[IDE] Slow Startup - because of events trigged by 'boardsCustomMenus'

I am doing some analysis to improve the IDE startup time (I am discussing the topic in the email list).

I found another problem that is related to the menus. In particular: `createBoardMenusAndCustomMenus`, and in the method: `filterVisibilityOfSubsequentBoardMenus`.

What happens is that for each menu on a board such as Esp8266, it is calling `LibrariesIndexer.rescanLibraries()`, and it ends up costing a lot of time at startup and also when selecting a board.

This is the stack (not an error ...):

> at processing.app.Base.onBoardOrPortChange (Base.java:1346)
> at processing.app.**Base $ 12.actionPerformed** (Base.java:1605)
> at processing.app.Base.filterVisibilityOfSubsequentBoardMenus (Base.java:1651)
> at processing.app.Base.access $ 0 (Base.java:1635)
> at processing.app.**Base $ 11.actionPerformed** (Base.java:1576)
> at processing.app.Base.rebuildBoardsMenu (Base.java:1550)
> at processing.app.Base. (Base.java:285)
> at processing.app.Base.main (Base.java:150)

As you can see for each menu item, he is manually calling 'actionPerformed', and doing a lot of unnecessary things
```
Set log4j store directory /home/ricardo/.arduino15
SLF4J: Class path contains multiple SLF4J bindings.
SLF4J: Found binding in [jar:file:/media/ricardo/Dados/Workspace/Arduino/arduino-master/arduino-core/lib/slf4j-simple-1.7.22.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: Found binding in [jar:file:/media/ricardo/Dados/Workspace/Arduino/arduino-master/app/lib/slf4j-simple-1.7.22.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: See http://www.slf4j.org/codes.html#multiple_bindings for an explanation.
SLF4J: Actual binding is of type [org.slf4j.impl.SimpleLoggerFactory]
(DEBUG)>>>>>>>>> menu javax.swing.JRadioButtonMenuItem[,0,0,0x0,invalid,alignmentX=0.0,alignmentY=0.0,border=javax.swing.plaf.synth.SynthBorder@48d7ad8b,flags=256,maximumSize=,minimumSize=,preferredSize=,defaultIcon=,disabledIcon=,disabledSelectedIcon=,margin=javax.swing.plaf.InsetsUIResource[top=0,left=0,bottom=0,right=0],paintBorder=false,paintFocus=false,pressedIcon=,rolloverEnabled=false,rolloverIcon=,rolloverSelectedIcon=,selectedIcon=,text=115200]
(DEBUG)>>>>>>>>> onBoardOrPortChange main
java.lang.Throwable
at processing.app.Base.onBoardOrPortChange(Base.java:1346)
at processing.app.Base$12.actionPerformed(Base.java:1605)
at processing.app.Base.filterVisibilityOfSubsequentBoardMenus(Base.java:1651)
at processing.app.Base.access$0(Base.java:1635)
at processing.app.Base$11.actionPerformed(Base.java:1576)
at processing.app.Base.rebuildBoardsMenu(Base.java:1550)
at processing.app.Base.(Base.java:285)
at processing.app.Base.main(Base.java:150)
(DEBUG)>>>>>>>>> rescanLibraries main
(DEBUG)>>>>>>>>> rescanLibraries main
(DEBUG)>>>>>>>>> menu javax.swing.JRadioButtonMenuItem[,0,0,0x0,invalid,alignmentX=0.0,alignmentY=0.0,border=javax.swing.plaf.synth.SynthBorder@a53bb6f,flags=256,maximumSize=,minimumSize=,preferredSize=,defaultIcon=,disabledIcon=,disabledSelectedIcon=,margin=javax.swing.plaf.InsetsUIResource[top=0,left=0,bottom=0,right=0],paintBorder=false,paintFocus=false,pressedIcon=,rolloverEnabled=false,rolloverIcon=,rolloverSelectedIcon=,selectedIcon=,text=80 MHz]
