How to associate touch coordinates with components in an MCU?

[Song-aff]

slint/api/rs/slint/mcu.md

Line 213 in 62bd0f3

# fn check_for_touch_event() -> Option<slint::platform::WindowEvent> { todo!() }

[ogoffart]

You ask the touch driver.

There are some example in the repository for a few different touch screens:

slint/examples/mcu-board-support/pico_st7789.rs

Lines 256 to 279 in c89af27

	// handle touch event
	let button = PointerEventButton::Left;
	if let Some(event) = self
	.touch
	.borrow_mut()
	.read()
	.map_err(|_| ())
	.unwrap()
	.map(|point| {
	let position = slint::PhysicalPosition::new(
	(point.x * DISPLAY_SIZE.width as f32) as _,
	(point.y * DISPLAY_SIZE.height as f32) as _,
	)
	.to_logical(window.scale_factor());
	match last_touch.replace(position) {
	Some(_) => WindowEvent::PointerMoved { position },
	None => WindowEvent::PointerPressed { position, button },
	}
	})
	.or_else(|| {
	last_touch
	.take()
	.map(|position| WindowEvent::PointerReleased { position, button })
	})

slint/examples/mcu-board-support/stm32h735g.rs

Lines 356 to 371 in c89af27

	// handle touch event
	let touch = ft5336.detect_touch(&mut inner.touch_i2c).unwrap();
	let button = slint::platform::PointerEventButton::Left;
	let event = if touch > 0 {
	let state = ft5336.get_touch(&mut inner.touch_i2c, 1).unwrap();
	let position = slint::PhysicalPosition::new(state.y as i32, state.x as i32)
	.to_logical(window.scale_factor());
	Some(match last_touch.replace(position) {
	Some(_) => slint::platform::WindowEvent::PointerMoved { position },
	None => slint::platform::WindowEvent::PointerPressed { position, button },
	})
	} else {
	last_touch.take().map(|position| {
	slint::platform::WindowEvent::PointerReleased { position, button }
	})
	};

slint/examples/mcu-board-support/esp32_s3_box.rs

Lines 139 to 174 in c89af27

	match touch.event() {
	// Ignore error because we sometimes get an error at the beginning
	Err(_) => (),
	Ok(tt21100::Event::Button(..)) => (),
	Ok(tt21100::Event::Touch { report: _, touches }) => {
	let button = slint::platform::PointerEventButton::Left;
	if let Some(event) = touches
	.0
	.map(|record| {
	let position = slint::PhysicalPosition::new(
	((319. - record.x as f32) * size.width as f32 / 319.) as _,
	(record.y as f32 * size.height as f32 / 239.) as _,
	)
	.to_logical(window.scale_factor());
	match last_touch.replace(position) {
	Some(_) => WindowEvent::PointerMoved { position },
	None => WindowEvent::PointerPressed { position, button },
	}
	})
	.or_else(|| {
	last_touch.take().map(|position| WindowEvent::PointerReleased {
	position,
	button,
	})
	})
	{
	let is_pointer_release_event =
	matches!(event, WindowEvent::PointerReleased { .. });
	window.dispatch_event(event);
	// removes hover state on widgets
	if is_pointer_release_event {
	window.dispatch_event(WindowEvent::PointerExited);
	}
	}

But this is going to be dependent of your touch driver.

I hope this helps.

[Song-aff]

Can I understand it this way? Define a touch event, provide the position, and then trigger it through dispatch_event. I don't need to record the position of a component on the screen.
let button = slint::platform::PointerEventButton::Left;
WindowEvent::PointerPressed { position, button }
window.dispatch_event(event);

[ogoffart]

Yes, exactly.

(And if there is are no touch or button pressed, you don't need to dispatch an event)