terminal: IND supports left/right margins

src/terminal/Terminal.zig

@@ -898,11 +898,16 @@ pub fn index(self: *Terminal) !void {
     // If the cursor is inside the scrolling region and on the bottom-most
     // line, then we scroll up. If our scrolling region is the full screen
     // we create scrollback.
-    if (self.screen.cursor.y == self.scrolling_region.bottom) {
+    if (self.screen.cursor.y == self.scrolling_region.bottom and
+        self.screen.cursor.x >= self.scrolling_region.left and
+        self.screen.cursor.x <= self.scrolling_region.right)
+    {
         // If our scrolling region is the full screen, we create scrollback.
         // Otherwise, we simply scroll the region.
         if (self.scrolling_region.top == 0 and
-            self.scrolling_region.bottom == self.rows - 1)
+            self.scrolling_region.bottom == self.rows - 1 and
+            self.scrolling_region.left == 0 and
+            self.scrolling_region.right == self.cols - 1)
         {
             try self.screen.scroll(.{ .screen = 1 });
         } else {
@@ -2919,6 +2924,47 @@ test "Terminal: index bottom of primary screen with scroll region" {
     }
 }
 
+test "Terminal: index outside left/right margin" {
+    const alloc = testing.allocator;
+    var t = try init(alloc, 10, 5);
+    defer t.deinit(alloc);
+
+    t.setScrollingRegion(1, 3);
+    t.scrolling_region.left = 3;
+    t.scrolling_region.right = 5;
+    t.setCursorPos(3, 3);
+    try t.print('A');
+    t.setCursorPos(3, 1);
+    try t.index();
+    try t.print('X');
+
+    {
+        var str = try t.plainString(testing.allocator);
+        defer testing.allocator.free(str);
+        try testing.expectEqualStrings("\n\nX A", str);
+    }
+}
+
+test "Terminal: index inside left/right margin" {
+    const alloc = testing.allocator;
+    var t = try init(alloc, 10, 5);
+    defer t.deinit(alloc);
+
+    t.setScrollingRegion(1, 3);
+    t.scrolling_region.left = 3;
+    t.scrolling_region.right = 5;
+    t.setCursorPos(3, 3);
+    try t.print('A');
+    try t.index();
+    try t.print('X');
+
+    {
+        var str = try t.plainString(testing.allocator);
+        defer testing.allocator.free(str);
+        try testing.expectEqualStrings("\n  A\n   X", str);
+    }
+}
+
 test "Terminal: DECALN" {
     const alloc = testing.allocator;
     var t = try init(alloc, 2, 2);

website/app/vt/ind/page.mdx

@@ -115,3 +115,25 @@ printf "X"
 |__________|
 |Xc________|
 ```
+
+### IND V-6: Outside of Left/Right Scroll Region
+
+```bash
+printf "\033[1;1H" # move to top-left
+printf "\033[0J" # clear screen
+printf "\033[?69h" # enable left/right margins
+printf "\033[1;3r" # scroll region top/bottom
+printf "\033[3;5s" # scroll region left/right
+printf "\033[3;3H"
+printf "A"
+printf "\033[3;1H"
+printf "\033D" # index
+printf "X"
+```
+
+```
+|__________|
+|__________|
+|XcA_______|
+```
+