{"id":1329,"date":"2013-10-01T19:08:12","date_gmt":"2013-10-01T19:08:12","guid":{"rendered":"https:\/\/clarionsharp.com\/blog\/?p=1329"},"modified":"2013-10-01T19:08:12","modified_gmt":"2013-10-01T19:08:12","slug":"reports-in-the-new-rtl","status":"publish","type":"post","link":"https:\/\/clarionsharp.com\/blog\/reports-in-the-new-rtl\/","title":{"rendered":"REPORTs in the new RTL"},"content":{"rendered":"

Clarion uses Windows metafiles to generate reports since the very first version of Clarion for Windows. A metafile is a sequence of records containing a list of GDI functions and parameters. Metafiles are created in memory and can be written to disk files. The RTL also uses metafiles to handle direct drawing operations like ARC() or PIE() in both WINDOWs and REPORTs. A metafile is a simple way to store drawing operations but there are several issues:<\/p>\n

    \n
  1. Windows metafiles do not support all GDI functions used for drawing. For example, images with semi-transparent parts cannot be stored in Windows metafiles.<\/li>\n
  2. Reports are sequences of bands and bands consist of controls and can be nested. Multiple drawing operations can be required to draw individual controls. For example, multiple lines and multiple strings must be drawn for LIST controls. Reports are best represented as a tree structure, and metafiles with their linear organization are not an easy\/adequate way to represent them.<\/li>\n
  3. The RTL must carefully track images, pens and fonts used in metafiles to avoid leaking of resources.<\/li>\n<\/ol>\n

    Problem (1) can be solved by use of Enhanced metafiles (EMF) instead of Windows metafiles (WMF). But other problems exist for both types of metafiles. The RTL must enumerate metafile records every time some delayed action needs to be executed, for example when processing widow\/orphan settings to find end of page. The RTL inserts additional records into metafiles to mark logically related records and assist in enumeration and parsing both during report generation and during conversion metafiles to text\/PDF\/XML\/HTML format.<\/p>\n

    \"ReportsTree\"<\/a><\/p>\n

    The new RTL won\u2019t use metafiles for direct drawing operations or during report generation. Instead it will produce a dynamic tree structure matching the Report with a sequence of drawing operations. Every tree node is a class instance derived from the MetaNode class:
    \nMetaNode\u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0CLASS,TYPE
    \nNext\u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0&MetaNode
    \nBounds\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0LIKE(RECT)
    \nFlags\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0ULONG
    \nCustom1\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0LONG
    \nCustom2\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0LONG
    \nDraw\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0PROCEDURE (LONG context),VIRTUAL
    \nEND<\/p>\n

    ContainerNode\u00a0 CLASS(MetaNode),TYPE
    \nNested\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 &MetaNode
    \nEND<\/p>\n

    PageNode\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 CLASS(ContainerNode),TYPE
    \nPrint\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 PROCEDURE (HDC, ULONG skipmask)
    \nEND<\/p>\n

    IndirectNode\u00a0\u00a0 CLASS(MetaNode),TYPE
    \nActual\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 &ContainerNode
    \nEND<\/p>\n

    There are 3 categories of nodes:<\/p>\n

      \n
    1. Nodes with information to execute a direct draw operation or to draw a control. A Nodes\u2019 classes have fields for all values required to perform both drawing and post-processing: fonts, colors, pen style and width, value of the EXTEND attribute, etc.<\/li>\n
    2. Container nodes used for referencing a list of nested nodes.<\/li>\n
    3. Indirect nodes referencing some Container node.<\/li>\n<\/ol>\n

      The container node class for a report page has a function to start drawing or printing. The call to this function initiates iteration of the page sub-tree and calls the Draw method for every node. This approach provides a very easy method to get a page in any required form:<\/p>\n