Resolving HMIRuntime VBScript Error in WinCC Static Text Tooltips

Problem Overview

In a Siemens WinCC V7.5 picture (PDL) that contains a Static Text object, configuring a dynamic tooltip that reads the configured documentation comment of a process tag fails with the following diagnostic output in the Global Script diagnostic window (GDI):

Microsoft VBScript runtime error
Picture   : BOILER7.pdl_Triggers
Function  : Function StaticX0020Text59_ToolTipText_Trigger(ByVal Item)
Line      : 6
Error     : Object doesn't support this property or method: 'HMIRuntime'

Two distinct authoring patterns raise the same error:

1. A picture-level ToolTipText_Trigger function that addresses the static object through HMIRuntime.ActiveScreen.ScreenItems.Item("Static Text58").
2. A per-object property trigger auto-generated by WinCC (named StaticX0020Text59_ToolTipText_Trigger) where the developer has pasted picture-level code without removing the HMIRuntime.ActiveScreen.ScreenItems.Item(...) indirection.

Both patterns fail because the script engine resolves the bare identifier HMIRuntime against the wrong scope. This article documents the WinCC V7.5 SP2 VBScript object model that governs the two patterns, the exact corrected code for each, and the engineering checklist that prevents the error from recurring across large picture libraries.

Root Cause: Trigger Function Scoping

WinCC V7.5 generates per-object trigger functions under two naming conventions, and the rules for addressing runtime objects differ between them.

1. Picture-level trigger — a function named PictureName_Triggers that you author yourself. It receives no implicit object reference. Inside the function you must address the runtime object model through the global HMIRuntime root.
2. Object-level property or event trigger — a function named ObjectName_PropertyName_Trigger (for example, StaticX0020Text59_ToolTipText_Trigger) that the runtime calls on every value change of the bound property. The Item parameter is the HMI runtime object instance of the triggering object itself.

The error is reproducible when code written for a picture-level trigger is copied into an object-level trigger without removing the HMIRuntime.ActiveScreen.ScreenItems.Item(...) indirection. Inside the per-object callback, line 6 dereferences the HMIRuntime identifier, but the VBScript engine has already bound the Item reference to the current object. The dot-member access pattern that Visual Basic mandates for every member lookup is described in the Microsoft Learn reference on Objects and Classes in Visual Basic; the Microsoft Learn reference on Determining Object Type documents the TypeName() and TypeOf ... Is operators that should be used to confirm the type of a runtime variable before its members are dereferenced.

Corrected Code: Per-Object ToolTipText Trigger

For an object-level property trigger on a Static Text object named "Static Text59" in picture BOILER7.pdl, the auto-generated function name is StaticX0020Text59_ToolTipText_Trigger. The Item parameter already references the object instance, so the body is a single line:

Function StaticX0020Text59_ToolTipText_Trigger(ByVal Item)
    Item.TooltipText = HMIRuntime.Tags("B7_AirFlow").Comment
End Function

Engineering notes for this implementation:

• Item is of type IHMIStaticText, the WinCC runtime wrapper for a static text. All HMIObject base-class members are reachable, including TooltipText, BackColor, ForeColor, FontName, Layer, Left, Top, Width, and Height.
• HMIRuntime.Tags("B7_AirFlow") returns an IHMITag object. Reading the .Comment property returns the multi-language comment string configured in the tag's Properties > Comment field.
• TooltipText accepts a Variant containing a String. For a multi-line tooltip, embed vbCrLf in the comment field or assemble the string with Chr(13) & Chr(10) in the trigger body.
• VBScript is case-insensitive for identifiers, but the canonical WinCC casing TooltipText, Comment, and HMIRuntime is used throughout the Siemens V7.5 SP2 reference.
• The trigger fires according to the configured trigger of the ToolTipText property (default "On Change"). Avoid setting the trigger to a 250 ms cyclic cycle unless the tooltip is genuinely time-varying.

WinCC VBScript Object Name Encoding

WinCC generates per-object trigger function names by replacing every character in the picture-designer object name that is illegal in a VBScript identifier with its four-digit hexadecimal Unicode escape preceded by X. The space character (U+0020) is encoded as X0020. The most common encodings encountered in stock WinCC pictures are:

The escape sequence is always uppercase and always four hex digits, matching the VBScript ChrW() semantics. The complete runtime mapping is the responsibility of the WinCC Graphics Designer; the application developer does not encode names manually but must know the encoding to address per-object triggers.

