The "Attributes" tab in the "Label Thematic Map" window is primarily used to configure display parameters for label objects (text) in the current label thematic map. It should be noted that the "Attributes" tab parameters are identical for Uniform Label thematic maps, Ranges Label thematic maps, Composite Label thematic maps, and Custom Style Label thematic maps.

• Label Expression

  Specifies the thematic variable used by the current label thematic map, which determines the text content displayed on labels. The thematic variable can be a single property field or a mathematical expression of fields.

  • The dropdown list contains all property field names from the vector dataset used to create the current label thematic map. Users may select any field to change the thematic variable. Input field names must exist in the dropdown list. Upon confirmation, the map will re-label objects using the new variable.
  • To use mathematical expressions of property fields as thematic variables, select "Expression..." from the dropdown list. Build the expression in the pop-up SQL Expression dialog. After completion, the map will re-label objects with the new variable.
  • To display multiple fields using connectors, select "Expression..." and construct the field expression in the SQL Expression dialog. Detailed instructions can be found in Label Thematic Map Annotation Expressions.

Note:

• When connecting multiple fields via SQL Expression containing text-type fields with null values, labels will not display properly due to SQL's null handling limitations. As shown in Figure 1, connecting Name (text field) and GDP_2000 fields results in missing labels for objects with null Name values.
• To resolve null value issues in text fields, use database-specific functions to convert nulls to empty strings in SQL Expressions. For example, in MySQL: ifnull(Name,"") || GDP_2000 returns empty strings for null Name values, achieving proper label display as shown in Figure 2.

  

• For Oracle Plus and SQL Plus engine data, field expressions must be field values or arithmetic operations (e.g., SmID or SmID+1). Conditional expressions like "SmID > 100" will cause thematic map creation failures.

• Labels Are Enumeration Information

Requires the selected field in Label Expression to have predefined domain values. Configure domain settings through:

Right-click dataset → Properties → Range tab in the Properties panel.

Comparison of label display effects with/without "Labels are enumeration information":

• Background Settings Area

Adds specified shape and style backgrounds to label text objects, distinct from text character backgrounds.

Background Shape: Controls text background shape options:

• Default: No background decoration.
• Rectangle, Rounded Rectangle, Ellipse, Diamond, Triangle: Uses these shapes as text backgrounds. The "Style" button becomes available for background styling.
• Point Symbol: Uses point symbols as text backgrounds.

Background Style: Configures background shape style. Click "Style" to open Fill Symbol Style Settings for geometric shapes, or Point Symbol Style Settings for point symbols.

Background Margin: Sets distance between text and background border in pixels. Note: Only applicable for Rectangle/Rounded Rectangle shapes with System 0 or System 1 styles.

Background Shadow: Configures shadow properties after setting background shape:

• Color: Shadow color (default: #7F7F7F).
• Offset X: Horizontal shadow offset.
• Offset Y: Vertical shadow offset.

• Offset Settings Area

  Adjusts label display positioning.

  • Offset Unit: Sets offset measurement unit (0.1mm or map coordinate units).
  • Offset X: Horizontal label offset from feature. Can input value or use numeric field values.
  • Offset Y: Vertical label offset from feature. Can input value or use numeric field values.

Note: Field-based offsets only work for point label thematic maps.

• Show Leader Line：

  When checked, displays connecting lines between offset labels and their features.

  • Line Type: Straight or polyline connections.
  • Line Symbol: Configures leader line style via Line Symbol Style Settings.
  • Anchor Point: Sets leader line start position relative to feature (8 available directions).
• Effect Settings Area

  Controls advanced label display effects.

  • Flow: Enables dynamic label repositioning during map navigation. Disable partial refresh when using this feature. (Not supported for point layers)
  • Superscript/Subscript: Implements superior/inferior text display. Limitations:
    • Incompatible with along-line labels, rotation angles, and multi-line displays.
    • Doesn't support expressions with separators.
    • Conflicts with strikethrough/underline effects.

    See Superscript/Subscript for details.

  • Show Slivers: Displays labels for small features that might otherwise be omitted at certain scales.
  • Vertical Text: Displays labels vertically. Note: Conflicts with along-line labels and rotated text.
  • Labels Always Top: Keeps labels above other layers in layer groups. Display order follows layer stacking when multiple label layers use this setting.
  • Label Mask: Clears space under labels for better readability, particularly useful for contour labels.
  • No Overlap: Automatically adjusts labels to prevent overlapping:
    • Two-Way Avoidance: Adjusts labels between symmetrical anchor points (e.g., top-left vs. top-right).
    • Four-Direction Avoidance: Tries label positions in four quadrants (lower-left, upper-left, lower-right, upper-right).
    • Eight-Direction Avoidance: Tests eight possible anchor positions around features.
    • Peripheral Avoidance: Places labels around feature bounding boxes.
  • Numerical Precision: Sets decimal precision for numeric labels. Applies only to pure numerical expressions. Offers 9 precision levels from 0.00000001 to 1. Default shows raw values.

Important Notes: