/// <summary>
/// Read the registry to learn about the preview handlers that are available on this machine
/// Return a structure containing 2 collections. One of all the file extensions and whether we found a preview handler
/// registered, and one of the preview handlers and their CLSIDs
/// </summary>
internal static RegistrationData LoadRegistrationInformation()
{
// Load and sort all preview handler information from registry
List<PreviewHandlerInfo> handlers = new List<PreviewHandlerInfo>();
using (RegistryKey handlersKey = Registry.LocalMachine.OpenSubKey(
BaseRegistryKey))
{
foreach (string id in handlersKey.GetValueNames())
{
PreviewHandlerInfo handler = new PreviewHandlerInfo();
handler.ID = id;
handler.Name = handlersKey.GetValue(id, null) as string;
handlers.Add(handler);
}
}
handlers.Sort(delegate(PreviewHandlerInfo first, PreviewHandlerInfo second)
{
if (first.Name == null) return 1;
else if (second.Name == null) return -1;
else return first.Name.CompareTo(second.Name);
});
// Create a lookup table of preview handler ID -> PreviewHandlerInfo
Dictionary<string, PreviewHandlerInfo> handlerMapping = new Dictionary<string, PreviewHandlerInfo>(handlers.Count);
foreach (PreviewHandlerInfo handler in handlers)
{
handlerMapping.Add(handler.ID, handler);
}
// Get all classes/extensions from registry
string[] extensions = Registry.ClassesRoot.GetSubKeyNames();
// Find out what each extension is registered to be previewed with
List<ExtensionInfo> extensionInfos = new List<ExtensionInfo>(extensions.Length);
foreach (string extension in extensions)
{
if (extension.StartsWith("."))
{
ExtensionInfo info = new ExtensionInfo();
info.Extension = extension;
string id = Registry.GetValue(
string.Format(BaseClsIDKey, extension),
null, null) as string;
if (id == null)
id = Registry.GetValue(
string.Format(BaseClsIdKey2, extension),
null, null) as string;
PreviewHandlerInfo mappedHandler;
if (id != null && handlerMapping.TryGetValue(id, out mappedHandler)) info.Handler = mappedHandler;
extensionInfos.Add(info);
}
}
// Return the information
RegistrationData data = new RegistrationData();
data.Handlers = handlers;
data.Extensions = extensionInfos;
return data;
}
/// <summary>
/// 1) Look up the preview handler associated with the file extension
/// 2) Create an instance of the handler using its CLSID and reflection
/// 3) Check if it is a file or stream handler
/// 4) Initialize with File or Stream using Initialize from the appropriate interface
/// 5) Call SetWindow passing in a handle to this control and the bounds of the control
/// 6) Call DoPreview
/// </summary>
private void GeneratePreview()
{
lblMessage.Visible = false;
if (_comInstance != null)
{
((IPreviewHandler)_comInstance).Unload();
}
RECT r;
r.top = 0;
r.bottom = this.Height;
r.left = 0;
r.right = this.Width;
RegistrationData data = PreviewHandlerRegistryAccessor.LoadRegistrationInformation();
PreviewHandlerInfo handler = null;
foreach (ExtensionInfo ei in data.Extensions)
{
if (_filePath.ToUpper().EndsWith(ei.Extension.ToUpper()))
{
handler = ei.Handler;
if (handler != null)
{
break;
}
}
}
if (handler == null)
{
lblMessage.Visible = true;
lblMessage.Text = "No Preview Available";
return;
}
Type comType = Type.GetTypeFromCLSID(new Guid(handler.ID));
try
{
// Create an instance of the preview handler
_comInstance = Activator.CreateInstance(comType);
// Check if it is a stream or file handler
if (_comInstance is IInitializeWithFile)
{
((IInitializeWithFile)_comInstance).Initialize(_filePath, 0);
}
else if (_comInstance is IInitializeWithStream)
{
if (File.Exists(_filePath))
{
StreamWrapper stream = new StreamWrapper(File.Open(_filePath, FileMode.Open));
((C4F.DevKit.PreviewHandler.PreviewHandlerFramework.IInitializeWithStream)_comInstance).Initialize(stream, 0);
}
else
{
throw new Exception("File not found");
}
}
((IPreviewHandler)_comInstance).SetWindow(this.Handle, ref r);
((IPreviewHandler)_comInstance).DoPreview();
}
catch (Exception ex)
{
_comInstance = null;
lblMessage.Visible = true;
lblMessage.Text = "Preview Generation Failed - " + ex.Message;
}
}
