forked from joejulian/gio
Elias Naur
103 lines
2.3 KiB
Go
103 lines
2.3 KiB
Go
// SPDX-License-Identifier: Unlicense OR MIT
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package layout
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import (
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"image"
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"time"
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"gioui.org/io/event"
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"gioui.org/io/system"
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"gioui.org/op"
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"gioui.org/unit"
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)
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// Context carries the state needed by almost all layouts and widgets.
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// A zero value Context never returns events, map units to pixels
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// with a scale of 1.0, and returns the zero time from Now.
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type Context struct {
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// Constraints track the constraints for the active widget or
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// layout.
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Constraints Constraints
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Metric unit.Metric
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// By convention, a nil Queue is a signal to widgets to draw themselves
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// in a disabled state.
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Queue event.Queue
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// Now is the animation time.
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Now time.Time
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// Locale provides information on the system's language preferences.
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// BUG(whereswaldon): this field is not currently populated automatically.
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// Interested users must look up and populate these values manually.
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Locale system.Locale
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*op.Ops
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}
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// NewContext is a shorthand for
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//
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// Context{
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// Ops: ops,
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// Now: e.Now,
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// Queue: e.Queue,
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// Config: e.Config,
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// Constraints: Exact(e.Size),
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// }
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//
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// NewContext calls ops.Reset and adjusts ops for e.Insets.
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func NewContext(ops *op.Ops, e system.FrameEvent) Context {
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ops.Reset()
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size := e.Size
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if e.Insets != (system.Insets{}) {
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left := e.Metric.Dp(e.Insets.Left)
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top := e.Metric.Dp(e.Insets.Top)
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op.Offset(image.Point{
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X: left,
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Y: top,
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}).Add(ops)
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size.X -= left + e.Metric.Dp(e.Insets.Right)
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size.Y -= top + e.Metric.Dp(e.Insets.Bottom)
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}
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return Context{
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Ops: ops,
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Now: e.Now,
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Queue: e.Queue,
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Metric: e.Metric,
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Constraints: Exact(size),
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}
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}
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// Dp converts v to pixels.
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func (c Context) Dp(v unit.Dp) int {
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return c.Metric.Dp(v)
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}
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// Sp converts v to pixels.
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func (c Context) Sp(v unit.Sp) int {
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return c.Metric.Sp(v)
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}
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// Events returns the events available for the key. If no
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// queue is configured, Events returns nil.
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func (c Context) Events(k event.Tag) []event.Event {
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if c.Queue == nil {
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return nil
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}
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return c.Queue.Events(k)
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}
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// Disabled returns a copy of this context with a nil Queue,
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// blocking events to widgets using it.
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//
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// By convention, a nil Queue is a signal to widgets to draw themselves
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// in a disabled state.
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func (c Context) Disabled() Context {
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c.Queue = nil
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return c
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}
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