stone/buffer.go

package stone

import "sync"

// Color represents all the different colors a cell can be.
type Color uint8

const (
	ColorBackground  Color = 0x0
	ColorForeground  Color = 0x1
	ColorDim         Color = 0x2
	ColorRed         Color = 0x3
	ColorYellow      Color = 0x4
	ColorGreen       Color = 0x5
	ColorBlue        Color = 0x6
	ColorPurple      Color = 0x7
)

// Style contains styling information about cells. These properties can be or'd
// together to combine them.
type Style uint8

const (
	StyleNormal     Style = iota
	StyleBold       Style = iota >> 1
	StyleItalic
	StyleUnderline
	StyleHighlight
	StyleBoldItalic Style = StyleBold | StyleItalic
)

// Cell is a grid-aligned rune in a buffer with associated styling and color
// informaiton.
type Cell struct {
	color   Color
	style   Style
	content rune
}

// Color returns the cell's color.
func (cell Cell) Color () (color Color) {
	color = cell.color
	return
}

// Style returns the styling information associated with the cell
func (cell Cell) Style (style Style) {
	style = cell.style
	return
}

// Rune returns the rune in the cell
func (cell Cell) Rune () (content rune) {
	content = cell.content
	return
}

// Buffer represents a two dimensional text buffer.
type Buffer interface {
	Size     () (with, height int)
	Cell     (x, y int) (cell Cell)
	SetColor (x, y int, color Color)
	SetSize  (with, height int)
	SetStyle (x, y int, style Style)
	SetRune  (x, y int, content rune)
	Clear    ()
}

// DamageBuffer is a two dimensional text buffer that stores a grid of cells, as
// well as information stating whether each cell is clean or dirty. Cells are
// dirty by default, are only clean when marked as clean, and become dirty again
// when they are altered in some way.
type DamageBuffer struct {
	content  []Cell
	onScreen []Cell
	
	width  int
	height int
	dot struct {
		x int
		y int
	}

	// This should be write locked when resizing the buffer, and read locked
	// when writing to cells or reading information about the buffer.
	lock sync.RWMutex
}

func (buffer *DamageBuffer) isOutOfBounds (x, y int) (outOfBounds bool) {
	outOfBounds =
		x < 0 ||
		y < 0 ||
		x >= buffer.width ||
		y >= buffer.height
	return
}

// Size returns the width and height of the buffer.
func (buffer *DamageBuffer) Size () (width, height int) {
	buffer.lock.RLock()
	defer buffer.lock.RUnlock()
	
	width  = buffer.width
	height = buffer.height
	return
}

// SetDot sets the buffer's text insertion position relative to the buffer
// origin point (0, 0).
func (buffer *DamageBuffer) SetDot (x, y int) {
	buffer.dot.x = x
	buffer.dot.y = y
}

// Cell returns the cell at the specified x and y coordinates. If the
// coordinates are out of bounds, this method will return a blank cell.
func (buffer *DamageBuffer) Cell (x, y int) (cell Cell) {
	buffer.lock.RLock()
	defer buffer.lock.RUnlock()
	
	if buffer.isOutOfBounds(x, y) { return }
	cell = buffer.content[x + y * buffer.width]
	return
}

// SetColor sets the color of the cell at the specified x and y coordinates.
func (buffer *DamageBuffer) SetColor (x, y int, color Color) {
	buffer.lock.RLock()
	defer buffer.lock.RUnlock()
	
	if buffer.isOutOfBounds(x, y) { return }
	buffer.content[x + y * buffer.width].color = color
}

// SetSize sets the width and height of the buffer. This clears all data in the
// buffer. If the width or height is negative, this method does nothing.
func (buffer *DamageBuffer) SetSize (width, height int) {
	buffer.lock.Lock()
	defer buffer.lock.Unlock()
	
	if width < 0 || height < 0 { return }
	buffer.width    = width
	buffer.height   = height
	buffer.content  = make([]Cell, width * height)
	buffer.onScreen = make([]Cell, width * height)
	for index := 0; index < len(buffer.content); index ++ {
		buffer.content[index].color = ColorForeground
	}
}

// SetStyle sets the style of the cell at the specified x and y coordinates.
func (buffer *DamageBuffer) SetStyle (x, y int, style Style) {
	buffer.lock.RLock()
	defer buffer.lock.RUnlock()
	
	if buffer.isOutOfBounds(x, y) { return }
	buffer.content[x + y * buffer.width].style = style
}

// SetRune sets the rune of the cell at the specified x and y coordinates.
func (buffer *DamageBuffer) SetRune (x, y int, content rune) {
	buffer.lock.RLock()
	defer buffer.lock.RUnlock()
	
	buffer.setRune(x, y, content)
}

// Clear resets the entire buffer.
func (buffer *DamageBuffer) Clear () {
	buffer.lock.RLock()
	defer buffer.lock.RUnlock()

	for index := 0; index < len(buffer.content); index ++ {
		buffer.content[index] = Cell {
			color: ColorForeground,
		}
	}
}

func (buffer *DamageBuffer) setRune (x, y int, content rune) {
	if buffer.isOutOfBounds(x, y) { return }
	buffer.content[x + y * buffer.width].content = content
}

// Write writes data stored in a byte slice to the buffer at the current dot
// position. This makes Buffer an io.Writer.
func (buffer *DamageBuffer) Write (bytes []byte) (bytesWritten int, err error) {
	buffer.lock.RLock()
	defer buffer.lock.RUnlock()
	
	text := string(bytes)
	bytesWritten = len(bytes)
	
	for _, character := range text {
		buffer.setRune(buffer.dot.x, buffer.dot.y, character)
		buffer.dot.x ++
		if buffer.dot.x > buffer.width { break }
	}
	
	return
}

// Clean returns whether or not the cell at the specified x and y coordinates is
// clean.
func (buffer *DamageBuffer) Clean (x, y int) (clean bool) {
	buffer.lock.RLock()
	defer buffer.lock.RUnlock()
	
	if buffer.isOutOfBounds(x, y) { return }
	index := x + y * buffer.width
	clean = buffer.content[index] == buffer.onScreen[index]
	return
}

// GetForRendering returns the cell at the specified x and y coordinates and
// marks it as clean.
func (buffer *DamageBuffer) GetForRendering (x, y int) (cell Cell) {
	buffer.lock.RLock()
	defer buffer.lock.RUnlock()
	
	if buffer.isOutOfBounds(x, y) { return }
	index := x + y * buffer.width
	buffer.onScreen[index] = buffer.content[index]
	cell = buffer.content[index]
	return
}