export default function (scrawl, el) {Editable header text colorizer and animation effect snippets
Related files:
Purpose: Displays text with an animated gradient over the text fill
Function input:
Customisation: The snippet can be customised using the following --data-??? CSS custom properties:
--data-main-color - any CSS color string (default: black)--data-dark-main-color - any CSS color string (default: ivory)--data-highlight-color - any CSS color string (default: lightgreen)--data-dark-highlight-color - any CSS color string (default: darkgreen)--data-gradient-easing - (string) easing function, for example: linear, easeOutIn3, etc (default: linear)--data-gradient-skew-x - (-2 - 2) skew the gradient pattern horizontally (default: 0)--data-gradient-skew-y - (-2 - 2) skew the gradient pattern vertically (default: 0)--data-gradient-stretch-x - (0 - 4) stretch the gradient pattern horizontally (default: 1)--data-gradient-stretch-y - (0 - 4) stretch the gradient pattern vertically (default: 1)--data-contrast-color - any CSS color string, used when user has set prefers-contrast: more (default: black)data-dark-contrast-color - any CSS color string, used when user has set prefers-contrast: more (default: white)Function output: a Javascript object will be returned, containing the following attributes
{
element // the Scrawl-canvas wrapper for the DOM element supplied to the function
canvas // the Scrawl-canvas wrapper for the snippet's canvas
animation // the Scrawl-canvas animation object
demolish // remove the snippet from the Scrawl-canvas library
}
import * as scrawl from 'path/to/scrawl-canvas/library';
import mySnippet from './relative/or/absolute/path/to/this/file.js';
let myElements = document.querySelectorAll('.some-class');
myElements.forEach(el => mySnippet(scrawl, el));
Effects on the element:
transparenttransparentexport default function (scrawl, el) {Boilerplate - namespacing
const namespace = el.id;
const name = (val) => `${namespace}-${val}`;Only progress if the supplied element has an id attribute
if (namespace) {Create the snippet for this DOM element
const snippet = scrawl.makeSnippet({
domElement: el,
});Only proceed if the snippet is successfully generated
if (snippet) {Unpack the snippet into the parts we’ll be using
const canvas = snippet.canvas,
animation = snippet.animation,
demolishAction = snippet.demolish,
compStyles = snippet.element.elementComputedStyles;Boilerplate - text processing
const addTextNode = () => {
const shy = document.createTextNode('!');
el.appendChild(shy);
};
const processText = t => {
t = t.replace(/<canvas.*<\/canvas>/gi, '');
t = t.replace(/<button.*<\/button>/gi, '');
if (!t.length) {
addTextNode();
t = '!';
}
return t;
}Boilerplate - demolish/kill functionality
const additionalDemolishActions = [];
snippet.demolish = () => {
additionalDemolishActions.forEach(f => f());
scrawl.purge(namespace);
demolishAction();
};This makes the canvas element’s base cell the default group for everything we create
canvas.setAsCurrentCanvas();Boilerplate - fix for text alignment
const getJustifyLine = (val) => {
if (val === 'justify') return 'space-between';
if (val === 'justify-all') return 'space-around';
if (val === 'match-parent') return 'start';
return val;
};Boilerplate - fix for lineSpacing/lineHeight
const getLineSpacing = () => parseFloat(compStyles.lineHeight) / parseFloat(compStyles.fontSize);Initialize and collect developer-supplied data
const userData = {
direction: compStyles.direction || 'ltr',
fontStretch: compStyles.fontStretch || 'normal',
letterSpacing: compStyles.letterSpacing || '0px',
wordSpacing: compStyles.wordSpacing || '0px',
