Live Preview and SlintPad hide "Style" even when imported .slint file contains std-widgets

[tasuku-suzuki-signalslot]

Bug Description

In tools/lsp/preview.rs, the existence of the import from std-widgets.slint is checked only for the opened file itself. However, if the opened file imports another .slint file that, in turn, includes an import from std-widgets.slint, the style should also be changable accordingly.

Reproducible Code (if applicable)

// main.slint
import {Sub} from "sub.slint";

export component Demo inherits Sub {
}

// sub.slint
import { AboutSlint, Button, VerticalBox } from "std-widgets.slint";

export component Sub {
    VerticalBox {
        alignment: start;
        Text {
            text: "Hello World!";
            font-size: 24px;
            horizontal-alignment: center;
        }
        AboutSlint {
            preferred-height: 150px;
        }
        HorizontalLayout { alignment: center; Button { text: "OK!"; } }
    }
}

Environment Details

• Slint Version:
• Platform/OS:
• Programming Language:
• Backend/Renderer:

Product Impact

No response