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ASP.NET Web PDF Document Viewer/Editor Control Library

When providing toolbars (and also menus), it is nice to be able to add icons to each action. To avoid having to ship your application executable with a collection of icon image files, you can use resources. By building an XML-based qrc file and adding a RESOURCES line to your project file, you can embed files in your executable. At run-time, you can access the files by adding the : prefix to the file name. Providing icons for the application s executable is one of the few platform-dependent tasks you have to manage when using Qt. For Windows and Mac OS X, there are standardized ways to add icons to an executable; on Unix, you still have to target your install package to a specific distribution. Much work is being done here so I am sure that there will be a standard way available soon. This chapter showed you what is possible to do by using the framework available for main windows in Qt. You will use the QMainWindow class in applications later on in this book, so there is more to come!

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Unfortunately, some COM components have properties that work in a slightly different way, and these are called indexed properties. Whereas in C#, indexers are a type-level feature, in COM, any individual property may define an indexer. COM properties are really just method calls just like in C#, but with an indexed property, the explicit code would look more like this:

someObject.set_MyProperty("foo", 42);

Indexed properties require fewer objects. The traditional C# interpretation requires MyProperty to return a distinct object whose job is to provide the indexer, through which we access the values of interest. But with indexed properties, no intermediate object is required someObject provides accessors that give us direct access.

Compiling and building this application should not be any different from building the original application. All that you have to do is make sure that the compiler can find the Qt headers and that the linker can find the Qt library files. To handle all this smoothly and in a cross-platform manner, Qt comes with the QMake tool, which can create Makefiles for a range of different compilers. It even creates the project definition file for you if you want it to. Try this by building a simple application. Start by creating a directory called testing. Then put the code from Listing 1-6 inside this directory. You can call the file anything as long as it has the cpp extension. Listing 1-6. A trivial example #include <QtDebug> int main( ) { qDebug() << "Hello Qt World!"; return 0; } Now open a command line and change your working directory to the one that you just created. Then type qmake -project and press Enter, which should generate a file named testing.pro. My version of that file is shown in Listing 1-7.

Before C# 4.0, the only way to use indexed properties was via the method call syntax. But now you can use the indexer syntax, which will tend to make the code look more natural, since that s how the author of the COM component would have expected the property to be used.

C# 4.0 adds the ability to consume indexed properties, but you cannot write your own. The C# designers do not want to add confusion by providing two different idioms there s only one way to write a property that provides this syntax, which is one less decision developers have to make. Support for indexed properties is only present to make interop easier.

As we saw in 18, some COM components have methods where optional arguments are declared as ref object, meaning that the argument is a reference to an object reference. This led to some rather ugly code, such as that shown in Example 19-4.

<button targetElement="enabledButton"> <click> <invokeMethod target="setEnabled" method="evaluateIn" /> </click> </button>

object fileName = @"WordFile.docx"; object missing = System.Reflection.Missing.Value; object readOnly = true; var doc = wordApp.Documents.Open(ref fileName, ref missing, ref readOnly, ref missing, ref missing, ref missing, ref missing, ref missing, ref missing, ref missing, ref missing, ref missing, ref missing, ref missing, ref missing, ref missing);

If you are running the open-source version of Qt in Windows, you have an application called someTip thing like Qt 4.2.2 Command Prompt in the Start menu folder that was created when you installed Qt. Run this application and use the cd command to change the directory. For example, first locate your folder using Explorer; then copy the entire path (it should be similar to c:\foo\bar\baz\testing). Now type cd, followed by a space at the command prompt before you right-click, select Paste, and then press Enter. That should get you to the right working directory in a snap.

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