ESPTerm web interface submodule, separated to make testing and development easier
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espterm-front-end/js/term/screen_renderer.js

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const {
themes,
buildColorTable,
getColor
} = require('./themes')
const {
ATTR_FG,
ATTR_BG,
ATTR_BOLD,
ATTR_UNDERLINE,
ATTR_INVERSE,
ATTR_BLINK,
ATTR_ITALIC,
ATTR_STRIKE,
ATTR_OVERLINE,
ATTR_FAINT,
ATTR_FRAKTUR
} = require('./screen_attr_bits')
// Some non-bold Fraktur symbols are outside the contiguous block
const frakturExceptions = {
'C': '\u212d',
'H': '\u210c',
'I': '\u2111',
'R': '\u211c',
'Z': '\u2128'
}
module.exports = class ScreenRenderer {
constructor (screen) {
this.screen = screen
this.ctx = screen.ctx
this._palette = null // colors 0-15
this.defaultBgNum = 0
this.defaultFgNum = 7
// 256color lookup table
// should not be used to look up 0-15 (will return transparent)
this.colorTable256 = buildColorTable()
this.resetDrawn()
this.blinkStyleOn = false
this.blinkInterval = null
this.cursorBlinkOn = false
this.cursorBlinkInterval = null
// start blink timers
this.resetBlink()
this.resetCursorBlink()
}
resetDrawn () {
// used to determine if a cell should be redrawn; storing the current state
// as it is on screen
if (this.screen.window && this.screen.window.debug) {
console.log('Resetting drawn screen')
}
this.drawnScreen = []
this.drawnScreenFG = []
this.drawnScreenBG = []
this.drawnScreenAttrs = []
this.drawnCursor = [-1, -1, '']
}
/**
* The color palette. Should define 16 colors in an array.
* @type {string[]}
*/
get palette () {
return this._palette || themes[0]
}
/** @type {string[]} */
set palette (palette) {
if (this._palette !== palette) {
this._palette = palette
this.resetDrawn()
this.scheduleDraw('palette')
}
}
loadTheme (i) {
if (i in themes) this.palette = themes[i]
}
setDefaultColors (fg, bg) {
if (fg !== this.defaultFgNum || bg !== this.defaultBgNum) {
this.resetDrawn()
this.defaultFgNum = fg
this.defaultBgNum = bg
this.scheduleDraw('default-colors')
// full bg with default color (goes behind the image)
this.screen.canvas.style.backgroundColor = this.getColor(bg)
}
}
/**
* Schedule a draw in the next millisecond
* @param {string} why - the reason why the draw occured (for debugging)
* @param {number} [aggregateTime] - time to wait for more scheduleDraw calls
* to occur. 1 ms by default.
*/
scheduleDraw (why, aggregateTime = 1) {
clearTimeout(this._scheduledDraw)
this._scheduledDraw = setTimeout(() => this.draw(why), aggregateTime)
}
/**
* Returns the specified color. If `i` is in the palette, it will return the
* palette color. If `i` is between 16 and 255, it will return the 256color
* value. If `i` is larger than 255, it will return an RGB color value. If `i`
* is -1 (foreground) or -2 (background), it will return the selection colors.
* @param {number} i - the color
* @returns {string} the CSS color
*/
getColor (i) {
return getColor(i, this.palette)
}
/**
* Resets the cursor blink to on and restarts the timer
*/
resetCursorBlink () {
this.cursorBlinkOn = true
clearInterval(this.cursorBlinkInterval)
this.cursorBlinkInterval = setInterval(() => {
this.cursorBlinkOn = this.screen.cursor.blinking
? !this.cursorBlinkOn
: true
if (this.screen.cursor.blinking) this.scheduleDraw('cursor-blink')
}, 500)
}
/**
* Resets the blink style to on and restarts the timer
*/
resetBlink () {
this.blinkStyleOn = true
clearInterval(this.blinkInterval)
let intervals = 0
this.blinkInterval = setInterval(() => {
if (this.screen.blinkingCellCount <= 0) return
intervals++
if (intervals >= 4 && this.blinkStyleOn) {
this.blinkStyleOn = false
intervals = 0
this.scheduleDraw('blink-style')
} else if (intervals >= 1 && !this.blinkStyleOn) {
this.blinkStyleOn = true
intervals = 0
this.scheduleDraw('blink-style')
}
}, 200)
}
/**
* Draws a cell's background with the given parameters.
