Bug 17009: Pref to suppress some modifier key events

383b8e7e · Arthur Edelstein · Georg Koppen · a65b5269 · 383b8e7e · 383b8e7e
Commit 383b8e7e authored Sep 23, 2015 by Arthur Edelstein Committed by Georg Koppen Mar 3, 2017
--- a/layout/base/nsIPresShell.h
+++ b/layout/base/nsIPresShell.h
@@ -1813,6 +1813,9 @@ protected:
  // to true, so we can avoid any paint calls for widget related to this
  // presshell.
  bool mIsNeverPainting;
+
+  // If true, don't report Alt, Shift, and AltGr KeyboardEvents to content.
+  static bool sSuppressModifierKeyEvents;
 };

 NS_DEFINE_STATIC_IID_ACCESSOR(nsIPresShell, NS_IPRESSHELL_IID)

--- a/layout/base/nsPresShell.cpp
+++ b/layout/base/nsPresShell.cpp
@@ -209,6 +209,7 @@ CapturingContentInfo nsIPresShell::gCaptureInfo =
 nsIContent* nsIPresShell::gKeyDownTarget;
 nsClassHashtable<nsUint32HashKey, nsIPresShell::PointerCaptureInfo>* nsIPresShell::gPointerCaptureList;
 nsClassHashtable<nsUint32HashKey, nsIPresShell::PointerInfo>* nsIPresShell::gActivePointersIds;
+bool nsIPresShell::sSuppressModifierKeyEvents = false;

 // RangePaintInfo is used to paint ranges to offscreen buffers
 struct RangePaintInfo {
@@ -6881,6 +6882,16 @@ PresShell::HandleKeyboardEvent(nsINode* aTarget,
                               nsEventStatus* aStatus,
                               EventDispatchingCallback* aEventCB)
 {
+  if (nsContentUtils::ResistFingerprinting() && sSuppressModifierKeyEvents) {
+    nsString keyName;
+    aEvent.GetDOMKeyName(keyName);
+    if (keyName.Equals(NS_LITERAL_STRING("Shift")) ||
+        keyName.Equals(NS_LITERAL_STRING("Alt")) ||
+        keyName.Equals(NS_LITERAL_STRING("AltGraph"))) {
+      aEvent.mFlags.mOnlyChromeDispatch = true;
+    }
+  }
+
  if (aEvent.mMessage == eKeyPress ||
      !BeforeAfterKeyboardEventEnabled()) {
    EventDispatcher::Dispatch(aTarget, mPresContext,
@@ -10545,6 +10556,8 @@ void nsIPresShell::InitializeStatics()
  NS_ASSERTION(!gPointerCaptureList, "InitializeStatics called multiple times!");
  gPointerCaptureList = new nsClassHashtable<nsUint32HashKey, PointerCaptureInfo>;
  gActivePointersIds = new nsClassHashtable<nsUint32HashKey, PointerInfo>;
+  Preferences::AddBoolVarCache(&sSuppressModifierKeyEvents,
+                               "privacy.suppressModifierKeyEvents", false);
 }

 void nsIPresShell::ReleaseStatics()