The HMIRuntime Object Model

Inside a WinCC V7.5 picture trigger (picture-level or object-level) the following runtime objects are reachable from the global HMIRuntime root:

Standard property assignment uses the VBScript Set statement for object references and direct assignment for value types. The dot-member access rule is the same pattern that the Microsoft Learn reference on Objects and Classes in Visual Basic documents. TypeName(Item) (from the Determining Object Type reference) is the safest way to confirm the runtime type of a variable before member access.

Reading the Tag Comment Property

Every WinCC tag exposes the configured documentation string through the IHMITag.Comment property. The string is set in the tag editor under Properties > Comment and is one of the values exported by the project documentation tool. The supported read pattern is:

Dim sComment
sComment = HMIRuntime.Tags("B7_AirFlow")
' sComment is a Variant containing the String value of the comment

Performance characteristics of reading Comment in a high-frequency trigger:

• .Comment is a static configuration string (not a polled value). It is read once per trigger evaluation and is not subject to the WinCC acquisition cycle.
• Trigger frequency is governed by the configured trigger of the bound property. For a ToolTipText trigger the default trigger is "On Change"; the body is evaluated only when the underlying trigger fires (typically on tag value change for connected objects, or on picture open for the ToolTipText itself).
• Do not place a heavy loop in the trigger body. VBScript triggers in WinCC are single-threaded; a slow body will delay the runtime scheduler and freeze the picture.
• Reading Comment does not register a subscription, does not increment the tag's update counter, and does not appear in the tag logging statistics.

If the comment string contains placeholders such as %s or {VALUE}, perform the substitution with the VBScript Replace() function before assigning the result to Item.TooltipText:

Dim sTpl, sValue
sTpl   = HMIRuntime.Tags("B7_AirFlow")
sValue = CStr(HMIRuntime.Tags("B7_AirFlow").Read)
Item.TooltipText = Replace(sTpl, "{VALUE}", sValue)

Alternatives: Picture-Level Trigger

When the same tooltip must be assigned to many objects, write a picture-level trigger instead of a per-object trigger. The function name is PictureName_Triggers (for the BOILER7 picture: BOILER7_Triggers), and the body uses the HMIRuntime.ActiveScreen.ScreenItems collection directly:

Function BOILER7_Triggers(ByVal Item)
    Dim objText, tagComment
    Set objText  = HMIRuntime.ActiveScreen.ScreenItems.Item("Static Text58")
    tagComment   = HMIRuntime.Tags("B7_AirFlow")
    objText.TooltipText = tagComment
End Function

This pattern works because HMIRuntime is a globally available identifier inside the picture-level trigger scope, and the Item parameter is the trigger-callback handle (it can be ignored). The picture-level trigger fires on the configured trigger condition of the picture; configure it to "On Change" of the source tag for the lowest CPU cost.

Generating Triggers Programmatically

For large pictures with dozens of Static Text objects that should each reflect a tag comment, manual per-object triggers do not scale. A common pattern is a single picture-level trigger that iterates ScreenItems by name prefix and assigns the tooltip by a naming convention such as Tag_<index>:

Sub AssignTagCommentsAsTooltips()
    Dim objItem, sName
    For Each objItem In HMIRuntime.ActiveScreen.ScreenItems
        sName = objItem.ObjectName
        If Left(sName, 11) = "Static Text" Then
            objItem.TooltipText = _
                HMIRuntime.Tags("Tag_" & Mid(sName, 12)).Comment
        End If
    Next
End Sub

Call the routine once on picture open by binding it to the picture's OpenPicture event trigger. The ObjectName property returns the designer-time name; use it as the lookup key, not the Name property (which is the internal alias and can differ). For runtime type checking, gate the assignment with the TypeName() function as recommended by the VB object-type determination reference:

For Each objItem In HMIRuntime.ActiveScreen.ScreenItems
    If TypeName(objItem) = "HMIStaticText" Then
        objItem.TooltipText = HMIRuntime.Tags("B7_AirFlow")
    End If
Next

Note: TypeOf objItem Is IHMIStaticText is not directly available in WinCC VBScript because the COM type library does not expose runtime type identifiers in the query-able form. Use the TypeName() string comparison or the object name prefix instead.

