terminal/new: detect empty rows

src/terminal/new/Screen.zig

@@ -87,6 +87,10 @@ pub fn dumpString(
             break :cells cells[0..self.pages.cols];
         };
 
+        if (!pagepkg.Cell.hasText(cells)) {
+            blank_rows += 1;
+            continue;
+        }
         if (blank_rows > 0) {
             for (0..blank_rows) |_| try writer.writeByte('\n');
             blank_rows = 0;

src/terminal/new/page.zig

@@ -198,6 +198,15 @@ pub const Row = packed struct(u18) {
 pub const Cell = packed struct(u32) {
     codepoint: u21 = 0,
     _padding: u11 = 0,
+
+    /// Returns true if the set of cells has text in it.
+    pub fn hasText(cells: []const Cell) bool {
+        for (cells) |cell| {
+            if (cell.codepoint != 0) return true;
+        }
+
+        return false;
+    }
 };
 
 // Uncomment this when you want to do some math.