How to update block attributes with setAttributes before post is saved?

[qarayahya]

Hi, I’m working with a core block, and I need to update one of its attributes when the user hits the “Save” button, but before the post content is actually saved.

I tried using the isSavingPost() function from the data store, but it seems that block attributes are updated after the save is completed, which is too late for what I’m trying to do.

Is there a reliable way to hook into the save process and call setAttributes({ ... }) just before the post is committed?

Any guidance or example would be greatly appreciated!

Thanks!

[t-hamano]

Hi,

Is there a reliable way to hook into the save process and call setAttributes({ ... }) just before the post is committed?

As far as I know, I don't know such a way, but if you could explain in a bit more detail what you want to do, we might be able to offer some suggestions.

[qarayahya]

Here’s the situation:
I have a block attribute called breakpointsManager that stores different values based on the current deviceType. The structure looks like this:

breakpointsManager: {
		desktop: {
			typography: {
				fontSize: { preset: "large" },
			},
		},
		tablet: {
			typography: {
				fontSize: { preset: "medium" },
			},
		},
		mobile: {
			typography: {
				fontSize: { preset: "small" },
			},
		},
	}

When the user adjusts the font size, I store it in breakpointsManager[deviceType].typography.fontSize. I also track changes to deviceType and update the visible fontSize attribute so the preview reflects the current device's value.

The problem:
If a user clicks "Save" while previewing the mobile or tablet layout, the fontSize attribute ends up saving the mobile or tablet value—when what I really need is for it to always save the desktop font size.

Gutenberg.Save.Attribute.mp4

[t-hamano]

I also track changes to deviceType and update the visible fontSize attribute so the preview reflects the current device's value.

Does this mean that you are running setAttributes every time the device type has changed? Perhaps you want to extend the core typography support somehow, but it seems like it would be easier to develop your own control.