(DEBUG)>>>>>>>>> onBoardOrPortChange main
java.lang.Throwable
at processing.app.Base.onBoardOrPortChange(Base.java:1346)
at processing.app.Base$12.actionPerformed(Base.java:1605)
at processing.app.Base.filterVisibilityOfSubsequentBoardMenus(Base.java:1651)
at processing.app.Base.access$0(Base.java:1635)
at processing.app.Base$11.actionPerformed(Base.java:1576)
at processing.app.Base.rebuildBoardsMenu(Base.java:1550)
at processing.app.Base.(Base.java:285)
at processing.app.Base.main(Base.java:150)
(DEBUG)>>>>>>>>> rescanLibraries main
(DEBUG)>>>>>>>>> rescanLibraries main
(DEBUG)>>>>>>>>> menu javax.swing.JRadioButtonMenuItem[,0,0,0x0,invalid,alignmentX=0.0,alignmentY=0.0,border=javax.swing.plaf.synth.SynthBorder@6759f091,flags=256,maximumSize=,minimumSize=,preferredSize=,defaultIcon=,disabledIcon=,disabledSelectedIcon=,margin=javax.swing.plaf.InsetsUIResource[top=0,left=0,bottom=0,right=0],paintBorder=false,paintFocus=false,pressedIcon=,rolloverEnabled=false,rolloverIcon=,rolloverSelectedIcon=,selectedIcon=,text=26 MHz]
(DEBUG)>>>>>>>>> onBoardOrPortChange main
java.lang.Throwable
at processing.app.Base.onBoardOrPortChange(Base.java:1346)
at processing.app.Base$12.actionPerformed(Base.java:1605)
at processing.app.Base.filterVisibilityOfSubsequentBoardMenus(Base.java:1651)
at processing.app.Base.access$0(Base.java:1635)
at processing.app.Base$11.actionPerformed(Base.java:1576)
at processing.app.Base.rebuildBoardsMenu(Base.java:1550)
at processing.app.Base.(Base.java:285)
at processing.app.Base.main(Base.java:150)
(DEBUG)>>>>>>>>> rescanLibraries main
(DEBUG)>>>>>>>>> rescanLibraries main
(DEBUG)>>>>>>>>> menu javax.swing.JRadioButtonMenuItem[,0,0,0x0,invalid,alignmentX=0.0,alignmentY=0.0,border=javax.swing.plaf.synth.SynthBorder@14a54ef6,flags=256,maximumSize=,minimumSize=,preferredSize=,defaultIcon=,disabledIcon=,disabledSelectedIcon=,margin=javax.swing.plaf.InsetsUIResource[top=0,left=0,bottom=0,right=0],paintBorder=false,paintFocus=false,pressedIcon=,rolloverEnabled=false,rolloverIcon=,rolloverSelectedIcon=,selectedIcon=,text=512K (no SPIFFS)]
(DEBUG)>>>>>>>>> onBoardOrPortChange main
java.lang.Throwable
at processing.app.Base.onBoardOrPortChange(Base.java:1346)
at processing.app.Base$12.actionPerformed(Base.java:1605)
at processing.app.Base.filterVisibilityOfSubsequentBoardMenus(Base.java:1651)
at processing.app.Base.access$0(Base.java:1635)
at processing.app.Base$11.actionPerformed(Base.java:1576)
at processing.app.Base.rebuildBoardsMenu(Base.java:1550)
at processing.app.Base.(Base.java:285)
at processing.app.Base.main(Base.java:150)
(DEBUG)>>>>>>>>> rescanLibraries main
(DEBUG)>>>>>>>>> rescanLibraries main
