140612: Introduce tab usage pref accessibility.tabfocus, to allow tab to go only to form elements or only to text controls. (r,sr)=(bryner,sfraser)

content/events/src/nsEventStateManager.cpp

@@ -140,6 +140,8 @@ nsIContent * gLastFocusedContent = 0; // Strong reference
 nsIDocument * gLastFocusedDocument = 0; // Strong reference
 nsIPresContext* gLastFocusedPresContext = 0; // Weak reference
 
+PRInt32 nsEventStateManager::sTabFocusModel = eTabFocus_unset;
+
 PRUint32 nsEventStateManager::mInstanceCount = 0;
 PRInt32 nsEventStateManager::gGeneralAccesskeyModifier = -1; // magic value of -1 means uninitialized
 
@@ -3286,7 +3288,7 @@ nsEventStateManager::GetNextTabbableContent(nsIContent* aRootContent, nsIFrame*
   if (mCurrentFocus) {
     nsCOMPtr<nsIAtom> tag;
     mCurrentFocus->GetTag(*getter_AddRefs(tag));
-    if(nsHTMLAtoms::area==tag.get()) {
+    if(nsHTMLAtoms::area==tag) {
       //Focus is in an imagemap area
       nsCOMPtr<nsIPresShell> presShell;
       if (mPresContext) {
@@ -3366,10 +3368,22 @@ nsEventStateManager::GetNextTabbableContent(nsIContent* aRootContent, nsIFrame*
       PRBool disabled = PR_TRUE;
       PRBool hidden = PR_FALSE;
 
+      // Tab focus mode is constant across all windows.
+      // It would be nicer if ESM had a prefs callback,
+      // so we could store this and change behavior when it changes.
+      // But until the pref is exposed, that doesn't matter.
+      if (sTabFocusModel == eTabFocus_unset) {
+        sTabFocusModel = (eTabFocus_textControlsMask | eTabFocus_formElementsMask
+                          | eTabFocus_linksMask);
+        nsresult rv = getPrefService();
+        if (NS_SUCCEEDED(rv))
+          mPrefService->GetIntPref("accessibility.tabfocus", &sTabFocusModel);
+      }
+
       child->GetTag(*getter_AddRefs(tag));
       nsCOMPtr<nsIDOMHTMLElement> htmlElement(do_QueryInterface(child));
       if (htmlElement) {
-        if (nsHTMLAtoms::input==tag.get()) {
+        if (nsHTMLAtoms::input==tag) {
           nsCOMPtr<nsIDOMHTMLInputElement> nextInput(do_QueryInterface(child));
           if (nextInput) {
             nextInput->GetDisabled(&disabled);
@@ -3377,30 +3391,49 @@ nsEventStateManager::GetNextTabbableContent(nsIContent* aRootContent, nsIFrame*
 
