A reused command pane leaves the last program's screen modes before the next command

A program that crashed out of a full screen left the command pane's emulator
in the alternate screen with mouse reports, bracketed paste or a hidden cursor
on, and the next command ran in that. Before the '% line' separator the pane
now leaves the alternate screen, turns those modes off and soft-resets
(DECSTR). The docs add that a command which clears the screen and its
scrollback erases the pane's history above it.

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

1 files changed, 7 insertions, 0 deletions

diff --git a/src/Terminal.zig b/src/Terminal.zig
index cd292e5f..e204b44c 100644
--- a/src/Terminal.zig
+++ b/src/Terminal.zig
@@ -932,6 +932,13 @@ test "raw terminal output needs no position tracking allocations" {
     try std.testing.expectEqual(pins, pane.terminal.?.vt.screens.active.pages.countTrackedPins());
 }
 
+/// A full-screen program has the emulator on its alternate screen.
+pub fn onAlternateScreen(pane: *const Pane) bool {
+    if (comptime !enabled) return false;
+    const state = pane.terminal orelse return false;
+    return state.vt.screens.active_key == .alternate;
+}
+
 pub fn promptInputReady(pane: *const Pane) bool {
     if (comptime !enabled) return false;
     const state = pane.terminal orelse return false;