What this does

A stylus or pen drag now selects text in the editor on Android, the same as it
already does on iOS. A finger drag still scrolls, and the mouse is unchanged.

Why

The editor only sends pointer input through PointerEventHandler, the handler
that lets a pen select while touch scrolls, on iOS or on Android when
platform.isMobile is true. platform.isMobile looks for a "Mobi" token in the
user agent, and Android tablets usually leave that token out. So on a tablet the
editor fell back to TouchHandler, and a stylus could only scroll, never select.
Android phones were unaffected because their user agent carries "Mobi".

Background: microsoft/vscode#198578 added the pen/stylus selection path for
mobile; this extends it to Android tablets.

The change

One line, in a new patch (patches/pen-support.diff):

-             const isPhone = platform.isIOS || (platform.isAndroid && platform.isMobile);
+             const isPhone = platform.isIOS || platform.isAndroid;

The iOS branch is left as is. The only difference is that Android no longer
requires the isMobile flag to reach PointerEventHandler.

Testing

Built and run on a Samsung tablet with an S Pen, in Chrome:

• Pen drag across text selects it.
• Finger drag scrolls.
• Pen barrel button plus a tap opens the context menu.
• Mouse selection and right-click are unchanged.

Also reproducible in desktop Chrome with DevTools device mode set to an Android
tablet user agent that has no "Mobi" token.

Notes

iPad and iPhone are unaffected; the iOS branch is untouched. Android phones are
unaffected too, since they already satisfied isMobile.