Typing latency in the editor due to folding

Description

What steps will reproduce the problem?

After release of 4.2.2, I noticed typing latency in the Editor. I know that we had solved performance issues with Editor in the past, but it seems to have resurfaced.

I suspect the issue was introduced with PR #13864 since I don’t see the issue in artifact from PR #14719.

Illustrated in the attached gif: note the hiccups while typing “jumped over the lazy dog”. That sequence was typed (relatively) smoothly, but you can see the latency followed by bursts.

Versions

• Spyder version: 4.2.2
• Python version: 3.9.1
• Qt version: 5.12.10
• PyQt5 version: 5.12.3
• Operating System: Darwin 19.6.0

Dependencies

# Mandatory:
applaunchservices >=0.1.7       :  0.2.1 (OK)
atomicwrites >=1.2.0            :  1.4.0 (OK)
chardet >=2.0.0                 :  4.0.0 (OK)
cloudpickle >=0.5.0             :  1.6.0 (OK)
diff_match_patch >=20181111     :  20200713 (OK)
intervaltree >=3.0.2            :  3.1.0 (OK)
IPython >=7.6.0                 :  7.20.0 (OK)
jedi =0.17.2                    :  0.17.2 (OK)
jsonschema >=3.2.0              :  3.2.0 (OK)
keyring >=17.0.0                :  22.0.1 (OK)
nbconvert >=4.0                 :  6.0.7 (OK)
numpydoc >=0.6.0                :  1.1.0 (OK)
parso =0.7.0                    :  0.7.0 (OK)
pexpect >=4.4.0                 :  4.8.0 (OK)
pickleshare >=0.4               :  0.7.5 (OK)
psutil >=5.3                    :  5.8.0 (OK)
pygments >=2.0                  :  2.8.0 (OK)
pylint >=1.0                    :  2.7.0 (OK)
pyls >=0.36.2;<1.0.0            :  0.36.2 (OK)
pyls_black >=0.4.6              :  0.4.6 (OK)
pyls_spyder >=0.3.2             :  0.3.2 (OK)
qdarkstyle >=2.8                :  2.8.1 (OK)
qtawesome >=0.5.7               :  1.0.2 (OK)
qtconsole >=5.0.1               :  5.0.2 (OK)
qtpy >=1.5.0                    :  1.9.0 (OK)
setuptools >=39.0.0             :  52.0.0 (OK)
sphinx >=0.6.6                  :  3.5.1 (OK)
spyder_kernels >=1.10.2;<1.11.0 :  1.10.2 (OK)
textdistance >=4.2.0            :  4.2.1 (OK)
three_merge >=0.1.1             :  0.1.1 (OK)
watchdog >=0.10.3;<2.0.0        :  1.0.2 (OK)
zmq >=17                        :  22.0.3 (OK)

# Optional:
cython >=0.21                   :  0.29.22 (OK)
matplotlib >=2.0.0              :  3.3.4 (OK)
numpy >=1.7                     :  1.20.1 (OK)
pandas >=1.1.1                  :  1.2.2 (OK)
scipy >=0.17.0                  :  1.6.1 (OK)
sympy >=0.7.3                   :  1.7.1 (OK)

[mrclary]

@lamorton, I recommend using the macOS app bundle instead of the conda version of Spyder. I find it is more responsive. Let me know if that helps at all. But the typing latency, in general, is still an issue.

[mrclary]

With all the following preferences enabled simultaneously, and indent guides and code folding disabled, there are no issues whatsoever.

• class and function selector
• enable code completions
  • show completion details (1000ms)
  • show completions on the fly (1000ms)
• enable basic linting
• underline errors and warnings
• introspection (all basic features)
• enable code style linting
• enable fallback completions

With either indent guides or code folding individually enabled, the issue manifests.

• indent guides -> bad
• code folding -> bad
• indent guides + code folding -> bad + high probability of crashing.