Integrating the Cross-Tab-Copy-Paste correctly

[Stefan Höhn]

I recently discovered this awesome plugin:

https://github.com/google/blockly-samples/tree/master/plugins/cross-tab-copy-paste

and I immediately jumped on it and integrated it into our application (openHAB).

However, there is a bit of an issue: it turns out that this plugin must be loaded ONLY ONCE. Even when recreating a new workspace it must not be loaded again, otherwise it throws an exception complaining that it already exists.

While for example the Zoom-Control-Plugin links to the workspace like so

const zoomToFit = new ZoomToFitControl(this.workspace)
zoomToFit.init()

it seems that I have to use a GLOBAL variable make sure that the plugin is not yet loaded like so

if (!copyPastePluginInitialized) {
   const copyAndPasteOptions = { ... }
   const copyAndPastePlugin = new CrossTabCopyPaste()
    copyAndPastePlugin.init(copyAndPasteOptions, () => {
     console.log('There has been a block type error during copying and pasting')
    })

    copyPastePluginInitialized = true

} 

but even then sometimes it seems that this doesn't really prevent it. 

I wonder if there is a better of doing it to make it fail-save or why the plugin was created that way?

TIA

Stefan

PS: As a sidenote, I upgraded from 6.x to 9.2 and the migration was amazingly smooth! Well done, team!

 

[Stefan Höhn]

As an additional information: The error message is 

Error while retrieving Blockly data - Error: Menu item with ID "blockCopyToStorage" is already registered.:undefined

Maybe that allows us to "query" or detect somehow that the plugin has already been installed?

[Maribeth Bottorff]

The reason for this is Blockly's shortcut registry is a singleton; all workspaces share a single shortcut registry. So it doesn't make sense to add this plugin multiple times, even if you have multiple workspaces.

 It would be best to initialize this plugin only once. Since it's not associated with a workspace, there's no need to call it every time you create a workspace, and you can do it once per application load.

Maribeth

[Stefan Höhn]

Thanks Maribeth,

is there an easy way to detect if the singleton is already loaded? Currently I am using a global variable but that doesn't sound like an elegant solution

Stefan

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[Maribeth Bottorff]

You could check if one of the registry items is already present, e.g. 

Blockly.ContextMenuRegistry.registry.getItem('blockCopyToStorage')

Or you could put the code in a location you know will only run once and not have to check.

Btw, glad to hear your upgrade experience was smooth! Best,

Maribeth

[Stefan Höhn]

This

Blockly.ContextMenuRegistry.registry.getItem('blockCopyToStorage')

seems to be exactly what I was looking for.

Thanks Maribeth!

Cheers

Stefan

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