Proposed change

PREHEATING was added as an HVACAction a while ago, but the history charts do not shade the area under the current temperature which they do if the HVACAction is HEATING.

Original architecture discussion: home-assistant/architecture#710
Original Core PR: home-assistant/core#94677
Original Frontend PR: #16922

Issue: #23876

This PR uses CLIMATE_HVAC_ACTION_TO_MODE to map the HVACAction to a mode in the same way that the thermostat card does to colour the background when heating or cooling. It does mean that HVACAction.DEFROSTING is also captured by this change.

As a side note, I don't understand why defrosting is mapped to heat, the architectural discussion for defrost specifically says the system is not currently generating heat. In my view, defrosting should be mapped to off, but that would be the topic of a separate discussion.

As second side note, on the defrosting discussion there seemed to be some confusion about what preheating means. When a device is heating, it is heating up to a set temperature. When preheating, it is heating to a future set temperature. See the images on the linked issue.

This is my first PR to Home Assistant Core or Frontend, so if I have missed anything let me know.

Type of change

• Dependency upgrade
• Bugfix (non-breaking change which fixes an issue)
• New feature (thank you!)
• Breaking change (fix/feature causing existing functionality to break)
• Code quality improvements to existing code or addition of tests

Example configuration

Additional information

• This PR fixes or closes issue: fixes hvac_action of preheating not shown #23876
• This PR is related to issue or discussion:
• Link to documentation pull request:

Checklist

• The code change is tested and works locally.
• There is no commented out code in this PR.
• Tests have been added to verify that the new code works.

If user exposed functionality or configuration variables are added/changed:

• Documentation added/updated for www.home-assistant.io