contrib/docs/latex/ogl/topics.tex

   1 \chapter{Topic overviews}
   2 \setheader{{\it CHAPTER \thechapter}}{}{}{}{}{{\it CHAPTER \thechapter}}%
   3 \setfooter{\thepage}{}{}{}{}{\thepage}
   4
   5 The following sections describe particular topics.
   6
   7 \section{OGL overview}\label{ogloverview}
   8
   9 \helpref{wxShapeCanvas}{wxshapecanvas}, derived from {\bf wxCanvas}, is the drawing area
  10 for a number of \helpref{wxShape}{wxshape} instances. Everything drawn on a
  11 wxShapeCanvas is derived from wxShape, which provides virtual
  12 member functions for redrawing, creating and destroying
  13 resize/selection `handles', movement and erasing behaviour, mouse
  14 click behaviour, calculating the bounding box of the shape, linking
  15 nodes with arcs, and so on.
  16
  17 The way a client application copes with `damage' to the canvas is to
  18 erase (white out) anything should no longer be displayed, redraw the shape,
  19 and then redraw everything on the canvas to repair any damage. If quick edit
  20 mode is on for the canvas, the complete should be omitted by OGL and the
  21 application.
  22
  23 Selection handles (called control points in the code) are implemented as
  24 wxRectangleShapes.
  25
  26 Events are passed to shapes by the canvas in a high-level form, for example {\bf OnLeftClick},
  27 {\bf OnBeginDragLeft}, {\bf OnDragLeft}, {\bf OnEndDragLeft}. The canvas decides
  28 what is a click and what is a drag, whether it is on a shape or the canvas itself,
  29 and (by interrogating the shape) which attachment point the click is associated with.
  30
  31 In order to provide event-handling flexibility, each shapes has an `event handler' associated with it,
  32 which by default is the shape itself (all shapes derive from wxShapeEvtHandler).
  33 An application can modify the event-handling behaviour simply by plugging a new
  34 event handler into the shape. This can avoid the need for multiple inheritance when
  35 new properties and behaviour are required for a number of different shape classes: instead
  36 of overriding each class, one new event handler class can be defined and used for all
  37 existing shape classes.
  38
  39 A range of shapes have been predefined in the library, including rectangles, ellipses,
  40 polygons. A client application can derive from these shapes and/or derive entirely
  41 new shapes from wxShape.
  42
  43 Instances of a class called \helpref{wxDiagram}{wxdiagram} organise collections of
  44 shapes, providing default file input and output behaviour.
  45
  46 \section{wxDividedShape overview}\label{dividedshapeoverview}
  47
  48 Classes: \helpref{wxDividedShape}{wxdividedshape}
  49
  50 A wxDividedShape is a rectangle with a number of vertical divisions. Each
  51 division may have its text formatted with independent characteristics, and
  52 the size of each division relative to the whole image may be specified.
  53
  54 Once a wxDividedShape has been created, the user may move the divisions with the
  55 mouse. By pressing Ctrl while right-clicking, the region attributes can be edited.
