update plan

README.md

@@ -42,6 +42,9 @@ Programming:
     - Use techniques suitable for cross platform applications. I.e., avoid platform specific SDKs like Metal, DirectX, AppKit, CUDA, ...
     - I don't expect that you really port to all platforms, but it should at least be possible without major difficulties.
 - Implement some nice-to-have features in the whiteboard:
+    - Pen input
+        - Google's [ink-stroke-modeler](https://github.com/google/ink-stroke-modeler) works pretty well for smoothing
+        - Still, constructing shapes for rendering from pen inputs is non-trivial and there are different trade-offs one can make.
     - PDF integration via [PDFium](https://pdfium.googlesource.com/pdfium/)
         - If you want to publish on iOS, this is really your only choice for a PDF library since GPL/AGPL is supposedly incompatible with the App Store.
     - End-to-end encryption