From 6ca055bb25abfd1232279e696e8c573ec67ed927 Mon Sep 17 00:00:00 2001
From: Fredrik Fornwall <fredrik@fornwall.net>
Date: Thu, 25 Feb 2016 16:33:00 +0100
Subject: [PATCH] Fix tabs to not overwrite cells

---
 app/build.gradle                              |  4 +--
 .../com/termux/terminal/TerminalEmulator.java | 31 ++++++++++---------
 .../termux/terminal/CursorAndScreenTest.java  |  7 ++++-
 .../com/termux/terminal/TerminalTest.java     |  5 +++
 4 files changed, 30 insertions(+), 17 deletions(-)

diff --git a/app/build.gradle b/app/build.gradle
index e5bed900..6cde3610 100644
--- a/app/build.gradle
+++ b/app/build.gradle
@@ -18,8 +18,8 @@ android {
         applicationId "com.termux"
         minSdkVersion 21
         targetSdkVersion 23
-        versionCode 29
-        versionName "0.29"
+        versionCode 30
+        versionName "0.30"
     }
 
     buildTypes {
diff --git a/app/src/main/java/com/termux/terminal/TerminalEmulator.java b/app/src/main/java/com/termux/terminal/TerminalEmulator.java
index 94d2807d..f3cb0456 100644
--- a/app/src/main/java/com/termux/terminal/TerminalEmulator.java
+++ b/app/src/main/java/com/termux/terminal/TerminalEmulator.java
@@ -425,9 +425,9 @@ public final class TerminalEmulator {
 						processCodePoint((codePoint & 0x7F) + 0x40);
 					} else {
 						switch (Character.getType(codePoint)) {
-							case Character.UNASSIGNED:
-							case Character.SURROGATE:
-								codePoint = UNICODE_REPLACEMENT_CHAR;
+						case Character.UNASSIGNED:
+						case Character.SURROGATE:
+							codePoint = UNICODE_REPLACEMENT_CHAR;
 						}
 						processCodePoint(codePoint);
 					}
@@ -474,16 +474,19 @@ public final class TerminalEmulator {
 			else
 				mSession.onBell();
 			break;
-		case 8: // BS
-			setCursorCol(Math.max(mLeftMargin, mCursorCol - 1));
-			break;
-		case 9: // Horizontal tab - move to next tab stop, but not past edge of screen
-			int nextTabStop = nextTabStop(1);
-			while (mCursorCol < nextTabStop) {
-				// Emit newlines to get background color right.
-				processCodePoint(' ');
-			}
-			break;
+        case 8: // Backspace (BS, ^H).
+            setCursorCol(Math.max(mLeftMargin, mCursorCol - 1));
+            break;
+        case 9: // Horizontal tab (HT, \t) - move to next tab stop, but not past edge of screen
+		    // XXX: Should perhaps use color if writing to new cells. Try with
+		    //       printf "\033[41m\tXX\033[0m\n"
+		    // The OSX Terminal.app colors the spaces from the tab red, but xterm does not.
+		    // Note that Terminal.app only colors on new cells, in e.g.
+		    //       printf "\033[41m\t\r\033[42m\tXX\033[0m\n"
+		    // the first cells are created with a red background, but when tabbing over
+		    // them again with a green background they are not overwritten.
+            mCursorCol = nextTabStop(1);
+            break;
 		case 10: // Line feed (LF, \n).
 		case 11: // Vertical tab (VT, \v).
 		case 12: // Form feed (FF, \f).
@@ -1331,7 +1334,7 @@ public final class TerminalEmulator {
 			continueSequence(ESC_CSI_ARGS_ASTERIX);
 			break;
 		case '@': {
-			// "CSI{n}@" -  Insert ${n} space characters (ICH) - http://www.vt100.net/docs/vt510-rm/ICH.
+			// "CSI{n}@" - Insert ${n} space characters (ICH) - http://www.vt100.net/docs/vt510-rm/ICH.
 			mAboutToAutoWrap = false;
 			int columnsAfterCursor = mColumns - mCursorCol;
 			int spacesToInsert = Math.min(getArg0(1), columnsAfterCursor);
diff --git a/app/src/test/java/com/termux/terminal/CursorAndScreenTest.java b/app/src/test/java/com/termux/terminal/CursorAndScreenTest.java
index 0df78fc1..6e39ed19 100644
--- a/app/src/test/java/com/termux/terminal/CursorAndScreenTest.java
+++ b/app/src/test/java/com/termux/terminal/CursorAndScreenTest.java
@@ -163,7 +163,12 @@ public class CursorAndScreenTest extends TerminalTestCase {
 		}
 	}
 
-	public void testHorizontalTabColorsBackground() {
+    /**
+     * See comments on horizontal tab handling in TerminalEmulator.java.
+     *
+     * We do not want to color already written cells when tabbing over them.
+     */
+	public void DISABLED_testHorizontalTabColorsBackground() {
 		withTerminalSized(10, 3).enterString("\033[48;5;15m").enterString("\t");
 		assertCursorAt(0, 8);
 		for (int i = 0; i < 10; i++) {
diff --git a/app/src/test/java/com/termux/terminal/TerminalTest.java b/app/src/test/java/com/termux/terminal/TerminalTest.java
index 9b43676c..f3939cfc 100644
--- a/app/src/test/java/com/termux/terminal/TerminalTest.java
+++ b/app/src/test/java/com/termux/terminal/TerminalTest.java
@@ -258,4 +258,9 @@ public class TerminalTest extends TerminalTestCase {
 		withTerminalSized(3, 3).enterString("abc\r ").assertLinesAre(" bc", "   ", "   ").assertCursorAt(0, 1);
 	}
 
+    public void testTab() {
+        withTerminalSized(11, 2).enterString("01234567890\r\tXX").assertLinesAre("01234567XX0", "           ");
+        withTerminalSized(11, 2).enterString("01234567890\033[44m\r\tXX").assertLinesAre("01234567XX0", "           ");
+    }
+
 }