> On 30 Oct 2015, at 18:00, Jérôme Godbout <jer...@bodycad.com> wrote:
>
> Hi,
>
> is their a way to adjust the width of a flow item to limit it to a maximum
> width of parent width but if content is smaller use the childrenRect.width
> without binding loop or running into problem with the binding on the first
> children set that the width is set and the flow go into column instead of row.
Flow is frustrating to use, I agree. A class of bugs in QtQuick.Dialogs come
from the fact that I used Flow for the row of buttons at the bottom, and it is
not helping me to figure out how much space the buttons really need, and I
couldn’t come up with 100% perfect workarounds in QML either.
I just did another experiment… it seems that if you at first set the Flow’s
width to parent.width, its implicitWidth will then be the necessary width to
contain the children, which will be less than the Flow’s width if they don’t
fill up the space. It’s not useful to bind to implicitWidth (because it will
lay out the children in a tall skinny column, as you said), but you can set its
width to the maximum available at first, and then set width to implicitWidth,
for example in Component.onCompleted (which is terribly ugly and not
declarative). Then it will be more hassle to do that again when the parent is
resized.
Even if you set the height, implicitWidth will not change. That seems like a
bug to me… the whole concept of flow comes from the fact that we read words
left to right first and top to bottom second (at least in western languages),
so this habit makes it feel natural to lay out buttons and such in the same
way. So why should Flow prefer to maximize height and minimize width, if
neither of them have been forced? Well, maybe you’d like to know the minimum
possible width… so implicitWidth can give you that. But what if height has
been forced? It has to be a bug that implicitWidth doesn’t change in that
case, right? What if we fix it? I wonder if any existing applications would
break. But approvers usually assume that changing behavior will break
something, so it’s hard to get such patches integrated.
If the Flow has not yet been given a width or height, its implicit width and
implicit height must depend on each other. It’s an arbitrary decision, whether
implicitWidth should be the sum of the widths of the children plus the
spacings, so that implicitHeight can be minimized, or whether it should be like
it is… because it has no hint yet of the space into which it needs to fit. It
has no maximumWidth or maximumHeight properties. Maybe we should add such
properties. Or maybe we should write a FlowLayout in QtQuick.Layouts with a
more advanced feature set, consistent with the other layouts in that package.
But that’s more work, of course. ;-)
How do you want it fixed?
import QtQuick 2.0
Rectangle {
width: 120
height: 120
Flow {
id: flow
spacing: 6
// width: Math.min(implicitWidth, parent.width - 12) // implicitWidth is
minimized to max of the children's width
width: parent.width - 12
x: 6
y: 6
Text { text: "list" }
Text { text: "of" }
Text { text: "too" }
Text { text: "many" }
Text { text: "words" }
Text { text: "to" }
Text { text: "fit" }
Text { text: "here" }
}
Rectangle {
color: "transparent"
border.color: "green"
anchors.top: flow.top
anchors.left: flow.left
width: flow.implicitWidth
height: flow.height
}
Component.onCompleted: flow.width = flow.implicitWidth
}
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