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tomo-old/element.go

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package tomo
import "image"
import "git.tebibyte.media/sashakoshka/tomo/input"
import "git.tebibyte.media/sashakoshka/tomo/canvas"
// Element represents a basic on-screen object.
type Element interface {
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// Bounds reports the element's bounding box. This must reflect the
// bounding last given to the element by DrawTo.
Bounds () image.Rectangle
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// MinimumSize specifies the minimum amount of pixels this element's
// width and height may be set to. If the element is given a resize
// event with dimensions smaller than this, it will use its minimum
// instead of the offending dimension(s).
MinimumSize () (width, height int)
// SetParent sets the parent container of the element. This should only
// be called by the parent when the element is adopted. If parent is set
// to nil, it will mark itself as not having a parent. If this method is
// passed a non-nil value and the element already has a parent, it will
// panic.
SetParent (Parent)
// DrawTo gives the element a canvas to draw on, along with a bounding
// box to be used for laying out the element. This should only be called
// by the parent element. This is typically a region of the parent
// element's canvas.
DrawTo (canvas canvas.Canvas, bounds image.Rectangle, onDamage func (region image.Rectangle))
}
// Focusable represents an element that has keyboard navigation support. This
// includes inputs, buttons, sliders, etc. as well as any elements that have
// children (so keyboard navigation events can be propagated downward).
type Focusable interface {
Element
// Focused returns whether or not this element or any of its children
// are currently focused.
Focused () bool
// Focus focuses this element, if its parent element grants the
// request.
Focus ()
// HandleFocus causes this element to mark itself as focused. If the
// element does not have children, it is disabled, or there are no more
// selectable children in the given direction, it should return false
// and do nothing. Otherwise, it should select itself and any children
// (if applicable) and return true.
HandleFocus (direction input.KeynavDirection) (accepted bool)
// HandleDeselection causes this element to mark itself and all of its
// children as unfocused.
HandleUnfocus ()
}
// KeyboardTarget represents an element that can receive keyboard input.
type KeyboardTarget interface {
Element
// HandleKeyDown is called when a key is pressed down or repeated while
// this element has keyboard focus. It is important to note that not
// every key down event is guaranteed to be paired with exactly one key
// up event. This is the reason a list of modifier keys held down at the
// time of the key press is given.
HandleKeyDown (key input.Key, modifiers input.Modifiers)
// HandleKeyUp is called when a key is released while this element has
// keyboard focus.
HandleKeyUp (key input.Key, modifiers input.Modifiers)
}
// MouseTarget represents an element that can receive mouse events.
type MouseTarget interface {
Element
// HandleMouseDown is called when a mouse button is pressed down on this
// element.
HandleMouseDown (x, y int, button input.Button)
// HandleMouseUp is called when a mouse button is released that was
// originally pressed down on this element.
HandleMouseUp (x, y int, button input.Button)
}
// MotionTarget represents an element that can receive mouse motion events.
type MotionTarget interface {
Element
// HandleMotion is called when the mouse is moved over this element,
// or the mouse is moving while being held down and originally pressed
// down on this element.
HandleMotion (x, y int)
}
// ScrollTarget represents an element that can receive mouse scroll events.
type ScrollTarget interface {
Element
// HandleScroll is called when the mouse is scrolled. The X and Y
// direction of the scroll event are passed as deltaX and deltaY.
HandleScroll (x, y int, deltaX, deltaY float64)
}
// Flexible represents an element who's preferred minimum height can change in
// response to its width.
type Flexible interface {
Element
// FlexibleHeightFor returns what the element's minimum height would be
// if resized to a specified width. This does not actually alter the
// state of the element in any way, but it may perform significant work,
// so it should be called sparingly.
//
// It is reccomended that parent containers check for this interface and
// take this method's value into account in order to support things like
// flow layouts and text wrapping, but it is not absolutely necessary.
// The element's MinimumSize method will still return the absolute
// minimum size that the element may be resized to.
//
// It is important to note that if a parent container checks for
// flexible chilren, it itself will likely need to be flexible.
FlexibleHeightFor (width int) int
}
// Scrollable represents an element that can be scrolled. It acts as a viewport
// through which its contents can be observed.
type Scrollable interface {
Element
// ScrollContentBounds returns the full content size of the element.
ScrollContentBounds () image.Rectangle
// ScrollViewportBounds returns the size and position of the element's
// viewport relative to ScrollBounds.
ScrollViewportBounds () image.Rectangle
// ScrollTo scrolls the viewport to the specified point relative to
// ScrollBounds.
ScrollTo (position image.Point)
// ScrollAxes returns the supported axes for scrolling.
ScrollAxes () (horizontal, vertical bool)
}
// Collapsible represents an element who's minimum width and height can be
// manually resized. Scrollable elements should implement this if possible.
type Collapsible interface {
Element
// Collapse collapses the element's minimum width and height. A value of
// zero for either means that the element's normal value is used.
Collapse (width, height int)
}
// Themeable represents an element that can modify its appearance to fit within
// a theme.
type Themeable interface {
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Element
// SetTheme sets the element's theme to something fulfilling the
// theme.Theme interface.
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SetTheme (Theme)
}
// Configurable represents an element that can modify its behavior to fit within
// a set of configuration parameters.
type Configurable interface {
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Element
// SetConfig sets the element's configuration to something fulfilling
// the config.Config interface.
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SetConfig (Config)
}