Fixed: Make ScrollDown escape respect margins

SD sequence (`${CSI}${N}T`) was scrolling the whole width
 of the terminal instead of just between the margins.
RI sequence (`${ESC}M`, move cursor up 1 line) was doing the same.
Fixed that.

Fixes #2576 where in tmux scrolling one of several
 side-by-side panels down resulted in all visually scrolling.

Author: evg-zhabotinsky

terminal-emulator/src/main/java/com/termux/terminal/TerminalEmulator.java

@@ -1415,8 +1415,8 @@ private void doEsc(int b) {
                 // http://www.vt100.net/docs/vt100-ug/chapter3.html: "Move the active position to the same horizontal
                 // position on the preceding line. If the active position is at the top margin, a scroll down is performed".
                 if (mCursorRow <= mTopMargin) {
-                    mScreen.blockCopy(0, mTopMargin, mColumns, mBottomMargin - (mTopMargin + 1), 0, mTopMargin + 1);
-                    blockClear(0, mTopMargin, mColumns);
+                    mScreen.blockCopy(mLeftMargin, mTopMargin, mRightMargin - mLeftMargin, mBottomMargin - (mTopMargin + 1), mLeftMargin, mTopMargin + 1);
+                    blockClear(mLeftMargin, mTopMargin, mRightMargin - mLeftMargin);
                 } else {
                     mCursorRow--;
                 }
@@ -1625,8 +1625,8 @@ private void doCsi(int b) {
                     final int linesToScrollArg = getArg0(1);
                     final int linesBetweenTopAndBottomMargins = mBottomMargin - mTopMargin;
                     final int linesToScroll = Math.min(linesBetweenTopAndBottomMargins, linesToScrollArg);
-                    mScreen.blockCopy(0, mTopMargin, mColumns, linesBetweenTopAndBottomMargins - linesToScroll, 0, mTopMargin + linesToScroll);
-                    blockClear(0, mTopMargin, mColumns, linesToScroll);
+                    mScreen.blockCopy(mLeftMargin, mTopMargin, mRightMargin - mLeftMargin, linesBetweenTopAndBottomMargins - linesToScroll, mLeftMargin, mTopMargin + linesToScroll);
+                    blockClear(mLeftMargin, mTopMargin, mRightMargin - mLeftMargin, linesToScroll);
                 } else {
                     // "${CSI}${func};${startx};${starty};${firstrow};${lastrow}T" - initiate highlight mouse tracking.
                     unimplementedSequence(b);

terminal-emulator/src/test/java/com/termux/terminal/ScrollRegionTest.java

@@ -75,6 +75,16 @@ public void testNELRespectsLeftMargin() {
 		withTerminalSized(3, 3).enterString("\033[?69h\033[2sABC\033[?6h\033ED").assertLinesAre("ABC", " D ", "   ");
 	}
 
+	public void testRiRespectsLeftMargin() {
+		// Reverse Index (RI), ${ESC}M, should respect horizontal margins:
+		withTerminalSized(4, 3).enterString("ABCD\033[?69h\033[2;3s\033[?6h\033M").assertLinesAre("A  D", " BC ", "    ");
+	}
+
+	public void testSdRespectsLeftMargin() {
+		// Scroll Down (SD), ${CSI}${N}T, should respect horizontal margins:
+		withTerminalSized(4, 3).enterString("ABCD\033[?69h\033[2;3s\033[?6h\033[2T").assertLinesAre("A  D", "    ", " BC ");
+	}
+
 	public void testBackwardIndex() {
 		// vttest "Menu 11.3.2: VT420 Cursor-Movement Test", test 7.
 		// Without margins: