Creating and keeping track of unique element on a page

[Tomas Hofmann]

Q: How do I create an keep track of a specific element on a page?

For example, let's say I want to create a path that I later might want to edit as a response to other changes.

A: Since paths aren't objects of themselves, you cannot add any custom entry or key by which to identify it later.

You can, however, create it as a Form XObject, give it a unique key and then reference this from the path you created.

Created the Form XObject is very similar to creating a regular object, it's just that you create it on the doc as opposed to the page.

Obj CreateMyFormXObject(string key, string val)

{

ElementWriter writer = new ElementWriter();

ElementBuilder eb = new ElementBuilder();

writer.Begin(doc);

eb.PathBegin();

eb.MoveTo(0, 0);

eb.CurveTo(500, 500, 125, 625, 0, 500);

eb.CurveTo(-125, 625, -500, 500, 0, 0);

Element heart = eb.PathEnd();

heart.SetPathFill(true);

heart.GetGState().SetFillColorSpace(ColorSpace.CreateDeviceRGB());

heart.GetGState().SetFillColor(new ColorPt(1, 0, 0));

writer.WriteElement(heart); 

Obj form_xobj_dict = writer.End();

form_xobj_dict.Put("Subtype", Obj.CreateName("Form")); // Set bounding box/clipping rectangle.

form_xobj_dict.Put("BBox", Rect.CreateSDFRect(0, 0, 400, 600));

// Add a custom key and value:

form_xobj_dict.PutString(key, val);

return form_xobj_dict;

}

More info about creating and processing Form XObjects

https://groups.google.com/forum/?fromgroups#!searchin/pdfnet-sdk/create$20form$20xobject/pdfnet-sdk/0N2oEZJyPNA/XYPFSuPqVbwJ

https://groups.google.com/forum/?fromgroups#!searchin/pdfnet-sdk/create$20form$20xobject/pdfnet-sdk/vaYdPU3hHOE/XYDZnQ6NP_sJ

More info about custom entries:

https://groups.google.com/forum/?fromgroups#!searchin/pdfnet-sdk/custom$20object/pdfnet-sdk/06RcZalQI0s/sS6Ge3YiZiMJ

ElementWriter pageWriter = new ElementWriter(); 

ElementBuilder pageBuilder = new ElementBuilder(); 

pageWriter.Begin(page); 

Obj form_xobj_dict = CreateMyFormXObject("MyUniqueKey", "MyUniqueObject1");

Element element = pageBuilder.CreateForm(form_xobj_dict); 

pageWriter.WritePlacedElement(element); 

pageWriter.End() 

Later, when we want to edit this path, we can edit this Form XObject instead. To edit the page where this is displayed, check the ElementEdit sample: http://www.pdftron.com/pdfnet/samplecode.html#ElementEdit

While looping through the elements, if the element is of type e_form, you can call element.GetXObject to get an pdftron.SDF.Obj object. To check if it's the object you created, you can use the following code:

try

{

DictIterator ditr = obj.Get("MyUniqueKey");

Obj val = ditr.Value();

string str = val.GetAsPDFText();

        // If str is "MyUniqueObject1" then you can edit obj using standard methods.

}