Hi, the feature is really nice, but I have some thoughts about implementation.

1. Looks like I cannot add a point out of the threshold rectangle (when Block is active). We should allow users to put points anywhere this time, and probably we should hide the threshold this time.
   

2. Why B? We discussed using Ctrl in both intelligent scissors and interactors. Probably it is better to decrease the variety of hotkeys if possible (like in this case when Block plays the same role). BTW, B is a neighbor of N, which stops drawing. It is also inconvenient.

3. Could you please add Block button also for interactors?

4. Let's use <StopOutlined /> icon from antd.

5. IMHO this tooltip is not informative. Maybe something like: "Postpone running the algorithm [B]" is better. You also can suggest your ideas.
   

6. When the cursor is near to the latest point, it disappears and the border shifts. Is it expected?
   

@klakhov
Could you please remove WIP from the PR title if it is ready?

@klakhov
Could you please remove WIP from the PR title if it is ready?

Sure

Found two issues with this path:

1. Block using Ctrl does not work (with both scissors and interactors) when start drawing using N hotkey.
2. When use interactors, we can press Block button. It becomes "blue", but requests are still send to the server.

When try to finish scissors when the algorithm blocked:

IndexSizeError: Failed to execute 'getImageData' on 'CanvasRenderingContext2D': The source width is 0.

When try to finish scissors when the algorithm blocked:

IndexSizeError: Failed to execute 'getImageData' on 'CanvasRenderingContext2D': The source width is 0

I've returned blocked mode check to final calculation and this error is gone now.

Please add a piece of information to CHANGELOG and update package versions for canvas and ui.

@aschernov @TOsmanov
Could you please update the user guide about using intelligent scissors according to new changes (pressing Ctrl enables blocking mode)?

@dvkruchinin
Could you please prepare a test for intelligent scissors blocking feature?

@aschernov @TOsmanov
Could you please update the user guide about using intelligent scissors according to new changes (pressing Ctrl enables blocking mode)?

@klakhov , yes, we will update the documentation

@klakhov
Sure. A test will be updated to cover this feature.

I found that when the restrictive threshold (red square) intelligent scissors (OpenCV) is resized using ctrl+mousewheel triggers the block too, is this expected behavior? I think this is inconvenient as it turns out that the user will not be able to change the size of the threshold without enabling blocking

@TOsmanov

I found that when the restrictive threshold (red square) intelligent scissors (OpenCV) is resized using ctrl+mousewheel triggers the block too, is this expected behavior?

It is expected.

it turns out that the user will not be able to change the size of the threshold without enabling blocking

It is possible. Why do you think it does not work? (If you use mousewheel during Ctrl is held, block will not be triggered)

@TOsmanov
As you can see on this gif, when we are resizing threshold using ctrl+mousewheel block remains disabled. But when the ctrl is pressed without threshold resizing block is triggered.

@bsekachev @klakhov , If you release ctrl a little later than scrolling the mouse wheel, the lock is triggered.

@TOsmanov
Could you please provide a .gif where threshold changing happens at the same time with locking?
I cannot reproduce

@bsekachev

I'm using the develop branch with the latest commit 0272384

@TOsmanov

Do you have any error message in the browser console this time?

@TOsmanov

Do you have any error message in the browser console this time?

In this moment no.

But I sometimes get an error message in cvat:

OpenCV.js processing error occured
8390056 - Exception catching is disabled, this exception cannot be caught. Compile with -s DISABLE_EXCEPTION_CATCHING=0 > or DISABLE_EXCEPTION_CATCHING=2 to catch.

@TOsmanov

As we can't easily reproduce this bug, could you please update the documentation and create an issue with more detailed information about your browser/operating system with steps to reproduce this bug?