is that the difference in GUI performance between a non-thematic and a thematic application (no matter which one turns out to be faster) causes you some concern.
The answer to this part is no. First, any performance impact you may have is related to the GUI. Secondly, the static graphical interface of Windows applications is much less demanding than any 3D game on which our computers are fully capable of working. And since the visual style was introduced with Windows XP, and then the computers had no performance problems when processing styles (they are used throughout the system), which talk about the performance of working themes in modern applications running on modern equipment, it's just a waste time.