I spent the evening moving three coloured rectangles around a blank window. This sounds less impressive than “working on the KDE 4 desktop,” which is precisely why it is a more accurate description.

The prototype is testing a Plasma idea: applets live in a containment, and the containment decides how available space is assigned. The applet should express useful size hints rather than assume that the panel is horizontal, 32 pixels high, and forever attached to the bottom edge.

My first attempt stored absolute geometry. Rotating the panel exposed the mistake immediately. The second stores constraints and lets the containment lay things out:

QSize Applet::minimumSize() const
{
    return QSize(24, 24);
}

QSize Applet::preferredSize() const
{
    return QSize(96, 32);
}

The prototype then reruns layout when its own size or form changes. Nothing here proves the final API. It proves that geometry policy has to live somewhere other than each applet’s collection of special cases.

Painting is the second experiment. Keeping content separate from the surrounding frame means a theme can alter margins and background without every applet learning the new decoration. That also means the layout must account for frame insets before assigning content space. I forgot this and produced a clock whose final digit lived just outside civilisation.

I prefer small visual prototypes with deliberately fake data at this stage. They make resizing, invalidation, and composition bugs obvious before a real calendar or device monitor introduces its own failures. The caveat is that rectangles do not exercise accessibility, input, localisation, or expensive content. A prototype can validate one mechanism while quietly avoiding four others.

I am saving each experiment as a tiny runnable case. When the graphics or layout API changes, these cases answer whether the concept still works without requiring a complete desktop session to survive long enough for the test.

There is no finished Plasma desktop hiding behind these rectangles. There are unresolved questions about applet lifecycle, configuration, persistence, and rendering. The useful result tonight is narrower: containment-driven layout survives changing orientation better than hard-coded applet geometry.

Tomorrow I may replace one rectangle with a clock. This will increase the prototype’s accuracy by one time zone and its bug count by an unknown but probably larger number.