* @param {Object} options
* @param {number} options.x - x in cells
* @param {number} options.y - y in cells
* @param {number} options.cellWidth - cell width in pixels
* @param {number} options.cellHeight - cell height in pixels
* @param {number} options.bg - the background color
* @param {number} options.isDefaultBG - if true, will draw image background if available
*/
drawBackground ({ x, y, cellWidth, cellHeight, bg, isDefaultBG }) {
const ctx = this.ctx
const { width, height } = this.screen.window
const padding = Math.round(this.screen._padding)
ctx.fillStyle = this.getColor(bg)
let screenX = x * cellWidth + padding
let screenY = y * cellHeight + padding
let isBorderCell = x === 0 || y === 0 || x === width - 1 || y === height - 1
let fillX, fillY, fillWidth, fillHeight
if (isBorderCell) {
let left = screenX
let top = screenY
let right = screenX + cellWidth
let bottom = screenY + cellHeight
if (x === 0) left -= padding
else if (x === width - 1) right += padding
if (y === 0) top -= padding
else if (y === height - 1) bottom += padding
fillX = left
fillY = top
fillWidth = right - left
fillHeight = bottom - top
} else {
fillX = screenX
fillY = screenY
fillWidth = cellWidth
fillHeight = cellHeight
}
ctx.clearRect(fillX, fillY, fillWidth, fillHeight)
if (!isDefaultBG || bg < 0 || !this.backgroundImage) {
ctx.fillRect(fillX, fillY, fillWidth, fillHeight)
}
}
/**
* Draws a cell's character with the given parameters. Won't do anything if
* text is an empty string.
* @param {Object} options
* @param {number} options.x - x in cells
* @param {number} options.y - y in cells
* @param {Object} options.charSize - the character size, an object with
* `width` and `height` in pixels
* @param {number} options.cellWidth - cell width in pixels
* @param {number} options.cellHeight - cell height in pixels
* @param {string} options.text - the cell content
* @param {number} options.fg - the foreground color
* @param {number} options.attrs - the cell's attributes
*/
drawCharacter ({ x, y, charSize, cellWidth, cellHeight, text, fg, attrs }) {
if (!text) return
const ctx = this.ctx
const padding = Math.round(this.screen._padding)
let underline = false
let strike = false
let overline = false
if (attrs & ATTR_FAINT) ctx.globalAlpha = 0.5
if (attrs & ATTR_UNDERLINE) underline = true
if (attrs & ATTR_FRAKTUR) text = ScreenRenderer.alphaToFraktur(text)
if (attrs & ATTR_STRIKE) strike = true
if (attrs & ATTR_OVERLINE) overline = true
ctx.fillStyle = this.getColor(fg)
let screenX = x * cellWidth + padding
let screenY = y * cellHeight + padding
let codePoint = text.codePointAt(0)
if (codePoint >= 0x2580 && codePoint <= 0x259F) {
