How to Open APL Technological Faceplates from Standard WinCC Screen Buttons Using APL Scripts

In SIMATIC PCS 7 V8.0 and V8.1, opening the faceplate of a technological block (such as OpTrig, MotL, or PIDConL) from a standard WinCC screen button or static rectangle rather than a generated block icon is accomplished using the APL faceplate open script functions. Standard APL faceplates are invoked via the C-script function 'APL_OpenFaceplate' or 'SSMOpenTopFieldFix'. To configure a standard Windows button to launch a specific faceplate, assign the technological block's tag prefix (e.g., 'Plant/Area/OpTrig_Instance') and faceplate type identifier to the button's mouse-click event using the WinCC Dynamic Wizard or direct APL API calls.

APL Faceplate Invocation Architecture: Block Icons vs Screen Objects

In standard SIMATIC PCS 7 operation, faceplates are opened by clicking an auto-generated block icon:
* The Block Icon Mechanism:
* The block icon contains internal system properties: type (e.g., @OpTrig/1), tag (the WinCC tag prefix), and ServerName.
* Clicking the icon triggers internal APL C-scripts (APL_OpenFaceplate), passing these attributes to the Picture Window manager.
* The Custom Interface Requirement:
* Engineers frequently design custom equipment graphics, high-density dashboard overviews, or simple operational buttons (e.g., Trigger Batch Flush) where displaying a full APL block icon is visually clunky.
* Opening the standard faceplate from a plain WinCC button or graphical shape requires passing the identical parameter payload directly to the APL faceplate engine.

Understanding the APL_OpenFaceplate C-Script Function and Parameters

The core APL C-function governing faceplate generation is declared in apdefap.h:

#include "apdefap.h"
void OnClick(char* lpszPictureName, char* lpszObjectName, char* lpszPropertyName)
{
    // Define the full tag path of the technological block
    char* pszTagPrefix = "Plant1/Area2/OpTrig_BatchStart";

    // Define the faceplate type identifier (matches block type)
    char* pszFaceplateType = "@OpTrig";

    // Call the standard APL faceplate opener
    // Parameters: Parent Picture, Calling Object, Tag Prefix, Faceplate Type
    APL_OpenFaceplate(lpszPictureName, lpszObjectName, pszTagPrefix, pszFaceplateType);
}

Required Parameters:
pszTagPrefix: The exact WinCC structure tag name corresponding to the CFC block instance.
pszFaceplateType: The faceplate template family (e.g., @OpTrig, @MotL, @PIDConL, @VlvL).

Configuring Standard Screen Buttons via the Dynamic Wizard

To avoid manual C-scripting, use the integrated WinCC Dynamic Wizard:

Draw Screen Button:
* In Graphics Designer, place a standard Windows Button on the canvas.
* Label the button: Open Trigger Control.
Launch Dynamic Wizard:
* Open the Dynamic Wizard pane: select the Picture Functions tab.
* Double-click Picture selection via measurement point / block icon (or Open faceplate).
Select Technological Block:
* In the wizard dialog, browse the plant hierarchy.
* Select the target block instance (e.g., OpTrig).
* The wizard generates the complete, error-free C-action on the button's Mouse Click event.

Handling Tag Prefixes and Coordinate Window Positioning

When invoking faceplates from custom screen objects:

Tag Prefix Binding: Standard APL faceplates (@PG_OpTrig_Standard.pdl) contain generic internal tags (e.g., .Out, .In). The TagPrefix property on the host Picture Window binds these generic fields to the physical instance tag.
Window Positioning (SSMOpenTopFieldFix):
By default, APL calculates faceplate coordinates to appear adjacent to the calling mouse cursor without overlapping screen boundaries or obscuring alarm banners.
Calling APL_OpenFaceplate ensures automatic multi-monitor desktop boundary detection.

Comparison of Faceplate Triggering Techniques in WinCC

The table below compares methods for launching APL faceplates in SIMATIC PCS 7.

Triggering TechniqueVisual CustomizationAlarm Badge DisplayEngineering EffortUpgradabilityStandard Block IconPredefined APL templatesAutomatic (Group Display)Zero (Auto-generated)100% Migration-ProofDynamic Wizard ButtonComplete freedom (Any shape)Manual (Optional)Low (Wizard guided)HighCustom APL_OpenFaceplateComplete freedomNoneLow (Simple C-Script)HighDirect SetVisible on PicturePoor (Hardcoded window)NoneHigh (Manual scripting)Poor (Breaks coordinate logic)

Verification

To confirm that the custom screen button opens the faceplate properly:
1. In Graphics Designer, save the modified process picture.
2. Activate WinCC Runtime.
3. Click the custom button: verify that the OpTrig faceplate opens immediately in front of the picture.
4. Verify that the faceplate header displays the correct tag name and plant hierarchy path.
5. Click the operator trigger command in the faceplate: confirm that the controller processes the pulse and updates feedback dynamically.
6. Verify that closing the faceplate cleanly releases the window handle without client memory leaks.

Limitations and Operational Precautions

Standard screen buttons lack integrated group displays; if alarm awareness is required for the technological block, use standard block icons or embed a group display object.
Always ensure that the user logged into WinCC possesses adequate authorization levels (Level 5 or Level 6) to operate the faceplate controls once opened.
Do not attempt to bypass APL_OpenFaceplate by directly manipulating Picture Window visibility flags, as this bypasses client multi-screen coordinate positioning.
Always validate final software licensing and system documentation against the applicable Siemens catalog and authorized distributor quotation.

Engineer FAQ

Can I open a MotL faceplate from a simple graphic rectangle?

Yes. Attach the APL_OpenFaceplate script to the rectangle's Mouse Click event with pszFaceplateType = '@MotL' and the motor's tag prefix.

Why did the faceplate open with blank fields and '#' symbols?

The pszTagPrefix passed to the script does not match the exact WinCC tag name generated during OS compilation; verify the tag name in WinCC Tag Management.