Almost every layout and widget need the ui.Config for its environment,
an ui.Ops to store operations. Stateful widgets need an input.Queue
for events.
Add all these common objects to Context, greatly simplifying the
function signatures for Gio programs.
Fixes gio#33
Signed-off-by: Elias Naur <mail@eliasnaur.com>
Context keeps the current Constraints and Dimensions so the layout
function scopes don't have to.
With
ctx := new(layout.Context)
a label with margins and alignment goes from
return al.Layout(ops, cs, func(cs layout.Constraints) layout.Dimensions {
in := layout.Inset{...}
return in.Layout(c, ops, cs, func(cs layout.Constraints) layout.Dimensions {
return text.Label{...}.Layout(ops, cs)
})
})
to
al.Layout(ops, ctx, func() {
in := layout.Inset{...}
in.Layout(c, ops, ctx, func() {
text.Label{...}.Layout(ops, ctx)
})
})
It was a difficult trade-off between the verbose functional approach
and the shorter but more complex Context.
Signed-off-by: Elias Naur <mail@eliasnaur.com>
Before this change, layout objects followed a pattern where a
begin method would set up the layout and return a tweaked set
of constraints, and a end method would take the widget dimensions
and return the tweaked dimensions.
As has been pointed out, this process is error prone, because the
scope of the layout objects are not clear and because it is easy
to swap two begins or two ends.
It turns out that it is possible to implement layout with function
scopes in garbage free way. A typical layout changes from
al := layout.Align{Alignment: layout.NE}
cs = al.Begin(ops, cs)
in := layout.Inset{Top: ui.Dp(16)}
cs = in.Begin(c, ops, cs)
txt := fmt.Sprintf("m: %d %s", mallocs, u.profile.Timings)
dims := text.Label{Material: theme.text, Face: u.face(fonts.mono, 10), Text: txt}.Layout(ops, cs)
dims = in.End(dims)
return al.End(dims)
to
al := layout.Align{Alignment: layout.NE}
return al.Layout(ops, cs, func(cs layout.Constraints) layout.Dimensions {
in := layout.Inset{Top: ui.Dp(16)}
return in.Layout(c, ops, cs, func(cs layout.Constraints) layout.Dimensions {
txt := fmt.Sprintf("m: %d %s", mallocs, u.profile.Timings)
return text.Label{Material: theme.text, Face: u.face(fonts.mono, 10), Text: txt}.Layout(ops, cs)
})
})
Signed-off-by: Elias Naur <mail@eliasnaur.com>
Elias Naur