Bug 950936 - Introduce ui.popup.disable_autohide pref to ease debugging popups. r=neil

layout/xul/nsXULPopupManager.cpp

@@ -109,6 +109,11 @@ void nsMenuChainItem::Detach(nsMenuChainItem** aRoot)
   }
 }
 
+bool nsXULPopupManager::sDevtoolsDisableAutoHide = false;
+
+const char* kPrefDevtoolsDisableAutoHide =
+  "ui.popup.disable_autohide";
+
 NS_IMPL_ISUPPORTS(nsXULPopupManager,
                   nsIDOMEventListener,
                   nsITimerCallback,
@@ -127,6 +132,8 @@ nsXULPopupManager::nsXULPopupManager() :
   if (obs) {
     obs->AddObserver(this, "xpcom-shutdown", false);
   }
+  Preferences::AddBoolVarCache(&sDevtoolsDisableAutoHide,
+                               kPrefDevtoolsDisableAutoHide, false);
 }
 
 nsXULPopupManager::~nsXULPopupManager() 
@@ -183,6 +190,15 @@ bool
 nsXULPopupManager::Rollup(uint32_t aCount, bool aFlush,
                           const nsIntPoint* pos, nsIContent** aLastRolledUp)
 {
+  // We can disable the autohide behavior via a pref to ease debugging.
+  if (nsXULPopupManager::sDevtoolsDisableAutoHide) {
+    // Required on linux to allow events to work on other targets.
+    if (mWidget) {
+      mWidget->CaptureRollupEvents(nullptr, false);
+    }
+    return false;
+  }
+
   bool consume = false;
 
   nsMenuChainItem* item = GetTopVisibleMenu();

layout/xul/nsXULPopupManager.h

@@ -778,6 +778,9 @@ protected:
   // the popup that is currently being opened, stored only during the
   // popupshowing event
   nsCOMPtr<nsIContent> mOpeningPopup;
+
+  // If true, all popups won't hide automatically on blur
+  static bool sDevtoolsDisableAutoHide;
 };
 
 #endif

modules/libpref/init/all.js

@@ -220,6 +220,9 @@ pref("ui.use_native_colors", true);
 pref("ui.click_hold_context_menus", false);
 // Duration of timeout of incremental search in menus (ms).  0 means infinite.
 pref("ui.menu.incremental_search.timeout", 1000);
+// If true, all popups won't hide automatically on blur
+pref("ui.popup.disable_autohide", false);
+
 pref("browser.display.use_document_fonts",  1);  // 0 = never, 1 = quick, 2 = always
 // 0 = default: always, except in high contrast mode
 // 1 = always