# Graphics Related Helper Code

Contains graphics related helper code. Lots of the draw and impress code is in this shared library.

- `xoutdev`

    this is where a lot of the work would happen to move to the canvas. (what does that mean?)

- `svdraw`

    transparent gradient stuff. [seriously? surely much more, too]

## SdrObject

The shapes you can see in LibreOffice (like rectangle, etc.) are SdrObjects.
They are declared as a hierarchy:

    SdrObject <- SdrAttrObj <- E3dObject <- E3dCompoundObject <- E3dCubeObj
        ^ ^ ^             ^            ^              | | ^ ^
        | | |             |            |              | | | +--- E3dExtrudeObj
        | | |             |            |              | | +----- E3dLatheObj
        | | |             |            |              | +------- E3dPolygonObj
        | | |             |            |              +--------- E3dSphereObj
        | | |             |            +--- E3dScene...
        | | |             |
        | | |             +--- SdrTextObj <- SdrObjCustomShape...
        | | |                   ^ ^ ^ ^ ^
        | | |                   | | | | +--- SdrEdgeObj...
        | | |                   | | | +----- SdrMeasureObj...
        | | |                   | | +------- SdrPathObj...
        | | |                   | +--------- SdrRectObj...
        | | |                   +----------- SdrTableObj...
        | | +--- SdrObjGroup...
        | + ---- SdrPageObj...
        +------- SdrVirtObj...

The above is incomplete of course.

## SdrModel / SdrView

Copied from `svdview.hxx`:

  First of all the app creates a `SdrModel`.
  Then it opens a Win and creates a `SdrView`.
  `ShowSdrPage()` announces a page at `SdrView`.
  It's possible to show `SdrView` in any Wins at once.

  `SdrView` can show as many Wins as it wants at once. Pages are announced
  or checked out with the help of `ShowSdrPage()`/`HideSdrPage()`. For every announced
  page there is a `SdrPageView` instance in container aPages. If more than one page
  is showed, you have to pay attention that the offset parameter of `ShowSdrPage()`
  is conformed to the size of the page (to prevent overlapping of two pages).

`SdrView` itself is inherited from many objects in a chain of inheritance (all
that starts with `SdrPaintView` - that is itself inherited from few classes
too):

    SdrPaintView <- SdrSnapView <- SdrMarkView <- SdrEditView <- SdrPolyEditView
                                                                     ^
    +----------------------------------------------------------------+
    |
    SdrGlueEditView <- SdrObjEditView <- SdrExchangeView <- SdrDragView
                                                                     ^
    +----------------------------------------------------------------+
    |
    SdrCreateView <- SdrView

From `SdrView` on, it is not flat, but a real hierarchy again.

## Drawing Layer / SdrObject(s)

See `drawinglayer/README.md` for general information about drawinglayer.

Below is the class diagram that comes from
<https://web.archive.org/web/20160827020830if_/http://www.openoffice.org:80/marketing/ooocon2006/presentations/wednesday_g11.odp>
slide number 6.

    .------- Model --------------.      .------- View -----------------------------------------.
    | SdrObject - ViewContact    | 1..* | ViewObjectContact                                    |
    |              getChild()    |------|    getPrimitiveList()  -----> Object(s) ---> SdrView |
    |              getVOC()      |      |    getRecPrimitiveList()      Contact                |
    |              getViewInd... |      |________|_____________________________________________|
    | ...ependentPrimitiveList() |               |
    |____________________________|            generates
                                                 |           ______
                                                 V          /      |
                                       .----------------------.    |
                                       | basePrimitive        |    |
                                       |   getRange()         |<---'
                                       |   getDecomposition() |
                                       |______________________|

For `SdrObjects`, there are own `DrawingLayer` primitives in
`svx/source/sdr/primitive2d`

The `ViewContact` / `ViewObject` / `ViewObjectContact` are in `svx/source/sdr/contact`
Decomposes the `SdrObjects`, and does all sort of operations on them.

If the number of visualizable objects (e.g. `SdrObjects`) is `X`, and the number of
`SdrViews` is `Y`, then:

- there are `X` `ViewContact` instances (1:1 relation with a visualizable object)
- there are `Y` `ObjectContact` instances (1:1 relation with an `SdrView`)
- there are `X*Y` `ViewObjectContact` instances (1:N relation to both
  visualizable objects and `SdrView`s)