(DEBUG)>>>>>>>>> menu javax.swing.JRadioButtonMenuItem[,0,0,0x0,invalid,alignmentX=0.0,alignmentY=0.0,border=javax.swing.plaf.synth.SynthBorder@3b8ee898,flags=256,maximumSize=,minimumSize=,preferredSize=,defaultIcon=,disabledIcon=,disabledSelectedIcon=,margin=javax.swing.plaf.InsetsUIResource[top=0,left=0,bottom=0,right=0],paintBorder=false,paintFocus=false,pressedIcon=,rolloverEnabled=false,rolloverIcon=,rolloverSelectedIcon=,selectedIcon=,text=QIO]
(DEBUG)>>>>>>>>> onBoardOrPortChange main
java.lang.Throwable
at processing.app.Base.onBoardOrPortChange(Base.java:1346)
at processing.app.Base$12.actionPerformed(Base.java:1605)
at processing.app.Base.filterVisibilityOfSubsequentBoardMenus(Base.java:1651)
at processing.app.Base.access$0(Base.java:1635)
at processing.app.Base$11.actionPerformed(Base.java:1576)
at processing.app.Base.rebuildBoardsMenu(Base.java:1550)
at processing.app.Base.(Base.java:285)
at processing.app.Base.main(Base.java:150)
(DEBUG)>>>>>>>>> rescanLibraries main
(DEBUG)>>>>>>>>> rescanLibraries main
(DEBUG)>>>>>>>>> menu javax.swing.JRadioButtonMenuItem[,0,0,0x0,invalid,alignmentX=0.0,alignmentY=0.0,border=javax.swing.plaf.synth.SynthBorder@294bdeb4,flags=256,maximumSize=,minimumSize=,preferredSize=,defaultIcon=,disabledIcon=,disabledSelectedIcon=,margin=javax.swing.plaf.InsetsUIResource[top=0,left=0,bottom=0,right=0],paintBorder=false,paintFocus=false,pressedIcon=,rolloverEnabled=false,rolloverIcon=,rolloverSelectedIcon=,selectedIcon=,text=40MHz]
(DEBUG)>>>>>>>>> onBoardOrPortChange main
java.lang.Throwable
at processing.app.Base.onBoardOrPortChange(Base.java:1346)
at processing.app.Base$12.actionPerformed(Base.java:1605)
at processing.app.Base.filterVisibilityOfSubsequentBoardMenus(Base.java:1651)
at processing.app.Base.access$0(Base.java:1635)
at processing.app.Base$11.actionPerformed(Base.java:1576)
at processing.app.Base.rebuildBoardsMenu(Base.java:1550)
at processing.app.Base.(Base.java:285)
at processing.app.Base.main(Base.java:150)
(DEBUG)>>>>>>>>> rescanLibraries main
(DEBUG)>>>>>>>>> rescanLibraries main
(DEBUG)>>>>>>>>> menu javax.swing.JRadioButtonMenuItem[,0,0,0x0,invalid,alignmentX=0.0,alignmentY=0.0,border=javax.swing.plaf.synth.SynthBorder@1f86099a,flags=256,maximumSize=,minimumSize=,preferredSize=,defaultIcon=,disabledIcon=,disabledSelectedIcon=,margin=javax.swing.plaf.InsetsUIResource[top=0,left=0,bottom=0,right=0],paintBorder=false,paintFocus=false,pressedIcon=,rolloverEnabled=false,rolloverIcon=,rolloverSelectedIcon=,selectedIcon=,text=ck]
(DEBUG)>>>>>>>>> onBoardOrPortChange main
java.lang.Throwable
at processing.app.Base.onBoardOrPortChange(Base.java:1346)
at processing.app.Base$12.actionPerformed(Base.java:1605)
at processing.app.Base.filterVisibilityOfSubsequentBoardMenus(Base.java:1651)
at processing.app.Base.access$0(Base.java:1635)
at processing.app.Base$11.actionPerformed(Base.java:1576)
at processing.app.Base.rebuildBoardsMenu(Base.java:1550)
at processing.app.Base.(Base.java:285)
at processing.app.Base.main(Base.java:150)
(DEBUG)>>>>>>>>> rescanLibraries main
(DEBUG)>>>>>>>>> rescanLibraries main
