On 14/07/2010, at 10:42 AM, ext Jason H wrote:
> But the ability to define and apply arbitrary property groups - be they be
> for
> themes or something else - has a good bit of support and application. Can we
> get
> the feature? Please?
>From my perspective, the main requirement is "make it easy for designers to
>change the visual aspects of a large QML project". The below approaches help
>to achieve that, and are available for use right now. For future releases (the
>feature set of 4.7 is essentially frozen), we should certainly look at how
>well this approach has served, and how we can better meet this goal. Something
>like PropertyGroups should be part of the research (we'll need to answer
>questions like how it fits in with states, or bindings (we often have things
>like color: focus ? "green" : "red"; how would that work?), what the
>performance implications are, and how much improvement it gives us for the
>costs). If you'd like to help, trying the techniques below in your project for
>a couple months, and providing feedback on what worked and what didn't as
>opposed to another system like CSS that you are familiar with, would be
>invaluable.
Current Approach 1
------------------
If you've got a single, unique set of properties to apply, Alan's first
suggestion of custom components works really well.
//BigText.qml
Text {
font.family: "Arial"
font.pointSize: 30
color: "red"
}
//everywhere else
BigText { test: "Hello" }
In my mind, this is essentially identical (at least in expressiveness) to:
Text {
text:"Hello"
properties: [bigText]
}
(i.e. when one PropertyGroup is applied.) One difference is that the BigText
approach would lead to a directory full of these small files, while the
PropertyGroup approach would lead to a file full of small snippets. In both
cases the potential navigation problems (lots of files or really large file)
should be solvable by good tooling.
Current Approach 2
------------------
Alan's second suggestion regarded a master theme file:
//the theme definition
QtObject {
id: bigText
property string family: "Arial"
property real pointSize: 30
property color color: "red"
}
QtObject {
id: anotherSetOfProperties
property color color: "purple"
}
//everywhere else
Text {
text: "Hello"
font.family: bigText.family
font.pointSize: bigText.fontSize
color: bigText.color
styleColor: anotherSetOfProperties.color
}
Like the PropertyGroup approach below, this allows applying global properties
that are defined in a single file.
Text {
text:"Hello"
properties: [bigText, anotherSetOfProperties]
}
Unlike the PropertyGroup approach, it is "fixed" what properties from what
groups apply. This has both pros (e.g. less possibility of unintended
side-effects) and cons (e.g. more work when adding a new property to a
"style"). It also requires more typing initially.
Hybrid Approach
---------------
You can also combine approach 1 and 2, e.g.
//BigText.qml
Text {
font.family: bigText.family
font.pointSize: bigText.fontSize
color: bigText.color
styleColor: anotherSetOfProperties.color
}
Regards,
Michael
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