[Qt-creator] Performance of the editor (with clang-format)

[Björn Schäpers]

Hi there,

I recently got a new machine at work, sadly with a new(ly configured) anti virus 
software. And the performance of QtCreator when editing went down. I thought the 
anti virus was to blame (in a way it is, because if it's deactivated everything 
is fine again), but when I debugged something in the creator I made a horrible 
observation.

If you use the clang-format plugin in every paint event of an editor the 
clang-format style is read, that explains the delay with the anti virus, it just 
has to check the .clang-format file if it is bad now...

Here the stacktrace:
1   ClangFormat::ClangFormatBaseIndenter::styleForFile 
clangformatbaseindenter.cpp 773  0x7ff833ea5c18

2   ClangFormat::ClangFormatIndenter::tabSettings 
 
                                     clangformatindenter.cpp     68   0x7ff833ed21e7

3   ClangFormat::ClangFormatForwardingIndenter::tabSettings 
 
                                     clangformatindenter.cpp     197  0x7ff833ed27f8

4   CppEditor::Internal::CppEditorDocument::tabSettings 
 
                                     cppeditordocument.cpp       436  0x7ffff44a13ae

5   TextEditor::Internal::PaintEventData::PaintEventData 
 
                                     texteditor.cpp              456  0x7ff816ff71cf

6   TextEditor::TextEditorWidget::paintEvent 
 
                                     texteditor.cpp              4877 
0x7ff816f82fca

It's really nice that I can edit my .clang-format file and immediately use that 
when pressing ctrl+i, so I understand to read the file in such a situation. But 
do we really need that check in the paint event?

Can't we cache the TabSettings? And emit a signal, when the file is read again 
and the value changed?

When I click into another editor (split view) or press F4 I've to wait about 3 
seconds before I can continue to work.

Kind regards,
Björn.