Bug 1737501 - Allow contextmenu option on Windows SystemStatusBar r=mconley

We want to be able to have a different behavior for interactions with an entry
in the Windows system tray - specifically, we want to be able to open a window
on left click, and show a menu on right click. This patch allows us to control
this with a "contextmenu" attribute on the menu passed in to `AddItem`, and
receive a "systemstatusbarclick" event in the case of a left click.

Regarding tests, I don't know that we have a good way of testing this?
Suggestions are of course welcome here.

Differential Revision: https://phabricator.services.mozilla.com/D129413

dom/events/EventNameList.h

@@ -422,6 +422,8 @@ NON_IDL_EVENT(overflow, eScrollPortOverflow, EventNameType_XUL,
               eBasicEventClass)
 NON_IDL_EVENT(underflow, eScrollPortUnderflow, EventNameType_XUL,
               eBasicEventClass)
+NON_IDL_EVENT(systemstatusbarclick, eXULSystemStatusBarClick, EventNameType_XUL,
+              eBasicEventClass)
 
 // Various SVG events
 NON_IDL_EVENT(SVGLoad, eSVGLoad, EventNameType_None, eBasicEventClass)

widget/EventMessageList.h

@@ -156,6 +156,7 @@ NS_EVENT_MESSAGE(eXULPopupHiding)
 NS_EVENT_MESSAGE(eXULPopupHidden)
 NS_EVENT_MESSAGE(eXULBroadcast)
 NS_EVENT_MESSAGE(eXULCommandUpdate)
+NS_EVENT_MESSAGE(eXULSystemStatusBarClick)
 
 // Legacy mouse scroll (wheel) events
 NS_EVENT_MESSAGE(eLegacyMouseLineOrPageScroll)

widget/windows/SystemStatusBar.cpp

@@ -10,6 +10,7 @@
 #include "mozilla/dom/Document.h"
 #include "mozilla/dom/Element.h"
 #include "mozilla/ClearOnShutdown.h"
+#include "mozilla/EventDispatcher.h"
 #include "mozilla/LinkedList.h"
 #include "mozilla/StaticPtr.h"
 #include "mozilla/widget/IconLoader.h"
@@ -212,6 +213,16 @@ LRESULT StatusBarEntry::OnMessage(HWND hWnd, UINT msg, WPARAM wp, LPARAM lp) {
       return TRUE;
     }
 
+    if (LOWORD(lp) == WM_LBUTTONUP &&
+        mMenu->HasAttr(kNameSpaceID_None, nsGkAtoms::contextmenu)) {
+      nsEventStatus status = nsEventStatus_eIgnore;
+      WidgetMouseEvent event(true, eXULSystemStatusBarClick, nullptr,
+                             WidgetMouseEvent::eReal);
+      EventDispatcher::Dispatch(mMenu, menu->PresContext(), &event, nullptr,
+                                &status);
+      return DefWindowProc(hWnd, msg, wp, lp);
+    }
+
     nsMenuPopupFrame* popupFrame = menu->GetPopup();
     if (!popupFrame) {
       return TRUE;

xpcom/ds/StaticAtoms.py

@@ -907,6 +907,7 @@ STATIC_ATOMS = [
     Atom("onstorage", "onstorage"),
     Atom("onsubmit", "onsubmit"),
     Atom("onsuccess", "onsuccess"),
+    Atom("onsystemstatusbarclick", "onsystemstatusbarclick"),
     Atom("ontypechange", "ontypechange"),
     Atom("onterminate", "onterminate"),
     Atom("ontext", "ontext"),