Preventing APL Faceplates from Snapping Back to Default Coordinates When Switching Views in PCS 7 V9.0

In SIMATIC PCS 7 V9.0, standard Advanced Process Library (APL) faceplates snapping back to their default screen coordinates when operators switch between views (such as Trend, Alarm, or Parameter views) is caused by a coordinate re-centering defect in the initial release of APL V9.0 @pg_template.pdl picture scripts. While clicking the Pin icon prevents faceplates from closing automatically, it does not lock relocated view coordinates in affected builds. To resolve this behavior, install SIMATIC PCS 7 V9.0 SP1 or APL V9.0 Update 2 (or higher), run the OS Project Editor with 'Complete configuration' to update the system PDL templates in the WinCC project directory, and recompile the OS.

APL Faceplate Window Architecture and Coordinate Caching

In SIMATIC PCS 7, Advanced Process Library (APL) faceplates (e.g., for MotL, VlvL, PIDConL, MonAnL) operate as modular, multi-tier picture windows instantiated dynamically at runtime. When an operator clicks a block icon in a process graphic, WinCC executes the global C-script APL_OpenFaceplate, which loads @pg_template.pdl into an active picture window (@FaceplateWindow).

The faceplate structure consists of:
- Header Bar: Displays the technological tag name, block icon status, operating permissions, and navigation buttons.
- View Container: An embedded picture window that dynamically swaps subordinate view PDLs (@pg_<type>_standard.pdl, @pg_<type>_alarm.pdl, @pg_<type>_trend.pdl, @pg_<type>_parameter.pdl).
- Pin Button (@Pin): Controls the auto-close behavior when another faceplate is opened.

Under normal operation, when an operator drags the parent faceplate window across the screen and clicks a view navigation button, the script must query the parent window's current Left and Top runtime properties and preserve them while updating the child picture.

Root Cause of Faceplate Coordinate Snapping in PCS 7 V9.0

In the initial release of SIMATIC PCS 7 V9.0 (APL V9.0 without updates), an internal logic bug in @pg_template.pdl and @apl_openfaceplate.fct failed to retain dynamically modified runtime coordinates when changing views. When the operator clicked a view tab (e.g. from Standard to Trend view), the script re-executed the default positioning calculation:

The function read the origin coordinate of the associated block icon (@PictureWindow origin) instead of reading the current GetLeft() and GetTop() values of the active faceplate picture window.
As a consequence, the entire faceplate snapped instantly back to its default calculated position adjacent to the block icon, frustrating operators who had intentionally moved the window to monitor underlying process graphics.
Operators often confused this defect with the Pin function. The Pin feature determines whether a faceplate remains visible when a new faceplate is selected, but it has no programmatic control over coordinate retention during internal view switching.

Comparison of Faceplate Window Behaviors Across APL Releases

The following table illustrates the behavior of APL faceplate positioning across PCS 7 versions:

PCS 7 / APL VersionBehavior When Moving and Switching ViewsPin Button EffectFix RequirementPCS 7 V8.1 / V8.2 (APL V8.1/8.2)Retains moved position across all view tabsKeeps faceplate open; coordinates stay fixedStable; standard behaviorPCS 7 V9.0 Initial Release (APL V9.0)Snaps back to default origin when switching viewsKeeps faceplate open; coordinates still resetAffected by coordinate script bugPCS 7 V9.0 Update Rollup (APL Upd1)Snaps back under multi-monitor configurationsKeeps faceplate open; intermittent snappingPartial resolutionPCS 7 V9.0 SP1 / APL V9.0 SP1 Upd2Retains moved position across single and multi-screenKeeps faceplate open; coordinates preservedFully resolved via updated @pg_template.pdlPCS 7 V9.1 (APL V9.1+)Retains coordinates and remembers last closed positionLocks coordinates and multi-window dockingAdvanced window manager integrated

Step-by-Step Procedure to Resolve Faceplate Snapping

Follow this procedure to permanently resolve the faceplate coordinate snapping defect:

Acquire and Install the APL Update / Service Pack:
- Download the latest available software update for SIMATIC PCS 7 V9.0 (specifically PCS 7 V9.0 SP1 or APL V9.0 Update 2 / SP1 Update 2, 6ES7658-1EX58-0YA5).
- Install the update package on the Engineering Station and all OS Server / OS Client stations.
Update Project System Pictures via OS Project Editor:
- Installing software updates does not automatically overwrite modified system pictures inside existing WinCC projects.
- In WinCC Explorer on the Engineering Station, open the OS Project Editor (OS-Projekteditor).
- Under the General tab, select your monitor layout resolution.
- Under the Basic Data tab, ensure that @pg_template.pdl, @pg_overview.pdl, and all @apl_*.pdl system screens are selected to be replaced from template.
- Click OK to execute the complete configuration. The updated scripts are deployed to the GraCS directory.
Compile OS and Deploy to Runtime Stations:
- In SIMATIC Manager, perform an AS-OS compilation targeting all OS stations.
- Download the updated OS project to OS Servers and OS Clients.
- Restart WinCC Runtime on the operator stations.

Verification

Verify the resolution in WinCC Runtime:
1. Open any standard APL faceplate (e.g., MotL or PIDConL) from a process graphic.
2. Drag the faceplate across the screen to a distant quadrant or secondary monitor.
3. Click the Trend View button on the faceplate header. Verify that the window switches to the trend display while remaining exactly at the new dragged coordinates.
4. Click the Alarm View and Parameter View buttons. Verify that coordinates remain completely stationary during all transitions.

Limitations and Operational Precautions

Customized System Pictures Overwritten: Running the OS Project Editor with 'Complete configuration' replaces customized @pg_*.pdl or @apl_*.pdl files with factory templates. Any bespoke visual modifications made directly to system templates must be backed up before running the editor.
Multi-Screen Layout Configuration: If multi-screen monitors (@Screen.pdl) are improperly configured in the OS Project Editor, faceplates dragged across physical monitor boundaries may clip or wrap. Always match the exact monitor configuration in the Layout tab.
Station-Wide Deployment Mandatory: The updated APL libraries and system screens must be deployed identically across all OS Clients and OS Web Navigator servers; otherwise, client workstations will continue executing cached local scripts.

Engineer FAQ

Does the Pin button fix the faceplate coordinate snapping issue?

No. The Pin button on APL faceplates controls lifetime management, preventing the faceplate from auto-closing when an operator clicks another block icon. It has no effect on coordinate calculations during view switching.

Why did installing the APL update on the ES not fix the problem on OS Clients?

Software updates installed on the ES update master templates in C:\Program Files (x86)\Siemens\WinCC\options\pdl\. To apply them to an existing project, you must run the OS Project Editor in WinCC Explorer and download the project to the OS Clients.

Can I manually edit the C-script to fix coordinates without installing a service pack?

While theoretically possible by editing the mouse-click action scripts in @pg_template.pdl to store GetLeft() and GetTop() in local script variables before changing picture window contents, this violates Siemens validation and will be overwritten during the next OS compile or project editor run. Installing the official update is mandatory.