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tomo-old/elements/core/propagator.go

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package core
import "image"
import "git.tebibyte.media/sashakoshka/tomo/input"
import "git.tebibyte.media/sashakoshka/tomo/theme"
import "git.tebibyte.media/sashakoshka/tomo/config"
import "git.tebibyte.media/sashakoshka/tomo/elements"
// Parent represents an object that can provide access to a list of child
// elements.
type Parent interface {
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Child (index int) elements.Element
CountChildren () int
}
// Propagator is a struct that can be embedded into elements that contain one or
// more children in order to propagate events to them without having to write
// all of the event handlers. It also implements standard behavior for focus
// propagation and keyboard navigation.
type Propagator struct {
parent Parent
drags [10]elements.MouseTarget
focused bool
onFocusRequest func () (granted bool)
}
// NewPropagator creates a new event propagator that uses the specified parent
// to access a list of child elements that will have events propagated to them.
// If parent is nil, the function will return nil.
func NewPropagator (parent Parent) (propagator *Propagator) {
if parent == nil { return nil }
propagator = &Propagator {
parent: parent,
}
return
}
// ----------- Interface fulfillment methods ----------- //
// Focused returns whether or not this element or any of its children
// are currently focused.
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func (propagator *Propagator) Focused () (focused bool) {
return propagator.focused
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}
// Focus focuses this element, if its parent element grants the
// request.
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func (propagator *Propagator) Focus () {
if propagator.onFocusRequest != nil {
propagator.onFocusRequest()
}
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}
// HandleFocus causes this element to mark itself as focused. If the
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// element does not have children or there are no more focusable children in
// the given direction, it should return false and do nothing. Otherwise, it
// marks itself as focused along with any applicable children and returns
// true.
func (propagator *Propagator) HandleFocus (direction input.KeynavDirection) (accepted bool) {
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direction = direction.Canon()
firstFocused := propagator.firstFocused()
if firstFocused < 0 {
// no element is currently focused, so we need to focus either
// the first or last focusable element depending on the
// direction.
switch direction {
case input.KeynavDirectionForward:
// if we recieve a forward direction, focus the first
// focusable element.
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return propagator.focusFirstFocusableElement(direction)
case input.KeynavDirectionBackward:
// if we recieve a backward direction, focus the last
// focusable element.
return propagator.focusLastFocusableElement(direction)
case input.KeynavDirectionNeutral:
// if we recieve a neutral direction, just focus this
// element and nothing else.
propagator.focused = true
return true
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}
} else {
// an element is currently focused, so we need to move the
// focus in the specified direction
firstFocusedChild :=
propagator.parent.Child(firstFocused).
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(elements.Focusable)
// before we move the focus, the currently focused child
// may also be able to move its focus. if the child is able
// to do that, we will let it and not move ours.
if firstFocusedChild.HandleFocus(direction) {
return true
}
// find the previous/next focusable element relative to the
// currently focused element, if it exists.
for index := firstFocused + int(direction);
index < propagator.parent.CountChildren() && index >= 0;
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index += int(direction) {
child, focusable :=
propagator.parent.Child(index).
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(elements.Focusable)
if focusable && child.HandleFocus(direction) {
// we have found one, so we now actually move
// the focus.
firstFocusedChild.HandleUnfocus()
propagator.focused = true
return true
}
}
}
return false
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}
// HandleDeselection causes this element to mark itself and all of its children
// as unfocused.
func (propagator *Propagator) HandleUnfocus () {
propagator.forFocusable (func (child elements.Focusable) bool {
child.HandleUnfocus()
return true
})
propagator.focused = false
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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. If the parent element returns true, the
// element acts as if a HandleFocus call was made with KeynavDirectionNeutral.
func (propagator *Propagator) OnFocusRequest (callback func () (granted bool)) {
propagator.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.
func (propagator *Propagator) OnFocusMotionRequest (
callback func (direction input.KeynavDirection) (granted bool),
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) { }
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// HandleKeyDown propogates the keyboard event to the currently selected child.
func (propagator *Propagator) HandleKeyDown (key input.Key, modifiers input.Modifiers) {
propagator.forFocused (func (child elements.Focusable) bool {
typedChild, handlesKeyboard := child.(elements.KeyboardTarget)
if handlesKeyboard {
typedChild.HandleKeyDown(key, modifiers)
}
return true
})
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}
// HandleKeyUp propogates the keyboard event to the currently selected child.
func (propagator *Propagator) HandleKeyUp (key input.Key, modifiers input.Modifiers) {
propagator.forFocused (func (child elements.Focusable) bool {
typedChild, handlesKeyboard := child.(elements.KeyboardTarget)
if handlesKeyboard {
typedChild.HandleKeyUp(key, modifiers)
}
return true
})
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}
// HandleMouseDown propagates the mouse event to the element under the mouse
// pointer.
func (propagator *Propagator) HandleMouseDown (x, y int, button input.Button) {
child, handlesMouse :=
propagator.childAt(image.Pt(x, y)).
