terminal: add assertion to page integrity that row/col count > 0

src/terminal/PageList.zig

@@ -1976,13 +1976,17 @@ pub fn eraseRows(
     while (it.next()) |chunk| {
         // If the chunk is a full page, deinit thit page and remove it from
         // the linked list.
-        if (chunk.fullPage()) full_page: {
+        if (chunk.fullPage()) {
             // A rare special case is that we're deleting everything
             // in our linked list. erasePage requires at least one other
-            // page so to handle this we break out of this handling and
-            // do a normal row by row erase.
+            // page so to handle this we reinit this page, set it to zero
+            // size which will let us grow our active area back.
             if (chunk.page.next == null and chunk.page.prev == null) {
-                break :full_page;
+                const page = &chunk.page.data;
+                erased += page.size.rows;
+                page.reinit();
+                page.size.rows = 0;
+                break;
             }
 
             self.erasePage(chunk.page);

src/terminal/page.zig

@@ -175,7 +175,15 @@ pub const Page = struct {
         self.* = undefined;
     }
 
+    /// Reinitialize the page with the same capacity.
+    pub fn reinit(self: *Page) void {
+        @memset(self.memory, 0);
+        self.* = initBuf(OffsetBuf.init(self.memory), layout(self.capacity));
+    }
+
     pub const IntegrityError = error{
+        ZeroRowCount,
+        ZeroColCount,
         UnmarkedGraphemeRow,
         MissingGraphemeData,
         InvalidGraphemeCount,
@@ -212,6 +220,15 @@ pub const Page = struct {
         //   used for the same reason as styles above.
         //
 
+        if (self.size.rows == 0) {
+            log.warn("page integrity violation zero row count", .{});
+            return IntegrityError.ZeroRowCount;
+        }
+        if (self.size.cols == 0) {
+            log.warn("page integrity violation zero col count", .{});
+            return IntegrityError.ZeroColCount;
+        }
+
         var arena = ArenaAllocator.init(alloc_gpa);
         defer arena.deinit();
         const alloc = arena.allocator();
@@ -1742,3 +1759,31 @@ test "Page verifyIntegrity styles ref count mismatch" {
         page.verifyIntegrity(testing.allocator),
     );
 }
+
+test "Page verifyIntegrity zero rows" {
+    var page = try Page.init(.{
+        .cols = 10,
+        .rows = 10,
+        .styles = 8,
+    });
+    defer page.deinit();
+    page.size.rows = 0;
+    try testing.expectError(
+        Page.IntegrityError.ZeroRowCount,
+        page.verifyIntegrity(testing.allocator),
+    );
+}
+
+test "Page verifyIntegrity zero cols" {
+    var page = try Page.init(.{
+        .cols = 10,
+        .rows = 10,
+        .styles = 8,
+    });
+    defer page.deinit();
+    page.size.cols = 0;
+    try testing.expectError(
+        Page.IntegrityError.ZeroColCount,
+        page.verifyIntegrity(testing.allocator),
+    );
+}