Simplify singleton handling.

While working on the visual-mode code, it became apparent that our
current "singleton" implementation is unnecessarily complicated.

This simplifies it.  The keys are now required to be strings.

(Previously, they could be any object; which meant we needed to gove
objects an identity.  All of which was complicated.)

6 files changed, 12 insertions, 34 deletions

diff --git a/content_scripts/mode.coffee b/content_scripts/mode.coffee
index 205b8288..d5775ad7 100644
--- a/content_scripts/mode.coffee
+++ b/content_scripts/mode.coffee
@@ -109,15 +109,14 @@ class Mode
         "scroll": (event) => @alwaysContinueBubbling => @exit event
 
     # Some modes are singletons: there may be at most one instance active at any time.  A mode is a singleton
-    # if @options.singleton is truthy.  The value of @options.singleton should be the key which is intended to
-    # be unique.  New instances deactivate existing instances with the same key.
+    # if @options.singleton is set.  The value of @options.singleton should be the key which is intended to be
+    # unique.  New instances deactivate existing instances with the same key.
     if @options.singleton
-      do =>
-        singletons = Mode.singletons ||= {}
-        key = Utils.getIdentity @options.singleton
-        @onExit -> delete singletons[key]
-        @deactivateSingleton @options.singleton
-        singletons[key] = this
+      singletons = Mode.singletons ||= {}
+      key = @options.singleton
+      @onExit -> delete singletons[key]
+      singletons[key]?.exit()
+      singletons[key] = this
 
     # If @options.passInitialKeyupEvents is set, then we pass initial non-printable keyup events to the page
     # or to other extensions (because the corresponding keydown events were passed).  This is used when
@@ -182,9 +181,6 @@ class Mode
       @modeIsActive = false
       @setIndicator()
 
-  deactivateSingleton: (singleton) ->
-    Mode.singletons?[Utils.getIdentity singleton]?.exit()
-
   # Shorthand for an otherwise long name.  This wraps a handler with an arbitrary return value, and always
   # yields @continueBubbling instead.  This simplifies handlers if they always continue bubbling (a common
   # case), because they do not need to be concerned with the value they yield.
diff --git a/content_scripts/mode_find.coffee b/content_scripts/mode_find.coffee
index e863b553..ad7cc136 100644
--- a/content_scripts/mode_find.coffee
+++ b/content_scripts/mode_find.coffee
@@ -33,8 +33,8 @@ class PostFindMode extends SuppressPrintable
 
     super
       name: "post-find"
-      # PostFindMode shares a singleton with the modes launched by focusInput; each displaces the other.
-      singleton: element
+      # PostFindMode shares a singleton with focusInput; each displaces the other.
+      singleton: "post-find-mode/focus-input"
       exitOnBlur: element
       exitOnClick: true
       keydown: (event) -> InsertMode.suppressEvent event # Always truthy, so always continues bubbling.
diff --git a/content_scripts/mode_visual.coffee b/content_scripts/mode_visual.coffee
index 20560298..a6102987 100644
--- a/content_scripts/mode_visual.coffee
+++ b/content_scripts/mode_visual.coffee
@@ -212,9 +212,6 @@ class VisualMode extends KeyHandlerMode
     "c": -> @movement.collapseSelectionToAnchor(); new CaretMode
     "o": -> @movement.reverseSelection()
 
-    # TODO(smblott): "aw", etc.
-    # TODO(smblott): simplify singletons.
-
   constructor: (options = {}) ->
     @movement = new Movement options.alterMethod ? "extend"
     @selection = @movement.selection
@@ -236,7 +233,7 @@ class VisualMode extends KeyHandlerMode
     super extend options,
       name: options.name ? "visual"
       indicator: options.indicator ? "Visual mode"
-      singleton: VisualMode
+      singleton: "visual-mode-group" # Visual mode, visual-line mode and caret mode each displace each other.
       exitOnEscape: true
       suppressAllKeyboardEvents: true
       keyMapping: keyMapping
diff --git a/content_scripts/vimium_frontend.coffee b/content_scripts/vimium_frontend.coffee
index ade14029..1801a3fd 100644
--- a/content_scripts/vimium_frontend.coffee
+++ b/content_scripts/vimium_frontend.coffee
@@ -392,8 +392,6 @@ extend window,
                 selectedInputIndex += hints.length + (if event.shiftKey then -1 else 1)
                 selectedInputIndex %= hints.length
                 hints[selectedInputIndex].classList.add 'internalVimiumSelectedInputHint'
-                # Deactivate any active modes on this element (PostFindMode, or a suspended edit mode).
-                @deactivateSingleton visibleInputs[selectedInputIndex].element
                 DomUtils.simulateSelect visibleInputs[selectedInputIndex].element
                 @suppressEvent
               else unless event.keyCode == KeyboardUtils.keyCodes.shiftKey
@@ -405,8 +403,6 @@ extend window,
             id: "vimiumInputMarkerContainer"
             className: "vimiumReset"
 
-          # Deactivate any active modes on this element (PostFindMode, or a suspended edit mode).
-          @deactivateSingleton visibleInputs[selectedInputIndex].element
           DomUtils.simulateSelect visibleInputs[selectedInputIndex].element
           if visibleInputs.length == 1
             @exit()
@@ -419,7 +415,7 @@ extend window,
           DomUtils.removeElement @hintContainingDiv
           if mode and document.activeElement and DomUtils.isEditable document.activeElement
             new mode
-              singleton: document.activeElement
+              singleton: "post-find-mode/focus-input"
               targetElement: document.activeElement
               indicator: false
 
diff --git a/lib/utils.coffee b/lib/utils.coffee
index 31f4bec6..60d29998 100644
--- a/lib/utils.coffee
+++ b/lib/utils.coffee
@@ -197,17 +197,6 @@ Utils =
   # locale-sensitive uppercase detection
   hasUpperCase: (s) -> s.toLowerCase() != s
 
-  # Give objects (including elements) distinct identities.
-  getIdentity: do ->
-    identities = []
-
-    (obj) ->
-      index = identities.indexOf obj
-      if index < 0
-        index = identities.length
-        identities.push obj
-      "identity-" + index
-
   # Return a copy of object, but with some of its properties omitted.
   copyObjectOmittingProperties: (obj, properties...) ->
     obj = extend {}, obj
diff --git a/tests/dom_tests/dom_tests.coffee b/tests/dom_tests/dom_tests.coffee
index dad4def9..979500f5 100644
--- a/tests/dom_tests/dom_tests.coffee
+++ b/tests/dom_tests/dom_tests.coffee
@@ -744,7 +744,7 @@ context "Mode utilities",
     count = 0
 
     class Test extends Mode
-      constructor: -> count += 1; super singleton: Test
+      constructor: -> count += 1; super singleton: "test"
       exit: -> count -= 1; super()
 
     assert.isTrue count == 0