CSS Extensions – CSS Vendor Prefixes – Aspose.HTML for .NET

CSS Vendor Prefixes

CSS vendor prefixes, sometimes called CSS browser prefixes, are used in CSS property names to implement experimental or pre-release CSS features that are not yet standardized or may have limited support in certain browsers. In other words, the reason for the existence of prefixes was to specify browser-specific features.

Historically, browser vendors use the prefixes for nonstandard CSS features. Following is the list of the major browsers prefixes:

• -webkit- (Chrome, Safari, newer versions of Opera, almost all iOS browsers (including Firefox for iOS); basically, any WebKit based browser)
• -moz- (Mozilla-based browsers such as Firefox)
• -o- (Old, pre-WebKit, versions of Opera)
• -ms- (Internet Explorer and Microsoft Edge)

According to the CSS specification, CSS vendor-specific extensions must start with a dash or underscore and have the following format:

['-' or '_'] + [vendor identifier] + ['-'] + [name]

For example, the -webkit-text-stroke CSS property is a vendor-prefixed property used to specify the width and color of strokes for text characters in WebKit-based browsers, and -moz-border-radius is a vendor-prefixed property that allows you to round the corners of elements to create a visually appealing and modern design in Mozilla-based browsers, such as Firefox.

CSS Extensions – Aspose.HTML

The prefix that is used by Aspose.HTML library looks like -aspose- and gives you some experimental features. Following is a list of CSS functions that can be enabled by using -aspose- prefix:

Function Name	Description
currentPageNumber	This function returns the number of the current rendering page.
totalPagesNumber	This function returns the number of the total pages in the document.

Aspose CSS Extension – C# Example

The next code snippet demonstrates how to use CSS extensions to create custom marks on document margins:

//  Initialize a configuration object and set up page-margins for a document
using (Configuration configuration = new Configuration())
{
    // Get the User Agent service
    var userAgent = configuration.GetService<IUserAgentService>();

    // Set the style of custom margins and create marks on it
    userAgent.UserStyleSheet = @"@page 
                    {
                        /* Page margins should be not empty in order to write content inside the margin-boxes */
                        margin-top: 1cm;
                        margin-left: 2cm;
                        margin-right: 2cm;
                        margin-bottom: 2cm;
                        /* Page counter located at the bottom of the page */
                        @bottom-right
                        {
                            -aspose-content: ""Page "" currentPageNumber() "" of "" totalPagesNumber();
                            color: green;
                        }

                        /* Page title located at the top-center box */
                        @top-center
                        {
                            -aspose-content: ""Hello, World Document Title!!!"";
                            vertical-align: bottom;
                            color: blue;
                        }    
                    }";

    //  Initialize an HTML document 
    using HTMLDocument document = new HTMLDocument("<div>Hello, World!!!</div>", ".", configuration);
    
    //  Initialize an output device
    using (PdfDevice device = new PdfDevice(Path.Combine(OutputDir, "output.pdf")))
    {
        // Send the document to the output device
        document.RenderTo(device);
    }                
}

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