From 2a36b915cbb201bda9b77431ae6d670961cee67a Mon Sep 17 00:00:00 2001
From: iamahuman <iamahuman@users.noreply.github.com>
Date: Fri, 25 Jan 2019 12:31:35 +0900
Subject: [PATCH] Implement CSI 3 J - Clear transcript

---
 .../java/com/termux/terminal/TerminalBuffer.java | 12 ++++++++++++
 .../com/termux/terminal/TerminalEmulator.java    |  5 ++++-
 .../terminal/ControlSequenceIntroducerTest.java  | 16 ++++++++++++++++
 .../main/java/com/termux/view/TerminalView.java  |  4 +++-
 4 files changed, 35 insertions(+), 2 deletions(-)

diff --git a/terminal-emulator/src/main/java/com/termux/terminal/TerminalBuffer.java b/terminal-emulator/src/main/java/com/termux/terminal/TerminalBuffer.java
index df9b58b3..b5002c70 100644
--- a/terminal-emulator/src/main/java/com/termux/terminal/TerminalBuffer.java
+++ b/terminal-emulator/src/main/java/com/termux/terminal/TerminalBuffer.java
@@ -1,5 +1,7 @@
 package com.termux.terminal;
 
+import java.util.Arrays;
+
 /**
  * A circular buffer of {@link TerminalRow}:s which keeps notes about what is visible on a logical screen and the scroll
  * history.
@@ -422,4 +424,14 @@ public final class TerminalBuffer {
         }
     }
 
+    public void clearTranscript() {
+        if (mScreenFirstRow < mActiveTranscriptRows) {
+            Arrays.fill(mLines, mTotalRows + mScreenFirstRow - mActiveTranscriptRows, mTotalRows, null);
+            Arrays.fill(mLines, 0, mScreenFirstRow, null);
+        } else {
+            Arrays.fill(mLines, mScreenFirstRow - mActiveTranscriptRows, mScreenFirstRow, null);
+        }
+        mActiveTranscriptRows = 0;
+    }
+
 }
diff --git a/terminal-emulator/src/main/java/com/termux/terminal/TerminalEmulator.java b/terminal-emulator/src/main/java/com/termux/terminal/TerminalEmulator.java
index 6827f20c..f778cf92 100644
--- a/terminal-emulator/src/main/java/com/termux/terminal/TerminalEmulator.java
+++ b/terminal-emulator/src/main/java/com/termux/terminal/TerminalEmulator.java
@@ -1404,7 +1404,7 @@ public final class TerminalEmulator {
             case 'I': // Cursor Horizontal Forward Tabulation (CHT). Move the active position n tabs forward.
                 setCursorCol(nextTabStop(getArg0(1)));
                 break;
-            case 'J': // "${CSI}${0,1,2}J" - Erase in Display (ED)
+            case 'J': // "${CSI}${0,1,2,3}J" - Erase in Display (ED)
                 // ED ignores the scrolling margins.
                 switch (getArg0(0)) {
                     case 0: // Erase from the active position to the end of the screen, inclusive (default).
@@ -1419,6 +1419,9 @@ public final class TerminalEmulator {
                         // move..
                         blockClear(0, 0, mColumns, mRows);
                         break;
+                    case 3: // Delete all lines saved in the scrollback buffer (xterm etc)
+                        mMainBuffer.clearTranscript();
+                        break;
                     default:
                         unknownSequence(b);
                         return;
diff --git a/terminal-emulator/src/test/java/com/termux/terminal/ControlSequenceIntroducerTest.java b/terminal-emulator/src/test/java/com/termux/terminal/ControlSequenceIntroducerTest.java
index 88b8e026..62e898c0 100644
--- a/terminal-emulator/src/test/java/com/termux/terminal/ControlSequenceIntroducerTest.java
+++ b/terminal-emulator/src/test/java/com/termux/terminal/ControlSequenceIntroducerTest.java
@@ -46,4 +46,20 @@ public class ControlSequenceIntroducerTest extends TerminalTestCase {
         withTerminalSized(5, 2).enterString("abcde\033[2G\033[2b\n").assertLinesAre("aeede", "     ");
     }
 
+    /** CSI 3 J  Clear scrollback (xterm, libvte; non-standard). */
+    public void testCsi3J() {
+        withTerminalSized(3, 2).enterString("a\r\nb\r\nc\r\nd");
+        assertEquals("a\nb\nc\nd", mTerminal.getScreen().getTranscriptText());
+        enterString("\033[3J");
+        assertEquals("c\nd", mTerminal.getScreen().getTranscriptText());
+
+        withTerminalSized(3, 2).enterString("Lorem_ipsum");
+        assertEquals("Lorem_ipsum", mTerminal.getScreen().getTranscriptText());
+        enterString("\033[3J");
+        assertEquals("ipsum", mTerminal.getScreen().getTranscriptText());
+
+        withTerminalSized(3, 2).enterString("w\r\nx\r\ny\r\nz\033[?1049h\033[3J\033[?1049l");
+        assertEquals("y\nz", mTerminal.getScreen().getTranscriptText());
+    }
+
 }
diff --git a/terminal-view/src/main/java/com/termux/view/TerminalView.java b/terminal-view/src/main/java/com/termux/view/TerminalView.java
index 3fb6af11..9ec39804 100644
--- a/terminal-view/src/main/java/com/termux/view/TerminalView.java
+++ b/terminal-view/src/main/java/com/termux/view/TerminalView.java
@@ -358,10 +358,12 @@ public final class TerminalView extends View {
     public void onScreenUpdated() {
         if (mEmulator == null) return;
 
+        int rowsInHistory = mEmulator.getScreen().getActiveTranscriptRows();
+        if (mTopRow < -rowsInHistory) mTopRow = -rowsInHistory;
+
         boolean skipScrolling = false;
         if (mIsSelectingText) {
             // Do not scroll when selecting text.
-            int rowsInHistory = mEmulator.getScreen().getActiveTranscriptRows();
             int rowShift = mEmulator.getScrollCounter();
             if (-mTopRow + rowShift > rowsInHistory) {
                 // .. unless we're hitting the end of history transcript, in which