Redrawing the grapher after layout
When a layout algorithm is executed, it moves the nodes and/or reshapes the links of the graph. If the graph is displayed on a screen, its display must be updated to reflect the changes made by the layout.
If you use a diagram component (a subclass of
IlvDiagrammer)), the updating is done automatically.
If you call layout by using the method
performLayout, you have more detailed control on the redraw mechanism, as explained in the following sections:
Rogue Wave® JViews provides complete flexibility, concerning the redraw of an
IlvGrapher instance that has undergone layout. Your choice will depend on your particular application. The following scenarios are possible:
Automatic and selective redraw
If you just want the grapher to be automatically redrawn after the layout, simply call the following method with the value true for the redraw argument:
IlvGraphLayoutReport performLayout(boolean force, boolean redraw)
When you do this, an
initReDraws/
reDrawViews session is initiated automatically. When the nodes and the links are moved or reshaped, the value
true is passed for the
redraw argument of the appropriate methods of
IlvGrapher. At the end of the layout, the
initReDraws/reDrawViews session is ended. This produces a selective redraw of the invalid regions of the views where the graph is displayed.
Nonautomatic and complete redraw
If all the nodes are moved by the layout, it may be more efficient to redraw the entire graph at the end of the layout instead of using the mechanism of the invalid regions provided by IlvGrapher. In this case, you can use the following code:
try {
layout.performLayout(false, false); // argument redraw at false
} catch (IlvGraphLayoutException e) {
e.printStackTrace();
} finally {
// redraw in the final clause to ensure that the redraw
// is performed even if an exception occurs
grapher.reDraw();
}
This completely redraws the grapher in all its visible views. Alternatively, you can call the method repaint on some of its views.
Delayed redraw
After the layout, you may want to perform other changes in the grapher before redrawing. You can start the
initReDraws/
reDrawViews session on your own to control the point in time when the redraw is performed. You can use the following code:
grapher.initReDraws();
try {
layout.performLayout(false, true);
} catch (IlvGraphLayoutException e) {
e.printStackTrace();
} finally {
grapher.moveObject(..., false); // some other changes in the grapher
grapher.reDrawViews();
}
No redraw at all
Sometimes, the layout may need to be performed without any display of the grapher. For instance, this can be done to automatically produce
.ivl files containing the result of the layout for future use. To avoid any redraw during the layout, just call the method
performLayout with the value
false for the
redraw argument.
NOTE During animated layout (for layouts supporting this option), the grapher needs to be redrawn after each step to produce the animation effect. Therefore, you need to pass the value
true for the
redraw argument of the method
performLayout. In this case, the
initReDraws/
reDrawViews session is automatically used for each animation step. Users should not add their own
initReDraw/reDrawViews session because this would prevent the graph from being redrawn during the animation.
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