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Export System

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The Export System in MeasureLab provides a modular plugin architecture for serializing measurement data from the ComparisonManager into various file formats. It supports advanced features such as CSV injection sanitization, automated X-axis interpolation for merged exports, and proprietary .mlcomp serialization for cross-session data persistence.

Architecture Overview

The system is built around a centralized manager that handles the registration and retrieval of specialized exporter plugins. All data exported through this system originates as ComparisonTrace objects, which contain the raw measurement arrays and associated metadata (axes, units, timestamps).

Core Components

Component Class/Entity Responsibility
Export Manager ExportManager Singleton registry for exporter plugins. src/core/export/manager.py:10-11
Plugin Base BaseTraceExporter Abstract base class defining the interface for new formats. src/core/export/base.py:6
CSV Exporter CsvTraceExporter Handles tabular data with interpolation and sanitization. src/core/export/csv_exporter.py:12
JSON Exporter JsonTraceExporter Handles .mlcomp proprietary JSON serialization. src/core/export/json_exporter.py:11
Export Dialog ExportSettingsDialog UI for selecting targets, formats, and layout options. src/gui/widgets/export_dialog.py:31

Data Flow Diagram

This diagram illustrates the flow from raw ComparisonTrace objects through the ExportManager to the filesystem.

Export System Data Flow

graph TD
    subgraph "Natural Language Space"
        UserAction["User clicks Export"]
        Selection["Select Traces & Format"]
    end

    subgraph "Code Entity Space"
        CT["ComparisonTrace Object"]
        ED["ExportSettingsDialog"]
        EM["ExportManager"]
        BTE["BaseTraceExporter Implementation"]
        FS["File System"]

        ED -- "1. Requests Exporters" --> EM
        EM -- "2. Returns dict[id, Exporter]" --> ED
        ED -- "3. Passes CT list + options" --> BTE
        BTE -- "4. Serialization" --> FS
    end

    UserAction --> ED
    Selection --> ED
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Sources: src/core/export/manager.py:10-39, src/gui/widgets/export_dialog.py:32-40, src/core/export/base.py:31-34

Export Plugins

BaseTraceExporter

The BaseTraceExporter is an abstract base class (ABC) that enforces a consistent interface for all file formats. Every exporter must provide:

  • format_id: A unique string identifier (e.g., "csv"). src/core/export/base.py:9
  • name: A localized display name for the UI. src/core/export/base.py:17
  • file_filter: The string used by QFileDialog. src/core/export/base.py:22
  • export_traces(): The method implementing the actual file writing logic. src/core/export/base.py:32

CsvTraceExporter

The CSV exporter is the most complex plugin, supporting multiple layout modes and security features.

CSV Injection Sanitization

To prevent Formula Injection (CSV Injection), the exporter implements _sanitize_csv_field. It checks if a string field starts with dangerous characters (=, +, -, @, \t) and prepends a single quote ' to ensure spreadsheet software treats the content as literal text. src/core/export/csv_exporter.py:29-35

Export Layouts

  1. Merged (_export_merged): Combines multiple traces into a single table. If traces have different X-axis samples, the exporter generates a common x_grid (either from a reference trace or a union of all points) and uses np.interp to align Y-data. src/core/export/csv_exporter.py:65-154
  2. Independent (_export_independent): Writes traces side-by-side with their own X and Y columns, padded with empty strings where row counts differ. src/core/export/csv_exporter.py:156-200

JsonTraceExporter

This exporter handles the MeasureLab Comparison (.mlcomp) format. It leverages the to_dict() method of ComparisonTrace to serialize complex measurement data into a JSON structure, including versioning metadata. src/core/export/json_exporter.py:28-33

Sources: src/core/export/csv_exporter.py:12-200, src/core/export/json_exporter.py:11-39, src/core/export/base.py:6-34

Export Manager

The ExportManager is a singleton that manages the lifecycle of exporter plugins. It is initialized with the default JsonTraceExporter and CsvTraceExporter during its first call to instance(). src/core/export/manager.py:10-28

Key Methods:

  • register_exporter(exporter): Adds a new format to the system at runtime. src/core/export/manager.py:30-32
  • get_exporter(format_id): Retrieves a specific plugin by its ID. src/core/export/manager.py:34-35

Sources: src/core/export/manager.py:10-39

UI Integration: ExportSettingsDialog

The ExportSettingsDialog provides a unified interface for the export process. It dynamically adjusts its options based on the selected format using a QStackedWidget. src/gui/widgets/export_dialog.py:90-92

Logic and Configuration

  • Target Selection: Users can toggle specific traces for export using a QListWidget with checkable items. src/gui/widgets/export_dialog.py:62-72
  • Format Switching: When the format changes, on_format_changed updates the QStackedWidget to show format-specific settings (e.g., CSV delimiters vs. JSON versioning). src/gui/widgets/export_dialog.py:230-237
  • Scheme Handling: Supports "Combine into a single file" or "Export as individual files". If individual files are chosen, the dialog automatically generates filenames based on trace names and a sanitized path. src/gui/widgets/export_dialog.py:75-88, src/gui/widgets/export_dialog.py:280-310

Export Interaction Model

sequenceDiagram
    participant UI as ExportSettingsDialog
    participant EM as ExportManager
    participant BTE as BaseTraceExporter

    UI->>EM: get_all_exporters()
    EM-->>UI: return dict
    Note over UI: User selects CSV format
    UI->>UI: show csv_widget (QStackedWidget)
    Note over UI: User clicks Export
    UI->>BTE: export_traces(filepath, traces, options)
    BTE->>BTE: _sanitize_csv_field()
    BTE-->>UI: return success/fail
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Sources: src/gui/widgets/export_dialog.py:31-310, src/core/export/csv_exporter.py:37-63

Trace Serialization

Traces are serialized from ComparisonTrace objects. These objects act as the standard data container within the export system.

Field Type Description
x_data List[float] Primary independent variable array.
y_data List[float] Primary dependent variable array.
y2_data Optional[List[float]] Secondary dependent variable (e.g., Phase).
x_axis AxisMetadata Metadata including dimension and unit (e.g., "Frequency", "Hz").

When exporting to CSV, the system uses these metadata objects to generate localized headers, such as Frequency (Hz) or Voltage (dBV). src/core/export/csv_exporter.py:84-101

Sources: src/core/export/csv_exporter.py:84-115, tests/core/export/test_csv_exporter.py:29-53

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