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94 lines
2.6 KiB
JavaScript
94 lines
2.6 KiB
JavaScript
let next_property_id = 1;
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// Generate a unique property name on the form --prop-N.
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function generate_name() {
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return `--prop-${next_property_id++}`;
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}
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// Produce a compatible initial value for the specified syntax.
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function any_initial_value(syntax) {
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let components = syntax.split('|').map(x => x.trim())
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let first_component = components[0];
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if (first_component.endsWith('+') || first_component.endsWith('#'))
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first_component = first_component.slice(0, -1);
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switch (first_component) {
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case '*':
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case '<custom-ident>':
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return 'NULL';
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case '<angle>':
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return '0deg';
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case '<color>':
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return 'rgb(0, 0, 0)';
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case '<image>':
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case '<url>':
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return 'url(0)';
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case '<integer>':
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case '<length-percentage>':
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case '<length>':
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case '<number>':
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return '0';
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case '<percentage>':
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return '0%';
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case '<resolution>':
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return '0dpi';
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case '<time>':
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return '0s';
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case '<transform-function>':
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case '<transform-list>':
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return 'matrix(0, 0, 0, 0, 0, 0)';
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default:
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// We assume syntax is a specific custom ident.
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return first_component;
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}
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}
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// Registers a unique property on the form '--prop-N' and returns the name.
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// Any value except 'syntax' may be omitted, in which case the property will
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// not inherit, and some undefined (but compatible) initial value will be
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// generated. If a single string is used as the argument, it is assumed to be
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// the syntax.
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function generate_property(reg) {
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// Verify that only valid keys are specified. This prevents the caller from
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// accidentally supplying 'inherited' instead of 'inherits', for example.
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if (typeof(reg) === 'object') {
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const permitted = new Set(['name', 'syntax', 'initialValue', 'inherits']);
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if (!Object.keys(reg).every(k => permitted.has(k)))
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throw new Error('generate_property: invalid parameter');
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}
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let syntax = typeof(reg) === 'string' ? reg : reg.syntax;
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let initial = typeof(reg.initialValue) === 'undefined' ? any_initial_value(syntax)
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: reg.initialValue;
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let inherits = typeof(reg.inherits) === 'undefined' ? false : reg.inherits;
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let name = generate_name();
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CSS.registerProperty({
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name: name,
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syntax: syntax,
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initialValue: initial,
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inherits: inherits
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});
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return name;
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}
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function all_syntaxes() {
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return [
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'*',
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'<angle>',
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'<color>',
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'<custom-ident>',
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'<image>',
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'<integer>',
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'<length-percentage>',
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'<length>',
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'<number>',
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'<percentage>',
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'<resolution>',
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'<time>',
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'<transform-function>',
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'<transform-list>',
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'<url>'
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]
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}
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