Heat Index Feature

[ClementGre]

Hi, I use your app every day to compare the outside/inside temperature, but the temperature is not enough to compare wether or not to open the windows. That's why I developed a feature that calculates and display the heat index for sensors that support both temperature and humidity measurement.

What I've done

• Adding a function to calculate heat index in unitemp.c.
• Sensors.c calls this function to calculate heat index when updating sensor data.
• Adding a new function in General_view.c to draw the heat index for sensors of type UT_DATA_TYPE_TEMP_HUM, with a new icon derivated from the temp_C and temp_F icon.
• Adding an option in the settings to disable the heat index calculation and display of the heat index.

What you could add to my code to integrate it better to the app

• Maybe update the new icon that might not be explicit enough.
• Supporting the display of head index for sensors of type UT_DATA_TYPE_TEMP_HUM_CO2 (this will require to change _draw_co2 to support custom coordinates). As long as there is no sensor that supports temp, hum, co2 and press, there is anyway enough room to show the heat index.
• The heat index could be shown smaller because it is not a directly measured by the sensor, it is a calculation, but it would require to change even more the layout of the measures tiles.
• Adding a new scene that shows all the heat indices of all sensors would allow an easier comparaison.