Do not limit cursor movement to scroll region

The scrolling region set by DECSTBM should not affect the
Cursor Down (CUD) and Cursor Up (CUU) escape sequences.

Fixes #1340.

Author: fornwall

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

@@ -1376,10 +1376,10 @@ private void doCsi(int b) {
             }
             break;
             case 'A': // "CSI${n}A" - Cursor up (CUU) ${n} rows.
-                setCursorRow(Math.max(mTopMargin, mCursorRow - getArg0(1)));
+                setCursorRow(Math.max(0, mCursorRow - getArg0(1)));
                 break;
             case 'B': // "CSI${n}B" - Cursor down (CUD) ${n} rows.
-                setCursorRow(Math.min(mBottomMargin - 1, mCursorRow + getArg0(1)));
+                setCursorRow(Math.min(mRows - 1, mCursorRow + getArg0(1)));
                 break;
             case 'C': // "CSI${n}C" - Cursor forward (CUF).
             case 'a': // "CSI${n}a" - Horizontal position relative (HPR). From ISO-6428/ECMA-48.

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

@@ -107,4 +107,24 @@ public void testScrollDownBelowScrollRegion() {
 		assertLinesAre("1 ", "2 ", "3 ", "QQ", "YY");
 	}
 
+    /** See https://github.com/termux/termux-app/issues/1340 */
+    public void testScrollRegionDoesNotLimitCursorMovement() {
+        withTerminalSized(6, 4)
+            .enterString("\033[4;7r\033[3;1Haaa\033[Axxx")
+            .assertLinesAre(
+                "      ",
+                "   xxx",
+                "aaa   ",
+                "      "
+            );
+
+        withTerminalSized(6, 4)
+            .enterString("\033[1;3r\033[3;1Haaa\033[Bxxx")
+            .assertLinesAre(
+                "      ",
+                "      ",
+                "aaa   ",
+                "   xxx"
+            );
+    }
 }