@maxgraph/core
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    Class PrintPreview

    Implements printing of a diagram across multiple pages.

    The following opens a print preview for an existing graph:

    const preview = new PrintPreview(graph);
    preview.open();

    Use getScaleForPageCount as follows in order to print the graph across a given number of pages:

    const pageCount = window.prompt('Enter page count', '1');
    if (pageCount) {
      const scale = printUtils.getScaleForPageCount(pageCount, graph);
      const preview = new PrintPreview(graph, scale);
      preview.open();
    }

    To add additional pages before and after the output, getCoverPages and getAppendices can be used, respectively.

    const preview = new PrintPreview(graph, 1);

    preview.getCoverPages = function(w, h) {
      return [this.renderPage(w, h, 0, 0, (div) => {
        div.innerHTML = '<div style="position:relative;margin:4px;">Cover Page</p>'
      }];
    };

    preview.getAppendices = function(w, h) {
      return [this.renderPage(w, h, 0, 0, (div) => {
        div.innerHTML = '<div style="position:relative;margin:4px;">Appendix</p>'
      }];
    };
    preview.open();

    The CSS from the original page is not carried over to the print preview. To add CSS to the page, use the css argument in the open function or override writeHead to add the respective link tags as follows:

    const writeHead = preview.writeHead;
    preview.writeHead = function(doc: Document, css: string | null): void {
      writeHead.apply(this, [doc, css]);
      doc.writeln('<link rel="stylesheet" type="text/css" href="style.css">');
    };

    To add a padding to the page in the preview (but not the print output), use the following code:

    preview.writeHead = function(doc: Document, css: string | null): void {
      writeHead.apply(this, [doc, css]);

      doc.writeln('<style type="text/css">');
      doc.writeln('@media screen {');
      doc.writeln('  body > div { padding-top:30px;padding-left:40px;box-sizing:content-box; }');
      doc.writeln('}');
      doc.writeln('</style>');
    };

    Apart from setting the title argument in the PrintPreview constructor you can override renderPage as follows to add a header to any page:

    const renderPage = printPreview.renderPage;
    printPreview.renderPage = function(w, h, x, y, content, pageNumber) {
      const div = renderPage.apply(this, [w, h, x, y, content, pageNumber]);

      const header = document.createElement('div');
      header.style.position = 'absolute';
      header.style.top = '0px';
      header.style.width = '100%';
      header.style.textAlign = 'right';
      domUtils.write(header, 'Your header here');
      div.firstChild.appendChild(header);

      return div;
    };

    The pageNumber argument contains the number of the current page, starting at

    1. To display a header on the first page only, check pageNumber and add a vertical offset in the constructor call for the height of the header.

    Page Format

    For landscape printing, use PAGE_FORMAT_A4_LANDSCAPE as the pageFormat in getScaleForPageCount and PrintPreview. Keep in mind that one can not set the defaults for the print dialog of the operating system from JavaScript so the user must manually choose a page format that matches this setting.

    You can try passing the following CSS directive to open to set the page format in the print dialog to landscape. However, this CSS directive seems to be ignored in most major browsers, including IE.

    @page {
      size: landscape;
    }
    Index

    Constructors

    constructor

    Properties

    autoOrigin backgroundColor border borderColor clipping graph marginBottom marginTop pageCount pageFormat pageSelector printBackgroundImage printControls printOverlays scale targetWindow title wnd x0 y0

    Methods

    addGraphFragment addPageBreak appendGraph close closeDocument createPageSelector getAppendices getCoverPages getDoctype getLinkForCellState getRoot getWindow insertBackgroundImage open print renderPage useCssTransforms writeHead writePostfix

    Constructors

    • Parameters

      • graph: Graph
      • scale: null | number = null
      • pageFormat: null | Rectangle = null
      • border: null | number = null
      • x0: number = 0
      • y0: number = 0
      • borderColor: null | string = null
      • title: string = 'Printer-friendly version'
      • pageSelector: null | boolean = null

      Returns PrintPreview

    Properties

    autoOrigin: boolean = true

    Specifies if the origin should be automatically computed based on the top, left corner of the actual diagram contents. The required offset will be added to x0 and y0 in open.

    true
    backgroundColor: string = '#ffffff'

    Holds the color value for the page background color.

    '#ffffff'
    border: number = 0

    The border inset around each side of every page in the preview. This is set to 0 if autoOrigin is false.