(DEBUG)>>>>>>>>> menu javax.swing.JRadioButtonMenuItem[,0,0,0x0,invalid,alignmentX=0.0,alignmentY=0.0,border=javax.swing.plaf.synth.SynthBorder@f2c488,flags=256,maximumSize=,minimumSize=,preferredSize=,defaultIcon=,disabledIcon=,disabledSelectedIcon=,margin=javax.swing.plaf.InsetsUIResource[top=0,left=0,bottom=0,right=0],paintBorder=false,paintFocus=false,pressedIcon=,rolloverEnabled=false,rolloverIcon=,rolloverSelectedIcon=,selectedIcon=,text=Disabled]
(DEBUG)>>>>>>>>> onBoardOrPortChange main
java.lang.Throwable
at processing.app.Base.onBoardOrPortChange(Base.java:1346)
at processing.app.Base$12.actionPerformed(Base.java:1605)
at processing.app.Base.filterVisibilityOfSubsequentBoardMenus(Base.java:1651)
at processing.app.Base.access$0(Base.java:1635)
at processing.app.Base$11.actionPerformed(Base.java:1576)
at processing.app.Base.rebuildBoardsMenu(Base.java:1550)
at processing.app.Base.(Base.java:285)
at processing.app.Base.main(Base.java:150)
(DEBUG)>>>>>>>>> rescanLibraries main
(DEBUG)>>>>>>>>> rescanLibraries main
(DEBUG)>>>>>>>>> menu javax.swing.JRadioButtonMenuItem[,0,0,0x0,invalid,alignmentX=0.0,alignmentY=0.0,border=javax.swing.plaf.synth.SynthBorder@7bc9e6ab,flags=256,maximumSize=,minimumSize=,preferredSize=,defaultIcon=,disabledIcon=,disabledSelectedIcon=,margin=javax.swing.plaf.InsetsUIResource[top=0,left=0,bottom=0,right=0],paintBorder=false,paintFocus=false,pressedIcon=,rolloverEnabled=false,rolloverIcon=,rolloverSelectedIcon=,selectedIcon=,text=None]
(DEBUG)>>>>>>>>> onBoardOrPortChange main
java.lang.Throwable
at processing.app.Base.onBoardOrPortChange(Base.java:1346)
at processing.app.Base$12.actionPerformed(Base.java:1605)
at processing.app.Base.filterVisibilityOfSubsequentBoardMenus(Base.java:1651)
at processing.app.Base.access$0(Base.java:1635)
at processing.app.Base$11.actionPerformed(Base.java:1576)
at processing.app.Base.rebuildBoardsMenu(Base.java:1550)
at processing.app.Base.(Base.java:285)
at processing.app.Base.main(Base.java:150)
(DEBUG)>>>>>>>>> rescanLibraries main
(DEBUG)>>>>>>>>> rescanLibraries main
(DEBUG)>>>>>>>>> menu javax.swing.JRadioButtonMenuItem[,0,0,0x0,invalid,alignmentX=0.0,alignmentY=0.0,border=javax.swing.plaf.synth.SynthBorder@4248ed58,flags=256,maximumSize=,minimumSize=,preferredSize=,defaultIcon=,disabledIcon=,disabledSelectedIcon=,margin=javax.swing.plaf.InsetsUIResource[top=0,left=0,bottom=0,right=0],paintBorder=false,paintFocus=false,pressedIcon=,rolloverEnabled=false,rolloverIcon=,rolloverSelectedIcon=,selectedIcon=,text=v2 Lower Memory]
(DEBUG)>>>>>>>>> onBoardOrPortChange main
java.lang.Throwable
at processing.app.Base.onBoardOrPortChange(Base.java:1346)
at processing.app.Base$12.actionPerformed(Base.java:1605)
at processing.app.Base.filterVisibilityOfSubsequentBoardMenus(Base.java:1651)
at processing.app.Base.access$0(Base.java:1635)
at processing.app.Base$11.actionPerformed(Base.java:1576)
at processing.app.Base.rebuildBoardsMenu(Base.java:1550)
at processing.app.Base.(Base.java:285)
at processing.app.Base.main(Base.java:150)
(DEBUG)>>>>>>>>> rescanLibraries main
(DEBUG)>>>>>>>>> rescanLibraries main
