UnicodeTranscript: add fast path for getLine() on an entire FullUnicodeLine

getLine() is called frequently during screen drawing and other
operations, usually with a request for the contents of an entire line.
We have a fast path for this case with basic lines; something similar
works for FullUnicodeLines, so let's do that too.

Also, update the documentation to reflect the fact that the array
returned from getLine() will not be null-terminated if the array size
exactly matches the length of the requested text.

Author: steven676

libraries/emulatorview/src/jackpal/androidterm/emulatorview/UnicodeTranscript.java

@@ -563,9 +563,10 @@ public static int charWidth(char[] chars, int index) {
      * Get the contents of a line (or part of a line) of the transcript.
      *
      * The char[] array returned may be part of the internal representation
-     * of the line -- make a copy first if you want to modify it.  The last
-     * character requested will be followed by a NUL; the contents of the rest
-     * of the array could potentially be garbage.
+     * of the line -- make a copy first if you want to modify it.  The returned
+     * array may be longer than the requested portion of the transcript; in
+     * this case, the last character requested will be followed by a NUL, and
+     * the contents of the rest of the array could potentially be garbage.
      *
      * @param row The row number to get (-mActiveTranscriptRows..mScreenRows-1)
      * @param x1 The first screen position that's wanted
@@ -602,6 +603,17 @@ public char[] getLine(int row, int x1, int x2) {
         // Figure out how long the array needs to be
         FullUnicodeLine line = (FullUnicodeLine) mLines[row];
         char[] rawLine = line.getLine();
+
+        if (x1 == 0 && x2 == columns) {
+            /* We can return the raw line after ensuring it's NUL-terminated at
+             * the appropriate place */
+            int spaceUsed = line.getSpaceUsed();
+            if (spaceUsed < rawLine.length) {
+                rawLine[spaceUsed] = 0;
+            }
+            return rawLine;
+        }
+
         x1 = line.findStartOfColumn(x1);
         if (x2 < columns) {
             x2 = line.findStartOfColumn(x2);