Add documents for the spell checker framework and the input method subtype

Bug: 4973788

Change-Id: I7e650f336ba1bb8949899e8b2355e6d492a2e4b2

2 files changed, 70 insertions, 0 deletions

diff --git a/core/java/android/view/textservice/SpellCheckerSession.java b/core/java/android/view/textservice/SpellCheckerSession.java
index b940b80..793f514 100644
--- a/core/java/android/view/textservice/SpellCheckerSession.java
+++ b/core/java/android/view/textservice/SpellCheckerSession.java
@@ -34,6 +34,51 @@ import java.util.Queue;
 
 /**
  * The SpellCheckerSession interface provides the per client functionality of SpellCheckerService.
+ *
+ *
+ * <a name="Applications"></a>
+ * <h3>Applications</h3>
+ *
+ * <p>In most cases, applications that are using the standard
+ * {@link android.widget.TextView} or its subclasses will have little they need
+ * to do to work well with spell checker services.  The main things you need to
+ * be aware of are:</p>
+ *
+ * <ul>
+ * <li> Properly set the {@link android.R.attr#inputType} in your editable
+ * text views, so that the spell checker will have enough context to help the
+ * user in editing text in them.
+ * </ul>
+ *
+ * <p>For the rare people amongst us writing client applications that use the spell checker service
+ * directly, you will need to use {@link #getSuggestions(TextInfo, int)} or
+ * {@link #getSuggestions(TextInfo[], int, boolean)} for obtaining results from the spell checker
+ * service by yourself.</p>
+ *
+ * <h3>Security</h3>
+ *
+ * <p>There are a lot of security issues associated with spell checkers,
+ * since they could monitor all the text being sent to them
+ * through, for instance, {@link android.widget.TextView}.
+ * The Android spell checker framework also allows
+ * arbitrary third party spell checkers, so care must be taken to restrict their
+ * selection and interactions.</p>
+ *
+ * <p>Here are some key points about the security architecture behind the
+ * spell checker framework:</p>
+ *
+ * <ul>
+ * <li>Only the system is allowed to directly access a spell checker framework's
+ * {@link android.service.textservice.SpellCheckerService} interface, via the
+ * {@link android.Manifest.permission#BIND_TEXT_SERVICE} permission.  This is
+ * enforced in the system by not binding to a spell checker service that does
+ * not require this permission.
+ *
+ * <li>The user must explicitly enable a new spell checker in settings before
+ * they can be enabled, to confirm with the system that they know about it
+ * and want to make it available for use.
+ * </ul>
+ *
  */
 public class SpellCheckerSession {
     private static final String TAG = SpellCheckerSession.class.getSimpleName();
diff --git a/core/java/android/view/textservice/TextServicesManager.java b/core/java/android/view/textservice/TextServicesManager.java
index b06c112..69f88a5 100644
--- a/core/java/android/view/textservice/TextServicesManager.java
+++ b/core/java/android/view/textservice/TextServicesManager.java
@@ -35,6 +35,31 @@ import java.util.Locale;
  *
  * The user can change the current text services in Settings. And also applications can specify
  * the target text services.
+ *
+ * <h3>Architecture Overview</h3>
+ *
+ * <p>There are three primary parties involved in the text services
+ * framework (TSF) architecture:</p>
+ *
+ * <ul>
+ * <li> The <strong>text services manager</strong> as expressed by this class
+ * is the central point of the system that manages interaction between all
+ * other parts.  It is expressed as the client-side API here which exists
+ * in each application context and communicates with a global system service
+ * that manages the interaction across all processes.
+ * <li> A <strong>text service</strong> implements a particular
+ * interaction model allowing the client application to retrieve information of text.
+ * The system binds to the current text service that is in use, causing it to be created and run.
+ * <li> Multiple <strong>client applications</strong> arbitrate with the text service
+ * manager for connections to text services.
+ * </ul>
+ *
+ * <h3>Text services sessions</h3>
+ * <ul>
+ * <li>The <strong>spell checker session</strong> is one of the text services.
+ * {@link android.view.textservice.SpellCheckerSession}</li>
+ * </ul>
+ *
  */
 public final class TextServicesManager {
     private static final String TAG = TextServicesManager.class.getSimpleName();