From ad1cdbcd593bee7f102700c1a6ee1c49632a7cd3 Mon Sep 17 00:00:00 2001
From: Mitchell Hashimoto <mitchell.hashimoto@gmail.com>
Date: Tue, 9 Aug 2022 09:22:34 -0700
Subject: [PATCH] implement erase display scrollback ("clear" command)

---
 src/terminal/Screen.zig   |  2 --
 src/terminal/Terminal.zig | 12 +++++++++---
 2 files changed, 9 insertions(+), 5 deletions(-)

diff --git a/src/terminal/Screen.zig b/src/terminal/Screen.zig
index afcb9ed0d..817c7d8fe 100644
--- a/src/terminal/Screen.zig
+++ b/src/terminal/Screen.zig
@@ -116,8 +116,6 @@ pub const RowIndex = union(RowIndexTag) {
     /// The index is from the top of the history (scrollback) to just
     /// prior to the active area.
     history: usize,
-
-    // TODO: others
 };
 
 /// The tags of RowIndex
diff --git a/src/terminal/Terminal.zig b/src/terminal/Terminal.zig
index 179ee743c..ac934263b 100644
--- a/src/terminal/Terminal.zig
+++ b/src/terminal/Terminal.zig
@@ -597,9 +597,15 @@ pub fn eraseDisplay(
             self.screen.cursor.pending_wrap = false;
         },
 
-        else => {
-            log.err("unimplemented display mode: {}", .{mode});
-            @panic("unimplemented");
+        .scrollback => {
+            const region = self.screen.region(.history);
+            std.mem.set(Screen.Cell, region[0], self.screen.cursor.pen);
+            std.mem.set(Screen.Cell, region[1], self.screen.cursor.pen);
+
+            // TODO: move this logic to the Screen implementation
+            self.screen.top = self.screen.visible_offset;
+            self.screen.bottom = self.screen.bottom - self.screen.visible_offset;
+            self.screen.visible_offset = 0;
         },
     }
 }