terminal: change pagelist linked list to an intrusive linked list

src/datastruct/intrusive_linked_list.zig

@@ -11,15 +11,19 @@ pub fn DoublyLinkedList(comptime T: type) type {
     return struct {
         const Self = @This();
 
-        first: ?*T = null,
-        last: ?*T = null,
+        /// The type of the node in the list. This makes it easy to get the
+        /// node type from the list type.
+        pub const Node = T;
+
+        first: ?*Node = null,
+        last: ?*Node = null,
 
         /// Insert a new node after an existing one.
         ///
         /// Arguments:
         ///     node: Pointer to a node in the list.
         ///     new_node: Pointer to the new node to insert.
-        pub fn insertAfter(list: *Self, node: *T, new_node: *T) void {
+        pub fn insertAfter(list: *Self, node: *Node, new_node: *Node) void {
             new_node.prev = node;
             if (node.next) |next_node| {
                 // Intermediate node.
@@ -38,7 +42,7 @@ pub fn DoublyLinkedList(comptime T: type) type {
         /// Arguments:
         ///     node: Pointer to a node in the list.
         ///     new_node: Pointer to the new node to insert.
-        pub fn insertBefore(list: *Self, node: *T, new_node: *T) void {
+        pub fn insertBefore(list: *Self, node: *Node, new_node: *Node) void {
             new_node.next = node;
             if (node.prev) |prev_node| {
                 // Intermediate node.
@@ -56,7 +60,7 @@ pub fn DoublyLinkedList(comptime T: type) type {
         ///
         /// Arguments:
         ///     new_node: Pointer to the new node to insert.
-        pub fn append(list: *Self, new_node: *T) void {
+        pub fn append(list: *Self, new_node: *Node) void {
             if (list.last) |last| {
                 // Insert after last.
                 list.insertAfter(last, new_node);
@@ -70,7 +74,7 @@ pub fn DoublyLinkedList(comptime T: type) type {
         ///
         /// Arguments:
         ///     new_node: Pointer to the new node to insert.
-        pub fn prepend(list: *Self, new_node: *T) void {
+        pub fn prepend(list: *Self, new_node: *Node) void {
             if (list.first) |first| {
                 // Insert before first.
                 list.insertBefore(first, new_node);
@@ -87,7 +91,7 @@ pub fn DoublyLinkedList(comptime T: type) type {
         ///
         /// Arguments:
         ///     node: Pointer to the node to be removed.
-        pub fn remove(list: *Self, node: *T) void {
+        pub fn remove(list: *Self, node: *Node) void {
             if (node.prev) |prev_node| {
                 // Intermediate node.
                 prev_node.next = node.next;
@@ -109,7 +113,7 @@ pub fn DoublyLinkedList(comptime T: type) type {
         ///
         /// Returns:
         ///     A pointer to the last node in the list.
-        pub fn pop(list: *Self) ?*T {
+        pub fn pop(list: *Self) ?*Node {
             const last = list.last orelse return null;
             list.remove(last);
             return last;
@@ -119,7 +123,7 @@ pub fn DoublyLinkedList(comptime T: type) type {
         ///
         /// Returns:
         ///     A pointer to the first node in the list.
-        pub fn popFirst(list: *Self) ?*T {
+        pub fn popFirst(list: *Self) ?*Node {
             const first = list.first orelse return null;
             list.remove(first);
             return first;

src/terminal/PageList.zig

@@ -7,8 +7,9 @@ const std = @import("std");
 const build_config = @import("../build_config.zig");
 const Allocator = std.mem.Allocator;
 const assert = std.debug.assert;
-const color = @import("color.zig");
 const fastmem = @import("../fastmem.zig");
+const DoublyLinkedList = @import("../datastruct/main.zig").IntrusiveDoublyLinkedList;
+const color = @import("color.zig");
 const kitty = @import("kitty.zig");
 const point = @import("point.zig");
 const pagepkg = @import("page.zig");
@@ -33,7 +34,16 @@ const page_preheat = 4;
 /// The list of pages in the screen. These are expected to be in order
 /// where the first page is the topmost page (scrollback) and the last is
 /// the bottommost page (the current active page).
-pub const List = std.DoublyLinkedList(Page);
+pub const List = DoublyLinkedList(Node);
+
+/// A single node within the PageList linked list.
+///
+/// This isn't pub because you can access the type via List.Node.
+const Node = struct {
+    prev: ?*Node = null,
+    next: ?*Node = null,
+    data: Page,
+};
 
 /// The memory pool we get page nodes from.
 const NodePool = std.heap.MemoryPool(List.Node);
@@ -1699,7 +1709,8 @@ pub fn grow(self: *PageList) !?*List.Node {
     // reuses the popped page. It is possible to have a single page and
     // exceed the max size if that page was adjusted to be larger after
     // initial allocation.
-    if (self.pages.len > 1 and
+    if (self.pages.first != null and
+        self.pages.first != self.pages.last and
         self.page_size + PagePool.item_size > self.maxSize())
     prune: {
         // If we need to add more memory to ensure our active area is