From d57d1d2395c9f80ecdb7be4cd58858b299f95c42 Mon Sep 17 00:00:00 2001
From: Mitchell Hashimoto <m@mitchellh.com>
Date: Mon, 2 Dec 2024 09:39:21 -0500
Subject: [PATCH 1/3] terminal: failing tracked pin test on fullReset

---
 src/terminal/PageList.zig |  6 +++++-
 src/terminal/Terminal.zig | 10 ++++++++++
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/src/terminal/PageList.zig b/src/terminal/PageList.zig
index 70f972ebe..3d67278ba 100644
--- a/src/terminal/PageList.zig
+++ b/src/terminal/PageList.zig
@@ -2356,7 +2356,11 @@ pub fn countTrackedPins(self: *const PageList) usize {
 /// Checks if a pin is valid for this pagelist. This is a very slow and
 /// expensive operation since we traverse the entire linked list in the
 /// worst case. Only for runtime safety/debug.
-fn pinIsValid(self: *const PageList, p: Pin) bool {
+pub fn pinIsValid(self: *const PageList, p: Pin) bool {
+    // This is very slow so we want to ensure we only ever
+    // call this during slow runtime safety builds.
+    comptime assert(build_config.slow_runtime_safety);
+
     var it = self.pages.first;
     while (it) |node| : (it = node.next) {
         if (node != p.node) continue;
diff --git a/src/terminal/Terminal.zig b/src/terminal/Terminal.zig
index a2cf510b1..0a2914f10 100644
--- a/src/terminal/Terminal.zig
+++ b/src/terminal/Terminal.zig
@@ -10575,6 +10575,16 @@ test "Terminal: fullReset default modes" {
     try testing.expect(t.modes.get(.grapheme_cluster));
 }
 
+test "Terminal: fullReset tracked pins" {
+    var t = try init(testing.allocator, .{ .cols = 80, .rows = 80 });
+    defer t.deinit(testing.allocator);
+
+    // Create a tracked pin
+    const p = try t.screen.pages.trackPin(t.screen.cursor.page_pin.*);
+    t.fullReset();
+    try testing.expect(t.screen.pages.pinIsValid(p.*));
+}
+
 // https://github.com/mitchellh/ghostty/issues/272
 // This is also tested in depth in screen resize tests but I want to keep
 // this test around to ensure we don't regress at multiple layers.

From d7fcaefdf3622a3aefadbf788c062065576ff928 Mon Sep 17 00:00:00 2001
From: Mitchell Hashimoto <m@mitchellh.com>
Date: Mon, 2 Dec 2024 17:25:17 -0500
Subject: [PATCH 2/3] terminal: PageList.reset

---
 src/terminal/PageList.zig | 134 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 134 insertions(+)

diff --git a/src/terminal/PageList.zig b/src/terminal/PageList.zig
index 3d67278ba..aec0af278 100644
--- a/src/terminal/PageList.zig
+++ b/src/terminal/PageList.zig
@@ -330,6 +330,77 @@ pub fn deinit(self: *PageList) void {
     }
 }
 
+/// Reset the PageList back to an empty state. This is similar to
+/// deinit and reinit but it importantly preserves the pointer
+/// stability of tracked pins (they're moved to the top-left since
+/// all contents are cleared).
+///
+/// This can't fail because we always retain at least enough allocated
+/// memory to fit the active area.
+pub fn reset(self: *PageList) void {
+    // We need enough pages/nodes to keep our active area. This should
+    // never fail since we by definition have allocated a page already
+    // that fits our size but I'm not confident to make that assertion.
+    const cap = std_capacity.adjust(
+        .{ .cols = self.cols },
+    ) catch @panic("reset: std_capacity.adjust failed");
+    assert(cap.rows > 0); // adjust should never return 0 rows
+
+    // The number of pages we need is the number of rows in the active
+    // area divided by the row capacity of a page.
+    const page_count = std.math.divCeil(
+        usize,
+        self.rows,
+        cap.rows,
+    ) catch unreachable;
+
+    // Before resetting our pools we need to free any pages that
+    // are non-standard size since those were allocated outside
+    // the pool.
+    {
+        const page_alloc = self.pool.pages.arena.child_allocator;
+        var it = self.pages.first;
+        while (it) |node| : (it = node.next) {
+            if (node.data.memory.len > std_size) {
+                page_alloc.free(node.data.memory);
+            }
+        }
+    }
+
+    // Reset our pools to free as much memory as possible while retaining
+    // the capacity for at least the minimum number of pages we need.
+    // The return value is whether memory was reclaimed or not, but in
+    // either case the pool is left in a valid state.
+    _ = self.pool.pages.reset(.{
+        .retain_with_limit = page_count * PagePool.item_size,
+    });
+    _ = self.pool.nodes.reset(.{
+        .retain_with_limit = page_count * NodePool.item_size,
+    });
+
+    // Initialize our pages. This should not be able to fail since
+    // we retained the capacity for the minimum number of pages we need.
+    self.pages, self.page_size = initPages(
+        &self.pool,
+        self.cols,
+        self.rows,
+    ) catch @panic("initPages failed");
+
+    // Update all our tracked pins to point to our first page top-left
+    {
+        var it = self.tracked_pins.iterator();
+        while (it.next()) |entry| {
+            const p: *Pin = entry.key_ptr.*;
+            p.node = self.pages.first.?;
+            p.x = 0;
+            p.y = 0;
+        }
+    }
+
+    // Move our viewport back to the active area since everything is gone.
+    self.viewport = .active;
+}
+
 pub const Clone = struct {
     /// The top and bottom (inclusive) points of the region to clone.
     /// The x coordinate is ignored; the full row is always cloned.
@@ -8195,3 +8266,66 @@ test "PageList resize reflow wrap moves kitty placeholder" {
     }
     try testing.expect(it.next() == null);
 }
+
+test "PageList reset" {
+    const testing = std.testing;
+    const alloc = testing.allocator;
+
+    var s = try init(alloc, 80, 24, null);
+    defer s.deinit();
+    s.reset();
+    try testing.expect(s.viewport == .active);
+    try testing.expect(s.pages.first != null);
+    try testing.expectEqual(@as(usize, s.rows), s.totalRows());
+
+    // Active area should be the top
+    try testing.expectEqual(Pin{
+        .node = s.pages.first.?,
+        .y = 0,
+        .x = 0,
+    }, s.getTopLeft(.active));
+}
+
+test "PageList reset across two pages" {
+    const testing = std.testing;
+    const alloc = testing.allocator;
+
+    // Find a cap that makes it so that rows don't fit on one page.
+    const rows = 100;
+    const cap = cap: {
+        var cap = try std_capacity.adjust(.{ .cols = 50 });
+        while (cap.rows >= rows) cap = try std_capacity.adjust(.{
+            .cols = cap.cols + 50,
+        });
+
+        break :cap cap;
+    };
+
+    // Init
+    var s = try init(alloc, cap.cols, rows, null);
+    defer s.deinit();
+    s.reset();
+    try testing.expect(s.viewport == .active);
+    try testing.expect(s.pages.first != null);
+    try testing.expectEqual(@as(usize, s.rows), s.totalRows());
+}
+
+test "PageList clears history" {
+    const testing = std.testing;
+    const alloc = testing.allocator;
+
+    var s = try init(alloc, 80, 24, null);
+    defer s.deinit();
+    try s.growRows(30);
+    s.reset();
+    try testing.expect(s.viewport == .active);
+    try testing.expect(s.pages.first != null);
+    try testing.expectEqual(@as(usize, s.rows), s.totalRows());
+
+    // Active area should be the top
+    try testing.expectEqual(Pin{
+        .node = s.pages.first.?,
+        .y = 0,
+        .x = 0,
+    }, s.getTopLeft(.active));
+}

From 212bd3d5fb5ced7866f459fdc80f757811f14b3e Mon Sep 17 00:00:00 2001
From: Mitchell Hashimoto <m@mitchellh.com>
Date: Mon, 2 Dec 2024 17:43:56 -0500
Subject: [PATCH 3/3] terminal: fullReset uses the new screen reset methods

---
 src/terminal/Screen.zig   | 48 +++++++++++++++++++++-
 src/terminal/Terminal.zig | 84 ++++++++++-----------------------------
 2 files changed, 66 insertions(+), 66 deletions(-)

diff --git a/src/terminal/Screen.zig b/src/terminal/Screen.zig
index 4f3fe270e..d8787487f 100644
--- a/src/terminal/Screen.zig
+++ b/src/terminal/Screen.zig
@@ -83,8 +83,8 @@ pub const Dirty = packed struct {
 /// The cursor position and style.
 pub const Cursor = struct {
     // The x/y position within the viewport.
-    x: size.CellCountInt,
-    y: size.CellCountInt,
+    x: size.CellCountInt = 0,
+    y: size.CellCountInt = 0,
 
     /// The visual style of the cursor. This defaults to block because
     /// it has to default to something, but users of this struct are
@@ -249,6 +249,50 @@ pub fn assertIntegrity(self: *const Screen) void {
     }
 }
 
