Expand __declspec documentation

Doc/Manual/Windows.html

@@ -387,10 +387,11 @@ Include it like you would any other interface file, for example:
 
 __declspec(dllexport) ULONG __stdcall foo(DWORD, __int32);
 </pre></div>
+
 <p>Note that if you follow Microsoft's recommendation of wrapping the
 <tt>__declspec</tt> calls in a preprocessor definition, you will need to
-make sure that the definition is included by SWIG as well, whether you define it
-manually or it is included in a header. For example, if you have specified the
+make sure that the definition is included by SWIG as well, by either defining it
+manually or via a header. For example, if you have specified the
 preprocessor definition in a header named <tt>export_lib.h</tt> and include
 other headers which depend on it, you should use the <tt>%include</tt> directive
 to include the definition explicitly. For example, if you had a header file,
@@ -398,12 +399,42 @@ to include the definition explicitly. For example, if you had a header file,
 file might look like:</p>
 
 <div class="code"><pre>
+// bar.i
 %module bar
 %include &lt;windows.i&gt;
 %include "export_lib.h"
 %include "bar.h"
 </pre></div>
 
+<p>
+where export_lib.h may contain:
+</p>
+
+<div class="code"><pre>
+// export_lib.h
+#define BAR_API __declspec(dllexport)
+</pre></div>
+
+<p>
+and bar.h may look like:
+</p>
+
+<div class="code"><pre>
+// bar.h
+#include "export_lib.h"
+BAR_API void bar_function(int, double);
+</pre></div>
+
+<p>
+Using the preprocessor to remove BAR_API is a popular simpler solution:
+</p>
+
+<div class="code"><pre>
+// bar.i
+%module bar
+#define BAR_API
+%include "bar.h"
+</pre></div>
 
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