Initial implementation for decoding HW key events (B3)

Bug: 5037589
Change-Id: I829f70a258de58ef8d2b836a9b435198a226e37f

java/src/com/android/inputmethod/event/Event.java

@@ -29,8 +29,56 @@ package com.android.inputmethod.event;
  * The combiner should figure out what to do with this.
  */
 public class Event {
+    // Should the types below be represented by separate classes instead? It would be cleaner
+    // but probably a bit too much
+    // An event we don't handle in Latin IME, for example pressing Ctrl on a hardware keyboard.
+    final public static int EVENT_NOT_HANDLED = 0;
+    // A character that is already final, for example pressing an alphabetic character on a
+    // hardware qwerty keyboard.
+    final public static int EVENT_COMMITTABLE = 1;
+    // A dead key, which means a character that should combine with what is coming next. Examples
+    // include the "^" character on an azerty keyboard which combines with "e" to make "ê", or
+    // AltGr+' on a dvorak international keyboard which combines with "e" to make "é". This is
+    // true regardless of the language or combining mode, and should be seen as a property of the
+    // key - a dead key followed by another key with which it can combine should be regarded as if
+    // the keyboard actually had such a key.
+    final public static int EVENT_DEAD = 2;
+    // A toggle event is triggered by a key that affects the previous character. An example would
+    // be a numeric key on a 10-key keyboard, which would toggle between 1 - a - b - c with
+    // repeated presses.
+    final public static int EVENT_TOGGLE = 3;
+    // A mode event instructs the combiner to change modes. The canonical example would be the
+    // hankaku/zenkaku key on a Japanese keyboard, or even the caps lock key on a qwerty keyboard
+    // if handled at the combiner level.
+    final public static int EVENT_MODE_KEY = 4;
+
+    final private static int NOT_A_CODE_POINT = 0;
+
+    private int mType; // The type of event - one of the constants above
+    // The code point associated with the event, if relevant. This is a unicode code point, and
+    // has nothing to do with other representations of the key. It is only relevant if this event
+    // is the right type: COMMITTABLE or DEAD or TOGGLE, but for a mode key like hankaku/zenkaku or
+    // ctrl, there is no code point associated so this should be NOT_A_CODE_POINT to avoid
+    // unintentional use of its value when it's not relevant.
+    private int mCodePoint;
+
     static Event obtainEvent() {
         // TODO: create an event pool instead
         return new Event();
     }
+
+    public void setDeadEvent(final int codePoint) {
+        mType = EVENT_DEAD;
+        mCodePoint = codePoint;
+    }
+
+    public void setCommittableEvent(final int codePoint) {
+        mType = EVENT_COMMITTABLE;
+        mCodePoint = codePoint;
+    }
+
+    public void setNotHandledEvent() {
+        mType = EVENT_NOT_HANDLED;
+        mCodePoint = NOT_A_CODE_POINT; // Just in case
+    }
 }

java/src/com/android/inputmethod/event/HardwareKeyboardEventDecoder.java

@@ -16,10 +16,15 @@
 
 package com.android.inputmethod.event;
 
+import android.view.KeyCharacterMap;
 import android.view.KeyEvent;
 
 /**
  * A hardware event decoder for a hardware qwerty-ish keyboard.
+ *
+ * The events are always hardware keypresses, but they can be key down or key up events, they
+ * can be dead keys, they can be meta keys like shift or ctrl... This does not deal with
+ * 10-key like keyboards; a different decoder is used for this.
  */
 public class HardwareKeyboardEventDecoder implements HardwareEventDecoder {
     final int mDeviceId;
@@ -31,6 +36,23 @@ public class HardwareKeyboardEventDecoder implements HardwareEventDecoder {
 
     @Override
     public Event decodeHardwareKey(final KeyEvent keyEvent) {
-        return Event.obtainEvent();
+        final Event event = Event.obtainEvent();
+        // KeyEvent#getUnicodeChar() does not exactly returns a unicode char, but rather a value
+        // that includes both the unicode char in the lower 21 bits and flags in the upper bits,
+        // hence the name "codePointAndFlags". {@see KeyEvent#getUnicodeChar()} for more info.
+        final int codePointAndFlags = keyEvent.getUnicodeChar();
+        if (keyEvent.isPrintingKey()) {
+            if (0 != (codePointAndFlags & KeyCharacterMap.COMBINING_ACCENT)) {
+                // A dead key.
+                event.setDeadEvent(codePointAndFlags & KeyCharacterMap.COMBINING_ACCENT_MASK);
+            } else {
+                // A committable character. This should be committed right away, taking into
+                // account the current state.
+                event.setCommittableEvent(codePointAndFlags);
+            }
+        } else {
+            event.setNotHandledEvent();
+        }
+        return event;
     }
 }

java/src/com/android/inputmethod/event/SoftwareEventDecoder.java

@@ -17,7 +17,12 @@
 package com.android.inputmethod.event;
 
 /**
- * An event decoder for software events.
+ * An event decoder for events out of a software keyboard.
+ *
+ * This defines the interface for an event decoder that supports events out of a software keyboard.
+ * This differs significantly from hardware keyboard event decoders in several respects. First,
+ * a software keyboard does not have a scancode/layout system; the keypresses that insert
+ * characters output unicode characters directly.
  */
 public interface SoftwareEventDecoder extends EventDecoder {
     public Event decodeSoftwareEvent();