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Appendix: Miscellaneous Widget-Building Tips

Here are some general widget-building tips (in no particular order):

• Never call PgSetRegion().
• Never call PtDamageWidget() from a Draw method.
• Never call Pg... functions from anywhere except the Draw method.
• You don't need to call PtDamageWidget() after calling PtRealizeWidget().
• In the modify functions, don't call the widget's Extent method directly. Instead, set Pt_WIDGET_RESIZE in the widget's Pt_ARG_FLAGS resource; the widget library will calculate the widget's extent and perform any visual cleanup at the appropriate time.
• If you must calculate the extent immediately, call PtExtentWidget(), not your widget's Extent method.
• Use PtSetResources() to set the resources of subordinate (procreated) widgets.
• Avoid calling PgFlush() — the library will call it automatically when required.
• Never call PtBkgdHandlerProcess() from a Draw method.
• It's generally best to create subordinate children in your Defaults method; this way they can be modified as needed via resources before being realized. Another upside to this is that the widgets exist at the time the parent is being realized.

  When creating the widgets in methods from Initialization to Connect, the widgets don't exist at the time of realization and may be skipped. In this case, you need to have a Realized method in which you realize the children you want visible.

  It's also important to have an Unrealized method in which you destroy the subordinates or you must check to make sure you don't already have the subordinates in your Initialization method. Failing to do either of these will likely produce a memory leak.

• If you have an Extent method, it must actually calculate the extent of the widget. It's a fairly common mistake to do lots of dimension, layout, and area calculations and then forget to actually set the widget's extent. Setting the extent is usually accomplished via calling:

  PtSuperClassExtent( PtBasic "or another superclass", widget);
    

• If your widget's subordinate children aren't being displayed, check the widget's resize policy (Pt_ARG_RESIZE_FLAGS). This resource indicates whether or not the widget's size is adjusted based on the size and location of its children.
• If you have a Draw method defined, make sure you call PtClipRemove() if you called PtClipAdd() earlier in the function. Don't adjust the draw offset via PgSetTranslation() because the translation is already set up before your Draw function is called. If you really do want to change the translation, change it back before exiting your Draw method.