Issue with 100% height sizing within TabSet (Firefox, not all skins)

[Crack]

Hello,

I have a modal Window with a tabbed form, with one page containing an element that is set up to take up as much vertical space as possible. This causes TabSet to change its height depending on active tab, causing the window to jump up and down.

This happens in Firefox on Windows (tested on 138.0.1), and works correctly in Chrome.
Affected themes: Graphite, Enterprise, Enterprise Blue, Black Ops, Tree Fog (others work correctly).

Simplified test case:

isc.defineClass("DynamicHeightItem", "CanvasItem").addProperties({
  height: "100%", // *
  createCanvas() {
    return isc.Canvas.create({contents: "custom editor", backgroundColor: "lightblue"});
  },
});

isc.TabSet.create({
  backgroundColor: "gray",
  width: "100%",
  overflow: "visible",
  minHeight: 160,
  paneContainerOverflow: "visible", // *
  tabs: [{
    title: "Tab 1",
    pane: isc.DynamicForm.create({
      height: "100%",
      fields: [
        {name: "f1", showTitle: false, colSpan: 2, type: "DynamicHeightItem"},
      ]
    })
  }, {
    title: "Tab 2",
    pane: isc.Canvas.create({contents: "tab 2"})
  }]
})

Note the 1px difference in tab height. Is this an issue with my code, or a framework bug?

Tested on:

• v13.1p_2025-05-14/AllModules Development Only (https://smartclient.com/smartclient-...sizeIncrease=2)
• v14.1p_2025-05-14/AllModules Development Only (https://smartclient.com/smartclient-...sizeIncrease=2)