How can you dynamically add a new tab to a tab-panel in Red

Let's say you have a tab-panel like so :

editor: layout [
    below
    t: tab-panel 350x350 [
        "tab 1" [
            below
            b: button 75x25 "Interpret" on-click [do a/text ]
            a: area 320x250
        ]
    ]
]

view editor

How could I dynamically add a new tab to it so that has the contents of the current tab?

Solution

They are several ways to add a new tab dynamically, but in all cases, it boils down to adding:

A tab label as a string! to t/data block.
A corresponding panel face object! to t/pane block.

Here is a fully working example code:

tab1: [
    below
    button 75x25 "Interpret" on-click [do face/parent/pane/2/text ]
    area 320x250
]

editor: layout compose/deep/only [
    below
    button "add tab" [
        append t/data "tab 2"
        append t/pane make face! [type: 'panel pane: layout/only tab1]
    ]
    t: tab-panel 350x350 ["tab 1" (tab1)]
]
view editor

Some remarks:

tab1 definition has been externalized, so its definition can be reused for another tab content (as per your request).
a: word has been removed as it cannot be duplicated, access to the current area face in current tab panel is now done by walking up the face tree. b: definition has been dropped for same reason (and it's not used anyway).

Examples of dynamic behaviors and dynamic face construction (without VID dialect) are available here. tab-panel face type is described there.