// block elements
ctx.beginPath()
const left = screenX
const top = screenY
const cw = cellWidth
const ch = cellHeight
const c2w = cellWidth / 2
const c2h = cellHeight / 2
// http://www.fileformat.info/info/unicode/block/block_elements/utf8test.htm
// 0x00 0x01 0x02 0x03 0x04 0x05 0x06 0x07 0x08 0x09 0x0A 0x0B 0x0C 0x0D 0x0E 0x0F
// 0x2580 ▀ ▁ ▂ ▃ ▄ ▅ ▆ ▇ █ ▉ ▊ ▋ ▌ ▍ ▎ ▏
// 0x2590 ▐ ░ ▒ ▓ ▔ ▕ ▖ ▗ ▘ ▙ ▚ ▛ ▜ ▝ ▞ ▟
if (codePoint === 0x2580) {
// upper half block >▀<
ctx.rect(left, top, cw, c2h)
} else if (codePoint <= 0x2588) {
// lower n eighth block (increasing) >▁< to >█<
let offset = (1 - (codePoint - 0x2580) / 8) * ch
ctx.rect(left, top + offset, cw, ch - offset)
} else if (codePoint <= 0x258F) {
// left n eighth block (decreasing) >▉< to >▏<
let offset = (codePoint - 0x2588) / 8 * cw
ctx.rect(left, top, cw - offset, ch)
} else if (codePoint === 0x2590) {
// right half block >▐<
ctx.rect(left + c2w, top, c2w, ch)
} else if (codePoint <= 0x2593) {
// shading >░< >▒< >▓<
// dot spacing by dividing cell size by a constant. This could be
// reworked to always return a whole number, but that would require
// prime factorization, and doing that without a loop would let you
// take over the world, which is not within the scope of this project.
let dotSpacingX, dotSpacingY, dotSize
if (codePoint === 0x2591) {
dotSpacingX = cw / 4
dotSpacingY = ch / 10
dotSize = 1
} else if (codePoint === 0x2592) {
dotSpacingX = cw / 6
dotSpacingY = cw / 10
dotSize = 1
} else if (codePoint === 0x2593) {
dotSpacingX = cw / 4
dotSpacingY = cw / 7
dotSize = 2
}
let alignRight = false
for (let dy = 0; dy < ch; dy += dotSpacingY) {
for (let dx = 0; dx < cw; dx += dotSpacingX) {
// prevent overflow
let dotSizeY = Math.min(dotSize, ch - dy)
ctx.rect(left + (alignRight ? cw - dx - dotSize : dx), top + dy, dotSize, dotSizeY)
}
alignRight = !alignRight
}
} else if (codePoint === 0x2594) {
// upper one eighth block >▔<
ctx.rect(left, top, cw, ch / 8)
} else if (codePoint === 0x2595) {
// right one eighth block >▕<
ctx.rect(left + (7 / 8) * cw, top, cw / 8, ch)
} else if (codePoint === 0x2596) {
// left bottom quadrant >▖<
ctx.rect(left, top + c2h, c2w, c2h)
} else if (codePoint === 0x2597) {
// right bottom quadrant >▗<
ctx.rect(left + c2w, top + c2h, c2w, c2h)
} else if (codePoint === 0x2598) {
// left top quadrant >▘<
ctx.rect(left, top, c2w, c2h)
} else if (codePoint === 0x2599) {
// left chair >▙<
ctx.rect(left, top, c2w, ch)
ctx.rect(left + c2w, top + c2h, c2w, c2h)
} else if (codePoint === 0x259A) {
// quadrants lt rb >▚<
ctx.rect(left, top, c2w, c2h)
ctx.rect(left + c2w, top + c2h, c2w, c2h)
} else if (codePoint === 0x259B) {
