Selection is very slow [$5 awarded]

[simonzack]

Selection & editing a selection are quite slow in the qt gui (when editing main.go in the lime source).

I understand that the qt gui is in early alpha and am not familiar with the code base, but just wanted to raise my concern as I think making the gui reasonably fast up front is rather important.

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[snowiow]

Isn't that the problem because of the millions of print outs, which are currently in the qml code? Didn't tested it without them yet, but always thought that they are slowing the gui down.

[quarnster]

I've not seen slow selection, but I have seen it freeze/hang completely after selecting a bit of text. Though I haven't had a chance to look into that yet.

[sardonic2]

I've seen the same thing. Text selection bogs down a bit, until it hangs / white screens completely. To add a bit to that, it looks to flatline a core to 100% CPU, and will not respond until I kill the proccess.

[pwaller]

Yes, the cursor movement in general is unusably slow for me.

[crr0004]

I know with selection at the moment there is possible issue with reverse selection and selecting outside the window causes a hang

[quarnster]

This was improved recently with d897c29. Was this the "slow selection" you talked about, or was it something else? The selection-hang is handled in #535

[pwaller]

I can confirm that Selection fluidity seems improved since last time I tried it. However, there are still a number of other selection and performance bugs. For example, double clicking on a word frequently doesn't select what I expect it to. And performance wise the editor takes quite a while to display the text with the correct indentation when it starts.

[quarnster]

@pwaller, yes, it's very early days still and we need more people helping out with tweaking all those bits (and many more). Please help us by keeping discussions about specific issues in separate issue numbers

[simonzack]

I just compiled this (on arch linux), and selection is still slow for lime_qml. The more lines I select the slower it becomes. Try selecting 20 lines and the editor becomes unusable.

[quarnster]

For that, the culprit is onSelectionModified in LimeView.qml as it takes longer and longer to complete the more lines are selected. It could be improved quite a bit by instead of completely re-creating all the selection regions for all selected lines, to just tweak the lines that have changed between the last selection and the new one. Marking as enhancement

[quarnster]

Or perhaps more correct, selection should be handled in the backend which has knowledge of color schemes etc. The frontend then only needs to track and render cursor positions seperately.