VB6 ImageList Frm Code Generation
- by DAC
Note: This is probably a shot in the dark, and its purely out of curiosity that I'm asking.
When using the ImageList control from the Microsoft Common Control lib (mscomctl.ocx) I have found that VB6 generates FRM code that doesn't resolve to real property/method names and I am curious as to how the resolution is made. An example of the generated FRM code is given below with an ImageList containing 3 images:
Begin MSComctlLib.ImageList ImageList1
BackColor = -2147483643
ImageWidth = 100
ImageHeight = 45
MaskColor = 12632256
BeginProperty Images {2C247F25-8591-11D1-B16A-00C0F0283628}
NumListImages = 3
BeginProperty ListImage1 {2C247F27-8591-11D1-B16A-00C0F0283628}
Picture = "Form1.frx":0054
Key = ""
EndProperty
BeginProperty ListImage2 {2C247F27-8591-11D1-B16A-00C0F0283628}
Picture = "Form1.frx":3562
Key = ""
EndProperty
BeginProperty ListImage3 {2C247F27-8591-11D1-B16A-00C0F0283628}
Picture = "Form1.frx":6A70
Key = ""
EndProperty
EndProperty
End
From my experience, a BeginProperty tag typically means a compound property (an object) is being assigned to, such as the Font object of most controls, for example:
Begin VB.Form Form1
Caption = "Form1"
ClientHeight = 10950
ClientLeft = 60
ClientTop = 450
ClientWidth = 7215
BeginProperty Font
Name = "MS Serif"
Size = 8.25
Charset = 0
Weight = 400
Underline = 0 'False
Italic = -1 'True
Strikethrough = 0 'False
EndProperty
End
Which can be easily seen to resolve to VB.Form.Font.<Property Name>.
With ImageList, there is no property called Images. The GUID associated with property Images indicates type ListImages which implements interface IImages. This type makes sense, as the ImageList control has a property called ListImages which is of type IImages. Secondly, properties ListImage1, ListImage2 and ListImage3 don't exist on type IImages, but the GUID associated with these properties indicates type ListImage which implements interface IImage. This type also makes sense, as IImages is in fact a collection of IImage.
What doesn't make sense to me is how VB6 makes these associations. How does VB6 know to make the association between the name Images - ListImages purely because of an associated type (provided by the GUID) - perhaps because it's the only property of that type? Secondly, how does it resolve ListImage1, ListImage2 and ListImage3 into additions to the collection IImages, and does it use the Add method? Or perhaps the ControlDefault property?
Perhaps VB6 has specific knowledge of this control and no logical resolution exists?
