Create gallery with images in Excel

Question

I am trying to make smth like this: 
For now I use the imageMso attribute
just for testing purposes. Even though, nothing really happens.
That's the XML for the gallery:
<customUI xmlns="http://schemas.microsoft.com/office/2009/07/customui" onLoad="Ribbon_Load">
<ribbon>
<tabs>
<tab idMso="TabAddIns" label="Gallery">
<group id="grpGallery" label="Example Gallery">
<gallery id="galleryID" label="My Gallery" columns="3" rows="2" size="large"
itemHeight="100" itemWidth="100"
getItemID="CallbackGetItemID"
getItemCount="CallbackGetItemsCount"
getItemImage="CallbackGetItemImage"
getItemScreentip="CallbackGetItemScreentip"
getItemSupertip="CallbackGetItemSupertip">
<item id="galImg1" imageMso="PictureBrightnessGallery"/>
<item id="galImg2" imageMso="ZoomPrintPreviewExcel"/>
</gallery>
And the VB code to it:
Public idCounter As Integer
Public Sub New()
idCounter = 0
End Sub
Public Function GetCustomUI(ByVal ribbonID As String) As String Implements Office.IRibbonExtensibility.GetCustomUI
Return GetResourceText("GalleryTest.Gallery.xml")
End Function
#Region "Ribbon Callbacks"
Public Sub Ribbon_Load(ByVal ribbonUI As Office.IRibbonUI)
Me.galleryRibbon = ribbonUI
End Sub
Public Sub CallbackGetItemID(control As Microsoft.Office.Core.IRibbonControl, _
index As Integer, ByRef itemID As Integer)
itemID = idCounter
idCounter += 1
End Sub
Public Sub CallbackGetItemsCount(control As Microsoft.Office.Core.IRibbonControl, _
ByRef count As Integer)
count = 6
End Sub
Public Sub CallbackGetItemScreentip(control As Microsoft.Office.Core.IRibbonControl, _
Index As Integer, ByRef screentip As String)
screentip = "Screentip"
End Sub
Public Sub CallbackGetItemSupertip(control As Microsoft.Office.Core.IRibbonControl, _
Index As Integer, ByRef supertip As String)
'TO DO'
End Sub
As you see, it's nothing fancy. I am just getting into the vb.net + excel world. What happens is that I get the "My Gallery" button for the dropdown, in the excel tab, but it is empty. No elements. Not even the dummy items.
Any suggestions?
P.S. I followed this documentation.

Answer 1

Try to return actual values in the callbacks. For example, I see non-existing IDs in the callback.
There is no need to add the CallbackGetItemsCount callback for the gallery control if you specified items explicitly.
You can read more about the Ribbon UI in the following series of articles in MSDN:
Customizing the 2007 Office Fluent Ribbon for Developers (Part 1 of 3)
Customizing the 2007 Office Fluent Ribbon for Developers (Part 2 of 3)
Customizing the 2007 Office Fluent Ribbon for Developers (Part 3 of 3)