// left chair upside down >▛<
ctx.rect(left, top, c2w, ch)
ctx.rect(left + c2w, top, c2w, c2h)
} else if (codePoint === 0x259C) {
// right chair upside down >▜<
ctx.rect(left, top, cw, c2h)
ctx.rect(left + c2w, top + c2h, c2w, c2h)
} else if (codePoint === 0x259D) {
// right top quadrant >▝<
ctx.rect(left + c2w, top, c2w, c2h)
} else if (codePoint === 0x259E) {
// quadrants lb rt >▞<
ctx.rect(left, top + c2h, c2w, c2h)
ctx.rect(left + c2w, top, c2w, c2h)
} else if (codePoint === 0x259F) {
// right chair upside down >▟<
ctx.rect(left, top + c2h, c2w, c2h)
ctx.rect(left + c2w, top, c2w, ch)
}
ctx.fill()
} else if (codePoint >= 0xE0B0 && codePoint <= 0xE0B3) {
// powerline symbols, except branch, line, and lock. Basically, just the triangles
ctx.beginPath()
if (codePoint === 0xE0B0 || codePoint === 0xE0B1) {
// right-pointing triangle
ctx.moveTo(screenX, screenY)
ctx.lineTo(screenX + cellWidth, screenY + cellHeight / 2)
ctx.lineTo(screenX, screenY + cellHeight)
} else if (codePoint === 0xE0B2 || codePoint === 0xE0B3) {
// left-pointing triangle
ctx.moveTo(screenX + cellWidth, screenY)
ctx.lineTo(screenX, screenY + cellHeight / 2)
ctx.lineTo(screenX + cellWidth, screenY + cellHeight)
}
if (codePoint % 2 === 0) {
// triangle
ctx.fill()
} else {
// chevron
ctx.strokeStyle = ctx.fillStyle
ctx.stroke()
}
} else {
// Draw other characters using the text renderer
ctx.fillText(text, screenX + 0.5 * cellWidth, screenY + 0.5 * cellHeight)
}
// -- line drawing - a reference for a possible future rect/line implementation ---
// http://www.fileformat.info/info/unicode/block/box_drawing/utf8test.htm
// 0x00 0x01 0x02 0x03 0x04 0x05 0x06 0x07 0x08 0x09 0x0A 0x0B 0x0C 0x0D 0x0E 0x0F
// 0x2500 ─ ━ │ ┃ ┄ ┅ ┆ ┇ ┈ ┉ ┊ ┋ ┌ ┍ ┎ ┏
// 0x2510 ┐ ┑ ┒ ┓ └ ┕ ┖ ┗ ┘ ┙ ┚ ┛ ├ ┝ ┞ ┟
// 0x2520 ┠ ┡ ┢ ┣ ┤ ┥ ┦ ┧ ┨ ┩ ┪ ┫ ┬ ┭ ┮ ┯
// 0x2530 ┰ ┱ ┲ ┳ ┴ ┵ ┶ ┷ ┸ ┹ ┺ ┻ ┼ ┽ ┾ ┿
// 0x2540 ╀ ╁ ╂ ╃ ╄ ╅ ╆ ╇ ╈ ╉ ╊ ╋ ╌ ╍ ╎ ╏
// 0x2550 ═ ║ ╒ ╓ ╔ ╕ ╖ ╗ ╘ ╙ ╚ ╛ ╜ ╝ ╞ ╟
// 0x2560 ╠ ╡ ╢ ╣ ╤ ╥ ╦ ╧ ╨ ╩ ╪ ╫ ╬ ╭ ╮ ╯
// 0x2570 ╰ ╱ ╲ ╳ ╴ ╵ ╶ ╷ ╸ ╹ ╺ ╻ ╼ ╽ ╾ ╿
if (underline || strike || overline) {
ctx.strokeStyle = this.getColor(fg)
ctx.lineWidth = 1
ctx.lineCap = 'round'
ctx.beginPath()
if (underline) {
let lineY = Math.round(screenY + charSize.height) + 0.5
ctx.moveTo(screenX, lineY)
ctx.lineTo(screenX + cellWidth, lineY)
}
if (strike) {
let lineY = Math.round(screenY + 0.5 * cellHeight) + 0.5
ctx.moveTo(screenX, lineY)
ctx.lineTo(screenX + cellWidth, lineY)
}
if (overline) {
let lineY = Math.round(screenY) + 0.5
ctx.moveTo(screenX, lineY)
ctx.lineTo(screenX + cellWidth, lineY)
}
ctx.stroke()
}
ctx.globalAlpha = 1
}
/**
* Returns all adjacent cell indices given a radius.
