VisClass: 9 Basic Summary

GEOS SDK TechDocs

8 Creating Specific UIs

Visible objects are involved in several basic operations, each of which has its own primary messages:

• Drawing
  Vis objects must handle MSG_VIS_DRAW ( MSG_VIS_DRAW ) if they are to draw after their window has been exposed. Objects wishing to redraw themselves outside of exposure events can call MSG_VIS_VUP_CREATE_GSTATE ( MSG_VIS_VUP_CREATE_GSTATE ) to create a GState in their view windows for drawing.
• Being added to an object tree
  When an object is added to a visible tree, it must then force a redraw of the tree. It can be added to the tree with MSG_VIS_ADD_CHILD ( MSG_VIS_ADD_CHILD ), and the tree can be updated with MSG_VIS_VUP_UPDATE_WIN_GROUP ( MSG_VIS_VUP_UPDATE_WIN_GROUP ).
• Being removed from an object tree
  A visible object may be removed from a visible tree with MSG_VIS_REMOVE ( MSG_VIS_REMOVE ). This message will close the object (take it off the screen) and then segregate it from its parent.
• Undergoing visual update
  The visual update mechanism is automatic for the most part. An object that requires visual update, however, can use MSG_VIS_MARK_INVALID ( MSG_VIS_MARK_INVALID ) in conjunction with MSG_VIS_VUP_UPDATE_WIN_GROUP ( MSG_VIS_VUP_UPDATE_WIN_GROUP ) to cause the update.
• Geometry management
  Geometry management of visible objects can be as simple as setting a few flags in the instance data or as complex as manually setting position and size of the objects. For a full description of geometry management of visible objects, see Positioning Visible Objects .
• Being Destroyed
  Visible objects may be destroyed even when they are part of a visible tree that is on the screen. MSG_VIS_DESTROY ( MSG_VIS_DESTROY ) first removes the object from the tree (with MSG_VIS_REMOVE ) and then destroys it (through the MetaClass detach and destroy mechanisms).

GEOS SDK TechDocs

8 Creating Specific UIs