Measure styled smoke frames by visible cells

src/v1_smoke.zig

@@ -250,6 +250,28 @@ test "regular: ns8 local production smoke covers editor workflow before real-dev
 
 fn frameLinesFit(frame: []const u8, width: usize) bool {
     var lines = std.mem.splitScalar(u8, frame, '\n');
-    while (lines.next()) |line| if (line.len > width) return false;
+    while (lines.next()) |line| if (visibleCells(line) > width) return false;
     return true;
 }
+
+fn visibleCells(line: []const u8) usize {
+    var cells: usize = 0;
+    var i: usize = 0;
+    while (i < line.len) {
+        if (line[i] == 0x1b and i + 1 < line.len and line[i + 1] == '[') {
+            i += 2;
+            while (i < line.len) : (i += 1) {
+                const byte = line[i];
+                if ((byte >= 'A' and byte <= 'Z') or (byte >= 'a' and byte <= 'z')) {
+                    i += 1;
+                    break;
+                }
+            }
+            continue;
+        }
+        const len = std.unicode.utf8ByteSequenceLength(line[i]) catch 1;
+        cells += 1;
+        i += @min(len, line.len - i);
+    }
+    return cells;
+}