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tomo-old/elements/core/selectable.go

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package core
import "git.tebibyte.media/sashakoshka/tomo"
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// FocusableCore is a struct that can be embedded into objects to make them
// focusable, giving them the default keynav behavior.
type FocusableCore struct {
focused bool
enabled bool
drawFocusChange func ()
onFocusRequest func () (granted bool)
onFocusMotionRequest func(tomo.KeynavDirection) (granted bool)
}
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// NewFocusableCore creates a new focusability core and its corresponding
// control. If your element needs to visually update itself when it's focus
// state changes (which it should), a callback to draw and push the update can
// be specified.
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func NewFocusableCore (
drawFocusChange func (),
) (
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core *FocusableCore,
control FocusableCoreControl,
) {
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core = &FocusableCore {
drawFocusChange: drawFocusChange,
enabled: true,
}
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control = FocusableCoreControl { core: core }
return
}
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// Focused returns whether or not this element is currently focused.
func (core *FocusableCore) Focused () (focused bool) {
return core.focused
}
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// Focus focuses this element, if its parent element grants the request.
func (core *FocusableCore) Focus () {
if !core.enabled { return }
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if core.onFocusRequest != nil {
core.onFocusRequest()
}
}
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// HandleFocus causes this element to mark itself as focused, if it can
// currently be. Otherwise, it will return false and do nothing.
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func (core *FocusableCore) HandleFocus (
direction tomo.KeynavDirection,
) (
accepted bool,
) {
direction = direction.Canon()
if !core.enabled { return false }
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if core.focused && direction != tomo.KeynavDirectionNeutral {
return false
}
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core.focused = true
if core.drawFocusChange != nil { core.drawFocusChange() }
return true
}
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// HandleUnfocus causes this element to mark itself as unfocused.
func (core *FocusableCore) HandleUnfocus () {
core.focused = false
if core.drawFocusChange != nil { core.drawFocusChange() }
}
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// OnFocusRequest sets a function to be called when this element
// wants its parent element to focus it. Parent elements should return
// true if the request was granted, and false if it was not.
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func (core *FocusableCore) OnFocusRequest (callback func () (granted bool)) {
core.onFocusRequest = callback
}
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// OnFocusMotionRequest sets a function to be called when this
// element wants its parent element to focus the element behind or in
// front of it, depending on the specified direction. Parent elements
// should return true if the request was granted, and false if it was
// not.
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func (core *FocusableCore) OnFocusMotionRequest (
callback func (direction tomo.KeynavDirection) (granted bool),
) {
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core.onFocusMotionRequest = callback
}
// Enabled returns whether or not the element is enabled.
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func (core *FocusableCore) Enabled () (enabled bool) {
return core.enabled
}
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// FocusableCoreControl is a struct that can be used to exert control over a
// focusability core. It must not be directly embedded into an element, but
// instead kept as a private member. When a FocusableCore struct is created, a
// corresponding FocusableCoreControl struct is linked to it and returned
// alongside it.
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type FocusableCoreControl struct {
core *FocusableCore
}
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// SetEnabled sets whether the focusability core is enabled. If the state
// changes, this will call drawFocusChange.
func (control FocusableCoreControl) SetEnabled (enabled bool) {
if control.core.enabled == enabled { return }
control.core.enabled = enabled
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if !enabled { control.core.focused = false }
if control.core.drawFocusChange != nil {
control.core.drawFocusChange()
}
}