terminal/new: use new pagelist grow mechanism that prunes

src/terminal/new/PageList.zig

@@ -258,7 +258,9 @@ pub fn scroll(self: *PageList, behavior: Scroll) void {
 /// This may allocate, but also may not if our current page has more
 /// capacity we can use. This will prune scrollback if necessary to
 /// adhere to max_size.
-pub fn grow2(self: *PageList) !?*List.Node {
+///
+/// This returns the newly allocated page node if there is one.
+pub fn grow(self: *PageList) !?*List.Node {
     const last = self.pages.last.?;
     if (last.data.capacity.rows > last.data.size.rows) {
         // Fast path: we have capacity in the last page.
@@ -305,16 +307,6 @@ pub fn grow2(self: *PageList) !?*List.Node {
     return next_page;
 }
 
-/// Grow the page list by exactly one page and return the new page. The
-/// newly allocated page will be size 0 (but capacity is set).
-pub fn grow(self: *PageList) !*List.Node {
-    const next_page = try self.createPage();
-    // we don't errdefer this because we've added it to the linked
-    // list and its fine to have dangling unused pages.
-    self.pages.append(next_page);
-    return next_page;
-}
-
 /// Create a new page node. This does not add it to the list and this
 /// does not do any memory size accounting with max_size/page_size.
 fn createPage(self: *PageList) !*List.Node {
@@ -461,7 +453,7 @@ fn growRows(self: *PageList, n: usize) !void {
     }
 
     while (n_rem > 0) {
-        page = try self.grow();
+        page = (try self.grow()).?;
         const add = @min(n_rem, page.data.capacity.rows);
         page.data.size.rows = add;
         n_rem -= add;
@@ -847,7 +839,7 @@ test "PageList grow fit in capacity" {
     try testing.expect(last.size.rows < last.capacity.rows);
 
     // Grow
-    try testing.expect(try s.grow2() == null);
+    try testing.expect(try s.grow() == null);
     {
         const pt = s.getCell(.{ .active = .{} }).?.screenPoint();
         try testing.expectEqual(point.Point{ .screen = .{
@@ -868,11 +860,11 @@ test "PageList grow allocate" {
     const last_node = s.pages.last.?;
     const last = &s.pages.last.?.data;
     for (0..last.capacity.rows - last.size.rows) |_| {
-        try testing.expect(try s.grow2() == null);
+        try testing.expect(try s.grow() == null);
     }
 
     // Grow, should allocate
-    const new = (try s.grow2()).?;
+    const new = (try s.grow()).?;
     try testing.expect(s.pages.last.? == new);
     try testing.expect(last_node.next.? == new);
     {
@@ -897,14 +889,14 @@ test "PageList grow prune scrollback" {
     const page1_node = s.pages.last.?;
     const page1 = page1_node.data;
     for (0..page1.capacity.rows - page1.size.rows) |_| {
-        try testing.expect(try s.grow2() == null);
+        try testing.expect(try s.grow() == null);
     }
 
     // Grow and allocate one more page. Then fill that page up.
-    const page2_node = (try s.grow2()).?;
+    const page2_node = (try s.grow()).?;
     const page2 = page2_node.data;
     for (0..page2.capacity.rows - page2.size.rows) |_| {
-        try testing.expect(try s.grow2() == null);
+        try testing.expect(try s.grow() == null);
     }
 
     // Get our page size
@@ -912,7 +904,7 @@ test "PageList grow prune scrollback" {
 
     // Next should create a new page, but it should reuse our first
     // page since we're at max size.
-    const new = (try s.grow2()).?;
+    const new = (try s.grow()).?;
     try testing.expect(s.pages.last.? == new);
     try testing.expectEqual(s.page_size, old_page_size);
 

src/terminal/new/Screen.zig

@@ -226,31 +226,14 @@ pub fn cursorAbsolute(self: *Screen, x: size.CellCountInt, y: size.CellCountInt)
 pub fn cursorDownScroll(self: *Screen) !void {
     assert(self.cursor.y == self.pages.rows - 1);
 
-    const cursor_page = self.cursor.page_offset.page;
+    // Grow our pages by one row. The PageList will handle if we need to
-    if (cursor_page.data.capacity.rows > cursor_page.data.size.rows) {
+    // allocate, prune scrollback, whatever.
-        // If we have cap space in our current cursor page then we can take
+    _ = try self.pages.grow();
-        // a fast path: update the size, recalculate the row/cell cursor pointers.
-        cursor_page.data.size.rows += 1;
-
     const page_offset = self.cursor.page_offset.forward(1).?;
     const page_rac = page_offset.rowAndCell(self.cursor.x);
     self.cursor.page_offset = page_offset;
     self.cursor.page_row = page_rac.row;
     self.cursor.page_cell = page_rac.cell;
-    } else {
-        // No space, we need to allocate a new page and move the cursor to it.
-        const new_page = try self.pages.grow();
-        assert(new_page.data.size.rows == 0);
-        new_page.data.size.rows = 1;
-        const page_offset: PageList.RowOffset = .{
-            .page = new_page,
-            .row_offset = 0,
-        };
-        const page_rac = page_offset.rowAndCell(self.cursor.x);
-        self.cursor.page_offset = page_offset;
-        self.cursor.page_row = page_rac.row;
-        self.cursor.page_cell = page_rac.cell;
-    }
 
     // The newly created line needs to be styled according to the bg color
     // if it is set.