The Reusable Progress Indicator

So you’ve written a beautiful piece of code, a macro that does everything it needs to do… the only thing is that, well, it takes a while to complete. Oh, it’s as efficient as it gets, you’ve put it up for peer review on Code Review Stack Exchange, and the reviewers helped you optimize it. You need a way to report progress to your users.

There are several possible solutions.

Updating Application.StatusBar

If the macro is written in such a way that the user could very well continue using Excel while the code is running, then why disturb their workflow – simply updating the application’s status bar is definitely the best way to do it.

You could use a small procedure to do it:

Public Sub UpdateStatus(Optional ByVal msg As String = vbNullString)
 
    Dim isUpdating As Boolean
    isUpdating = Application.ScreenUpdating
 
    'we need ScreenUpdating toggled on to do this:
    If Not isUpdating Then Application.ScreenUpdating = True
 
    'if msg is empty, status goes to "Ready"
    Application.StatusBar = msg
 
    'make sure the update gets displayed (we might be in a tight loop)
    DoEvents
 
    'if ScreenUpdating was off, toggle it back off:
    Application.ScreenUpdating = isUpdating
 
End Sub

It’s critical to understand that the user can change the ActiveSheet at any time, so if your long-running macro involves code that implicitly (or explicitly) refers to the active worksheet, you’ll run into problems. Rubberduck has an inspection that specifically locates these implicit references though, so you’ll do fine.

Modeless Progress Indicator

A commonly blogged-about solution is to display a modeless UserForm and update it from the worker code. I dislike this solution, for several reasons:

  • The user is free to interact with the workbook and change the ActiveSheet at any time, but the progress is reported in an invasive dialog that the user needs to drag around to move out of the way as they navigate the worksheets.
  • It pollutes the worker code with form member calls; the worker code decides when to display and when to hide and destroy the form.
  • It feels like a work-around: we’d like a modal UserForm, but we don’t know how to make that work nicely.

“Smart UI” Modal Progress Indicator

If we only care to make it work yesterday, a “Smart UI” works: we get a modal dialog, so the user can’t use the workbook while we’re modifying it. What’s the problem then?

The form is running the show – the “worker” code needs to be in the code-behind, or invoked from it. That is the problem: if you want to reuse that code, in another project, you need to carefully scrap the worker code. If you want to reuse that code in the same project, you’re out of luck – either you duplicate the “indicator” code and reimplement the other “worker” code in another form’s code-behind, or the form now has “modes” and some conditional logic determines which worker code will get to run: you can imagine how well that scales if you have a project that needs a progress indicator for 20 features.

“Smart UI” can’t be good either. So, what’s the real solution then?

A Reusable Progress Indicator

We want a modal indicator (so that the user can’t interfere with our modifications), but one that doesn’t run the show: we want the UserForm to be responsible for nothing more than keeping its indicator representative of the current progress.

This solution is based on a piece of code I posted on Code Review back in 2015; you can find the original post here. This version is better though, be it only because of how it deals with cancellation.

The solution is implemented across two components: a form, and a class module.

ProgressView

First, a UserForm, obviously.

ProgressView

Nothing really fancy here. The form is named ProgressView. There’s a ProgressLabel, a 228×24 DecorativeFrame, and inside that Frame control, a ProgressBar label using the Highlight color from the System palette. Here’s the complete code-behind:

Option Explicit
Private Const PROGRESSBAR_MAXWIDTH As Integer = 224
Public Event Activated()
Public Event Cancelled()

Private Sub UserForm_Activate()
    ProgressBar.Width = 0
    RaiseEvent Activated
End Sub

Public Sub Update(ByVal percentValue As Single, Optional ByVal labelValue As String, Optional ByVal captionValue As String)
    If labelValue  vbNullString Then ProgressLabel.Caption = labelValue 
    If captionValue  vbNullString Then Me.Caption = captionValue
    ProgressBar.Width = percentValue * PROGRESSBAR_MAXWIDTH
    DoEvents 
End Sub

