Event bubbling seems not to be possible - but it would solve a lot of things?

[sandreas]

Hello,

I have a very specific use case, where specific user touch display interaction (touch, scroll, click, navigate, etc.) should trigger a "sleep timer reset". Now I have a whole UI and it could possibly worked into every single handler in there, but this would also bring a lot of added complexity.

Another use case I have is a GestureHandler that should work as a Navigation action (e.g. swipe to go back to the last view), but still be able to use Sliders, which is kind of impossible depending on the size of the TouchArea overlapping the slider and not being able to control the events inplace.

So I would like to ask, if it would be a good idea to implement event handling similar to the Browsers approach (JavaScript):

• A capturing phase going from Top (MainWindow) to Bottom (Slider)
• Target phase - Event reaches the Target (Slider)
• A bubbling phase going from Bottom (Slider) to Top (MainWindow) and can be intercepted by e.stopPropagation() and e.preventDefault()

Here is a pretty good overview of how this works in the Browser:
https://www.freecodecamp.org/news/event-bubbling-and-event-capturing-in-javascript/

You can also interact with the handlers using the capture phase explicitly, e.g. if you'd like to check if a section is disabled before passing events to it:

document.body.addEventListener('click', (e) => {
    if (e.target.closest('.disabled')) {
        e.stopPropagation();
        return false;
    }
}, true); // Capture - runs FIRST

This way you could solve the slider problem (by forcing stopPropagation() on the element as well as the global handler problem (by leaving the bubbling intact).

I don't know of any other way to solve my use case with Slint otherwise without a drastically higher effort of manual implementation instead of using a global TouchArea.pointer-event handler.

Here are some related discussions (some without solution) that I collected on my way:

• Receive all input events #2182
• Temporarily blocking all input / window events #10781
• Mouse event bubbling functionality? #4563
• Nested `TouchArea`: catch the same event at different levels. #3255

Is there a way to intercept all input events in rust code?

What do you think?

[sandreas]

In the meantime I solved my personal use case by hooking into /dev/input/event1 (the touchscreen) via evdev crate and reseting the timer on every event occurring - but I'd rather solve this in slint directly, which would be portable, way more elegant and also less resource hungry.