Aspose::Words::Layout::IPageLayoutCallback interface

IPageLayoutCallback interface

Implement this interface if you want to have your own custom method called during build and rendering of page layout model.

class IPageLayoutCallback : public virtual System::Object

Methods

Method	Description
GetType() const override
Is(const System::TypeInfo&) const override
virtual Notify(System::SharedPtr<Aspose::Words::Layout::PageLayoutCallbackArgs>)	This is called to notify of layout build and rendering progress.
static Type()

Remarks

The primary use for this interface is to allow application code to abort build process.

It is possible to build page layout model for only a few pages at start of the document then abort process and render only what has been built already.

Note, however, that rendering results may not match what would be rendered for each page if process would have finished.

This technique may not work for every document or may fail completely.

Examples

Shows how to track layout changes with a layout callback.

void PageLayoutCallback()
{
    auto doc = MakeObject<Document>();
    doc->get_BuiltInDocumentProperties()->set_Title(u"My Document");

    auto builder = MakeObject<DocumentBuilder>(doc);
    builder->Writeln(u"Hello world!");

    doc->get_LayoutOptions()->set_Callback(MakeObject<ExLayout::RenderPageLayoutCallback>());
    doc->UpdatePageLayout();

    doc->Save(ArtifactsDir + u"Layout.PageLayoutCallback.pdf");
}

class RenderPageLayoutCallback : public IPageLayoutCallback
{
public:
    void Notify(SharedPtr<PageLayoutCallbackArgs> a) override
    {
        switch (a->get_Event())
        {
        case PageLayoutEvent::PartReflowFinished:
            NotifyPartFinished(a);
            break;

        case PageLayoutEvent::ConversionFinished:
            NotifyConversionFinished(a);
            break;

        default:
            break;
        }
    }

    RenderPageLayoutCallback() : mNum(0)
    {
    }

private:
    int mNum;

    void NotifyPartFinished(SharedPtr<PageLayoutCallbackArgs> a)
    {
        std::cout << "Part at page " << (a->get_PageIndex() + 1) << " reflow." << std::endl;
        RenderPage(a, a->get_PageIndex());
    }

    void NotifyConversionFinished(SharedPtr<PageLayoutCallbackArgs> a)
    {
        std::cout << "Document \"" << a->get_Document()->get_BuiltInDocumentProperties()->get_Title() << "\" converted to page format." << std::endl;
    }

    void RenderPage(SharedPtr<PageLayoutCallbackArgs> a, int pageIndex)
    {
        auto saveOptions = MakeObject<ImageSaveOptions>(SaveFormat::Png);
        saveOptions->set_PageSet(MakeObject<PageSet>(pageIndex));

        {
            auto stream = MakeObject<System::IO::FileStream>(ArtifactsDir + String::Format(u"PageLayoutCallback.page-{0} {1}.png", pageIndex + 1, ++mNum),
                                                             System::IO::FileMode::Create);
            a->get_Document()->Save(stream, saveOptions);
        }
    }
};

See Also

• Namespace Aspose::Words::Layout
• Library Aspose.Words for C++