Bug reports:
https://github.com/notepad-plus-plus/notepad-plus-plus/issues/3895
https://sourceforge.net/p/scintilla/bugs/1983

If you, like me, value ‘tap twice’ word selection over ‘tap twice and drag’ multi-select, follow this workaround:

1. Go into Windows 10 ‘Touchpad settings’
2. Disable ‘Tap twice and drag to multi-select’

After installing and running (and looking at their documentation), here’s a simplified procedure:

1. Click (and drag) on Pick Window, and drag it into your NPP editing window.
2. In the Window Detective hierarcy pane (on the left), it will highlight a “Scintilla” row
3. RightClick on the highlighted “Scintilla” and select “Messages”
4. Click on the red STOP button to stop intercepting messages temporarily; the button will change to a green START button
5. Click on the eraser to the right of the START button, which will clear the screen
6. Click on the filter icon
   1. Exclude All
   2. Type WM_LBUTTON in the FIND box
   3. check ☑ WM_LBUTTONDBLCLK
   4. (and possibly ☑ WM_LBUTTONDOWN, ☑ WM_LBUTTONUP, if you want to watch all “left-click” messages)
   5. click OK
7. Click START button
8. Using mouse, double-click on something in your NPP window…
   1. You should see a → WM_LBUTTONDBLCLK and ← WM_LBUTTONDBLCLK indicating NPP was sent the DoubleClick, and responded
   2. If you filtered on the DOWN and UP, you’ll likely see other LBUTTON messages, too.
9. Double-tap on something else in that same window, and you should see another copy of the message
   1. If you see the → WM_LBUTTONDBLCLK and ← WM_LBUTTONDBLCLK, then NPP was sent the DoubleClick.
      1. If there, expand the ← WM_LBUTTONDBLCLK, which should show a return value of 0
   2. If all you see is UP and DOWN, without the DBLCLK, then windows isn’t seeing your DoubleClick to pass on to NPP
10. Click the STOP button again

When I ran this procedure, everything worked as I expected.

As far as I know, from the NPP (and internal scintilla) perspective, it’s getting a WM_LBUTTONDBLCLK message, and it doesn’t know whether it’s from the mouse/click or the touchpad/tap, so I don’t see how separate behavior could arise. But if you aren’t seeing the DBLCLK message when using the touchpad, then maybe something is wrong on the driver side, I think (though that doesn’t explain why it’s working in other apps).

Also, maybe play with “double-click speed” settings for either your mouse or touchpad, and see if maybe that will help.

Good luck.

Have you tried running without plugins (notepad++.exe -noPlugin, or rename the plugins\ subdirs in the notepad++ executable directory and/or the %AppData%\Notepad++\ directory)? Maybe one of your plugins is somehow interfering.

• Double tapping or double clicking on Windows Notepad highlights words and URL links, as expected.
• Double tapping or double clicking a word on Microsoft Word highlights the word.
• Double tapping or double clicking a URL link on Microsoft Word opens the link in the default browser, as expected.
• Behavior in NetBeans 8.2 also works the same as Word, as expected.

But the incorrect double tapping behavior remains on my install of Notepad++ 7.5.4, unfortunately.

i just tested np++ 7.5.4 x86 on w10pro x64 (1709 build 16299.192) with a touchpad and can not confirm this issue.
double tapping on a word highlights the word as expected
double tapping on a link opens the link in the default browser as expected

what happens if you double click a word in the default windows notepad or word ?
does it mark the whole word as it should ?