It would be a huge undertaking, especially if the DirectX types leaked into the rest of the application. DirectX 7 is from 1999, games like Half-Life 1 used it. This is when GPUs were mostly fixed-function. While nowadays a GPU is almost as versatile as a CPU.
The hardest/largest step would probably be to get it into this century, with the latest version of DirectX 9 (2005, Windows XP / Xbox 360 era). The step from 9 to 11 is also quite big, but a lot of APIs have stayed compatible.
The hardest/largest step would probably be to get it into this century, with the latest version of DirectX 9 (2005, Windows XP / Xbox 360 era). The step from 9 to 11 is also quite big, but a lot of APIs have stayed compatible.