note high-dpi issues

Author: jcupitt

README.md

@@ -263,6 +263,15 @@ Clone and run:
 
 ## TODO
 
+- add high-DPI support
+
+    for 2900% desktop scale (for example) we probably need to render our
+    256x256 tiles as 128x128 gtk pixels
+
+    however, this seems to cause filtering problems, mysteriously, see 
+    https://github.com/jcupitt/vipsdisp/tree/add-high-dpi for a quick test
+    hack
+
 - skip unknown files on next / prev?
 
     - need to add the test to next-image, not glob, since we can't test the