  56
  57 Here are examples of creating wxDividedShape objects:
  58
  59 {\small
  60 \begin{verbatim}
  61   /*
  62    * Divided rectangle with 3 regions
  63    *
  64    */
  65
  66   wxDividedShape *dividedRect = new wxDividedShape(50, 60);
  67
  68   wxShapeRegion *region = new wxShapeRegion;
  69   region->SetProportions(0.0, 0.25);
  70   dividedRect->AddRegion(region);
  71
  72   region = new wxShapeRegion;
  73   region->SetProportions(0.0, 0.5);
  74   dividedRect->AddRegion(region);
  75
  76   region = new wxShapeRegion;
  77   region->SetProportions(0.0, 0.25);
  78   dividedRect->AddRegion(region);
  79
  80   dividedRect->SetSize(50, 60); // Allow it to calculate region sizes
  81   dividedRect->SetPen(wxBLACK_PEN);
  82   dividedRect->SetBrush(wxWHITE_BRUSH);
  83   dividedRect->Show(TRUE);
  84   dividedRect->NameRegions();
  85
  86   /*
  87    * Divided rectangle with 3 regions, rounded
  88    *
  89    */
  90
  91   wxDividedShape *dividedRect3 = new wxDividedShape(50, 60);
  92   dividedRect3->SetCornerRadius(-0.4);
  93
  94   region = new wxShapeRegion;
  95   region->SetProportions(0.0, 0.25);
  96   dividedRect3->AddRegion(region);
  97
  98   region = new wxShapeRegion;
  99   region->SetProportions(0.0, 0.5);
 100   dividedRect3->AddRegion(region);
 101
 102   region = new wxShapeRegion;
 103   region->SetProportions(0.0, 0.25);
 104   dividedRect3->AddRegion(region);
 105
 106   dividedRect3->SetSize(50, 60); // Allow it to calculate region sizes
 107   dividedRect3->SetPen(wxBLACK_PEN);
 108   dividedRect3->SetBrush(wxWHITE_BRUSH);
 109   dividedRect3->Show(TRUE);
 110   dividedRect3->NameRegions();
 111 \end{verbatim}
 112 }
 113
 114 \section{wxCompositeShape overview}\label{compositeshapeoverview}
 115
 116 Classes: \helpref{wxCompositeShape}{wxcompositeshape}, \helpref{wxOGLConstraint}{wxoglconstraint}
 117
 118 The wxCompositeShape allows fairly complex shapes to be created, and maintains
 119 a set of constraints which specify the layout and proportions of child shapes.
 120
 121 Add child shapes to a wxCompositeShape using \helpref{AddChild}{wxcompositeshapeaddchild}, and
 122 add constraints using \helpref{AddConstraint}{wxcompositeshapeaddconstraint}.
 123
 124 After children and shapes have been added, call \helpref{Recompute}{wxcompositeshaperecompute} which
 125 will return TRUE is the constraints could be satisfied, FALSE otherwise. If
 126 constraints have been correctly and consistently specified, this call will succeed.
 127
 128 If there is more than one child, constraints must be specified: OGL cannot calculate
 129 the size and position of children otherwise. Don't assume that children will simply
 130 move relative to the parent without the use of constraints.
 131
 132 To specify a constraint, you need three things:
 133
 134 \begin{enumerate}\itemsep=0pt
 135 \item a constraint type, such as gyCONSTRAINT\_CENTRED\_VERTICALLY;
 136 \item a reference shape, with respect to which other shapes are going to be positioned - the\rtfsp
 137 {\it constraining} shape;
 138 \item a list of one or more shapes to be constrained: the {\it constrained} shapes.
 139 \end{enumerate}
 140
 141 The constraining shape can be either the parent of the constrained shapes, or a sibling. The
 142 constrained shapes must all be siblings of each other.
 143
 144 For an exhaustive list and description of the available constraint types, see the \helpref{wxOGLConstraint constructor}{wxoglconstraintconstr}.
 145 Note that most constraints operate in one dimension only (vertically or horizontally), so you will
 146 usually need to specify constraints in pairs.
 147
 148 You can set the spacing between constraining and constrained shapes by
 149 calling \helpref{wxOGLConstraint::SetSpacing}{wxoglconstraintsetspacing}.
 150
 151 Finally, a wxCompositeShape can have {\it divisions}, which are special child shapes of class
 152 wxDivisionShape (not to be confused with wxDividedShape). The purpose of this is to allow
 153 the composite to be divided into user-adjustable regions (divisions) into which other shapes
 154 can be dropped dynamically, given suitable application code. Divisons allow the child
 155 shapes to have an identity of their own - they can be manipulated independently of their container -
 156 but to behave as if they are contained with the division, moving with the parent shape.
 157 Divisions boundaries can themselves be moved using the mouse.
 158
 159 To create an initial division, call \helpref{wxCompositeShape::MakeContainer}{wxcompositeshapemakecontainer}.
 160 Make further divisions by calling \helpref{wxDivisionShape::Divide}{wxdivisionshapedivide}.
 161