* @param {number} cell - the center cell index
* @param {number} [radius] - the radius. 1 by default
* @returns {number[]} an array of cell indices
*/
getAdjacentCells (cell, radius = 1) {
const { width, height } = this.screen.window
const screenLength = width * height
let cells = []
for (let x = -radius; x <= radius; x++) {
for (let y = -radius; y <= radius; y++) {
if (x === 0 && y === 0) continue
cells.push(cell + x + y * width)
}
}
return cells.filter(cell => cell >= 0 && cell < screenLength)
}
/**
* Updates the screen.
* @param {string} why - the draw reason (for debugging)
*/
draw (why) {
const ctx = this.ctx
const {
width,
height,
devicePixelRatio,
statusScreen
} = this.screen.window
if (statusScreen) {
// draw status screen instead
this.drawStatus(statusScreen)
this.startDrawLoop()
return
} else this.stopDrawLoop()
const charSize = this.screen.getCharSize()
const { width: cellWidth, height: cellHeight } = this.screen.getCellSize()
const screenLength = width * height
ctx.setTransform(devicePixelRatio, 0, 0, devicePixelRatio, 0, 0)
if (this.screen.window.debug && this.screen._debug) this.screen._debug.drawStart(why)
ctx.font = this.screen.getFont()
ctx.textAlign = 'center'
ctx.textBaseline = 'middle'
// bits in the attr value that affect the font
const FONT_MASK = ATTR_BOLD | ATTR_ITALIC
// Map of (attrs & FONT_MASK) -> Array of cell indices
let fontGroups = new Map()
// Map of (cell index) -> boolean, whether or not a cell has updated
let updateMap = new Map()
for (let cell = 0; cell < screenLength; cell++) {
let x = cell % width
let y = Math.floor(cell / width)
let isCursor = this.cursorBlinkOn &&
this.screen.cursor.x === x &&
this.screen.cursor.y === y &&
this.screen.cursor.visible
let wasCursor = x === this.drawnCursor[0] && y === this.drawnCursor[1]
let inSelection = this.screen.isInSelection(x, y)
let text = this.screen.screen[cell]
let fg = this.screen.screenFG[cell] | 0
let bg = this.screen.screenBG[cell] | 0
let attrs = this.screen.screenAttrs[cell] | 0
let isDefaultBG = false
if (!(attrs & ATTR_FG)) fg = this.defaultFgNum
if (!(attrs & ATTR_BG)) {
bg = this.defaultBgNum
isDefaultBG = true
}
if (attrs & ATTR_INVERSE) [fg, bg] = [bg, fg] // swap - reversed character colors
if (this.screen.reverseVideo) [fg, bg] = [bg, fg] // swap - reversed all screen
if (attrs & ATTR_BLINK && !this.blinkStyleOn) {
// blinking is enabled and blink style is off
// set text to nothing so drawCharacter doesn't draw anything
text = ''
}
if (inSelection) {
fg = -1
bg = -2
}
let didUpdate = text !== this.drawnScreen[cell] || // text updated
fg !== this.drawnScreenFG[cell] || // foreground updated, and this cell has text
bg !== this.drawnScreenBG[cell] || // background updated
attrs !== this.drawnScreenAttrs[cell] || // attributes updated
isCursor !== wasCursor || // cursor blink/position updated
(isCursor && this.screen.cursor.style !== this.drawnCursor[2]) || // cursor style updated
(isCursor && this.screen.cursor.hanging !== this.drawnCursor[3]) // cursor hanging updated
let font = attrs & FONT_MASK
if (!fontGroups.has(font)) fontGroups.set(font, [])
fontGroups.get(font).push({ cell, x, y, text, fg, bg, attrs, isCursor, inSelection, isDefaultBG })
updateMap.set(cell, didUpdate)
}
// Map of (cell index) -> boolean, whether or not a cell should be redrawn
const redrawMap = new Map()
let isTextWide = text =>
text !== ' ' && ctx.measureText(text).width >= (cellWidth + 0.05)
// decide for each cell if it should be redrawn
let updateRedrawMapAt = cell => {
let shouldUpdate = updateMap.get(cell) || redrawMap.get(cell) || false
// TODO: fonts (necessary?)
