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pcb:connection_lookup [2018/11/11 12:04]
cparker
pcb:connection_lookup [2018/11/11 13:58] (current)
cparker
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 The connection lookup algorithm starts at an object and looks for any objects that touch the starting object or any object touching the starting object. This code is implemented in find.c and used throughout the code base for a variety of purposes. The connection lookup algorithm starts at an object and looks for any objects that touch the starting object or any object touching the starting object. This code is implemented in find.c and used throughout the code base for a variety of purposes.
  
-The connection lookup process starts at an object (pins/pads only?) and searches for intersecting objects. For each object it finds, it sets a specified flag. (todo: eventually this should build a list of objects instead).+The connection lookup process starts at an object (pins/pads only?) and searches for intersecting objects. For each object it finds, it sets a specified flag. (todo: eventually this should build a list of objects instead). These flags are used in a convoluted way to identify things that have already been found, and if the algorithm should continue looking for more objects. 
 + 
 +One of the tricks that the algorithm uses to restore the state of the flags in some cases is to use ClearFlagOnAllObjects to wipe out a flag (an undoable operation), then do everything without adding operations to the Undo stack, run ClearFlagsOnAllObjects a second time (without undo), and then Undo the first one. I guess the point of this is to prevent the undo system from sucking up resources during these operations? This has led to a global variable "​User"​ which has the effect of causing flag change operations to be added to the undo list. I think this is absolutely horrid. This variable needs to die. I think a better way of accomplishing this goal is by locking the undo system.
  
 ====Uses of the Connection Lookup Algorithm==== ====Uses of the Connection Lookup Algorithm====
pcb/connection_lookup.txt · Last modified: 2018/11/11 13:58 by cparker