Verification Procedure

1. In the WinCC Explorer, open Graphics Designer and load BOILER7.pdl.
2. Select the Static Text object ("Static Text59") and open Properties > Events > ToolTipText.
3. Confirm the trigger function name is StaticX0020Text59_ToolTipText_Trigger and the body contains only Item.TooltipText = HMIRuntime.Tags("B7_AirFlow").Comment.
4. Save the picture, then save and rebuild the project. The runtime loads the updated PDL on the next picture change.
5. Activate the runtime. Open Global Script > Diagnostics (GDI window) and confirm no runtime error is logged for the function.
6. Hover the mouse over the Static Text. The configured tag comment should appear in the tooltip after the configured tooltip delay (default 400 ms in WinCC V7.5 SP2; configurable per object under Properties > Miscellaneous > ToolTipDelay).
7. If the tooltip is blank, check the tag's Properties > Comment field in Tag Management — the field must be non-empty. A blank comment produces a blank tooltip without raising an error.
8. If the tooltip shows a literal string such as "B7_AirFlow", the trigger is reading the tag name rather than the comment. Inspect the property: HMIRuntime.Tags("B7_AirFlow").Comment in a one-shot test action to confirm the comment is populated.

Troubleshooting Matrix

Performance and Engineering Notes

• The Item parameter in a per-object trigger is the same runtime object that Graphics Designer instantiates. Reusing it (rather than calling ScreenItems.Item(...) again) is the documented hot-path pattern in the WinCC V7.5 SP2 VBScript reference; it saves a dictionary lookup per trigger evaluation.
• For very large pictures (more than 200 screen items) avoid iterating ScreenItems in a trigger that fires frequently. Cache the lookup in a project module-level dictionary if you must address many objects by name.
• Tooltip update latency in WinCC V7.5 SP2 is governed by the mouse-hover delay (default 400 ms, configurable per object) plus one VBScript scheduling tick. This is acceptable for human-in-the-loop HMI use cases; do not rely on it for control-loop feedback.
• When the comment string contains characters outside the Windows-1252 range, the WinCC runtime reads Comment as a Unicode string. The tooltip rendering supports Unicode out of the box; no codepage conversion is required.
• If a tag name is renamed, every per-object trigger that referenced that tag will fail to find the tag at runtime. WinCC does not automatically re-link; perform a project-wide search for the old tag name in Global Script before renaming.
• For multi-language projects, Comment returns the string in the currently active runtime language. No additional translation API is required; the runtime switches the comment based on the configured user language.
• The WinCC V7.5 SP2 VBScript model is identical in WinCC V7.0, V7.3, V7.4, V7.4 SP1, V7.5, and V7.5 SP2. WinCC V8 (TIA-based WinCC Unified) replaces the VBScript model with a JavaScript runtime and exposes a different browser-style event API; the patterns in this article do not apply directly to Unified.

Diagnostic Window: Reading the Stack Trace

The Global Script diagnostics window (GDI) is the only place where the runtime error is logged. The trace line indicates the picture, the function name, the line offset, and the message. When the function name is encoded, the trace also shows the encoded form (for example, StaticX0020Text59_ToolTipText_Trigger), which makes it possible to map the error back to the designer object name. The GDI window retains the last 200 messages; older messages roll off the buffer. To preserve a trace for post-mortem analysis, enable the WinCC Diagnostic Server (Start > Programs > Siemens Automation > WinCC > Tools > WinCC Diagnostic Server) and export the trace to CSV.

Migrating from V7.5 to WinCC Unified (V8)

The VBScript model documented above does not apply to WinCC Unified (TIA Portal V17/V18+). Unified exposes a JavaScript runtime with the following equivalents:

When porting a V7.5 picture to Unified, search the project for the X0020 pattern and replace it with the literal character (typically a space or underscore) in the new event handler. Confirm with the WinCC Unified engineering manual before deployment.

FAQ