let text = this.screen.screen[cell]
let isWideCell = isTextWide(text)
let checkRadius = isWideCell ? 2 : 1
if (!shouldUpdate) {
// check adjacent cells
let adjacentDidUpdate = false
for (let adjacentCell of this.getAdjacentCells(cell, checkRadius)) {
// update this cell if:
// - the adjacent cell updated (For now, this'll always be true because characters can be slightly larger than they say they are)
// - the adjacent cell updated and this cell or the adjacent cell is wide
if (updateMap.get(adjacentCell) && (this.screen.window.graphics < 2 || isWideCell || isTextWide(this.screen.screen[adjacentCell]))) {
adjacentDidUpdate = true
break
}
}
if (adjacentDidUpdate) shouldUpdate = true
}
redrawMap.set(cell, shouldUpdate)
}
for (let cell of updateMap.keys()) updateRedrawMapAt(cell)
// mask to redrawing regions only
if (this.screen.window.graphics >= 1) {
let debug = this.screen.window.debug && this.screen._debug
let padding = Math.round(this.screen._padding)
ctx.save()
ctx.beginPath()
for (let y = 0; y < height; y++) {
let regionStart = null
for (let x = 0; x < width; x++) {
let cell = y * width + x
let redrawing = redrawMap.get(cell)
if (redrawing && regionStart === null) regionStart = x
if (!redrawing && regionStart !== null) {
ctx.rect(padding + regionStart * cellWidth, padding + y * cellHeight, (x - regionStart) * cellWidth, cellHeight)
if (debug) this.screen._debug.clipRect(regionStart * cellWidth, y * cellHeight, (x - regionStart) * cellWidth, cellHeight)
regionStart = null
}
}
if (regionStart !== null) {
ctx.rect(padding + regionStart * cellWidth, padding + y * cellHeight, (width - regionStart) * cellWidth, cellHeight)
if (debug) this.screen._debug.clipRect(regionStart * cellWidth, y * cellHeight, (width - regionStart) * cellWidth, cellHeight)
}
}
ctx.clip()
}
// pass 1: backgrounds
for (let font of fontGroups.keys()) {
for (let data of fontGroups.get(font)) {
let { cell, x, y, text, bg, isDefaultBG } = data
if (redrawMap.get(cell)) {
this.drawBackground({ x, y, cellWidth, cellHeight, bg, isDefaultBG })
if (this.screen.window.debug && this.screen._debug) {
// set cell flags
let flags = (+redrawMap.get(cell))
flags |= (+updateMap.get(cell)) << 1
flags |= (+isTextWide(text)) << 2
this.screen._debug.setCell(cell, flags)
}
}
}
}
// reset drawn cursor
this.drawnCursor = [-1, -1, -1]
// pass 2: characters
for (let font of fontGroups.keys()) {
// set font once because in Firefox, this is a really slow action for some
// reason
let modifiers = {}
if (font & ATTR_BOLD) modifiers.weight = 'bold'
if (font & ATTR_ITALIC) modifiers.style = 'italic'
ctx.font = this.screen.getFont(modifiers)
for (let data of fontGroups.get(font)) {
let { cell, x, y, text, fg, bg, attrs, isCursor, inSelection } = data
if (redrawMap.get(cell)) {
this.drawCharacter({
x, y, charSize, cellWidth, cellHeight, text, fg, attrs
})
this.drawnScreen[cell] = text
this.drawnScreenFG[cell] = fg
this.drawnScreenBG[cell] = bg
this.drawnScreenAttrs[cell] = attrs
if (isCursor) this.drawnCursor = [x, y, this.screen.cursor.style, this.screen.cursor.hanging]
// draw cursor
if (isCursor && !inSelection) {
ctx.save()
ctx.beginPath()
let cursorX = x
let cursorY = y
