tomo/object.go

package tomo

import "image"
import "image/color"
import "golang.org/x/image/font"
import "git.tebibyte.media/tomo/tomo/data"
import "git.tebibyte.media/tomo/tomo/event"
import "git.tebibyte.media/tomo/tomo/input"
import "git.tebibyte.media/tomo/tomo/canvas"

// Side represents one side of a rectangle.
type Side int; const (
	SideTop Side = iota
	SideRight
	SideBottom
	SideLeft
)

type Inset [4]int

// I allows you to create an inset in a CSS-ish way:
//
//   - One argument: all sides are set to this value
//   - Two arguments: the top and bottom sides are set to the first value, and
//     the left and right sides are set to the second value.
//   - Three arguments: the top side is set by the first value, the left and
//     right sides are set by the second vaue, and the bottom side is set by the
//     third value.
//   - Four arguments: each value corresponds to a side.
//
// This function will panic if an argument count that isn't one of these is
// given.
func I (sides ...int) Inset {
	switch len(sides) {
	case 1: return Inset { sides[0], sides[0], sides[0], sides[0] }
	case 2: return Inset { sides[0], sides[1], sides[0], sides[1] }
	case 3: return Inset { sides[0], sides[1], sides[2], sides[1] }
	case 4: return Inset { sides[0], sides[1], sides[2], sides[3] }
	default: panic("I: illegal argument count.")
	}
}

// Apply returns the given rectangle, shrunk on all four sides by the given
// inset. If a measurment of the inset is negative, that side will instead be
// expanded outward. If the rectangle's dimensions cannot be reduced any
// further, an empty rectangle near its center will be returned.
func (inset Inset) Apply (bigger image.Rectangle) (smaller image.Rectangle) {
	smaller = bigger
	if smaller.Dx() < inset[3] + inset[1] {
		smaller.Min.X = (smaller.Min.X + smaller.Max.X) / 2
		smaller.Max.X = smaller.Min.X
	} else {
		smaller.Min.X += inset[3]
		smaller.Max.X -= inset[1]
	}

	if smaller.Dy() < inset[0] + inset[2] {
		smaller.Min.Y = (smaller.Min.Y + smaller.Max.Y) / 2
		smaller.Max.Y = smaller.Min.Y
	} else {
		smaller.Min.Y += inset[0]
		smaller.Max.Y -= inset[2]
	}
	return
}

// Inverse returns a negated version of the inset.
func (inset Inset) Inverse () (prime Inset) {
	return Inset {
		inset[0] * -1,
		inset[1] * -1,
		inset[2] * -1,
		inset[3] * -1,
	}
}

// Horizontal returns the sum of SideRight and SideLeft.
func (inset Inset) Horizontal () int {
	return inset[SideRight] + inset[SideLeft]
}

// Vertical returns the sum of SideTop and SideBottom.
func (inset Inset) Vertical () int {
	return inset[SideTop] + inset[SideBottom]
}

type Border struct {
	Width Inset
	Color [4]color.Color
}

type Align int; const (
	AlignStart Align = iota // similar to left-aligned text
	AlignMiddle             // similar to center-aligned text
	AlignEnd                // similar to right-aligned text
	AlignEven               // similar to justified text
)

// Object is any obscreen object. Each object must be linked to a box, even if
// it is that box.
type Object interface {
	Box () Box
}

// Box is a basic styled box.
type Box interface {
	Object

	Window         () Window
	Bounds         () image.Rectangle
	InnerBounds    () image.Rectangle
	SetBounds      (image.Rectangle)
	SetColor       (color.Color)
	SetBorder      (...Border)
	SetMinimumSize (int, int)
	SetPadding     (Inset)

	SetDNDData   (data.Data)
	SetDNDAccept (...data.Mime)
	SetFocused   (bool)
	SetFocusable (bool)
	
	Focused       () bool
	Modifiers     () input.Modifiers
	MousePosition () image.Point

	OnFocusEnter  (func ()) event.Cookie
	OnFocusLeave  (func ()) event.Cookie
	OnDNDEnter    (func ()) event.Cookie
	OnDNDLeave    (func ()) event.Cookie
	OnDNDDrop     (func (data.Data)) event.Cookie
	OnMouseEnter  (func ()) event.Cookie
	OnMouseLeave  (func ()) event.Cookie
	OnMouseMove   (func ()) event.Cookie
	OnMouseDown   (func (input.Button)) event.Cookie
	OnMouseUp     (func (input.Button)) event.Cookie
	OnScroll      (func (deltaX, deltaY float64)) event.Cookie
	OnKeyDown     (func (key input.Key, numberPad bool)) event.Cookie
	OnKeyUp       (func (key input.Key, numberPad bool)) event.Cookie
}

// CanvasBox is a box that can be drawn to.
type CanvasBox interface {
	Box
	SetDrawer  (canvas.Drawer)
	Invalidate ()
}

// ContentBox is an abstract box that has some kind of content. Its only purpose
// is to be embedded into TextBox and ContainerBox.
type ContentBox interface {
	Box
	SetOverflow           (horizontal, vertical bool)
	ContentBounds         () image.Rectangle
	ScrollTo              (image.Point)
	OnContentBoundsChange (func ()) event.Cookie
}

// TextBox is a box that contains text content.
type TextBox interface {
	ContentBox
	SetTextColor (color.Color)
	SetFace      (font.Face)
	SetHAlign    (Align)
	SetVAlign    (Align)
}

// ContentBox is a box that can contain child objects. It arranges them
// according to a layout rule.
type ContainerBox interface {
	ContentBox
	SetGap    (image.Point)
	Add       (Object)
	Delete    (Object)
	Insert    (child Object, before Object)
	Clear     ()
	Length    () int
	At        (int) Object
	SetLayout (Layout)
}

// LayoutHints are passed to a layout to tell it how to arrange child boxes.
type LayoutHints struct {
	Bounds image.Rectangle
	OverflowX bool
	OverflowY bool
	Gap image.Point
}

// Layout can be given to a ContainerBox to arrange child objects.
type Layout interface {
	MinimumSize (LayoutHints, []Box) image.Point
	Arrange     (LayoutHints, []Box)
}

// Window is an operating system window. It can contain one object.
type Window interface {
	SetRoot  (Object)
	SetTitle (string)
	SetIcon  (sizes []image.Image)
	NewMenu  (image.Rectangle) (Window, error)
	NewModal (image.Rectangle) (Window, error)
	Widget   () (Window, error)
	Copy     (data.Data)
	Paste    (callback func (data.Data, error), accept ...data.Mime)
	Show     ()
	Hide     ()
	Close    ()
	OnClose  (func ()) event.Cookie
}

// MainWindow is a top-level operating system window.
type MainWindow interface {
	Window
	NewChild (image.Rectangle) (Window, error)
}