Private Sub UserForm_QueryClose(Cancel As Integer, CloseMode As Integer)
    If CloseMode = VbQueryClose.vbFormControlMenu Then
        Cancel = True
        RaiseEvent Cancelled
    End If
End Sub

Clearly this isn’t a Smart UI: the form doesn’t even have a concept of “worker code”, it’s blissfully unaware of what it’s being used for. In fact, on its own, it’s pretty useless. Modally showing the default instance of this form leaves you with only the VBE’s “Stop” button to close it, because its QueryClose handler is actively preventing the user from “x-ing out” of it. Obviously that form is rather useless on its own – it’s not responsible for anything beyond updating itself and notifying the ProgressIndicator when it’s ready to start reporting progress – or when the user means to cancel the long-running operation.

ProgressIndicator

This is the class that the client code will be using. A PredeclaredId attribute gives it a default instance, which is used to expose a factory method.

Here’s the full code – walkthrough follows:

Option Explicit

Private Declare PtrSafe Sub Sleep Lib "kernel32" (ByVal dwMilliseconds As Long)

Private Const DEFAULT_CAPTION As String = "Progress"
Private Const DEFAULT_LABEL As String = "Please wait..."

Private Const ERR_NOT_INITIALIZED As String = "ProgressIndicator is not initialized."
Private Const ERR_PROC_NOT_FOUND As String = "Specified macro or object member was not found."
Private Const ERR_INVALID_OPERATION As String = "Worker procedure cannot be cancelled by assigning to this property."
Private Const VBERR_MEMBER_NOT_FOUND As Long = 438

Public Enum ProgressIndicatorError
    Error_NotInitialized = vbObjectError + 1001
    Error_ProcedureNotFound
    Error_InvalidOperation
End Enum

Private Type TProgressIndicator
    procedure As String
    instance As Object
    sleepDelay As Long
    canCancel As Boolean
    cancelling As Boolean
    currentProgressValue As Double
End Type

Private this As TProgressIndicator
Private WithEvents view As ProgressView

Private Sub Class_Initialize()
    Set view = New ProgressView
    view.Caption = DEFAULT_CAPTION
    view.ProgressLabel = DEFAULT_LABEL
End Sub

Private Sub Class_Terminate()
    Set view = Nothing
    Set this.instance = Nothing
End Sub

Private Function QualifyMacroName(ByVal book As Workbook, ByVal procedure As String) As String
    QualifyMacroName = "'" & book.FullName & "'!" & procedure
End Function

Public Function Create(ByVal procedure As String, Optional instance As Object = Nothing, Optional ByVal initialLabelValue As String, Optional ByVal initialCaptionValue As String, Optional ByVal completedSleepMilliseconds As Long = 1000, Optional canCancel As Boolean = False) As ProgressIndicator
 
    Dim result As ProgressIndicator
    Set result = New ProgressIndicator
 
    result.Cancellable = canCancel
    result.SleepMilliseconds = completedSleepMilliseconds
 
    If Not instance Is Nothing Then
        Set result.OwnerInstance = instance
    ElseIf InStr(procedure, "'!") = 0 Then
        procedure = QualifyMacroName(Application.ActiveWorkbook, procedure)
    End If
 
    result.ProcedureName = procedure
 
    If initialLabelValue  vbNullString Then result.ProgressView.ProgressLabel = initialLabelValue
    If initialCaptionValue  vbNullString Then result.ProgressView.Caption = initialCaptionValue

    Set Create = result
 
End Function

Friend Property Get ProgressView() As ProgressView
    Set ProgressView = view
End Property

Friend Property Get ProcedureName() As String
    ProcedureName = this.procedure
End Property

Friend Property Let ProcedureName(ByVal value As String)
    this.procedure = value
End Property

Friend Property Get OwnerInstance() As Object
    Set OwnerInstance = this.instance
End Property