+/// Reset the screen according to the logic of a DEC RIS sequence.
+///
+/// - Clears the screen and attempts to reclaim memory.
+/// - Moves the cursor to the top-left.
+/// - Clears any cursor state: style, hyperlink, etc.
+/// - Resets the charset
+/// - Clears the selection
+/// - Deletes all Kitty graphics
+/// - Resets Kitty Keyboard settings
+/// - Disables protection mode
+///
+pub fn reset(self: *Screen) void {
+    // Reset our pages
+    self.pages.reset();
+
+    // The above reset preserves tracked pins so we can still use
+    // our cursor pin, which should be at the top-left already.
+    const cursor_pin: *PageList.Pin = self.cursor.page_pin;
+    assert(cursor_pin.node == self.pages.pages.first.?);
+    assert(cursor_pin.x == 0);
+    assert(cursor_pin.y == 0);
+    const cursor_rac = cursor_pin.rowAndCell();
+    self.cursor.deinit(self.alloc);
+    self.cursor = .{
+        .page_pin = cursor_pin,
+        .page_row = cursor_rac.row,
+        .page_cell = cursor_rac.cell,
+    };
+
+    // Clear kitty graphics
+    self.kitty_images.delete(
+        self.alloc,
+        undefined, // All image deletion doesn't need the terminal
+        .{ .all = true },
+    );
+
+    // Reset our basic state
+    self.saved_cursor = null;
+    self.charset = .{};
+    self.kitty_keyboard = .{};
+    self.protected_mode = .off;
+    self.clearSelection();
+}
+
 /// Clone the screen.
 ///
 /// This will copy:
diff --git a/src/terminal/Terminal.zig b/src/terminal/Terminal.zig
index 0a2914f10..a11028304 100644
--- a/src/terminal/Terminal.zig
+++ b/src/terminal/Terminal.zig
@@ -2627,82 +2627,38 @@ pub fn plainStringUnwrapped(self: *Terminal, alloc: Allocator) ![]const u8 {
 
 /// Full reset.
 ///
-/// This will attempt to free the existing screen memory and allocate
-/// new screens but if that fails this will reuse the existing memory
-/// from the prior screens. In the latter case, memory may be wasted
-/// (since its unused) but it isn't leaked.
+/// This will attempt to free the existing screen memory but if that fails
+/// this will reuse the existing memory. In the latter case, memory may
+/// be wasted (since its unused) but it isn't leaked.
 pub fn fullReset(self: *Terminal) void {
-    // Attempt to initialize new screens.
-    var new_primary = Screen.init(
-        self.screen.alloc,
-        self.cols,
-        self.rows,
-        self.screen.pages.explicit_max_size,
-    ) catch |err| {
-        log.warn("failed to allocate new primary screen, reusing old memory err={}", .{err});
-        self.fallbackReset();
-        return;
-    };
-    const new_secondary = Screen.init(
-        self.secondary_screen.alloc,
-        self.cols,
-        self.rows,
-        0,
-    ) catch |err| {
-        log.warn("failed to allocate new secondary screen, reusing old memory err={}", .{err});
-        new_primary.deinit();
-        self.fallbackReset();
-        return;
-    };
+    // Reset our screens
+    self.screen.reset();
+    self.secondary_screen.reset();
 
-    // If we got here, both new screens were successfully allocated
-    // and we can deinitialize the old screens.
-    self.screen.deinit();
-    self.secondary_screen.deinit();
+    // Ensure we're back on primary screen
+    if (self.active_screen != .primary) {
+        const old = self.screen;
+        self.screen = self.secondary_screen;
+        self.secondary_screen = old;
+        self.active_screen = .primary;
+    }
 
-    // Replace with the newly allocated screens.
-    self.screen = new_primary;
-    self.secondary_screen = new_secondary;
-
-    self.resetCommonState();
-}
-
-fn fallbackReset(self: *Terminal) void {
-    // Clear existing screens without reallocation
-    self.primaryScreen(.{ .clear_on_exit = true, .cursor_save = false });
-    self.screen.clearSelection();
-    self.eraseDisplay(.scrollback, false);
-    self.eraseDisplay(.complete, false);
-    self.screen.cursorAbsolute(0, 0);
-    self.resetCommonState();
-}
-
-fn resetCommonState(self: *Terminal) void {
-    // We set the saved cursor to null and then restore. This will force
-    // our cursor to go back to the default which will also move the cursor
-    // to the top-left.
-    self.screen.saved_cursor = null;
-    self.restoreCursor() catch |err| {
-        log.warn("restore cursor on primary screen failed err={}", .{err});
-    };
-
-    self.screen.endHyperlink();
-    self.screen.charset = .{};
+    // Rest our basic state
     self.modes.reset();
     self.flags = .{};
     self.tabstops.reset(TABSTOP_INTERVAL);
-    self.screen.kitty_keyboard = .{};
-    self.secondary_screen.kitty_keyboard = .{};
-    self.screen.protected_mode = .off;
+    self.previous_char = null;
+    self.pwd.clearRetainingCapacity();
+    self.status_display = .main;
     self.scrolling_region = .{
         .top = 0,
         .bottom = self.rows - 1,
         .left = 0,
         .right = self.cols - 1,
     };
-    self.previous_char = null;
-    self.pwd.clearRetainingCapacity();
-    self.status_display = .main;
+
+    // Always mark dirty so we redraw everything
+    self.flags.dirty.clear = true;
 }
 
 /// Returns true if the point is dirty, used for testing.