Q:

Red Reactive : cannot get true value for face data

From Red-lang book example about reactive programming, I added test button, weirdly I can get true data value for slider but not for progress bar: for this latter it's always the initial value (20%). How to get the actual value for this latter ?
        view [
            origin 0x0 space 0x0
            tab-panel 500x100 [
        "Tab 1 " [
                    p: progress 100x20 data 20% react [face/data: s/data]
                    s: slider 100x20 data 20%

                    button "test" [
                        vs: s/data
                        vp: p/data
                        ?? vs
                        ?? vp
                    ]
                ]
        "Tab 2 " [
                    p: progress 100x20 20%
                    slider 100x20 data 20% [p/data: face/data]
                ]

            ]
        ]

A:

You set p twice and the last one is valid.
Therefore your p points to your second progress bar in Tab 2 and vp is always 20% as long as you move only the slider in Tab 1. So either move the slider in Tab 2 before hitting the button or better name the progress bar in Tab 2 with a different word.
e.g
        "Tab 2 " [
                p2: progress 100x20 20%
                slider 100x20 data 20% [p2/data: face/data]
         ]

