# Your First Plugin (Mac)

This guide walks you through your first plugin for Rhino for Mac using RhinoCommon and Visual Studio for Mac.

It is presumed you already have the necessary tools installed and are ready to go. If you are not there yet, see Installing Tools (Mac).

## HelloRhinoCommon

We will use the Rhino Xamarin Addin/Extension to create a new, basic, command plugin called HelloRhinoCommon.

If you are familiar with Visual Studio for Windows or Visual Studio for Mac, these step-by-step instructions may be overly detailed for you. The executive summary: create a new Solution using the RhinoCommon Plugin template, build and run, and then make a change.

We are presuming you have never used Visual Studio for Mac before, so we’ll go through this one step at a time.

### File New

1. If you have not done so already, launch Visual Studio for Mac.
2. Navigate to File > New > Solution
3. A New Project wizard should appear. In the left column, find the Other > Miscellaneous section. Under General, select the RhinoCommon Plug-In template…
4. Click the Next button.
5. You will now Configure your new project. For the purposes of this Guide, we will name our demo plugin HelloRhinoCommon. Fill in the Project Name field. Browse and select a location for this plugin on your Mac…
6. Check Create a project within the solution directory. Note: This is optional depending on how you want to structure your projects.
7. Click the Create button. Note: You don’t have to create a .git repository for this demo.
8. A new solution called HelloRhinoCommon should open…
9. Right-click on the HelloRhinoCommon project and select Set As Startup Project from the menu.

### Boilerplate Build

1. Before we do anything, let’s build and run HelloRhinoCommon to make sure everything is working as expected. We’ll just build the boilerplate Plugin template. Click the large Build > Run (play) button in the upper-left corner of Visual Studio for Mac…
2. Rhinoceros launches. Create a New Model
3. Enter the HelloRhinoCommonCommand command. Notice that the command autocompletes…
4. The HelloRhinoCommonCommand command begins and prompts you…
5. Notice there is also a command status in Rhino’s command history area when the command begins…
6. Also note there is a command status in Rhino’s command history area when the command ends…
7. Quit Rhinoceros. This stops the session. Go back to Visual Studio for Mac. Let’s take a look at the…

### Plugin Anatomy

1. Use the Solution Explorer to expand the Solution (.sln) so that it looks like this…
2. The HelloRhinoCommon project (.csproj) has the same name as its parent solution…this is the project that was created for us by the RhinoCommon Plugin template wizard earlier.
3. References: Just as with most projects, you will be referencing other libraries. The RhinoCommon Plugin template added the necessary references to create a basic RhinoCommon plugin.
4. Eto is the cross-platform User Interface (UI) library Rhino uses. If you examine its properties, you will notice it comes bundled as part of Rhino for Mac.
5. Rhino.UI is the Rhino-specific User Interface (UI) library associated with…
6. RhinoCommon is the critical reference for our purposes here.
7. System, System.Core, and System.Drawing are .NET foundational libraries…in this case, we are referencing the Mono versions of these libraries (on Windows, these references will point to the canonical, Microsoft-provided, versions).
8. Packages is used the the NuGet package-manager. There are no referenced packages in this boilerplate project, but note that Visual Studio for Mac supports NuGet, just like Visual Studio for Windows does.
9. Properties contains the AssemblyInfo.cs source file. This file contains the meta-data (author, version, etc), including the very-important Guid, which identifies the plugin.
10. HelloRhinoCommonPlugin.cs is where this template plugin derives from Rhino.Plugins.Plugin and returns a static Instance of itself.
11. HelloRhinoCommonCommand.cs is where the action is. Let’s take a look at this file…

### Make Changes

1. Open HelloRhinoCommonCommand.cs in Visual Studio for Mac’s Source Editor (if it isn’t already).
2. Notice that HelloRhinoCommonCommand inherits from Rhino.Commands.Command

 public class HelloRhinoCommonCommand : Rhino.Commands.Command

3. …and overrides one inherited property called EnglishName

 public override string EnglishName {
get { return "HelloRhinoCommonCommand"; }
}

4. All Rhino commands must have a EnglishName property. This command name is not very accurate. We know from running the boilerplate code that this command prompts the user to draw a line. Let’s rename the command to HelloDrawLine:

 public override string EnglishName {
get { return "HelloDrawLine"; }
}

5. Further down, notice that HelloRhinoCommandCommand overrides the RunCommand method:

 protected override Result RunCommand (Rhino.RhinoDoc doc, RunMode mode)

6. All Rhino commands must have a RunCommand method. As you can see, this is where the action happens. Let’s create an intermediary line object that we can feed to the AddLine method. Find the spot in RunCommand after the user has been prompted to select two points. Type in…

 Rhino.Geometry.Line line1 = new Line (pt0, pt1);

7. Notice that - as you type - Visual Studio for Mac uses IntelliSense, just like Visual Studio for Windows (and many other editors). Now, feed line1 as an argument to the doc.Objects.AddLine method…

 doc.Objects.AddLine (line1);

8. Now that we have a line of our own, let’s examine it…

### Debugging

1. Set a breakpoint on line1 55 of HelloRhinoCommonCommand.cs. You set breakpoints in Visual Studio for Mac by clicking in the gutter…
2. Build and Run. Run HelloDrawLine in Rhino. Create the two points…as soon as you do, you should hit your breakpoint and pause…
3. With Rhino paused, in Visual Studio for Mac switch to the Locals tab. In the list, find the line1 object we authored. Click the dropdown arrow to expand the list of members on line1. Our line1 is a Rhino.Geometry.Line this class has a Length property…
4. Continue Executing in Rhino by pressing the Play button in the upper navigation menu of Visual Studio for Mac
5. Control is passed back to Rhino and your command finishes. Quit Rhino or Stop the debugging session.
6. Remove the breakpoint you created above by clicking on it in the gutter.
7. Now, let’s use the Length value to report something to the user. Near the very end of RunCommand, add the following line…

 RhinoApp.WriteLine ("The distance between the two points is {0}.", line1.Length);

8. Build and Run. Run HelloDrawLine in Rhino yet again (create the two points…). Rhino now reports the length of the line you created. However, this is not very clean.
9. Quit Rhino to Stop the debugging session once more.
10. Let’s add a unit system and be explicit about what we’re reporting…

 RhinoApp.WriteLine ("The distance between the two points is {0} {1}.", line1.Length, doc.ModelUnitSystem.ToString().ToLower());

11. Build and Run again. Now we’re reporting the length of the line we created with the document’s unit system (doc.ModelUnitSystem) with the proper case (ToLower()). Much better.

DONE!

Well, we could go on and on - line1 was never necessary, we could have just used pt0.DistanceTo(pt1).ToString(), etc. - but that is beside the point:

Congratulations! You have just built your first RhinoCommon plugin for Rhino for Mac. Now what?

## Next Steps

You’re using RhinoCommon, so this plugin will actually run on both platforms. Check out the Your First Plugin (Cross Platform) guide.

## Footnotes

1. Line numbers in Visual Studio for Mac can be enabled and disabled in Visual Studio > Preferences… > Text Editor section > Markers and Rulers entry > check Show line numbers