Add option to not clean display on startup

[NicolaiPetri]

Hi,
It would be very nice to not erase display content on initialization. This would work great with ESPHome in deep sleep, then display would only be redrawn after wakeup, network initialization and data received from Home Assistant.
With current driver, it takes approx. 10 seconds with a blank screen before startup is completed and data is visible again.
Besides that everything works great - thanks for the good work.

[Torch1969]

Hello @tiaanv i have the same question. Any suggestions where to suppress this clearing of the display directly after wake up from deep sleep can be done?

@NicolaiPetri did you find a solution?

[juleskers]

I like the idea of keeping the previous state while waking up from deep-sleep, so I did some digging.
I'm fairly certain that this clean() + display() in the setup() section is the responsible.

esphome-components/components/t547/t547.cpp

Lines 14 to 20 in b826ba8

	static const char *const TAG = "t574";
	void T547::setup() {
	this->initialize_();
	this->clean();
	this->display();
	}

What I am not sure about, is how one would read the config that early in setup(), where stuff like that usually isn't available yet.
Or can ESPHome (which I've only just discovered) 'hard-code' yaml-config into C-const during compile-time?

The laziest solution would be to just remove the this->clean(); this->display().
Worst case, whatever 'old' content/garbage is on-screen will survive a bit longer.

The critical idea is that an update() happens before the first display (probably in loop(), to populate the internal pixel-buffer.
Right now, setup() starts a fresh, empty buffer, and displays that.