Canvas

Canvas is a panel widget that allows you to explicitly set coordinates for children widgets. It is useful when you need to manually control position of children widgets (like potions on the image above). As any other panel widget, it does not have its own graphical representation, so the image above shows only its positioning capabilities. Root UI node is also canvas, so any widgets that are not attached to any other widgets can have explicit position.

How to create

Use CanvasBuilder to create Canvas instance:

#![allow(unused)]
fn main() {
extern crate fyrox;
use fyrox::{
    core::pool::Handle,
    gui::{canvas::CanvasBuilder, widget::WidgetBuilder, BuildContext, UiNode},
};

fn create_canvas(ctx: &mut BuildContext) -> Handle<UiNode> {
    CanvasBuilder::new(WidgetBuilder::new()).build(ctx)
}
}

Canvas does not have any specific options, so its creation is probably simplest of all widgets.

How to position children nodes

Use .with_desired_position on children widgets to set specific position:

#![allow(unused)]
fn main() {
extern crate fyrox;
use fyrox::{
    core::{algebra::Vector2, pool::Handle},
    gui::{
        button::ButtonBuilder, canvas::CanvasBuilder, text::TextBuilder, widget::WidgetBuilder,
        BuildContext, UiNode,
    },
};

fn create_canvas_with_children_widgets(ctx: &mut BuildContext) -> Handle<UiNode> {
    CanvasBuilder::new(
        WidgetBuilder::new()
            .with_child(
                TextBuilder::new(
                    WidgetBuilder::new().with_desired_position(Vector2::new(100.0, 200.0)),
                )
                .with_text("Simple Text at (100.0, 200.0)")
                .build(ctx),
            )
            .with_child(
                ButtonBuilder::new(
                    WidgetBuilder::new().with_desired_position(Vector2::new(200.0, 100.0)),
                )
                .with_text("Simple Button at (200.0, 100.0)")
                .build(ctx),
            ),
    )
    .build(ctx)
}
}

The code snippet will create a canvas with a text widget located at (100.0, 200.0) relative to top-left corner of the canvas and a button located at (200.0, 100.0).

Tips

Canvas provides infinite bounds for children widgets, this means that children nodes will not be stretched, instead they'll shrink to fit their content. For example, a button with a text will take slightly bigger rectangle than the text bounds.