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bloodsugar-cursor

A cool way to update your cursor to reflect your blood sugar values.

The main idea here is to poll against your Nightscout API every 5 minutes and update the color of your mouse cursor to help indicate your current level.

For right now, the colors are:

  • green = in range
  • yellow = high
  • red = low

Included are the cursor files that will be loaded based on this status. You can run this via AutoHotkey and PowerShell for right now, and is very Windows centric.

A known issue is how the cursor is rendered when running the PowerShell script. It's currently quite blurry and there seems to be a need to activate something to kick in better rendering. AutoHotkey doesn't have this problem.

I HIGHLY recommend using this with AutoHotkey since PowerShell has so many issues (from the blurry cursor to the inability to have a decent Cron job implementation). https://www.autohotkey.com/

Technical Details

Windows has certain APIs available to update the cursor. Mainly, LoadCursorFromFile and SetSystemCursor are leveraged.

https://learn.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-setsystemcursor https://learn.microsoft.com/en-us/windows/win32/menurc/about-cursors http://www.jasinskionline.com/windowsapi/ref/s/setsystemcursor.html

Each value below is a DWORD value, which identifies a cursor.

  • 32512 = NORMAL
  • 32513 = IBEAM
  • 32514 = WAIT
  • 32515 = CROSS
  • 32516 = UP
  • 32631 = PEN
  • 32642 = SIZENWSE
  • 32643 = SIZENESW
  • 32644 = SIZEWE
  • 32645 = SIZENS
  • 32646 = SIZEALL
  • 32648 = NO
  • 32649 = HAND
  • 32650 = APPSTARTING
  • 32651 = HELP
  • 32671 = PIN
  • 32672 = PERSON

Registry Keys

Within the Registry Editor, a couple places control mouse/cursor settings:

  • Computer/HKEY_CURRENT_USER
    • Control Panel
      • Cursors
      • Mouse
    • Software/Microsoft/Accessibility

You can see values corresponding to some defaults, which seem to be linked to the accessibility settings.

"Cursor Size" in Settings/Accessibility/Mouse pointer and touch is linked to Control Panel/Cursors -> CursorBaseSize in the Registry: 3 = 64 4 = 80

"Mouse pointer speed" in Settings/Bluetooth & devices/Mouse is linked to Control Panel/Mouse -> MouseSensitivity. The values are equivalent.

And finally "Mouse pointer style" in Settings/Accessibility/Mouse pointer and touch is linked to Software/Microsoft/Accessibility

There are four registry keys here:

  • CursorColor
  • CursorSize
  • CursorType
  • TextScaleFactor

The color can be seen to change from: Green = 12582656 (0x00bfff00) Yellow = 64250 (0x0000fafa)

Back at the Control Panel/Cursors entries, the file path for Arrow is this string: "C:\Users\[YOUR_USERNAME]\AppData\Local\Microsoft\Windows\Cursors\arrow_eoa.cur"

Going to that directory, we can find these cursor files. If we change the color in Settings now, we can see these files get updated.

AutoHotkey

This topic helped tremendously in doing this in AutoHotkey (v1): https://www.autohotkey.com/boards/viewtopic.php?t=81652

No major changes to the logic, other than updating the script to v2 syntax.

PowerShell

The PowerShell script is written in a way that is to be leveraged by Task Scheduler. This doesn't really work well with Task Scheduler because of this issue: PowerShell/PowerShell#3028.

The stupid PowerShell window keeps appearing and causing whatever window I'm on to lose focus.

The DLL is also called in a little bit of an odd way...

https://learn.microsoft.com/en-us/powershell/module/microsoft.powershell.utility/add-type?view=powershell-5.1#example-4-call-native-windows-apis

The above reference shows how you can leverage the Add-Type utility to add a Microsoft .NET class to a PowerShell session. Since .NET can make the DLL call, we have this nested logic of a DLL call within a .NET string defined within PowerShell. Yikes.

It's probably worth it to create an actual .NET solution for this instead of scripting it through PowerShell. So much for a PoC for PowerShell.