             nsAutoString type;
             nextInput->GetType(type);
-            if (type.EqualsIgnoreCase("hidden")) {
+            if (type.EqualsIgnoreCase("text")) {
+              // It's a text field
+              disabled = !(sTabFocusModel & eTabFocus_textControlsMask);
+            }
+            else if (type.EqualsIgnoreCase("hidden")) {
               hidden = PR_TRUE;
             }
             else if (type.EqualsIgnoreCase("file")) {
               disabled = PR_TRUE;
             }
+            else {
+              // it's some other type of form element
+              disabled = !(sTabFocusModel & eTabFocus_formElementsMask);
             }
           }
-        else if (nsHTMLAtoms::select==tag.get()) {
+        }
+        else if (nsHTMLAtoms::select==tag) {
+          // Select counts as form but not as text
+          disabled = !(sTabFocusModel & eTabFocus_formElementsMask);
+          if (!disabled) {
           nsCOMPtr<nsIDOMHTMLSelectElement> nextSelect(do_QueryInterface(child));
           if (nextSelect) {
             nextSelect->GetDisabled(&disabled);
             nextSelect->GetTabIndex(&tabIndex);
           }
         }
-        else if (nsHTMLAtoms::textarea==tag.get()) {
+        }
+        else if (nsHTMLAtoms::textarea==tag) {
+          // it's a textarea
+          disabled = !(sTabFocusModel & eTabFocus_textControlsMask);
+          if (!disabled) {
           nsCOMPtr<nsIDOMHTMLTextAreaElement> nextTextArea(do_QueryInterface(child));
           if (nextTextArea) {
             nextTextArea->GetDisabled(&disabled);
             nextTextArea->GetTabIndex(&tabIndex);
           }
         }
-        else if(nsHTMLAtoms::a==tag.get()) {
+        }
+        else if (nsHTMLAtoms::a==tag) {
+          // it's a link
+          disabled = !(sTabFocusModel & eTabFocus_linksMask);
           nsCOMPtr<nsIDOMHTMLAnchorElement> nextAnchor(do_QueryInterface(child));
+          if (!disabled) {
           if (nextAnchor)
             nextAnchor->GetTabIndex(&tabIndex);
           nsAutoString href;
@@ -3411,14 +3444,22 @@ nsEventStateManager::GetNextTabbableContent(nsIContent* aRootContent, nsIFrame*
             disabled = PR_FALSE;
           }
         }
-        else if(nsHTMLAtoms::button==tag.get()) {
+        }
+        else if (nsHTMLAtoms::button==tag) {
+          // Button counts as a form element but not as text
+          disabled = !(sTabFocusModel & eTabFocus_formElementsMask);
+          if (!disabled) {
           nsCOMPtr<nsIDOMHTMLButtonElement> nextButton(do_QueryInterface(child));
           if (nextButton) {
             nextButton->GetTabIndex(&tabIndex);
             nextButton->GetDisabled(&disabled);
           }
         }
-        else if(nsHTMLAtoms::img==tag.get()) {
+        }
+        else if (nsHTMLAtoms::img==tag) {
+          // Images are treated like links for tab focus purposes.
+          disabled = !(sTabFocusModel & eTabFocus_linksMask);
+          if (!disabled) {
           nsCOMPtr<nsIDOMHTMLImageElement> nextImage(do_QueryInterface(child));
           nsAutoString usemap;
           if (nextImage) {
@@ -3439,10 +3480,12 @@ nsEventStateManager::GetNextTabbableContent(nsIContent* aRootContent, nsIFrame*
                       PRInt32 val = 0;
                       TabIndexFrom(childArea, &val);
                       if (mCurrentTabIndex == val) {
-                        //mCurrentFocus is in this map so we must start iterating past it.
-                        //We skip the case where mCurrentFocus has the same tab index
-                        //as mCurrentTabIndex since the next tab ordered element might
-                        //be before it (or after for backwards) in the child list.
+                          // mCurrentFocus is in this map so we must start
+                          // iterating past it.
+                          // We skip the case where mCurrentFocus has the
+                          // same tab index as mCurrentTabIndex since the
+                          // next tab ordered element might be before it
+                          // (or after for backwards) in the child list.
                         break;
                       }
                     }
@@ -3468,20 +3511,27 @@ nsEventStateManager::GetNextTabbableContent(nsIContent* aRootContent, nsIFrame*
             }
           }
         }
-        else if(nsHTMLAtoms::object==tag.get()) {
+        }
+        else if (nsHTMLAtoms::object==tag) {
+          // OBJECT is treated as a form element.
+          disabled = !(sTabFocusModel & eTabFocus_formElementsMask);
+          if (!disabled) {
           nsCOMPtr<nsIDOMHTMLObjectElement> nextObject(do_QueryInterface(child));
           if (nextObject) 
             nextObject->GetTabIndex(&tabIndex);
           disabled = PR_FALSE;
         }
-        else if (nsHTMLAtoms::iframe==tag.get()) {
+        }
+        else if (nsHTMLAtoms::iframe==tag) {
           disabled = PR_FALSE;
         } 
-        else if (nsHTMLAtoms::frame==tag.get()) {
+        else if (nsHTMLAtoms::frame==tag) {
           disabled = PR_FALSE;
         }
       }
-      else {
+      // Check the tabindex attribute, unless the model specifies text only.
+      // If the model is unset then we'll depend on tabindex.
+      else if (sTabFocusModel != eTabFocus_textControlsMask) {
         nsAutoString value;
         child->GetAttr(kNameSpaceID_None, nsHTMLAtoms::disabled, value);
         nsAutoString tabStr;

content/events/src/nsEventStateManager.h

@@ -71,6 +71,13 @@ class nsEventStateManager : public nsSupportsWeakReference,
                             public nsIEventStateManager,
                             public nsIObserver
 {
+  // Tab focus model bit field:
+  enum nsTabFocusModel {
+    eTabFocus_unset = 0,                  // unset, check preferences
+    eTabFocus_textControlsMask = (1<<0),  // text elements
+    eTabFocus_formElementsMask = (1<<1),  // non-text form elements
+    eTabFocus_linksMask = (1<<2)          // links
+  };
 
 public:
   nsEventStateManager();
@@ -273,6 +280,10 @@ protected:
   // So we don't have to keep checking accessibility.browsewithcaret pref
   PRBool mBrowseWithCaret;
 
+  // Tab focus policy (static, constant across the app):
+  // Which types of elements are in the tab order?
+  static PRInt32 sTabFocusModel;
+
   // Recursion guard for tabbing
   PRBool mTabbedThroughDocument;
 

modules/libpref/src/init/all.js

@@ -125,6 +125,10 @@ pref("browser.helperApps.neverAsk.openFile", "");
 
 pref("accessibility.browsewithcaret", false);
 pref("accessibility.warn_on_browsewithcaret", true);
+// Tab focus model bit field:
+// 1 focuses text controls, 2 focuses other form elements, 4 adds links.
+// Most users will want 1, 3, or 7.
+pref("accessibility.tabfocus", 7);
 pref("accessibility.usetexttospeech", "");
 pref("accessibility.usebrailledisplay", "");
 pref("accessibility.accesskeycausesactivation", true);

modules/libpref/src/mac/macprefs.js

@@ -180,6 +180,10 @@ pref("font.size.fixed.zh-CN", 16);
 pref("font.size.variable.zh-TW", 15);
 pref("font.size.fixed.zh-TW", 16);
 
+// Tab focus model bit field:
+// 1 focuses text controls, 2 focuses other form elements, 4 adds links.
+pref("accessibility.tabfocus", 1);
+
 // Override the Windows settings: no menu key, meta accelerator key. ctrl for general access key in HTML/XUL
 // Use 17 for Ctrl, 18 for Option, 224 for Cmd, 0 for none
 pref("ui.key.menuAccessKey", 0);

modules/libpref/src/unix/unix.js

@@ -67,6 +67,10 @@ pref("clipboard.autocopy", true);
 
 pref("browser.urlbar.clickSelectsAll", false);
 
+// Tab focus model bit field:
+// 1 focuses text controls, 2 focuses other form elements, 4 adds links.
+pref("accessibility.tabfocus", 1);
+
 // override double-click word selection behavior.
 pref("layout.word_select.stop_at_punctuation", false);