skia2/modules/pathkit/helper.js

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// Adds any extra JS functions/helpers we want to the PathKit Library.
// Wrapped in a function to avoid leaking global variables.
(function(PathKit){
// Caching the Float32Arrays can save having to reallocate them
// over and over again.
var Float32ArrayCache = {};
// Takes a 2D array of commands and puts them into the WASM heap
// as a 1D array. This allows them to referenced from the C++ code.
// Returns a 2 element array, with the first item being essentially a
// pointer to the array and the second item being the length of
// the new 1D array.
//
// Example usage:
// let cmds = [
// [PathKit.MOVE_VERB, 0, 10],
// [PathKit.LINE_VERB, 30, 40],
// [PathKit.QUAD_VERB, 20, 50, 45, 60],
// ];
//
// // The following uses ES6 syntactic sugar "Array Destructuring".
// // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Destructuring_assignment#Array_destructuring
// let [ptr, len] = PathKit.loadCmdsTypedArray(cmds);
// let path = PathKit.FromCmds(ptr, len);
//
// If arguments at index 1... in each cmd row are strings, they will be
// parsed as hex, and then converted to floats using SkBits2FloatUnsigned
PathKit.loadCmdsTypedArray = function(arr) {
var len = 0;
for (var r = 0; r < arr.length; r++) {
len += arr[r].length;
}
var ta;
if (Float32ArrayCache[len]) {
ta = Float32ArrayCache[len];
} else {
ta = new Float32Array(len);
Float32ArrayCache[len] = ta;
}
// Flatten into a 1d array
var i = 0;
for (var r = 0; r < arr.length; r++) {
for (var c = 0; c < arr[r].length; c++) {
var item = arr[r][c];
if (typeof item === 'string') {
// Converts hex to an int, which can be passed to SkBits2FloatUnsigned
item = PathKit.SkBits2FloatUnsigned(parseInt(item));
}
ta[i] = item;
i++;
}
}
var ptr = PathKit._malloc(ta.length * ta.BYTES_PER_ELEMENT);
PathKit.HEAPF32.set(ta, ptr / ta.BYTES_PER_ELEMENT);
return [ptr, len];
}
// Experimentation has shown that using TypedArrays to pass arrays from
// JS to C++ is faster than passing the JS Arrays across.
// See above for example of cmds.
PathKit.FromCmds = function(cmds) {
var ptrLen = PathKit.loadCmdsTypedArray(cmds);
return PathKit._FromCmds(ptrLen[0], ptrLen[1]);
}
/**
* A common pattern is to call this function in sequence with the same
* params. We can just remember the last one to speed things up.
* Caching in this way is about a 10-15x speed up.
* See externs.js for this definition
* @type {CubicMap}
*/
var cachedMap;
var _cpx1, _cpy1, _cpx2, _cpy2;
PathKit.cubicYFromX = function(cpx1, cpy1, cpx2, cpy2, X) {
if (!cachedMap || _cpx1 !== cpx1 || _cpy1 !== cpy1 ||
_cpx2 !== cpx2 || _cpy2 !== cpy2) {
if (cachedMap) {
// Delete previous cached map to avoid memory leaks.
cachedMap.delete()
}
cachedMap = new PathKit._SkCubicMap([cpx1, cpy1], [cpx2, cpy2]);
_cpx1 = cpx1, _cpy1 = cpy1, _cpx2 = cpx2, _cpy2 = cpy2;
}
return cachedMap.computeYFromX(X);
}
PathKit.cubicPtFromT = function(cpx1, cpy1, cpx2, cpy2, T) {
if (!cachedMap || _cpx1 !== cpx1 || _cpy1 !== cpy1 ||
_cpx2 !== cpx2 || _cpy2 !== cpy2) {
if (cachedMap) {
// Delete previous cached map to avoid memory leaks.
cachedMap.delete()
}
cachedMap = new PathKit._SkCubicMap([cpx1, cpy1], [cpx2, cpy2]);
_cpx1 = cpx1, _cpy1 = cpy1, _cpx2 = cpx2, _cpy2 = cpy2;
}
return cachedMap.computePtFromT(T);
}
}(Module)); // When this file is loaded in, the high level object is "Module";