Friend Property Set OwnerInstance(ByVal value As Object)
    Set this.instance = value
End Property

Friend Property Get SleepMilliseconds() As Long
    SleepMilliseconds = this.sleepDelay
End Property

Friend Property Let SleepMilliseconds(ByVal value As Long)
    this.sleepDelay = value
End Property

Public Property Get CurrentProgress() As Double
    CurrentProgress = this.currentProgressValue
End Property

Public Property Get Cancellable() As Boolean
    Cancellable = this.canCancel
End Property

Friend Property Let Cancellable(ByVal value As Boolean)
    this.canCancel = value
End Property

Public Property Get IsCancelRequested() As Boolean
    IsCancelRequested = this.cancelling
End Property

Public Sub AbortCancellation()
    Debug.Assert this.cancelling
    this.cancelling = False
End Sub

Public Sub Execute()
    view.Show vbModal
End Sub

Public Sub Update(ByVal percentValue As Double, Optional ByVal labelValue As String, Optional ByVal captionValue As String)

    On Error GoTo CleanFail
    ThrowIfNotInitialized

    ValidatePercentValue percentValue
    this.currentProgressValue = percentValue
 
    view.Update this.currentProgressValue, labelValue

CleanExit:
    If percentValue = 1 Then Sleep 1000 ' pause on completion
    Exit Sub

CleanFail:
    MsgBox Err.Number & vbTab & Err.Description, vbCritical, "Error"
    Resume CleanExit
End Sub

Public Sub UpdatePercent(ByVal percentValue As Double, Optional ByVal captionValue As String)
    ValidatePercentValue percentValue
    Update percentValue, Format$(percentValue, "0.0% Completed")
End Sub

Private Sub ValidatePercentValue(ByRef percentValue As Double)
    If percentValue > 1 Then percentValue = percentValue / 100
End Sub

Private Sub ThrowIfNotInitialized()
    If this.procedure = vbNullString Then
        Err.Raise ProgressIndicatorError.Error_NotInitialized, TypeName(Me), ERR_NOT_INITIALIZED
    End If
End Sub

Private Sub view_Activated()

    On Error GoTo CleanFail
    ThrowIfNotInitialized

    If Not this.instance Is Nothing Then
        ExecuteInstanceMethod
    Else
        ExecuteMacro
    End If

CleanExit:
    view.Hide
    Exit Sub

CleanFail:
    MsgBox Err.Number & vbTab & Err.Description, vbCritical, "Error"
    Resume CleanExit
End Sub

Private Sub ExecuteMacro()
    On Error GoTo CleanFail
    Application.Run this.procedure, Me

CleanExit:
    Exit Sub

CleanFail:
    If Err.Number = VBERR_MEMBER_NOT_FOUND Then
        Err.Raise ProgressIndicatorError.Error_ProcedureNotFound, TypeName(Me), ERR_PROC_NOT_FOUND
    Else
        Err.Raise Err.Number, Err.Source, Err.Description, Err.HelpFile, Err.HelpContext
    End If
    Resume CleanExit
End Sub

Private Sub ExecuteInstanceMethod()
    On Error GoTo CleanFail
 
    Dim parameter As ProgressIndicator
    Set parameter = Me 'Me cannot be passed to CallByName directly

    CallByName this.instance, this.procedure, VbMethod, parameter

CleanExit:
    Exit Sub

CleanFail:
    If Err.Number = VBERR_MEMBER_NOT_FOUND Then
        Err.Raise ProgressIndicatorError.Error_ProcedureNotFound, TypeName(Me), ERR_PROC_NOT_FOUND
    Else
        Err.Raise Err.Number, Err.Source, Err.Description, Err.HelpFile, Err.HelpContext
    End If
    Resume CleanExit
End Sub

Private Sub view_Cancelled()
    If Not this.canCancel Then Exit Sub
    this.cancelling = True
End Sub

The Create method is intended to be invoked from the default instance, which means if you’re copy-pasting this code into the VBE, it won’t work. Instead, paste this header into notepad first:

VERSION 1.0 CLASS
BEGIN
 MultiUse = -1 'True
END
Attribute VB_Name = "ProgressIndicator"
Attribute VB_GlobalNameSpace = False
Attribute VB_Creatable = False
Attribute VB_PredeclaredId = True
Attribute VB_Exposed = True

Then paste the actual code underneath, save as ProgressIndicator.cls, and import the class module into the VBE. Note the VB_Exposed attribute: this makes the class usable in other VBA projects, so you could have this progress indicator solution in, say, an Excel add-in, and have “client” VBA projects that reference it. Friend members won’t be accessible from external code.

Here I’m Newing up the ProgressView directly in the Class_Initialize handler: this makes it tightly coupled with the ProgressIndicator. A better solution might have been to inject some IProgressView interface through the Create method, but then this would have required gymnastics to correctly expose the Activated and Cancelled view events, because events can’t simply be exposed as interface members – I’ll cover that in a future article, but the benefit of that would be loose coupling and enhanced testability: one could inject some MockProgressView implementation (just some class / not a form!), and just like that, the worker code could be unit tested without bringing up any form – but then again, that’s a bit beyond the scope of this article, and I’m drifting.

So the Create method takes the name of a procedure​, and uses it to set the ProcedureName property: this procedure name can be any Public Sub that takes a ProgressIndicator parameter. If it’s in a standard module, nothing else is needed. If it’s in a class module, the instance parameter needs to be specified so that we can later invoke the worker code off an instance of that class. The other parameters optionally configure the initial caption and label on the form (that’s not exactly how I’d write it today, but give me a break, that code is from 2015). If the worker code supports cancellation, the canCancelparameter should be supplied.

The next interesting member is the Execute method, which displays the modal form. Doing that soon triggers the Activated event, which we handle by first validating that we have a procedure to invoke, and then we either ExecuteInstanceMethod (given an instance), or ExecuteMacro​ – then we Hide the view and we’re done.

ExecuteMacro uses Application.Run to invoke the procedure; ExecuteInstanceMethod uses CallByName to invoke the member on the instance. In both cases, Me is passed to the invoked procedure as a parameter, and this is where the fun part begins.

The worker code is responsible for doing the work, and uses its ProgressIndicator parameter to Update the progress indicator as it goes, and periodically check if the user wants to cancel; the AbortCancellation method can be used to, well, cancel the cancellation, if that’s needed.

Client & Worker Code

The client code is responsible for registering the worker procedure, and executing it through the ProgressIndicator instance, for example like this:

Public Sub DoSomething()
    With ProgressIndicator.Create("DoWork", canCancel:=True)
        .Execute
    End With
End Sub

The above code registers the DoWork worker procedure, and executes it. DoWork could be any Public Sub in a standard module (.bas), taking a ProgressIndicator parameter:

Public Sub DoWork(ByVal progress As ProgressIndicator)
    Dim i As Long
    For i = 1 To 10000
        If ShouldCancel(progress) Then
            'here more complex worker code could rollback & cleanup
            Exit Sub
        End If
        ActiveSheet.Cells(1, 1) = i
        progress.Update i / 10000
    Next
End Sub

Private Function ShouldCancel(ByVal progress As ProgressIndicator) As Boolean
    If progress.IsCancelRequested Then 
        If MsgBox("Cancel this operation?", vbYesNo) = vbYes Then
            ShouldCancel = True
        Else
            progress.AbortCancellation
        End If
    End If
End Function

The Create method can also register a method defined in a class module, given an instance of that class – again as long as it’s a Public Sub taking a ProgressIndicator parameter:

Public Sub DoSomething()
    Dim foo As SomeClass
    Set foo = New SomeClass
    With ProgressIndicator.Create("DoWork", foo)
        .Execute
    End With
End Sub

Considerations

In order to use this ProgressIndicator solution as an Excel add-in, I would recommend renaming the VBA project (say, ReusableProgress), otherwise referencing a project named “VBAProject” from a project named “VBAProject” will surely get confusing 🙂

Note that this solution could easily be adapted to work in any VBA host application, by removing the “standard module” support and only invoking the worker code in a class module, with CallByName.

