Document View, etc.

Document View (class DocView)

The document view class runs in the back-end. It provides the glue between the document, the document manager, the grip manager and the selection manager. It is responsible for the rendering of a document's region (the view), which can consist of :

a single logical or physical page,
several logical pages (without any physical page),
several physical pages or
a group of objects (wherever, which can be in the main document layout or in a library).

A document definition needs following information :

The size of the view in document space, which defines how wide and tall the overall viewing box is or, in other words, how far the user may scroll.
One or several apertures defining the viewed root objects (be it logical pages, physical pages, groups, etc.) and their relative position to the viewing box.
The position of the view's center relative to the viewing box, expressed in %; an horizontal position of 0% means aligned with the left border, 100% means aligned with the right border; a vertical position of 0% means aligned with the bottom border, 100% means aligned with the top border.
The zoom factor used to render the document to the display; 100% should produce an output where (in a 1:1 scaled document) 1 mm should really measure 1 mm.
The layers which should be shown.
The orientation, which specified whether the document should be rotated (portrait, landscape).
The size of the view on the display (expressed in pixels).

To summarise, a view definition is represented by following objects :

[_{generic info=}_VIEW_{_BLOCK}
Info_generic₌_{VIEW_APERTURE} (one or multiple times) Info_generic₌_{VIEW_CENTER} Info_generic₌_{VIEW_ZOOM} Info_generic₌_{VIEW_LAYERS} Info_generic₌_{VIEW_ORIENTATION} Info_generic₌_{VIEW_DISPLAY}_{_SIZE}
]

Pages

The document contains physical and logical pages. There is exactly one physical page for every sheet printed by the application (single or double-sided). There can be zero, one or several logical pages on each side of a physical page.

Logical page

A logical page is defined by several objects stored together in a block. The block is in fact a group block where the group level is set to GROUP_PAGE. An additional information object (type UCID::Info_Generic) with an information ID set to LOG_PAGE_DEF defines the page size and the page number.

Logical pages are stored sequentially in a block of type UCID::Struct_LogPageRoot, itself located in a layout block. Usually, the logical page blocks are aliased (they are pointed to by both the root logical page block and a physical page).

The logical page is defined by following objects :

[_bbox
    ...
    Info_{generic=LOG_PAGE_DEF}
    Group_level₌_{GROUP_PAGE}
    ...
    graphical objects
    ...
]

Physical page

A physical page is defined by an information object block with an ID set to PHY_PAGE_DEF. The size of the physical page is stored in the generic information object.

Physical pages are stored sequentially in a block of type UCID::Struct_PhyPageRoot, itself located in a layout block.

A physical page block contains several links to logical pages, which are organised into two groups : the pages found on the front side of the sheet (stored in an information block with an ID set to PHY_PAGE_FRONT_BLOCK) and those found on the back side of the sheet (stored in an information block with an ID set to PHY_PAGE_BACK_BLOCK).

A physical page block may also contain additional information about the sheet, such as a link to a media definition object.

[_{generic info}₌_{PHY_PAGE_BLOCK}
    [_{generic info=}_PHY_{_PAGE_FRONT_BLOCK}
        ...
        [_bbox T-Linear Link_{logical page} ]
        ...
    ]
    [_{generic info=}_PHY_{_PAGE_BACK_BLOCK}         ...
        [_bbox T-Linear Link_{logical page} ]
        ...
    ]
]

Groups

Group objects are used to logically tie together objects in the document. There are several level for the groups : simple groups, pages and layers. A group is always defined inside a bounding-box block, where the bounding-box object records the overall size of the graphical objects found in the group.

[_bbox
    ...
    T-Group
    ...
    graphical objects
    ...
]

Geometric Transformations

Geometric transformations are implemented by management classes defined in the VP::DocTrans namespace. The most common transformation is DocTrans::Linear (apart from DocTrans::Group which is not really a transformation).

A transformation is defined by a block of objects; the block begin is of type UCID::Struct_BBox and the main block object is of type UCID::Trans_xxx. The following example shows a typical DocTrans::Linear transformation block (where the former xxx is replaced by Linear) :

[_bbox
    T-Linear
    ...
    graphical objects
    ...
]