Tutorial Scheduler Updating Widgets

Updating individual widgets

If you change a widget state through code, that widget is not updated automatically. Usually you want to call the 'update' method from the widget state; for example if we're in a callback:

use ez_term::*;
fn my_callback(context: Context) {

    let label_state = context.state_tree.get_mut("my_label").to_label_mut();
    label_state.set_text("new_text".to_string());

    // After changing the state we call the update method to call for a redraw
    label_state.update(context.scheduler);

}

The update method is in fact a convenience that calls "scheduler.update_widget". This scheduler method takes a full path parameter (IDs cannot be used here). It is therefore almost always more convenient to call 'update' on the widget state.

Global update (force redraw)

It is also possible to call a global screen update. In this case, all widgets, starting from the root layout, will be redrawn. For performance reasons, only changed pixels will actually be redrawn, but global updates will still be more costly than updating individual states. The option is made available but should generally not be used; try updating individual states rather than using this. If for whatever reason you do actually need to refresh the entire screen, this is how to do it:

use ez_term::*;
fn my_callback(context: Context) {

    let label_state = context.state_tree.get_mut("my_label").to_label_mut();
    label_state.set_text("new_text".to_string());

    scheduler.force_redraw();

}

Bound properties

If you bind a widget property to a (custom) property, and you change the value of the (custom) property, the widgets bound to it will update automatically. This is the only case in which you never have to call an update method. For example, if you bind the height of widget_2 to the height of widget_1, and the height of widget_1 changes, then widget_2 will be updated automatically.

Continue

The general tutorial continues with: Managing Selection.