forked from mirrors/gecko-dev
c26a6274cc
MozReview-Commit-ID: 6cLDkoCt0al --HG-- extra : rebase_source : 26e95a9320998085675a1f14bfa4442f4bbc38dc
94 lines
3 KiB
JavaScript
94 lines
3 KiB
JavaScript
/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this file,
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* You can obtain one at http://mozilla.org/MPL/2.0/. */
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"use strict";
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const HTML_NS = "http://www.w3.org/1999/xhtml";
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const WATERFALL_BACKGROUND_TICKS_MULTIPLE = 5; // ms
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const WATERFALL_BACKGROUND_TICKS_SCALES = 3;
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const WATERFALL_BACKGROUND_TICKS_SPACING_MIN = 10; // px
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const WATERFALL_BACKGROUND_TICKS_COLOR_RGB = [128, 136, 144];
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const WATERFALL_BACKGROUND_TICKS_OPACITY_MIN = 32; // byte
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const WATERFALL_BACKGROUND_TICKS_OPACITY_ADD = 32; // byte
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const FIND_OPTIMAL_TICK_INTERVAL_MAX_ITERS = 100;
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/**
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* Creates the background displayed on the marker's waterfall.
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*/
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function drawWaterfallBackground(doc, dataScale, waterfallWidth) {
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let canvas = doc.createElementNS(HTML_NS, "canvas");
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let ctx = canvas.getContext("2d");
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// Nuke the context.
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let canvasWidth = canvas.width = waterfallWidth;
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// Awww yeah, 1px, repeats on Y axis.
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let canvasHeight = canvas.height = 1;
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// Start over.
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let imageData = ctx.createImageData(canvasWidth, canvasHeight);
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let pixelArray = imageData.data;
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let buf = new ArrayBuffer(pixelArray.length);
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let view8bit = new Uint8ClampedArray(buf);
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let view32bit = new Uint32Array(buf);
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// Build new millisecond tick lines...
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let [r, g, b] = WATERFALL_BACKGROUND_TICKS_COLOR_RGB;
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let alphaComponent = WATERFALL_BACKGROUND_TICKS_OPACITY_MIN;
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let tickInterval = findOptimalTickInterval({
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ticksMultiple: WATERFALL_BACKGROUND_TICKS_MULTIPLE,
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ticksSpacingMin: WATERFALL_BACKGROUND_TICKS_SPACING_MIN,
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dataScale: dataScale
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});
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// Insert one pixel for each division on each scale.
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for (let i = 1; i <= WATERFALL_BACKGROUND_TICKS_SCALES; i++) {
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let increment = tickInterval * Math.pow(2, i);
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for (let x = 0; x < canvasWidth; x += increment) {
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let position = x | 0;
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view32bit[position] = (alphaComponent << 24) | (b << 16) | (g << 8) | r;
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}
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alphaComponent += WATERFALL_BACKGROUND_TICKS_OPACITY_ADD;
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}
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// Flush the image data and cache the waterfall background.
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pixelArray.set(view8bit);
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ctx.putImageData(imageData, 0, 0);
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doc.mozSetImageElement("waterfall-background", canvas);
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return canvas;
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}
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/**
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* Finds the optimal tick interval between time markers in this timeline.
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*
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* @param number ticksMultiple
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* @param number ticksSpacingMin
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* @param number dataScale
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* @return number
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*/
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function findOptimalTickInterval({ ticksMultiple, ticksSpacingMin, dataScale }) {
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let timingStep = ticksMultiple;
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let maxIters = FIND_OPTIMAL_TICK_INTERVAL_MAX_ITERS;
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let numIters = 0;
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if (dataScale > ticksSpacingMin) {
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return dataScale;
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}
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while (true) {
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let scaledStep = dataScale * timingStep;
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if (++numIters > maxIters) {
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return scaledStep;
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}
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if (scaledStep < ticksSpacingMin) {
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timingStep <<= 1;
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continue;
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}
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return scaledStep;
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}
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}
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exports.TickUtils = { findOptimalTickInterval, drawWaterfallBackground };
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