README
@blockly/block-extension-tooltip 
A Blockly block extension that adds support for custom tooltip rendering.
WARNING: This plugin is currently incompatible with the latest version of Blockly (v7.20211209.0). Please comment on https://github.com/google/blockly-samples/issues/899 if this is blocking you (we also welcome contributions).
Note:
- This plugin uses a block extension and as a result, it needs to be added to each block type. See test/index.ts
- This plugin is monkeypatching Blockly until we can make the correct change in core
Installation
Yarn
yarn add @blockly/block-extension-tooltip
npm
npm install @blockly/block-extension-tooltip --save
Usage

Register
Register the tooltip extension:
import * as Blockly from 'blockly';
import {registerTooltipExtension} from '@blockly/block-extension-tooltip';
registerTooltipExtension((block) => {
// Custom tooltip rendering method.
const el = document.createElement('div');
el.className = 'my-custom-tooltip';
el.textContent = block.getTooltip();
return el;
}, 'custom-tooltip-extension');
Block definition
Add the extension to your block definition using JSON:
Blockly.defineBlocksWithJsonArray([
{
"type": "my-block",
"extensions": ["custom-tooltip-extension"]
}
]);
or add the extension to your block definition using JavaScript:
Blockly.Blocks['my-block'] = {
init: function() {
Blockly.Extensions.apply('custom-tooltip-extension', this, false);
},
};
License
Apache 2.0