Lcd functions allow scripts to interact with the transmitter display. This access is limited to the run function of One-Time and Telemetry scripts, and the refresh function of Widget scripts on radios with color display.
The run function is periodically called when the screen is visible. In OpenTX 2.0 each invocation starts with a blank screen (unless lcd.lock() is used). Under OpenTX 2.1 screen state is always persisted across calls to the run function. Many scripts originally written for OpenTX 2.0 require a call to lcd.clear() at the beginning of their run function in order to display properly under 2.1 and 2.2.
For Widget scripts, lcd.clear() is not needed, as each invocation starts with a blank screen showing the theme background. But it can be used to overwrite the theme background with another color by calling lcd.clear(color).
Please see above for a description of the constants for flags and patterns, colors, and screen size that can be used with lcd drawing functions.