Notes from "Async and representation"

[Marco Martin]

On Friday 17 January 2014, Eike Hein wrote:
> General comment: Please note that these size hints aren't only
> there so the shell can decide which representation to pick, but
> at times also do things like:
> 
> * Set useful default sizes (e.g. for popups from panels) *before*
>   appearance.
> * Affect interaction behavior (e.g. lock down resizing in one
>   axis but allow it in the other, by setting min/max accordingly).
> * Programmatically resize things while shown.
> 
> Consider the Homerun Kicker launcher menu:
> 
> http://i.imgur.com/eiq6D5w.png
> http://i.imgur.com/h9Y5jH2.png
> http://i.imgur.com/o3s3Bzk.png
> http://i.imgur.com/KG2R98u.png
> 
> Here's a collection of things it does with sizing:
> 
> * Not shown on the screenshot, but the compact representation
>   shown on the panel supports custom non-square images that it
>   scales while preserving aspect ratio, so it needs to hint
>   that to the panel layout.
> 
> * When the popup opens with the full representation inside,
>   it's default size is optimized for its content.
> 
> * It lets you adjust the height of the popup, but not the
>   width ... which actually feels really nice when resizing,
>   but is actually just a side-effect (more on this later).
> 
> * It programmatically resizes its popup depending on the
>   appearance of thos extra search result columns.
> 
> Let's please avoid getting side-tracked with discussion over
> whether those specific use cases are things that should be
> done; the more interesting point is that someone ended up
> doing them in the real world, and that the set of legitimate
> use cases is at least conceivably really that wide.
> 
> The other thing is that this was actually pretty hard to pull
> off in Plasma 1. There are some redundant APIs in the
> plasmoid API in Plasma 1 - some prop-based, some procedural -
> and not all of them actually work. There are syncing and
> ordering problems with applying the root props to the popup
> applet, which e.g. necessitated locking down the horizontal
> axis to also be able to do the programmatic resize. I also got
> the feeling that props on the root vs. props on the compact
> repr were getting confused depending on the order in which
> things were set ... but I don't remember the details, sorry,
> I should have kept more extensive notes.
> 
> I think the guiding principle for redesigning this stuff in
> Plasma 2 should be "explicit is better than implicit". Let's
> try to avoid doing magic props that mean this thing in this
> circumstance and this other thing in this other circumstance,
> it's better to be expressive and be able to specify the props
> for each circumstance and give applet authors control. There
> is always another pressure acting on them not to abuse the
> control: Users don't like crap UI that does dumb things, so
> policing these things hard often isn't necessary and ends up
> limiting use cases instead.


so, at the moment, in my branch things are something like that:
root object is called Applet, so it has "real" properties 
compactRepresentation/fullRepresentation

those two components support an attached property called SizeHint,
so you have something like:

Applet {

    compactRepresentation: Component {
        PlasmaComponents.Button {
            text: i18n("Click me")
            onClicked: plasmoid.expanded = !plasmoid.expanded
        }
    }

    fullRepresentation: Component {
        PlasmaComponents.Label {
            SizeHint.minimumHeight: 300
            SizeHint.minimumWidth: 200
            //PlasmaCore.SizeHint.minimumHeight: 300
            text: i18n("Hello world")
        }
    }
}

dimensions of the applet in the panel or the dimensions of the pospup should 
follow size hints

to correctly switch it would also need something like a 
switchHeight/switchWidth properties in Applet, since fullRepresentation may 
not exist

this should cover most of the things you wrote about
(like a compactRepresentation that has minimumWidth: height*ratio should work 
just fine)

another thing that will be necessary is a way to make applets providing a 
single representation, like the taskbar doesn't have a compact one

only thing i'm afraid of, it becomes cooomplex, code-wise and for new 
developers to understand

Cheers,
Marco Martin