fontVariantCaps: compStyles.fontVariantCaps || 'normal',
lineAdjustment: compStyles.getPropertyValue('--data-line-adjustment') || '0',
justifyLine: getJustifyLine(compStyles.textAlign),
elBackgroundColor: compStyles.backgroundColor || 'transparent',
mainColor: compStyles.getPropertyValue('--data-main-color') || 'black',
darkMainColor: compStyles.getPropertyValue('--data-dark-main-color') || 'ivory',
highlightColor: compStyles.getPropertyValue('--data-highlight-color') || 'lightgreen',
darkHighlightColor: compStyles.getPropertyValue('--data-dark-highlight-color') || 'darkgreen',
gradientEasing: compStyles.getPropertyValue('--data-gradient-easing').trim() || 'linear',
gradientSkewX: compStyles.getPropertyValue('--data-gradient-skew-x') || '0',
gradientSkewY: compStyles.getPropertyValue('--data-gradient-skew-y') || '0',
gradientStretchX: compStyles.getPropertyValue('--data-gradient-stretch-x') || '1',
gradientStretchY: compStyles.getPropertyValue('--data-gradient-stretch-y') || '1',
contrastColor: compStyles.getPropertyValue('--data-contrast-color') || 'black',
darkContrastColor: compStyles.getPropertyValue('--data-dark-contrast-color') || 'white',
};Build the animated highlight gradient effect
const myGradient = scrawl.makeGradient({
name: name('highlight-gradient'),
colors: [
[0, userData.mainColor],
[199, userData.highlightColor],
[399, userData.mainColor],
[599, userData.highlightColor],
[799, userData.mainColor],
[999, userData.mainColor],
],
endY: '100%',
delta: {
paletteStart: -3,
paletteEnd: -3,
},
cyclePalette: true,
easing: userData.gradientEasing,
precision: 4,
animateByDelta: true,
});
const cell = canvas.buildCell({
name: name('highlight-gradient-cell'),
width: 16,
height: parseFloat(compStyles.lineHeight),
cleared: false,
compiled: false,
shown: false,
});
scrawl.makeBlock({
name: name('highlight-gradient-block'),
group: name('highlight-gradient-cell'),
dimensions: ['100%', '100%'],
fillStyle: name('highlight-gradient'),
});
scrawl.makePattern({
name: name('highlight-gradient-pattern'),
asset: name('highlight-gradient-cell'),
stretchX: parseFloat(userData.gradientStretchX),
stretchY: parseFloat(userData.gradientStretchY),
skewX: parseFloat(userData.gradientSkewX),
skewY: parseFloat(userData.gradientSkewY),
});
const template = scrawl.makeBlock({
name: name('template'),
dimensions: ['100%', '100%'],
visibility: false,
});
const label = scrawl.makeEnhancedLabel({
name: name('content'),
layoutTemplate: name('template'),
text: processText(el.innerHTML),
fontString: compStyles.font,
textHandleY: 'alphabetic',
visibility: false,
cacheOutput: false,
direction: userData.direction,
fontStretch: userData.fontStretch,
letterSpacing: userData.letterSpacing,
wordSpacing: userData.wordSpacing,
fontVariantCaps: userData.fontVariantCaps,
lineSpacing: getLineSpacing(),
justifyLine: userData.justifyLine,
fillStyle: name('highlight-gradient-pattern'),
});Boilerplate - font adjustments
let meta;
const getLineAdjustment = () => {
const size = parseFloat(compStyles.fontSize);
const ratio = size / 100;
return ratio * (meta.alphabeticBaseline + meta.verticalOffset + parseFloat(userData.lineAdjustment));
};
const updateOnFontLoad = () => {
const font = compStyles.fontFamily,
check = scrawl.checkFontIsLoaded(font);
if (check) {
el.style.backgroundColor = 'transparent';
el.style.color = 'transparent';
meta = scrawl.getFontMetadata(font);
const displacement = getLineAdjustment();
template.set({
startY: displacement,
handleY: displacement,
fillStyle: userData.elBackgroundColor,
visibility: true,
});
cell.set({
cleared: true,
compiled: true,
});
label.set({ visibility: true });
animation.updateHook('commence');
