Tuesday, June 30, 2009

Embedding Google Earth in a C# Application

Introduction

If you're interested in utilizing the Google Earth viewer as a control in a custom application, then continue reading. There are quite a few links around the Internet that provide information as to how to add references to your project, create a ApplicationGE, and control the Google Earth application. However, most of these tutorials do not focus on the details of embedding Google Earth in an application. That's what I will focus on here. From now on, GE means Google Earth.

The Code

You'll probably start off on your embedding adventure much like I did, with:


EARTHLib.ApplicationGE ge = new ApplicationGEClass();

If the GE process already exists, we will obtain a reference to it; if not, a new process will be created, and you would see the GE logo flash on the screen while loading. You will then see the main Google Earth screen with the embedded viewer. Since we are interested in embedding GE, we are not interested in having the main screen around, so we hide it!


ShowWindowAsync(ge.GetMainHwnd(), 0);

For all intensive purposes, we now have an empty screen. What we'd like to do next is embed the scene that GE renders into our application. We accomplish this by setting the render Hwnds parent to that of the window we would like to render to:

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SetParent(ge.GetRenderHwnd(), this.Handle.ToInt32());

In the example above, 'this' is a Windows Form. The end result, if you perform these same steps, should look similar to the image below, although I do warn that results may vary :-)

google_earth_embedded.jpg

You will notice that resizing the window has no effect on the scene. If you plan on embedding GE in an application for any useful purposes, you'll most likely need it to respond to resizing. I spent a bit of time sniffing into the events that were passed to the scene when I performed re-size of the main GE application window. This led me to a special event, WM_QT_PAINT, in addition to a sequence of others. It took a bit of tinkering to get it all right, but this appeared to work for me:


See full detail: http://www.codeproject.com/KB/miscctrl/google_earth_embed.aspx

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