#157 Legend shows only diagram "style" relevant legend entries

[kirchsth]

Related to #157 it could be that e.g. the "normal/default container" element is displayed in the legend but the diagram contains only "tagged container" and the "normal/default" is obsolete therefore it should not be displayed in the legend.

Based on that the legend contains only tag/default elements which are visible in the diagram.
Tags which are not direct visible (only via stereotypes) are not displayed in the legend because these tags lost relation between style and legend too,

It can be tested via my extended branch

@startuml
' convert it with additional command line argument -DRELATIVE_INCLUDE="." to use locally
!if %variable_exists("RELATIVE_INCLUDE")
  !include ./../C4_Component.puml
!else
  !include https://raw.githubusercontent.com/kirchsth/C4-PlantUML/extended/C4_Component.puml
!endif

AddElementTag("shapeRound", $shape=$ROUNDED_BOX)
AddElementTag("shapeOct", $shape=$EIGHT_SIDED)
AddElementTag("shadowed", $shadowing=true)
AddElementTag("shadowed2", $shadowing=false)
AddElementTag("yelloTagged", $fontColor=yellow, $borderColor=yellow)
AddElementTag("greenTagged", $borderColor=green, $bgColor=green)
AddElementTag("tagged container", $fontColor=white, $bgColor=red, $borderColor=$CONTAINER_BORDER_COLOR)
AddElementTag("tagged person", $fontColor=white, $bgColor=orange, $borderColor=$PERSON_BORDER_COLOR)

Container(c2, Container 2, tech, $tags="tagged container", "'tagged container' stereotype/tag overwrites all styles of container ($fontColor, $bgColor and $borderColor) the container is not important anymore and therefore not displayed in legend")
Person(p2, p2, $tags="tagged person", "produces no person legend entry too")

Person(p4, p4, $tags="yelloTagged", "'yelloTagged' stereotype/tag first and defines $fontColor and $borderColor (in legend), 'person' defines additional $bgColor (in legend too)")

' complete sample with all styles
' Component(comp3, comp3, "techn", $tags="yelloTagged+greenTagged+shapeRound+shapeOct+shadowed+shadowed2", "Complex sample with all styles")

SHOW_LEGEND(false)
@enduml

Best regards
Helmut