Support Home/End/Del in input buffer, fixes #63.

Also fix two subtle issues:

1. Enter (not Return) key now works in candidate list
2. Cursor index should be compared against builder's length, *not*
   composed string's length, because the former is counted in
   code point but the latter in UTF-16 units. The composed string's
   length might therefore be longer if the string contains
   codepoints > U+FFFF, which would cause the cursor mechanism to
   be off.

Source/InputMethodController.mm

@@ -87,6 +87,7 @@ static NSString *const kPlainBopomofoModeIdentifier = @"org.openvanilla.inputmet
 
 // key code enums
 enum {
+    kEnterKeyCode = 76,
     kUpKeyCode = 126,
     kDownKeyCode = 125,
     kLeftKeyCode = 123,
@@ -94,7 +95,8 @@ enum {
     kPageUpKeyCode = 116,
     kPageDownKeyCode = 121,
     kHomeKeyCode = 115,
-    kEndKeyCode = 119
+    kEndKeyCode = 119,
+    kDeleteKeyCode = 117
 };
 
 // a global object for saving the "learned" user candidate selections
@@ -524,7 +526,7 @@ public:
         [self updateClientComposingBuffer:_currentCandidateClient];
         return YES;
     }
-    else if (charCode == 13 || keyCode == 127) {
+    else if (charCode == 13 || keyCode == kEnterKeyCode) {
         [self candidateController:gCurrentCandidateController didSelectCandidateAtIndex:gCurrentCandidateController.selectedCandidateIndex];
         return YES;
     }
@@ -765,7 +767,6 @@ public:
         return [self handleCandidateEventWithInputText:inputText charCode:charCode keyCode:keyCode];
     }
     
-    
     // see if it's valid BPMF reading
     if (_bpmfReadingBuffer->isValidKey((char)charCode)) {
         _bpmfReadingBuffer->combineKey((char)charCode);
@@ -896,7 +897,7 @@ public:
                 return NO;
             }
 
-            if (_builder->cursorIndex() < [_composingBuffer length]) {
+            if (_builder->cursorIndex() < _builder->length()) {
                 _builder->setCursorIndex(_builder->cursorIndex() + 1);
             }
             else {
@@ -908,6 +909,48 @@ public:
         return YES;
     }
 
+    if (keyCode == kHomeKeyCode) {
+        if (!_bpmfReadingBuffer->isEmpty()) {
+            [self beep];
+        }
+        else {
+            if (![_composingBuffer length]) {
+                return NO;
+            }
+
+            if (_builder->cursorIndex()) {
+                _builder->setCursorIndex(0);
+            }
+            else {
+                [self beep];
+            }
+        }
+
+        [self updateClientComposingBuffer:client];
+        return YES;
+    }
+
+    if (keyCode == kEndKeyCode) {
+        if (!_bpmfReadingBuffer->isEmpty()) {
+            [self beep];
+        }
+        else {
+            if (![_composingBuffer length]) {
+                return NO;
+            }
+
+            if (_builder->cursorIndex() != _builder->length()) {
+                _builder->setCursorIndex(_builder->length());
+            }
+            else {
+                [self beep];
+            }
+        }
+
+        [self updateClientComposingBuffer:client];
+        return YES;
+    }
+
     if (keyCode == absorbedArrowKey || keyCode == extraChooseCandidateKey) {
         if (!_bpmfReadingBuffer->isEmpty()) {
             [self beep];
@@ -939,6 +982,30 @@ public:
         return YES;
     }
 
+    // Delete
+    if (keyCode == kDeleteKeyCode) {
+        if (_bpmfReadingBuffer->isEmpty()) {
+            if (![_composingBuffer length]) {
+                return NO;
+            }
+
+            if (_builder->cursorIndex() != _builder->length()) {
+                _builder->deleteReadingAfterCursor();
+                [self walk];
+            }
+            else {
+                [self beep];
+            }
+        }
+        else {
+            [self beep];
+        }
+
+        [self updateClientComposingBuffer:client];
+        return YES;
+    }
+
+
     // Enter
     if (charCode == 13) {
         if (![_composingBuffer length]) {