if (this.screen.cursor.hanging) {
// draw hanging cursor in the margin
cursorX += 1
}
let screenX = cursorX * cellWidth + this.screen._padding
let screenY = cursorY * cellHeight + this.screen._padding
if (this.screen.cursor.style === 'block') {
// block
ctx.rect(screenX, screenY, cellWidth, cellHeight)
} else if (this.screen.cursor.style === 'bar') {
// vertical bar
let barWidth = 2
ctx.rect(screenX, screenY, barWidth, cellHeight)
} else if (this.screen.cursor.style === 'line') {
// underline
let lineHeight = 2
ctx.rect(screenX, screenY + charSize.height, cellWidth, lineHeight)
}
ctx.clip()
// swap foreground/background
;[fg, bg] = [bg, fg]
// HACK: ensure cursor is visible
if (fg === bg) bg = fg === 0 ? 7 : 0
this.drawBackground({ x: cursorX, y: cursorY, cellWidth, cellHeight, bg })
this.drawCharacter({
x: cursorX, y: cursorY, charSize, cellWidth, cellHeight, text, fg, attrs
})
ctx.restore()
}
}
}
}
if (this.screen.window.graphics >= 1) ctx.restore()
if (this.screen.window.debug && this.screen._debug) this.screen._debug.drawEnd()
this.screen.emit('draw', why)
}
drawStatus (statusScreen) {
const ctx = this.ctx
const {
fontFamily,
width,
height,
devicePixelRatio
} = this.screen.window
// reset drawnScreen to force redraw when statusScreen is disabled
this.drawnScreen = []
const cellSize = this.screen.getCellSize()
const screenWidth = width * cellSize.width + 2 * this.screen._padding
const screenHeight = height * cellSize.height + 2 * this.screen._padding
ctx.setTransform(devicePixelRatio, 0, 0, devicePixelRatio, 0, 0)
ctx.fillStyle = this.getColor(this.defaultBgNum)
ctx.fillRect(0, 0, screenWidth, screenHeight)
ctx.font = `24px ${fontFamily}`
ctx.fillStyle = this.getColor(this.defaultFgNum)
ctx.textAlign = 'center'
ctx.textBaseline = 'middle'
ctx.fillText(statusScreen.title || '', screenWidth / 2, screenHeight / 2 - 50)
if (statusScreen.loading) {
// show loading spinner
ctx.save()
ctx.translate(screenWidth / 2, screenHeight / 2 + 20)
ctx.strokeStyle = this.getColor(this.defaultFgNum)
ctx.lineWidth = 5
ctx.lineCap = 'round'
let t = Date.now() / 1000
for (let i = 0; i < 12; i++) {
ctx.rotate(Math.PI / 6)
let offset = ((t * 12) - i) % 12
ctx.globalAlpha = Math.max(0.2, 1 - offset / 3)
ctx.beginPath()
ctx.moveTo(0, 15)
ctx.lineTo(0, 30)
ctx.stroke()
}
ctx.restore()
}
}
startDrawLoop () {
if (this._drawTimerThread) return
let threadID = Math.random().toString(36)
this._drawTimerThread = threadID
this.drawTimerLoop(threadID)
}
stopDrawLoop () {
this._drawTimerThread = null
}
drawTimerLoop (threadID) {
if (!threadID || threadID !== this._drawTimerThread) return
window.requestAnimationFrame(() => this.drawTimerLoop(threadID))
this.draw('draw-loop')
}
/**
* Converts an alphabetic character to its fraktur variant.
* @param {string} character - the character
* @returns {string} the converted character
*/
static alphaToFraktur (character) {
if (character >= 'a' && character <= 'z') {
character = String.fromCodePoint(0x1d51e - 0x61 + character.charCodeAt(0))
} else if (character >= 'A' && character <= 'Z') {
character = frakturExceptions[character] || String.fromCodePoint(0x1d504 - 0x41 + character.charCodeAt(0))
}
return character
}
}