Bug 572938 [terminal] reverse linefeed: Honour the scrolling region

The reverse linefeed should scroll down when the cursor is on the
first line of the scrolling region, not only on the first screen
line

Change-Id: I628ab135d48d868bc8e3eacd2ea57dda948873a8
Signed-off-by: Fabrizio Iannetti <fabrizio.iannetti@gmail.com>

terminal/plugins/org.eclipse.tm.terminal.control/src/org/eclipse/tm/internal/terminal/emulator/IVT100EmulatorBackend.java

@@ -219,4 +219,12 @@ public interface IVT100EmulatorBackend {
 	 * @param lines  number of lines to scroll
 	 */
 	void scrollDown(int lines);
+
+	/**
+	 * Process a reverse line feed/reverse index.
+	 *
+	 * The content is scrolled down if the cursor is at the top of the
+	 * scroll region.
+	 */
+	void processReverseLineFeed();
 }

terminal/plugins/org.eclipse.tm.terminal.control/src/org/eclipse/tm/internal/terminal/emulator/VT100BackendTraceDecorator.java

@@ -205,4 +205,10 @@ public class VT100BackendTraceDecorator implements IVT100EmulatorBackend {
 		fBackend.scrollDown(lines);
 	}
 
+	@Override
+	public void processReverseLineFeed() {
+		fWriter.println("processReverseLineFeed()"); //$NON-NLS-1$
+		fBackend.processReverseLineFeed();
+	}
+
 }

terminal/plugins/org.eclipse.tm.terminal.control/src/org/eclipse/tm/internal/terminal/emulator/VT100Emulator.java

@@ -398,9 +398,7 @@ public class VT100Emulator implements ControlListener {
 				case 'M':
 					// Reverse line feed
 					ansiState = ANSISTATE_INITIAL;
-					if (text.getCursorLine() == 0)
+					text.processReverseLineFeed();
-						text.scrollDown(1);
-					moveCursorUp(1);
 					break;
 
 				default:

terminal/plugins/org.eclipse.tm.terminal.control/src/org/eclipse/tm/internal/terminal/emulator/VT100EmulatorBackend.java

@@ -367,6 +367,20 @@ public class VT100EmulatorBackend implements IVT100EmulatorBackend {
 		}
 	}
 
+	private void doReverseLineFeed() {
+		if (fCursorLine == fScrollRegion.getTopLine())
+			scrollDown(1);
+		else
+			setCursorLine(fCursorLine - 1);
+	}
+
+	@Override
+	public void processReverseLineFeed() {
+		synchronized (fTerminal) {
+			doReverseLineFeed();
+		}
+	}
+
 	@Override
 	public int getCursorLine() {
 		synchronized (fTerminal) {

terminal/plugins/org.eclipse.tm.terminal.test/src/org/eclipse/tm/internal/terminal/emulator/VT100EmulatorTest.java

@@ -41,6 +41,10 @@ public class VT100EmulatorTest {
 		return "\033]0;" + title + "\007";
 	}
 
+	private static String SCROLL_REGION(int startRow, int endRow) {
+		return "\033[" + startRow + ";" + endRow + "r";
+	}
+
 	/**
 	 * Set the cursor position to line/column. Note that this is the logical
 	 * line and column, so 1, 1 is the top left.
@@ -310,4 +314,30 @@ public class VT100EmulatorTest {
 		assertAll(() -> assertCursorLocation(1, expected.get(1).length()), () -> assertTextEquals(expected));
 	}
 
+	/**
+	 * Runs what "up arrow" would send back to terminal in less/man/etc.
+	 * but with a scrolling region set
+	 */
+	@Test
+	public void testScrollReverseScrollingRegion() {
+		data.setMaxHeight(1000);
+		List<String> expected = new ArrayList<>();
+		for (int i = 0; i < WINDOW_LINES; i++) {
+			String line = "Hello " + i;
+			run(line);
+			expected.add(line);
+			run("\r\n");
+		}
+		assertAll(() -> assertCursorLocation(WINDOW_LINES, 0), () -> assertTextEquals(expected));
+		run(CURSOR_POSITION_TOP_LEFT + "\n");
+		assertAll(() -> assertCursorLocation(2, 0), () -> assertTextEquals(expected));
+		run(SCROLL_REGION(2, WINDOW_LINES));
+		run(SCROLL_REVERSE);
+		expected.add(2, "");
+		assertAll(() -> assertCursorLocation(2, 0), () -> assertTextEquals(expected));
+		run("New text on top line following scroll reverse");
+		expected.set(2, "New text on top line following scroll reverse");
+		assertAll(() -> assertCursorLocation(2, expected.get(2).length()), () -> assertTextEquals(expected));
+	}
+
 }