Symbol Layer Drawing

Feature Description

The Symbol Layer Drawing function is used to customize the draw order of symbols in a map, overriding the system's default drawing rules. When a symbol consists of multiple symbol layers (e.g., a road symbol with an outline), this function controls the draw order of these individual symbol layers within the symbol. Currently, this function is only supported for line layers, line unique value thematic map layers, and line graduated color thematic map layers.

This function is primarily applied in cartographic scenarios involving complex road networks, such as intersections, overpasses, underpasses, and other scenarios with complex road displays. By adjusting the draw order, gaps at road segment connections can be eliminated, achieving visual continuity and connectivity.

The following are the related terms for this function:

Symbol Class: A symbol used in a layer is called a symbol class.
- For a layer with a single symbol, the symbol itself is a symbol class.
- In a unique value or graduated color thematic map, the symbol used by each thematic item is a separate symbol class.
- After enabling this function, the draw order of symbols in the map is determined by the order in which the symbol classes are arranged.
Symbol Layer: A symbol layer is a constituent unit within a symbol. As shown in the following figure, for a road symbol consisting of a "main fill line" and an "outer contour line," each sub-line is an independent symbol layer.

Symbol Layer Drawing is divided into two interfaces: the Basic page and the Advanced page:

Basic page: Used to reorder symbol classes and select the drawing mode for each symbol class.
Advanced page: Used only in complex situations where cross-symbol class, fine-grained adjustment of every symbol layer's drawing order is needed. The custom order set in the Advanced page might not be representable in the Basic page; switching back to the Basic page will reset the settings to default.

This function is supported starting from SuperMap iDesktopX 2026 version.

Function Entrance

Layer Manager->context menu->Layer Style->Symbol Layer Drawing.

Operational Steps

The following sections introduce how to use the related functions in the Basic page and the Advanced page respectively:

Using the Basic Page

From the context menu of a line layer in the Layer Manager, enter the Symbol Layer Drawing interface of the Layer Style panel. On the Basic page, check the Enable Symbol Layer Painting checkbox to enable this function.
At this point, the order of symbol classes in the Draw Order list represents their drawing order from bottom to top. The symbol class at the bottom of the list is drawn first (displayed at the bottom), and the one at the top is drawn last (displayed at the top).
Select and drag a symbol class in the Draw Order list to re-adjust its draw order in the layer.
You can click the arrow in front of a symbol class to expand and view all its internal symbol layers. Alternatively, click the Expand All/Collapse All button in the upper right corner of the panel to expand or collapse all symbol classes simultaneously.

After enabling symbol layer painting, the system assigns a default drawing mode based on the symbol's structure. If a symbol consists of only one symbol layer, its default drawing mode is No Connection. If a symbol consists of multiple symbol layers, the default drawing mode is Join. You can manually adjust it according to the following table:

Drawing Mode	Detailed Description	Illustration	Notes
No Connection	The symbol is drawn independently; all its internal symbol layers are drawn simultaneously, with no sequential order. Suitable for simple symbols that do not require connection effects. The figure on the right shows two symbol classes set to No Connection.		A symbol with only one symbol layer can only have its drawing mode set to No Connection.
Join	Multiple symbol layers within a symbol will be drawn in layers from bottom to top (draw the bottom layer first, then the upper layers). This ensures visual continuity for lines of the same symbol class (e.g., a certain road level). The figure on the right shows two symbol classes both set to Join.
Join and Merge	This mode is suitable for connected display across symbol classes. A symbol class set to Join and Merge will merge and draw with the symbol class immediately above it in the Draw Order list. During drawing, the bottom-most layers of these two classes are drawn together first, followed by their upper layers in sequence. The figure on the right shows the symbol class lower in order set to Join and Merge, and the symbol class above it set to Join.		1. The topmost symbol class cannot use this mode. 2. If the symbol class immediately above is set to No Connection, this symbol class cannot use this mode. 3. If a symbol class using this mode is dragged below a symbol class set to No Connection, its setting will be automatically reset to Join.

Click the Reset button in the lower right corner of the panel to restore all symbol classes' drawing settings to default.

Using the Advanced Page

Use this page only when you need to reorder each symbol layer's draw order across symbol classes. The Advanced page organizes symbol layers into different drawing order Groups. All symbol layers within the same group are drawn simultaneously.
The structure of Groups in the Advanced page is determined by the order of symbol classes and the drawing mode set for each symbol class in the Basic page. The sorting is based first on the order of symbol classes from the Basic page, then further sorted by the drawing mode set for each symbol class.
- No Connection: All symbol layers are in one group and drawn simultaneously.
- Join: Each symbol layer of the symbol class is assigned to different groups in order for separate drawing.
- Join and Merge: For the multiple symbol classes involved in the merge, their corresponding bottom-most symbol layers are placed into the same group for simultaneous drawing. Their upper layers are then assigned to different groups in order for separate drawing.
You can drag an entire Group to adjust its order, or drag a single symbol layer between different Groups.
If you adjust the draw order of symbol layers across symbol classes, or change the drawing sequence of symbol layers within a symbol class on the Advanced page, it cannot be represented in the Basic page.
At this point, if you switch the interface back to the Basic page, a prompt box will appear: "This order cannot be represented in the Base page. Switching back to the Base page will restore the default drawing settings. Continue with the switch?"

If you click Yes, the interface switches to the Basic page, and the drawing modes are restored to default. If you click No, you remain on the Advanced page, and the drawing modes do not change.
Right-click a symbol layer and choose to Move to New Group. This symbol layer will then be added to a new group at the bottom of the Draw Order list.

Notes:

If Symbol Layer Drawing is enabled and related settings are made, modifying the marker style or making any changes to thematic map properties will reset Symbol Layer Drawing to its default state. It is recommended to configure Symbol Layer Drawing last, after completing all symbology settings.