Firefox Extension/Addon - Detect workspace locked

Question

I'm searching for a solution in my firefox addon to detect when the user workspace has locked/released. In google chrome there is an easy API chrome.idle.onStateChanged.addListener for it, is there something similar in firefox or any possibility to do that, platform independent? By the way, I use the addon sdk.

I've already tried the idle service:

Cc["@mozilla.org/widget/idleservice;1"].getService(Ci.nsIIdleService) 

but I just gives me access to some idle timeout or system when go to sleep and not to just workspace locked.

Edit: With "workspace locked" I mean the user lock the workspace with ctrl + alt + delete. I don't know how this exactly work on OSX or linux.

Edit2: I working in Windows 8.1 currently, but I guess the chrome.idle handler works cross platform.

Edit3: What i currently get out of current answers is 1. That there not exist a cross-platform solution, neither in chrome nor in firefox. chrome.idle.onStateChanged seems to work different on windows, linux and osx. Only windows can handle that "locked" behaviour as expected. I can't test OSX, on ubuntu 14 it doesn't work for me.
2. For firefox there some in-depth code things to try to make it working - see answer bellow from Noitidart in this topic.

Edit4: Noitidart have found a solution for windows - github link.

Answer 1

I don't know how to detect screen lock but there are these observer notifications:

https://developer.mozilla.org/en-US/docs/Observer_Notifications#Idle_Service

Also the computer sleep wake notifications. ill ask around for lock screen thats an interesting one.

Some useful chat about the subject, looking at how google chrome does it:

[12:33] ok guys question about actual work. anyone know how to detect if screen was locked? apparently google chrome has a method: https://developer.chrome.com/extensions/idle#event-onStateChanged

[12:45] anyone know of a MXR or DXR for google chromes codebase?

[12:46] mxr.mozilla.org/chromium

[12:52] Ms2ger: can you help me find how they test screen lock. im looking here: http://mxr.mozilla.org/chromium/source/src/chrome/browser/extensions/api/idle/idle_api_unittest.cc#84

[12:56] oh yuck it looks like they poll: http://mxr.mozilla.org/chromium/source/src/chrome/browser/extensions/api/idle/idle_manager.h#118

maybe they arent polling.

check this out:

http://mxr.mozilla.org/chromium/source/src/chrome/browser/extensions/api/idle/idle_manager.cc#246

244 void IdleManager::UpdateIdleStateCallback(int idle_time) {
245   DCHECK(thread_checker_.CalledOnValidThread());
246   bool locked = idle_time_provider_->CheckIdleStateIsLocked();
247   int listener_count = 0;

leads to: http://mxr.mozilla.org/chromium/source/src/chrome/browser/idle_win.cc#52

52 bool CheckIdleStateIsLocked() {
53   return ui::IsWorkstationLocked() || IsScreensaverRunning();
54 }

so this leads us to test if screensaver running or workstation locked

leads to:

• http://mxr.mozilla.org/chromium/search?string=IsWorkstationLocked

  • we see just one implementation (its curious because there is no linux support but it doesnt say so on the chrome docs page, so maybe i couldnt find it)

    • Windows

      • http://mxr.mozilla.org/chromium/source/src/ui/base/win/lock_state.cc#11

        11 bool IsWorkstationLocked() {
        12   bool is_locked = true;
        13   HDESK input_desk = ::OpenInputDesktop(0, 0, GENERIC_READ);
        14   if (input_desk) {
        15     wchar_t name[256] = {0};
        16     DWORD needed = 0;
        17     if (::GetUserObjectInformation(
        18             input_desk, UOI_NAME, name, sizeof(name), &needed)) {
        19       is_locked = lstrcmpi(name, L"default") != 0;
        20     }
        21     ::CloseDesktop(input_desk);
        22   }
        23   return is_locked;
        24 }
        

    • Mac
      • see the screensaver section below, the screenlock is handled via there as well

• http://mxr.mozilla.org/chromium/search?string=IsScreensaverRunning&find=&findi=&filter=^%5B^\0%5D*%24&hitlimit=&tree=chromium

  • we see in this search results 2 implementations, mac and windows it looks like no support for linux, which is curious because the chrome.idle page doesnt mention this on docs, maybe i just couldnt find it

    • windows implementation: http://mxr.mozilla.org/chromium/source/src/chrome/browser/idle_win.cc#39

      39 bool IsScreensaverRunning() {
      40   DWORD result = 0;
      41   if (::SystemParametersInfo(SPI_GETSCREENSAVERRUNNING, 0, &result, 0))
      42     return result != FALSE;
      43   return false;
      44 }
      45 
      

    • mac implementation: http://mxr.mozilla.org/chromium/source/src/chrome/browser/idle_mac.mm#28

      28 - (id)init {
      29   if ((self = [super init])) {
      30     NSDistributedNotificationCenter* distCenter =
      31           [NSDistributedNotificationCenter defaultCenter];
      32     [distCenter addObserver:self
      33                    selector:@selector(onScreenSaverStarted:)
      34                        name:@"com.apple.screensaver.didstart"
      35                      object:nil];
      36     [distCenter addObserver:self
      37                    selector:@selector(onScreenSaverStopped:)
      38                        name:@"com.apple.screensaver.didstop"
      39                      object:nil];
      40     [distCenter addObserver:self
      41                    selector:@selector(onScreenLocked:)
      42                        name:@"com.apple.screenIsLocked"
      43                      object:nil];
      44     [distCenter addObserver:self
      45                    selector:@selector(onScreenUnlocked:)
      46                        name:@"com.apple.screenIsUnlocked"
      47                      object:nil];
      48   }
      49   return self;
      50 }
      

so to sum this all up:

[13:32] for windows its peice of cake winapi has call to test if screen is locked or scrensaver running

[13:32] for mac they dont have screen lock test. they just have screensaver test, but its an observer method

[13:32] for linux they dont have screen lock nor screen saver test. real odd. ill ask the guy if he knows which os's they support chrome.idle in

edit: actually i found the linux implementation. back from the search results of: CheckIdleStateLocked: http://mxr.mozilla.org/chromium/search?string=CheckIdleStateIsLocked

• http://mxr.mozilla.org/chromium/source/src/chrome/browser/idle_linux.cc#24

  24 bool CheckIdleStateIsLocked() {
  25   // Usually the screensaver is used to lock the screen, so we do not need to
  26   // check if the workstation is locked.
  27 #if defined(OS_CHROMEOS)
  28   return false;
  29 #elif defined(USE_OZONE)
  30   return false;
  31 #else
  32   return ScreensaverWindowFinder::ScreensaverWindowExists();
  33 #endif
  34 }
  

• Leads to ask how is ScreensaverWindowExists we find this: http://mxr.mozilla.org/chromium/source/src/chrome/browser/screensaver_window_finder_x11.cc

  15 bool ScreensaverWindowFinder::ScreensaverWindowExists() {
  16   gfx::X11ErrorTracker err_tracker;
  17   ScreensaverWindowFinder finder;
  18   ui::EnumerateTopLevelWindows(&finder);
  19   return finder.exists_ && !err_tracker.FoundNewError();
  20 }
  

• Leads to what is EnumerateTopLevelWindows http://mxr.mozilla.org/chromium/source/src/ui/base/x/x11_util.cc#1059:

  1059 void EnumerateTopLevelWindows(ui::EnumerateWindowsDelegate* delegate) {
  1060   std::vector<XID> stack;
  1061   if (!ui::GetXWindowStack(ui::GetX11RootWindow(), &stack)) {
  1062     // Window Manager doesn't support _NET_CLIENT_LIST_STACKING, so fall back
  1063     // to old school enumeration of all X windows.  Some WMs parent 'top-level'
  1064     // windows in unnamed actual top-level windows (ion WM), so extend the
  1065     // search depth to all children of top-level windows.
  1066     const int kMaxSearchDepth = 1;
          1067     ui::EnumerateAllWindows(delegate, kMaxSearchDepth);
  1068     return;
  1069   }
  1070   XMenuList::GetInstance()->InsertMenuWindowXIDs(&stack);
  1071 
  1072   std::vector<XID>::iterator iter;
  1073   for (iter = stack.begin(); iter != stack.end(); iter++) {
  1074     if (delegate->ShouldStopIterating(*iter))
  1075       return;
  1076   }
  1077 }
  1078 
  

• We say they call delegate->ShouldStopIterating which was seen in same file as ScreensaverWindowExists: http://mxr.mozilla.org/chromium/source/src/chrome/browser/screensaver_window_finder_x11.cc

  22 bool ScreensaverWindowFinder::ShouldStopIterating(XID window) {
  23   if (!ui::IsWindowVisible(window) || !IsScreensaverWindow(window))
  24     return false;
  25   exists_ = true;
  26   return true;
  27 }
  

• Leads to ask what is IsWindowVisible and IsScreensaverWindow

*IsScreensaverWindow, in same file of ScreensaverWindowExists: http://mxr.mozilla.org/chromium/source/src/chrome/browser/screensaver_window_finder_x11.cc

    29 bool ScreensaverWindowFinder::IsScreensaverWindow(XID window) const {
    30   // It should occupy the full screen.
    31   if (!ui::IsX11WindowFullScreen(window))
    32     return false;
    33 
    34   // For xscreensaver, the window should have _SCREENSAVER_VERSION property.
    35   if (ui::PropertyExists(window, "_SCREENSAVER_VERSION"))
    36     return true;
    37 
    38   // For all others, like gnome-screensaver, the window's WM_CLASS property
    39   // should contain "screensaver".
    40   std::string value;
    41   if (!ui::GetStringProperty(window, "WM_CLASS", &value))
    42     return false;
    43 
    44   return value.find("screensaver") != std::string::npos;
    45 }

• IsWindowVisible: http://mxr.mozilla.org/chromium/source/src/ui/base/x/x11_util.cc#546

  546 bool IsWindowVisible(XID window) {
  547   TRACE_EVENT0("ui", "IsWindowVisible");
  548 
  549   XWindowAttributes win_attributes;
  550   if (!XGetWindowAttributes(gfx::GetXDisplay(), window, &win_attributes))
  551     return false;
  552   if (win_attributes.map_state != IsViewable)
  553     return false;
  554 
  555   // Minimized windows are not visible.
  556   std::vector<XAtom> wm_states;
  557   if (GetAtomArrayProperty(window, "_NET_WM_STATE", &wm_states)) {
  558     XAtom hidden_atom = GetAtom("_NET_WM_STATE_HIDDEN");
  559     if (std::find(wm_states.begin(), wm_states.end(), hidden_atom) !=
  560             wm_states.end()) {
  561       return false;
  562     }
  563   }