Visual Basic for Applications in IntelliCAD - Page 4 - cadinfo.net

This page describes the manipulation of layers in VBA, and present a function to create or set drawing layers. It also marks the beginning of the creation of a library of standard utility functions, to make general VBA programming in IntelliCAD quicker and more convenient.

The functions and examples presented here are included in a single VBA project.  The screen for this, when running, is shown below, while the files themselves comprise either the executable code (which contains the program code), in the file,

CommonProjects.Vbi

or the individual source code files,

UserForm1.Frm
UserForm1.Frx Module1.Bas

These files can be downloade in a single zip archive on teh previous page.

Note that if you want to use the "CommonProjects.Vbi" file you will have to copy this into your IntelliCAD directory.  There may already be a file of this name in the directory, so you should rename the existing file.  It might be dangerous to delete it as it may be part of some other application.

Getting the Current Layer Name

We'll start by just getting the current layer name (the name which is the currently active drawing layer) and displaying that on the screen.  This function has been presented previously, but makes a good point from which to expand on the subject of drawing layers.

The function operation is very simple. We first define a variable, called "LayerName", as a string. This will be used to store the actual layer name we get from VBA. We then use the "ActiveLayer" function and request its "Name" property. This returns us the name of the current drawing layer, which we store in the "LayerName" variable. Finally we display this on the computer screen using the standard VBA "MsgBox" (Message Box) command.

Our example "Layer Function" program's dialogue box, open on the IntelliCAD screen.  Our example "Layer Function" program's dialogue box, open on the IntelliCAD screen.

Getting an Entity Layer Name

While it's nice enough to be able to get the currently active drawing layer, it would be far more useful to get a display of the drawing layer for any entity.  That is, if you were to pick an entity, then its layer would be displayed.  The following function will perform this task.

Its operation should be fairly clear. We need to perform two basic operations.  We first need to pick an object on the screen, which is done using the "GetEntity" function, then we need to get its layer name, which is accessed using the "Layer" property of the selected object.

The "GetEntity" function requires three parameters. The first is an entity object (called "PickObj" here), which is returned by the function and stores the entity information for the particular item picked.  The second is a pick point, which is the location of your pick on the screen.  This is returned by the function, and stored in the "Pt1" variable here.  The third parameter is a prompt string, which will be displayed when the function executes.

We now have the entity data for an item which was selected on screen, and would like to get its name and layer.  The name is extracted using the "EntityName" property of the selected object (PickObj).  This value is stored in a variable called "Ename".  Note that the variables "Ename", "PickObj" and "Pt1" have been previously defined at the start of this function.

Like the entity name, the entity layer is a property of the selected object (PickObj), so this is easily accessed by requesting "PickObj.Layer". The entity name was obtained as a separate operation, whereas the layer name was obtained as part of the message box display function.  This data can be accessed in various ways.  If required, the message box function could just as easily have been rewritten as,

Also note the pair of commands,

are used here to allow interactivity with the user.  The form must be suppressed while the user selects an entity on the screen, to stop it getting in the way, then redisplayed after the selection has been made.  This procedure has been described more fully in a previous article.

Also, when trying this function, it's a good idea to first open an existing drawing, which contains a number of entities on different layers.  A new drawing will not provide anything for you to test it on.  Alternatively, create a test drawing comprising several lines, each on a different drawing layer.

Creating a New Layer

Having presented some ways to interrogate a drawing for information about existing layers, we now need to discuss how to create new layers.  To add a new layer to a drawing requires a single command, as shown below.

Here, we first need to define a layer object (called "Lyr" here) as an IntelliCAD Layer entity.  We then use the "Layers.Add" function to create a new layer, this layer having the name defined in the single function parameter (the name "TestLayer1" here).  Once the layer has been created we can manipulate its various properties by accessing and changing them, as shown in the last line of the function.  Here we set the layer colour to be yellow, by setting the "Color" property of the "Lyr" layer entity to be "vicYellow".

Note that "vicYellow" is a predefined constant in VBA which contains the numeric value for yellow.  It's easier to use (and remember) the "vicYellow" variable name than have to define it as a hexadecimal number.  A Routine to Create or Set Layers

One of the most useful AutoLisp functions I ever wrote was a routine to create or set drawing layers.  This operated by looking for a particular drawing layer.  If it existed then it was made the current drawing layer.  If it didn't exist then it was created.  When I moved to VBA this was one of the first functions I set out to create, and this is the function I shall now present.

The function is called "SetLayer" and its use is shown below.

The function is called with three parameters.  The first is the layer name, the second the layer colour and the third the line type for this layer.  The function will look to see if a layer with the specified name exists.  If it does then that layer will be set to be the current drawing layer.  If the layer does not exist then a new layer of that name will be created, using the specified colour and line type.  This function's best feature is its flexibility.  You don't need to keep track of layer names as it will take care of itself.

The following are the functions making up "SetLayer" and are modified from code obtained from various other sources, so I don't claim any ownership of this.  I've simply adapted the functions to my specific requirements.  There are three separate functions involved; the main "SetLayer" function, a function to check whether a layer exists and a function to set the required linetype.  The main "SetLayer" function is as follows.

This function operates as follows.  It first checks to see if the requested layer name already exists (using a function which will be described a little later).  If it does not exist then a new layer is created using the "Layers.Add" function.  It then has a colour assigned to it, and a line type (again using a function which will be described later). If the layer does exist then it is simply set to be the current drawing layer.

The function used to check whether the requested layer exists is as follows.