    0
    borderColor: null | string

    Holds the color value for the page border.

    clipping: boolean = true

    Specifies is clipping should be used to avoid creating too many cell states in large diagrams. The bounding box of the cells in the original diagram is used if this is enabled.

    true
    graph: Graph

    Reference to the graph that should be previewed.

    marginBottom: number = 0

    The margin at the bottom of the page (number).

    0
    marginTop: number = 0

    The margin at the top of the page (number).

    0
    pageCount: number = 0

    Holds the actual number of pages in the preview.

    pageFormat: Rectangle

    Holds the Rectangle that defines the page format.

    pageSelector: boolean

    Boolean that specifies if the page selector should be displayed.

    true
    printBackgroundImage: boolean = false

    Specifies if the background image should be printed.

    false
    printControls: boolean = false

    Specifies if controls (such as folding icons) should be printed. Default is false.

    printOverlays: boolean = false

    Specifies if overlays should be printed.

    false
    scale: number

    Holds the scale of the print preview.

    targetWindow: null | Window = null

    Assign any window here to redirect the rendering in open.

    title: string

    Holds the title of the preview window.

    wnd: null | Window = null

    Reference to the preview window.

    x0: number = 0

    Holds the horizontal offset of the output.

    y0: number = 0

    Holds the vertical offset of the output.

    Methods

    • Adds a graph fragment to the given div.

      Parameters

      • dx: number

        Horizontal translation for the diagram.

      • dy: number

        Vertical translation for the diagram.

      • scale: number

        Scale for the diagram.

      • pageNumber: number

        Number of the page to be rendered.

      • div: HTMLDivElement

        Div that contains the output.

      • clip: Rectangle

        Contains the clipping rectangle as an Rectangle.

      Returns void

    • Adds a page break to the given document.

      Parameters

      • doc: Document

      Returns void

    • Adds the given graph to the existing print preview.

      Parameters

      • graph: Graph
      • scale: number
      • x0: number
      • y0: number
      • forcePageBreaks: boolean
      • keepOpen: boolean

      Returns void

    • Creates the page selector table.

      Parameters

      • vpages: number
      • hpages: number

      Returns HTMLTableElement

    • Returns the pages to be added after the print output. This returns null.

      Parameters

      • _width: number
      • _height: number

      Returns null | HTMLElement[]

    • Returns the pages to be added before the print output. This returns null.

      Parameters

      • _width: number
      • _height: number

      Returns null | HTMLElement[]

    • Returns the string that should go before the HTML tag in the print preview page. This implementation returns an X-UA meta tag for IE5 in quirks mode, IE8 in IE8 standards mode and edge in IE9 standards mode.

      Returns string

    • Inserts the background image into the given div.

      Parameters

      • div: HTMLDivElement
      • dx: number
      • dy: number

      Returns void

    • Shows the print preview window. The window is created here if it does not exist.

      Parameters

      • css: null | string = null

        Optional CSS string to be used in the head section.

      • targetWindow: null | Window = null

        Optional window that should be used for rendering. If this is specified then no HEAD tag, CSS and BODY tag will be written.

      • forcePageBreaks: boolean = false
      • keepOpen: boolean = false

      Returns null | Window

    • Opens the print preview and shows the print dialog.

      Parameters

      • Optionalcss: string

        Optional CSS string to be used in the head section.

      Returns void

    • Creates a DIV that prints a single page of the given graph using the given scale and returns the DIV that represents the page.

      Parameters

      • w: number

        Width of the page in pixels.

      • h: number

        Height of the page in pixels.

      • dx: number

        Optional horizontal page offset in pixels (used internally).

      • dy: number

        Optional vertical page offset in pixels (used internally).

      • content: (div: HTMLDivElement) => void

        Callback that adds the HTML content to the inner div of a page. Takes the inner div as the argument.

      • OptionalpageNumber: number

        Integer representing the page number.

      Returns HTMLDivElement

    • Returns true if CSS transforms should be used for scaling content. This returns true if foreignObject is supported and we're not in Safari as it has clipping bugs for transformed CSS content with foreignObjects.

      Returns boolean

    • Writes the HEAD section into the given document, without the opening and closing HEAD tags.

      Parameters

      • doc: Document
      • css: null | string

      Returns void

    • Called before closing the body of the page. This implementation is empty.

      Parameters

      • doc: Document

      Returns any

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