I am using emacs 25.1, the "official" minGW build, on Windows 7. Opening a very simple text file, even with emacs -Q, leads to slow scrolling. Hit PgUp/Down and it takes time. This happens when I run emacs as a windows program. If I go into a command window, and run emacs -nw (either minGW or cygwin), scrolling is fine and fast.

So, what is wrong? This is super duper annoying. Modern computers are powerful enough to scroll a few pages of text instantly...

  • Does setting fast-but-imprecise-scrolling to t help any? Does the problem happen in fundamental-mode, or are you in text-mode with font-lock-mode globally enabled? When fast-but-imprecise-scrolling is set to t, the internal function window_scroll binds fontification_functions to nil.
    – lawlist
    Apr 22 '17 at 19:53
  • Hi, thanks, but changing it from nil to t doesn't help, in either text or fundamental modes. The same slowness also can happen if I move the cursor to the next screen just with up/down arrows. M-x describe-modes indicates a lot of minor modes are active. Can I turn them all off? I must be doing something wrong...
    – D Strozzi
    Apr 22 '17 at 22:09
  • I see you found the issue -- good job. When debugging, yes, turning off minor-modes to help narrow down the problem is sometimes helpful.
    – lawlist
    Apr 22 '17 at 22:53

OK I figured it out. The text file I was viewing had a special character in it. I did "C-x 8 RET 2207" to get the nabla symbol. Emacs renders it as a nabla. If I get rid of that char, scrolling is fine. I won't ask why scrolling is slow w/ the nabla, I am happy to understand the story. And see that emacs can actually scroll quickly on a 2 GHz 64-bit chip.

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