Conclusion

By using a reusable progress indicator like this, you never need to reimplement it ever again: you do it once, and then you can use it in 200 places across 100 projects if you like: not a single line of code in the ProgressIndicator or ProgressView classes needs to change – all you need to write is your worker code, and all the worker code needs to worry about is, well, its job.

Don’t hesitate to comment and suggest further improvements, suggestions are welcome – questions, too.

Downloads

I’ve bundled the code in this article into a Microsoft Excel add-in that I uploaded to dropbox (Progress.xlam).

Enjoy!

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9 thoughts on “The Reusable Progress Indicator”

  1. I also stumbled upon the ProgressIndicator code on Code Review Stack Exchange a few days before this post. First of all: Thank you very much for this article and congratulations being awarded as an MVP!

    If everything of the above code is put in one workbook the VBE claims that the function `Contain` inside of the `Create` function is not defined. In the Code Review code this originally was `Framework.Strings.Contains` which I also don’t know. But when I am not mistaken the line `ElseIf Not Contains(procedure, “‘!”) Then` could be replaced with `ElseIf InStr(procedure, “‘!”) > 0 Then` which would yield the same result, right? At least when I do so, everything works fine when everything is in one workbook. But when I move the `ProgressView` and `ProgressIndicator` to an AddIn, add a reference to the AddIn to the calling Workbook and run `DoSomething`, then I get an error message “1004 The macro ‘DoWork’ cannot be executed. […]”. (Hopefully this is the right translation.) Is the fault on my side or is there a bug in the code?

    Like

    1. Hey Stefan, thanks for the feedback!

      Indeed InStr would work – I tried to clean up the old code on-the-spot and admittedly should have done that in the actual VBE… `ElseIf InStr(procedure, “‘!”) = 0 Then` would be it – the condition is for making sure that the macro name is qualified, and otherwise qualifies it using the ActiveWorkbook.

      I’ve updated the post to fix that, copied the code from this article into the VBE (gosh if I only new how horrible that is… I’m so, so sorry! Running Rubberduck’s indenter removes all the hidden illegal characters that confuse the VBE), saved as an Excel add-in, then referenced that add-in from a fresh project where I pasted the client & worker code, and it indeed works as intended – I’ve named the add-in’s VBAProject “ReusableProgress”, but it appears to work even if I leave it with the default “VBAProject” project name, so.. I’m not sure what went wrong, but I can assure you that it works perfectly fine here.

      — EDIT —

      Just as I posted this comment I realized – with the “InStr”/”Contains” condition reversed, the macro name wouldn’t be properly qualified, hence why the macro couldn’t be found in the ActiveWorkbook. Just reverse the condition and it should work – enjoy!

      Like

      1. Of course. I also just realized that I missed the **`Not`** in `ElseIf Not Contains(procedure, “‘!”) Then`. So you are absolutely right with `ElseIf InStr(procedure, “‘!”) = 0 Then`. Many thanks again for the great work!

        PS: As was already requested in the comments from it would be great for (Excel) VBA beginners to have sample files that regard to the articles. Now that you already seem to have one for this article … 😉

        Like

  2. Thanks for your almost poetic articles. I like reading this.
    One question remains: Is it possible to use this progress view form in an Access module?
    I cannot get it to work, because it is looking for the activeWorkbook, which is nog available in Acces..
    What modifications should be made to make it work in Access?
    Thanks in advance,

    Like

    1. Thanks! Access will have a different way than Excel, to fully-qualify macros so they can be reliably invoked with Application.Run, so you’ll want to tweak how macros are qualified. OTOH not all VBA hosts have a Run method on their Application object, so a truly portable solution would only work off a class instance/CallByName.

      Like

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