pty/run after a clear answers what the command printed from the clear on, whole; cut only when its start really scrolled away

A clear (ED 2, ED 3, a reset) under a running command marked its output
lost, so `clear; ls` answered only "exit 0 cut". The output's start is
now pinned again at the screen's top after the erase: what the command
prints from there is its answer, whole, and a cut is said only when
that start leaves the scrollback.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

1 files changed, 26 insertions, 2 deletions

diff --git a/src/terminal.zig b/src/terminal.zig
index 0850267e..a0337ce7 100644
--- a/src/terminal.zig
+++ b/src/terminal.zig
@@ -106,12 +106,36 @@ pub const MarkedHandler = if (enabled) struct {
                 else => {},
             }
         }
-        if (comptime action == .erase_display_complete or action == .erase_display_scrollback or action == .full_reset) {
-            if (self.phase == .running) self.lost = true;
+        if (comptime action == .erase_display_complete or action == .erase_display_scrollback or
+            action == .erase_display_scroll_complete or action == .full_reset)
+        {
+            self.inner.vt(action, value);
+            // A `clear` under a running command: its output is what it
+            // prints from here, the screen's top, not lost. Only what the
+            // scrollback later loses is (the pin goes `garbage`).
+            if (self.phase == .running) self.pinTop(&self.out_start);
+            return;
         }
         self.inner.vt(action, value);
     }
 
+    /// Pins `slot` to the primary screen's top-left; lost when it cannot be.
+    fn pinTop(self: *@This(), slot: *?*ghostty_vt.Pin) void {
+        const screen = self.inner.terminal.screens.get(.primary) orelse return;
+        if (slot.*) |old| screen.pages.untrackPin(old);
+        slot.* = null;
+        if (self.inner.terminal.screens.active_key != .primary) {
+            self.lost = true;
+            return;
+        }
+        const top = screen.pages.pin(.{ .active = .{} }) orelse {
+            self.lost = true;
+            return;
+        };
+        slot.* = screen.pages.trackPin(top) catch null;
+        if (slot.* == null) self.lost = true;
+    }
+
     pub fn deinit(self: *@This()) void {
         self.inner.deinit();
     }