'----------------------------------------------------------
' Function to determine if a layer exists
'----------------------------------------------------------
Function LayerExist(ByVal LayerName As String) As Boolean Dim Element As Object
LayerExist = False For Each Element In Doc.Layers
If Element.Name = Ucase(LayerName)
Then LayerExist = True Set CurrentLayer = Element
Exit For
End If
Next
End Function
'----------------------------------------------------------

This is called with the specified layer name.  A flag called "LayerExist" is initially set to be false, assuming the layer does not exist.  We then move through each entry in the complete set (collection) of drawing layers, comparing their name to that of the layer we want.  If we find a match then we set the flag to be true, set the layer to be the current drawing layer and exit the function.  If we don't find a match then the function will exit after all the existing layer names have been checked, with the flag still set to be false.

Finally, the third function we need is a function to set the layer line type, shown below.  If you don't need line types other than "CONTINUOUS" then this can be ignored and the appropriate line in the "SetLayer" function removed.  Although this function should be able to load a new linetype, it is safer to have all the line types you may want to use already loaded into the drawing.  It's best to have these preloaded in your prototype (template) drawing file, so this routine will always work correctly.

As with the function to check if a layer exists, this operates in a similar way.  It sets a flag called "found" to initially be false, then progresses through all the linetypes in the drawing.  If a match is found the flag is set to be true then the function exits.  The linetype is actually set in the "SetLayer" function.  This routine only checks whether it must load a new linetype.  If no match is found the function attempts to load the requested linetype from the "ICAD.LIN" linetype file, then exits, for the new linetype to then be set in the "SetLayer" function.

As this is a generally useful function it should be included in a program module (MODULE1.BAS for example), as a public function, where it can be accessed from anywhere in your application.

The Sample Application

The code examples provided with this article illustrate the functions described above.  However, the "SetLayer" code example does a little more than just display the function operation.  We've included an example where you can choose a layer name and a layer colour from two list boxes, then create a new layer using these values with the "SetLayer" command.  This is a better guide to how you may want to employ this function in your own code, and also a good illustration of the flexibility of the "SetLayer" command itself.

Finding More About the Commands Available in IntelliCAD VBA

Following the previous article in this series, which dealt with object snap modes, the question was asked, "How did I know about all the OSNAP variable names?".  There is very little documentation available for VBA in IntelliCAD, so what reference sources exist to help you find which commands and functions are available to you?

There is a degree of help available in the IntelliCAD HELP files.  I'm basing this series on Cadopia's version of IntelliCAD, so this may vary slightly from some other versions.  If you access the HELP from the IntelliCAD drawing screen, and search through this using the Index, there are examples and information in there about how to use specific VBA commands.

Unfortunately, this assistance does not extend to the HELP system within the VBA Editor screen.  In a typical Visual Basic Editor it would be possible to highlight a single word or command, then press the <F1> key and have an appropriate screen of information about that command displayed.  In VBA here though, this would generally give you a message that there was no information available for the particular command.

To get a complete overview of the commands available for IntelliCAD within VBA, you will need to look at the "Object Browser", accessed from within the VBA Editor screen.  This is opened from one of the central icons on the top menu bar.

When selected, a dialogue box will appear displaying a list of all the functions available to you within VBA.

This is typically a long list, so we need to isolate only those commands relevant to IntelliCAD.  This is done by selecting the list box in the top left of the Object Browser dialogue box and choosing "IntelliCAD".  Normally all the available function libraries are displayed, but we can limit the functions shown to only a single library, which is what we've done here.

How to select only the IntelliCAD function library in the Object Browser.  Showing how to select only the "IntelliCAD" function library in the "Object Browser".  We are only interested in the commands related to IntelliCAD, so we need to remove all the other options from the display.

The purpose of the Object Browser is to allow you to see all the functions and associated items which are present in a particular library, and which you can access.  For example, if we consider the case of our previous article, where I needed to find all the snap modes provided within VBA, and the constant names they had been given, then this can be done with the Object Browser.  By selecting "ObjectSnapMode" in the left column I am then presented with all the available options in the right column.

The list of available Object Snap modes, accessed and displayed using the Object Browser.  The list of available Object Snap modes, accessed and displayed using the "Object Browser".

Although the Object Browser is not really an on-line help system, it does give an overview of the full range of functions available to you, and a general guide as to how they may work.  So, at worst, you can determine a particular operation is available, but you may have to experiment a bit in order to get it to work properly.

The Object Browser does have one additional feature.  It will offer a template as to how a particular function will operate.  For example, if you select "Document" in the left column, the right column will display all the options available.  If you then select, for example, the "GetVariable" function in the right column, the area at the bottom of the dialogue box will display the parameters which need to be passed to this function, their type and the value which would be returned.  In this case, the "GetVariable" function will need to have a variable name passed to it, in the form of a string, while the returned value will be the value of the chosen system variable.

Another example of using the "Object Browser".  Here we have found the "GetVariable" function for an IntelliCAD document.  Note that the format of the function is displayed in the box at the bottom of the screen.  This shows it requires a string variable to be passed to it (the variable name) and returns a system variable value.  With just a bit of guesswork you can generally find out how most of the IntelliCAD VBA functions operate.

Conclusion

In this article we've addressed several issues related to handling layers in IntelliCAD's VBA.  We've also described a few ways to get a little more information about the functions which are available to you.  In the next article we hope to present a simple programming application, to show how everything fits together.

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Visual Basic for Applications in IntelliCAD
A series of articles introducing custom programming of IntelliCAD and AutoCAD using Visual Basic for Applications (VBA). advertisement...

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