112 lines
3.6 KiB
Go
112 lines
3.6 KiB
Go
package core
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import "git.tebibyte.media/sashakoshka/tomo"
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// SelectableCore is a struct that can be embedded into objects to make them
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// selectable, giving them the default selectability behavior.
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type SelectableCore struct {
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selected bool
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enabled bool
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drawSelectionChange func ()
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onSelectionRequest func () (granted bool)
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onSelectionMotionRequest func(tomo.SelectionDirection) (granted bool)
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}
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// NewSelectableCore creates a new selectability core and its corresponding
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// control. If your element needs to visually update itself when it's selection
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// state changes (which it should), a callback to draw and push the update can
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// be specified.
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func NewSelectableCore (
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drawSelectionChange func (),
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) (
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core *SelectableCore,
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control SelectableCoreControl,
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) {
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core = &SelectableCore {
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drawSelectionChange: drawSelectionChange,
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enabled: true,
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}
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control = SelectableCoreControl { core: core }
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return
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}
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// Selected returns whether or not this element is currently selected.
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func (core *SelectableCore) Selected () (selected bool) {
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return core.selected
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}
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// Select selects this element, if its parent element grants the request.
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func (core *SelectableCore) Select () {
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if !core.enabled { return }
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if core.onSelectionRequest != nil {
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core.onSelectionRequest()
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}
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}
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// HandleSelection causes this element to mark itself as selected, if it can
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// currently be. Otherwise, it will return false and do nothing.
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func (core *SelectableCore) HandleSelection (
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direction tomo.SelectionDirection,
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) (
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accepted bool,
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) {
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direction = direction.Canon()
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if !core.enabled { return false }
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if core.selected && direction != tomo.SelectionDirectionNeutral {
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return false
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}
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core.selected = true
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if core.drawSelectionChange != nil { core.drawSelectionChange() }
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return true
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}
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// HandleDeselection causes this element to mark itself as deselected.
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func (core *SelectableCore) HandleDeselection () {
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core.selected = false
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if core.drawSelectionChange != nil { core.drawSelectionChange() }
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}
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// OnSelectionRequest sets a function to be called when this element
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// wants its parent element to select it. Parent elements should return
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// true if the request was granted, and false if it was not.
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func (core *SelectableCore) OnSelectionRequest (callback func () (granted bool)) {
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core.onSelectionRequest = callback
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}
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// OnSelectionMotionRequest sets a function to be called when this
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// element wants its parent element to select the element behind or in
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// front of it, depending on the specified direction. Parent elements
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// should return true if the request was granted, and false if it was
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// not.
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func (core *SelectableCore) OnSelectionMotionRequest (
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callback func (direction tomo.SelectionDirection) (granted bool),
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) {
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core.onSelectionMotionRequest = callback
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}
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// Enabled returns whether or not the element is enabled.
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func (core *SelectableCore) Enabled () (enabled bool) {
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return core.enabled
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}
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// SelectableCoreControl is a struct that can be used to exert control over a
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// selectability core. It must not be directly embedded into an element, but
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// instead kept as a private member. When a SelectableCore struct is created, a
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// corresponding SelectableCoreControl struct is linked to it and returned
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// alongside it.
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type SelectableCoreControl struct {
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core *SelectableCore
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}
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// SetEnabled sets whether the selectability core is enabled. If the state
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// changes, this will call drawSelectionChange.
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func (control SelectableCoreControl) SetEnabled (enabled bool) {
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if control.core.enabled == enabled { return }
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control.core.enabled = enabled
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if !enabled { control.core.selected = false }
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if control.core.drawSelectionChange != nil {
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control.core.drawSelectionChange()
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}
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}
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