Add criterium for enabling/disabling plugin

[pjankiewicz]

What problem does this solve or what need does it fill?

Adding criteria for plugins. I use a plugin for camera movement which I wanted to disable on egui widgets. The plugin consists of 2 systems.

app.add_system(camera_movement).add_system(camera_zoom);

What solution would you like?

I would like to use the plugin with ability to restrict it.

fn disable_on_egui_widget(mut egui_ctx: ResMut<EguiContext>) -> ShouldRun {
    if egui_ctx.ctx_mut().wants_pointer_input() || egui_ctx.ctx_mut().wants_keyboard_input() || egui_ctx.ctx_mut().is_pointer_over_area() {
        ShouldRun::No
    } else {
        ShouldRun::Yes
    }
}

app
    .add_plugin_with_criterium(PanCamPlugin, disable_on_egui_widget)

where criterium is some other system.

What alternative(s) have you considered?

The solution I found is I had to copy plugin code to my project and add these conditions in

fn camera_zoom(
    mut egui_ctx: ResMut<EguiContext>,
    mut query: Query<(&PanCam, &mut OrthographicProjection)>,
    mut scroll_events: EventReader<MouseWheel>,
) {
    // added condition to the system
    if egui_ctx.ctx_mut().wants_pointer_input() || egui_ctx.ctx_mut().wants_keyboard_input() || egui_ctx.ctx_mut().is_pointer_over_area() {
        return;
    }
}

Which is not ideal because I don't want to copy plugins into my project only to restrict when they run.

[alice-i-cecile]

Very much agree with this being a problem.

However, I'm going to close this as a duplicate of #2160 to keep the discussion centralized :)

[pjankiewicz]

@alice-i-cecile No problem. I will track the issue you mentioned.