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// SPDX-License-Identifier: Unlicense OR MIT
package layout
import (
"time"
"gioui.org/io/event"
"gioui.org/io/system"
"gioui.org/op"
"gioui.org/unit"
)
// Context carries the state needed by almost all layouts and widgets.
// A zero value Context never returns events, map units to pixels
// with a scale of 1.0, and returns the zero time from Now.
type Context struct {
// Constraints track the constraints for the active widget or
// layout.
Constraints Constraints
Metric unit.Metric
// By convention, a nil Queue is a signal to widgets to draw themselves
// in a disabled state.
Queue event.Queue
// Now is the animation time.
Now time.Time
*op.Ops
}
// NewContext is a shorthand for
//
// Context{
// Ops: ops,
// Now: e.Now,
// Queue: e.Queue,
// Config: e.Config,
// Constraints: Exact(e.Size),
// }
//
// NewContext calls ops.Reset.
func NewContext(ops *op.Ops, e system.FrameEvent) Context {
ops.Reset()
return Context{
Ops: ops,
Now: e.Now,
Queue: e.Queue,
Metric: e.Metric,
Constraints: Exact(e.Size),
}
}
// Px maps the value to pixels.
func (c Context) Px(v unit.Value) int {
return c.Metric.Px(v)
}
// Events returns the events available for the key. If no
// queue is configured, Events returns nil.
func (c Context) Events(k event.Tag) []event.Event {
if c.Queue == nil {
return nil
}
return c.Queue.Events(k)
}
// Disabled returns a copy of this context with a nil Queue,
// blocking events to widgets using it.
//
// By convention, a nil Queue is a signal to widgets to draw themselves
// in a disabled state.
func (c Context) Disabled() Context {
c.Queue = nil
return c
}
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