commit 166a752ab22ef1415c250eff37e1ada3f2f24915 Author: Tom Ritter tom@mozilla.com Date: Tue May 7 16:06:43 2019 +0000

Bug 1548634 - Update the default letterboxing behavior to use stepped ranges r=johannh

Differential Revision: https://phabricator.services.mozilla.com/D29759 --- .../browser/browser_dynamical_window_rounding.js | 11 ++++------ .../components/resistfingerprinting/RFPHelper.jsm | 25 +++++++++++++++++----- 2 files changed, 24 insertions(+), 12 deletions(-)

diff --git a/browser/components/resistfingerprinting/test/browser/browser_dynamical_window_rounding.js b/browser/components/resistfingerprinting/test/browser/browser_dynamical_window_rounding.js index ae8055a49ce5..784fb42b8631 100644 --- a/browser/components/resistfingerprinting/test/browser/browser_dynamical_window_rounding.js +++ b/browser/components/resistfingerprinting/test/browser/browser_dynamical_window_rounding.js @@ -11,9 +11,7 @@ */

const TEST_PATH = "http://example.net/browser/browser/components/resistfingerprinting/test/brow..."; - -const DEFAULT_ROUNDED_WIDTH_STEP = 200; -const DEFAULT_ROUNDED_HEIGHT_STEP = 100; +const { RFPHelper } = ChromeUtils.import("resource://gre/modules/RFPHelper.jsm");

// A set of test cases which defines the width and the height of the outer window. const TEST_CASES = [ @@ -50,10 +48,9 @@ function handleOSFuzziness(aContent, aTarget) {

function checkForDefaultSetting( aContentWidth, aContentHeight, aRealWidth, aRealHeight) { - // The default behavior for rounding is to round window with 200x100 stepping. - // So, we can get the rounded size by subtracting the remainder. - let targetWidth = aRealWidth - (aRealWidth % DEFAULT_ROUNDED_WIDTH_STEP); - let targetHeight = aRealHeight - (aRealHeight % DEFAULT_ROUNDED_HEIGHT_STEP); + // We can get the rounded size by subtracting twice the margin. + let targetWidth = aRealWidth - (2 * RFPHelper.steppedRange(aRealWidth)); + let targetHeight = aRealHeight - (2 * RFPHelper.steppedRange(aRealHeight));

// This platform-specific code is explained in the large comment below. if (getPlatform() != "linux") { diff --git a/toolkit/components/resistfingerprinting/RFPHelper.jsm b/toolkit/components/resistfingerprinting/RFPHelper.jsm index 2f3a1dd0e659..5f23d0679b53 100755 --- a/toolkit/components/resistfingerprinting/RFPHelper.jsm +++ b/toolkit/components/resistfingerprinting/RFPHelper.jsm @@ -21,9 +21,6 @@ const kPrefLetterboxingTesting = const kTopicDOMWindowOpened = "domwindowopened"; const kEventLetterboxingSizeUpdate = "Letterboxing:ContentSizeUpdated";

-const kDefaultWidthStepping = 200; -const kDefaultHeightStepping = 100; - var logConsole; function log(msg) { if (!logConsole) { @@ -338,6 +335,24 @@ class _RFPHelper { }

/** + * Given a width or height, returns the appropriate margin to apply. + */ + steppedRange(aDimension) { + let stepping; + if (aDimension <= 50) { + return 0; + } else if (aDimension <= 500) { + stepping = 50; + } else if (aDimension <= 1600) { + stepping = 100; + } else { + stepping = 200; + } + + return (aDimension % stepping) / 2; + } + + /** * The function will round the given browser by adding margins around the * content viewport. */ @@ -373,8 +388,8 @@ class _RFPHelper { // stepping size. if (!this._letterboxingDimensions.length) { result = { - width: (aWidth % kDefaultWidthStepping) / 2, - height: (aHeight % kDefaultHeightStepping) / 2, + width: this.steppedRange(aWidth), + height: this.steppedRange(aHeight), }; log("_roundContentView[" + logId + "] calcMargins(" + aWidth + ", " + aHeight + ") = " + result.width + " x " + result.height); return result;