(elements.MouseTarget)
if handlesMouse {
propagator.drags[button] = child
child.HandleMouseDown(x, y, button)
}
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}
// HandleMouseUp propagates the mouse event to the element that the released
// mouse button was originally pressed on.
func (propagator *Propagator) HandleMouseUp (x, y int, button input.Button) {
child := propagator.drags[button]
if child != nil {
propagator.drags[button] = nil
child.HandleMouseUp(x, y, button)
}
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}
// HandleMouseMove propagates the mouse event to the element that was last
// pressed down by the mouse if the mouse is currently being held down, else it
// propagates the event to whichever element is underneath the mouse pointer.
func (propagator *Propagator) HandleMouseMove (x, y int) {
handled := false
for _, child := range propagator.drags {
if child != nil {
child.HandleMouseMove(x, y)
handled = true
}
}
if handled {
child, handlesMouse :=
propagator.childAt(image.Pt(x, y)).
(elements.MouseTarget)
if handlesMouse {
child.HandleMouseMove(x, y)
}
}
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}
// HandleScroll propagates the mouse event to the element under the mouse
// pointer.
func (propagator *Propagator) HandleMouseScroll (x, y int, deltaX, deltaY float64) {
child, handlesMouse :=
propagator.childAt(image.Pt(x, y)).
(elements.MouseTarget)
if handlesMouse {
child.HandleMouseScroll(x, y, deltaX, deltaY)
}
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}
// SetTheme sets the theme of all children to the specified theme.
func (propagator *Propagator) SetTheme (theme theme.Theme) {
propagator.forChildren (func (child elements.Element) bool {
typedChild, themeable := child.(elements.Themeable)
if themeable {
typedChild.SetTheme(theme)
}
return true
})
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}
// SetConfig sets the theme of all children to the specified config.
func (propagator *Propagator) SetConfig (config config.Config) {
propagator.forChildren (func (child elements.Element) bool {
typedChild, configurable := child.(elements.Configurable)
if configurable {
typedChild.SetConfig(config)
}
return true
})
}
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// ----------- Focusing utilities ----------- //
func (propagator *Propagator) focusFirstFocusableElement (
direction input.KeynavDirection,
) (
ok bool,
) {
propagator.forFocusable (func (child elements.Focusable) bool {
if child.HandleFocus(direction) {
propagator.focused = true
ok = true
return false
}
return true
})
return
}
func (propagator *Propagator) focusLastFocusableElement (
direction input.KeynavDirection,
) (
ok bool,
) {
propagator.forChildrenReverse (func (child elements.Element) bool {
typedChild, focusable := child.(elements.Focusable)
if focusable && typedChild.HandleFocus(direction) {
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propagator.focused = true
ok = true
return false
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}
return true
})
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return
}
// ----------- Iterator utilities ----------- //
func (propagator *Propagator) forChildren (callback func (child elements.Element) bool) {
for index := 0; index < propagator.parent.CountChildren(); index ++ {
child := propagator.parent.Child(index)
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if child == nil { continue }
if !callback(child) { break }
}
}
func (propagator *Propagator) forChildrenReverse (callback func (child elements.Element) bool) {
for index := propagator.parent.CountChildren() - 1; index > 0; index -- {
child := propagator.parent.Child(index)
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if child == nil { continue }
if !callback(child) { break }
}
}
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func (propagator *Propagator) childAt (position image.Point) (child elements.Element) {
propagator.forChildren (func (current elements.Element) bool {
if position.In(current.Bounds()) {
child = current
}
return true
})
return
}
func (propagator *Propagator) forFocused (callback func (child elements.Focusable) bool) {
propagator.forChildren (func (child elements.Element) bool {
typedChild, focusable := child.(elements.Focusable)
if focusable && typedChild.Focused() {
if !callback(typedChild) { return false }
}
return true
})
}
func (propagator *Propagator) forFocusable (callback func (child elements.Focusable) bool) {
propagator.forChildren (func (child elements.Element) bool {
typedChild, focusable := child.(elements.Focusable)
if focusable {
if !callback(typedChild) { return false }
}
return true
})
}
func (propagator *Propagator) forFlexible (callback func (child elements.Flexible) bool) {
propagator.forChildren (func (child elements.Element) bool {
typedChild, flexible := child.(elements.Flexible)
if flexible {
if !callback(typedChild) { return false }
}
return true
})
}
func (propagator *Propagator) firstFocused () int {
for index := 0; index < propagator.parent.CountChildren(); index ++ {
child, focusable := propagator.parent.Child(index).(elements.Focusable)
if focusable && child.Focused() {
return index
}
}
return -1
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}