Recursive block selects firing with v12

[mikeharv]

Check for duplicates

• I have searched for similar issues before opening a new one.

Description

With v12.0.0, Blockly seems to be firing far more Blockly.Events.SELECTED events than normal. This is leading to performance issues.

Reproduction steps

1. Visit any v12 demo page, such as https://google.github.io/blockly-samples/plugins/field-grid-dropdown/test/index.html
2. Using the console, add a simple event listener to log block selection events. For example:

Blockly.getMainWorkspace().addChangeListener(e=>{if(e.type===Blockly.Events.SELECTED){console.log(e);}})

3. Drag a block out of the toolbox and connect it to another block.
4. Inspect the console. You will see over a dozen selection events.

This does not happen with v11, such as at https://blockly-demo.appspot.com/static/tests/playground.html

Stack trace

Screenshots

Browsers

No response

[BenHenning]

More selected events is definitely expected due to us now being a bit eager with firing selected events on each block focus/blur. This should be remediated slightly with #9082 (which isn't available yet) since I noticed that we were actually calling the lifecycle blur/focus callbacks multiple times for each focus. I think that means that selected events are roughly 6x more often than they were before, and after that PR will being 2x more often.

We would need to introduce some additional logic in order to get back to parity with v11. I'll be keen to see if #9082 is sufficient for the performance fix, or if we do need to do that additional logic.

[rachel-fenichel]

@BenHenning and @mikeharv were the fixes from $9082 sufficient to close this issue?