From 62a67c3b65538315934358ff5626c5aca8ee3231 Mon Sep 17 00:00:00 2001 From: Igor Oliveira Date: Sun, 10 Dec 2017 18:16:59 -0200 Subject: [PATCH] Bug 23104: Add a default line height compensation Many fonts have issues with their vertical metrics. they are used to influence the height of ascenders and depth of descenders. Gecko uses it to calculate the line height (font height + ascender + descender), however because of that idiosyncratic behavior across multiple operating systems, it can be used to identify the user's OS. The solution proposed in the patch uses a default factor to be multiplied with the font size, simulating the concept of ascender and descender. This way all operating systems will have the same line height only and only if the frame is outside the chrome. --- layout/generic/ReflowInput.cpp | 16 +++++++--- tbb-tests/mochitest.ini | 1 + tbb-tests/test_tor_bug23104.html | 51 ++++++++++++++++++++++++++++++++ 3 files changed, 64 insertions(+), 4 deletions(-) create mode 100644 tbb-tests/test_tor_bug23104.html diff --git a/layout/generic/ReflowInput.cpp b/layout/generic/ReflowInput.cpp index 42f4a24b53149..cda602c504314 100644 --- a/layout/generic/ReflowInput.cpp +++ b/layout/generic/ReflowInput.cpp @@ -30,6 +30,7 @@ #include "CounterStyleManager.h" #include #include "mozilla/dom/HTMLInputElement.h" +#include "nsContentUtils.h" #ifdef DEBUG #undef NOISY_VERTICAL_ALIGN @@ -2759,7 +2760,7 @@ ReflowInput::CalculateBlockSideMargins(nsIAtom* aFrameType) // For risk management, we use preference to control the behavior, and // eNoExternalLeading is the old behavior. static nscoord -GetNormalLineHeight(nsFontMetrics* aFontMetrics) +GetNormalLineHeight(nsIContent* aContent, nsFontMetrics* aFontMetrics) { NS_PRECONDITION(nullptr != aFontMetrics, "no font metrics"); @@ -2768,6 +2769,12 @@ GetNormalLineHeight(nsFontMetrics* aFontMetrics) nscoord externalLeading = aFontMetrics->ExternalLeading(); nscoord internalLeading = aFontMetrics->InternalLeading(); nscoord emHeight = aFontMetrics->EmHeight(); + + if (nsContentUtils::ShouldResistFingerprinting() && + !aContent->IsInChromeDocument()) { + return NSToCoordRound(emHeight * NORMAL_LINE_HEIGHT_FACTOR); + } + switch (GetNormalLineHeightCalcControl()) { case eIncludeExternalLeading: normalLineHeight = emHeight+ internalLeading + externalLeading; @@ -2786,7 +2793,8 @@ GetNormalLineHeight(nsFontMetrics* aFontMetrics) } static inline nscoord -ComputeLineHeight(nsStyleContext* aStyleContext, +ComputeLineHeight(nsIContent* aContent, + nsStyleContext* aStyleContext, nscoord aBlockBSize, float aFontSizeInflation) { @@ -2821,7 +2829,7 @@ ComputeLineHeight(nsStyleContext* aStyleContext, RefPtr fm = nsLayoutUtils:: GetFontMetricsForStyleContext(aStyleContext, aFontSizeInflation); - return GetNormalLineHeight(fm); + return GetNormalLineHeight(aContent, fm); } nscoord @@ -2844,7 +2852,7 @@ ReflowInput::CalcLineHeight(nsIContent* aContent, NS_PRECONDITION(aStyleContext, "Must have a style context"); nscoord lineHeight = - ComputeLineHeight(aStyleContext, aBlockBSize, aFontSizeInflation); + ComputeLineHeight(aContent, aStyleContext, aBlockBSize, aFontSizeInflation); NS_ASSERTION(lineHeight >= 0, "ComputeLineHeight screwed up"); diff --git a/tbb-tests/mochitest.ini b/tbb-tests/mochitest.ini index 3d2e7c9db8036..fca972a512111 100644 --- a/tbb-tests/mochitest.ini +++ b/tbb-tests/mochitest.ini @@ -10,3 +10,4 @@ support-files = [test_tor_bug2875.html] [test_tor_bug4755.html] [test_tor_bug5856.html] +[test_tor_bug23104.html] diff --git a/tbb-tests/test_tor_bug23104.html b/tbb-tests/test_tor_bug23104.html new file mode 100644 index 0000000000000..ae73a34460372 --- /dev/null +++ b/tbb-tests/test_tor_bug23104.html @@ -0,0 +1,51 @@ + + + + + Test for Tor Bug #23104: CSS line-height reveals the platform Tor browser is running + + + + + +Test1 +كلمة +ação + + + -- GitLab