b38dea0597
Share Gaia assets and adapters, keep private profiles and development documents local, and update both public READMEs.
86 lines
3.1 KiB
JavaScript
Executable file
86 lines
3.1 KiB
JavaScript
Executable file
'use strict';
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(function(exports) {
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/**
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* ScreenBrightnessTransition can be constructed whenever we need to
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* transition the brightness. The single instance can be reused too,
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* but you must abort() the transition before asking for a new transition.
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*
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* I intend to let ScreenManager re-use one instance but allow the future,
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* rewritten screen brightness controls create and throw instances (hence
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* the absence of start() and stop() methods.)
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*
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*/
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var ScreenBrightnessTransition = function ScreenBrightnessTransition() {
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this.isRunning = false;
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this._timer = undefined;
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};
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ScreenBrightnessTransition.prototype.STEP_INTERVAL_MS = 20;
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ScreenBrightnessTransition.prototype.STEP_DELTA = 0.01;
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ScreenBrightnessTransition.prototype.ontransitionbegin = null;
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ScreenBrightnessTransition.prototype.ontransitionend = null;
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ScreenBrightnessTransition.prototype.transitionTo = function(brightness) {
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if (this.isRunning) {
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throw new Error('ScreenBrightnessTransition: ' +
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'transitionTo() is called again during transition.');
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}
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this.isRunning = true;
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if (typeof this.ontransitionbegin === 'function') {
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this.ontransitionbegin();
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}
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// For now this is still an naive linear transition that takes the
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// brightness to whatever current value to the target value, as we
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// implemented in ScreenManager.
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// TODO Please improve this code by working on bug 1042673, bug 1064683,
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// and/or bug 819744.
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var currentBrightness = navigator.mozPower.screenBrightness;
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this._timer = setInterval(function brightnessTransitionTick() {
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// We should never read back the current brightness during transition
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// from mozPower coz it would be rounded to the nearest 1/256 value
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// (instead of being a real float) under the current Gonk implementation.
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// Noted that the actual brightness steps is hardware-dependent,
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// not 256 steps.
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// So in here, we simply add/substract currentBrightness to make it the
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// new value we want to be.
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var delta = this.STEP_DELTA * ((currentBrightness > brightness) ? -1 : 1);
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currentBrightness += delta;
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if ((delta < 0 && currentBrightness < brightness) ||
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(delta > 0 && currentBrightness > brightness)) {
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// If we are overshot the target brightness,
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// set the final value and stop.
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navigator.mozPower.screenBrightness = brightness;
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clearTimeout(this._timer);
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this.isRunning = false;
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if (typeof this.ontransitionend === 'function') {
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this.ontransitionend();
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}
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return;
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} else {
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// The show must go on; set the current value.
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navigator.mozPower.screenBrightness = currentBrightness;
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}
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}.bind(this), this.STEP_INTERVAL_MS);
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};
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ScreenBrightnessTransition.prototype.abort = function() {
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if (!this.isRunning) {
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throw new Error('ScreenBrightnessTransition: ' +
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'abort() is called but it is not currently in transition.');
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}
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clearTimeout(this._timer);
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this.isRunning = false;
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};
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exports.ScreenBrightnessTransition = ScreenBrightnessTransition;
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}(window));
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