[escher] Fix signed/unsigned int comparison

Change-Id: I72b6dc3f46ee585814a540fc999001e113db0ea1

escher/include/escher/text_input_helpers.h

@@ -2,10 +2,11 @@
 #define ESCHER_TEXT_INPUT_HELPERS_H
 
 #include <escher/i18n.h>
+#include <stddef.h>
 
 namespace TextInputHelpers {
 
-int CursorIndexInCommand(const char * text);
+size_t CursorIndexInCommand(const char * text);
 /* Returns the index of the cursor position in a Command, which is the smallest
  * index between :
  *   - The first EmptyChar index (which is the position of the first argument)

escher/src/text_area.cpp

@@ -294,7 +294,7 @@ TextArea::TextArea(Responder * parentResponder, char * textBuffer,
 bool TextArea::handleEventWithText(const char * text, bool indentation) {
   int nextCursorLocation = cursorLocation();
 
-  int cursorIndexInCommand = TextInputHelpers::CursorIndexInCommand(text);
+  size_t cursorIndexInCommand = TextInputHelpers::CursorIndexInCommand(text);
 
   size_t eventTextSize = strlen(text) + 1;
   char buffer[eventTextSize];

escher/src/text_input_helpers.cpp

@@ -4,16 +4,17 @@
 
 namespace TextInputHelpers {
 
-int CursorIndexInCommand(const char * text) {
-  int textLength = strlen(text);
-  for (int i = 0; i < textLength - 1; i++) {
-    if (text[i] == '\'' &&  text[i+1] == '\'') {
-      return i + 1;
-    } else if (text[i] == Ion::Charset::Empty) {
-      return i;
+size_t CursorIndexInCommand(const char * text) {
+  size_t index = 0;
+  while (text[index] != 0) {
+    if (text[index] == '\'' &&  text[index+1] == '\'') {
+      return index + 1;
+    } else if (text[index] == Ion::Charset::Empty) {
+      return index;
     }
+    index++;
   }
-  return textLength;
+  return index;
 }
 
 }