Why use `VarDisplay` instead of `Display7in5::default()`?

[hayd1n]

I apologize that this is not an issue about your project, but hopefully I can get your help. 🙏

I am working on some projects using ESP32 + Waveshare 7.5_V2. I am using the latest version of epd_waveshare.

I tried to create a display using Display7in5::default() but it never works, it's like ESP32 crashed. However I found out that your code uses VarDisplay::new() to create the display manually, so I tried that too and I found that it works. I looked at the epd_waveshare source code and I can't understand why this is happening, and would like to ask you why you are using VarDisplay::new() instead of Display7in5::default(), and what's the rationale behind this?