Release of touch input device results in wrong coordinates while using "invert-x/y" (lvgl-pointer-input) due to double inversion of coordinates

[faxe1008]

Discussed in #70500

^{Originally posted by Benni77 March 20, 2024}
I'm wondering if this is a bug with request for confirmation before I open an issue:

I'm using a gc9a01 display with CST816S touch controller with lvgl.
When I use the lvgl Dropdown Widget the selection of the list options is not working correctly.
Digging into it made me realize this only happens if invert-x or invert-y (propably with swap-xy as well) configuration is activated in zephyr,lvgl-pointer-input device:

lvgl_pointer {
     compatible = "zephyr,lvgl-pointer-input";
     input = <&cst816s>;
     invert-x;
     invert-y;
};

So i digged deeper:
In the input drivers input_cst816s.c processing function (cst816s_process()) a input is reported on release of the touch device in the else statement:

	if (pressed) {
		input_report_abs(dev, INPUT_ABS_X, col, false, K_FOREVER);
		input_report_abs(dev, INPUT_ABS_Y, row, false, K_FOREVER);
		input_report_key(dev, INPUT_BTN_TOUCH, 1, true, K_FOREVER);
	} else {
	        input_report_key(dev, INPUT_BTN_TOUCH, 0, true, K_FOREVER);
	}

Now in the lvgl_pointer_process_event() function in the lvgl_pointer_input.c file the coordinates of the input event get inverted:

	if (cfg->invert_x) {
		if (cap->current_orientation == DISPLAY_ORIENTATION_NORMAL ||
		    cap->current_orientation == DISPLAY_ORIENTATION_ROTATED_180) {
			point->x = cap->x_resolution - point->x;
		} else {
			point->x = cap->y_resolution - point->x;
		}
	}

	if (cfg->invert_y) {
		if (cap->current_orientation == DISPLAY_ORIENTATION_NORMAL ||
		    cap->current_orientation == DISPLAY_ORIENTATION_ROTATED_180) {
			point->y = cap->y_resolution - point->y;
		} else {
			point->y = cap->x_resolution - point->y;
		}
	}

Problem: Since this inversion also happens on the "RELEASE" event without new coordinates passed by the input device this results in a double inversion of the last coordinates: First when new coordinates are passed, second when "RELEASE" is passed.

Result: Since the Dropdown widget uses the double inverted coordinates from the "RELEASE" event, this unfortunately results in a malfunction of the widget. The list items can not be selected correctly.

For me it looks like a bug in the lvgl_pointer_process_event() function, which should not invert on "RELEASE" event, what do you guys think?

Cheers
Benjamin

[fabiobaltieri]

Yeah it's a bug in no prob that is , thanks for debugging it.

I'm thinking that the easiest way of handling this would be to refactor the point inversion and rotation into the switch statement, so that the data only gets processed when the raw point arrives. @faxe1008 what do you think?

[faxe1008]

Resolved via #70541