}
};
animation.updateHook('commence', updateOnFontLoad);Boilerplate user interaction - resizing the browser window
let resizeFlag = true,
lastResize = Date.now();
const resizeChoke = 200;
const setResizeFlag = () => {
resizeFlag = true;
const now = Date.now();Canvases don’t animate when outside of the browser viewport (to save CPU, battery, etc)
if (!animation.isRunning() && now > lastResize + resizeChoke) {
resizeAction();
animation.updateOnce();
lastResize = now;
}
};
const resizeAction = () => {
if (resizeFlag) {
resizeFlag = false;
cell.set({ height: parseFloat(compStyles.lineHeight) });
label.set({ fontString: compStyles.font });
if (meta) {
const displacement = getLineAdjustment();
template.set({
startY: displacement,
handleY: displacement,
});
label.set({
letterSpacing: compStyles.letterSpacing,
wordSpacing: compStyles.wordSpacing,
});
}
}
};
animation.updateHook('afterShow', resizeAction);
additionalDemolishActions.push(
scrawl.addNativeListener('resize', setResizeFlag, window),
);Boilerplate user interaction - editing the text
if (el.getAttribute('contenteditable')) {
const updateText = () => {
label.set({ text: processText(el.innerHTML) });
}
const focusText = () => {
el.style.color = 'rgb(0 0 0 / 0.4)';
}
const blurText = () => {
el.style.color = 'transparent';
}
additionalDemolishActions.push(
scrawl.addNativeListener('input', updateText, el),
scrawl.addNativeListener('focus', focusText, el),
scrawl.addNativeListener('blur', blurText, el),
);
}Boilerplate - animation control
if ('static' === compStyles.position) el.style.position = 'relative';
const control = document.createElement('button');
control.style.position = 'absolute';
control.style.fontSize = '12px';
control.style.display = 'block';
control.style.top = '0';
control.style.right = '0';
control.textContent = 'Halt';
control.setAttribute('contenteditable', 'false');
el.appendChild(control);
let isAnimated = true;
const stopStartAction = () => {
isAnimated = !isAnimated;
myGradient.set({ animateByDelta: isAnimated });
control.textContent = isAnimated ? 'Halt' : 'Play';
};
additionalDemolishActions.push(
scrawl.addNativeListener('click', stopStartAction, control)
);Accessibility
const reduceMotionAction = () => {
if (isAnimated) {
isAnimated = false;
myGradient.set({ animateByDelta: isAnimated });
control.textContent = 'Play';
}
};
const noPreferenceMotionAction = () => {
if (!isAnimated) {
isAnimated = true;
myGradient.set({ animateByDelta: isAnimated });
control.textContent = 'Halt';
}
};
const colorSchemeLightAction = () => {
myGradient.set({
colors: [
[0, userData.mainColor],
[199, userData.highlightColor],
[399, userData.mainColor],
[599, userData.highlightColor],
[799, userData.mainColor],
[999, userData.mainColor],
],
});
};
const colorSchemeDarkAction = () => {
myGradient.set({
colors: [
[0, userData.darkMainColor],
[199, userData.darkHighlightColor],
[399, userData.darkMainColor],
[599, userData.darkHighlightColor],
[799, userData.darkMainColor],
[999, userData.darkMainColor],
],
});
};
const moreContrastAction = () => {
const prefersDark = canvas.here.prefersDarkColorScheme;
const color = (prefersDark) ? userData.darkContrastColor : userData.contrastColor;
label.set({ fillStyle: color });
};
const otherContrastAction = () => {
label.set({ fillStyle: name('highlight-gradient-pattern') });
};
canvas.set({
colorSchemeLightAction,
colorSchemeDarkAction,
moreContrastAction,
otherContrastAction,
reduceMotionAction,
noPreferenceMotionAction,
});Render once, to get everything in place
animation.updateOnce();Return the snippet, so coders can access the snippet’s parts
return snippet;
}
}
return null;
}