(DEBUG)>>>>>>>>> menu javax.swing.JRadioButtonMenuItem[,0,0,0x0,invalid,alignmentX=0.0,alignmentY=0.0,border=javax.swing.plaf.synth.SynthBorder@4564e94b,flags=256,maximumSize=,minimumSize=,preferredSize=,defaultIcon=,disabledIcon=,disabledSelectedIcon=,margin=javax.swing.plaf.InsetsUIResource[top=0,left=0,bottom=0,right=0],paintBorder=false,paintFocus=false,pressedIcon=,rolloverEnabled=false,rolloverIcon=,rolloverSelectedIcon=,selectedIcon=,text=2]
(DEBUG)>>>>>>>>> onBoardOrPortChange main
java.lang.Throwable
at processing.app.Base.onBoardOrPortChange(Base.java:1346)
at processing.app.Base$12.actionPerformed(Base.java:1605)
at processing.app.Base.filterVisibilityOfSubsequentBoardMenus(Base.java:1651)
at processing.app.Base.access$0(Base.java:1635)
at processing.app.Base$11.actionPerformed(Base.java:1576)
at processing.app.Base.rebuildBoardsMenu(Base.java:1550)
at processing.app.Base.(Base.java:285)
at processing.app.Base.main(Base.java:150)
(DEBUG)>>>>>>>>> rescanLibraries main
(DEBUG)>>>>>>>>> rescanLibraries main
(DEBUG)>>>>>>>>> menu javax.swing.JRadioButtonMenuItem[,0,0,0x0,invalid,alignmentX=0.0,alignmentY=0.0,border=javax.swing.plaf.synth.SynthBorder@51745f40,flags=256,maximumSize=,minimumSize=,preferredSize=,defaultIcon=,disabledIcon=,disabledSelectedIcon=,margin=javax.swing.plaf.InsetsUIResource[top=0,left=0,bottom=0,right=0],paintBorder=false,paintFocus=false,pressedIcon=,rolloverEnabled=false,rolloverIcon=,rolloverSelectedIcon=,selectedIcon=,text=Only Sketch]
(DEBUG)>>>>>>>>> onBoardOrPortChange main
java.lang.Throwable
at processing.app.Base.onBoardOrPortChange(Base.java:1346)
at processing.app.Base$12.actionPerformed(Base.java:1605)
at processing.app.Base.filterVisibilityOfSubsequentBoardMenus(Base.java:1651)
at processing.app.Base.access$0(Base.java:1635)
at processing.app.Base$11.actionPerformed(Base.java:1576)
at processing.app.Base.rebuildBoardsMenu(Base.java:1550)
at processing.app.Base.(Base.java:285)
at processing.app.Base.main(Base.java:150)
(DEBUG)>>>>>>>>> rescanLibraries main
(DEBUG)>>>>>>>>> rescanLibraries main
(DEBUG)>>>>>>>>> onBoardOrPortChange main
java.lang.Throwable
at processing.app.Base.onBoardOrPortChange(Base.java:1346)
at processing.app.Base$11.actionPerformed(Base.java:1578)
at processing.app.Base.rebuildBoardsMenu(Base.java:1550)
at processing.app.Base.(Base.java:285)
at processing.app.Base.main(Base.java:150)
(DEBUG)>>>>>>>>> rescanLibraries main
(DEBUG)>>>>>>>>> rescanLibraries main
(DEBUG)>>>>>>>>> onBoardOrPortChange main
java.lang.Throwable
at processing.app.Base.onBoardOrPortChange(Base.java:1346)
at processing.app.Base$12.actionPerformed(Base.java:1605)
at processing.app.Base.rebuildBoardsMenu(Base.java:1550)
at processing.app.Base.(Base.java:285)
at processing.app.Base.main(Base.java:150)
(DEBUG)>>>>>>>>> rescanLibraries main
(DEBUG)>>>>>>>>> rescanLibraries main
(DEBUG)>>>>>>>>> onBoardOrPortChange main
java.lang.Throwable
at processing.app.Base.onBoardOrPortChange(Base.java:1346)
at processing.app.Base$12.actionPerformed(Base.java:1605)
at processing.app.Base.rebuildBoardsMenu(Base.java:1550)
at processing.app.Base.(Base.java:285)
at processing.app.Base.main(Base.java:150)
(DEBUG)>>>>>>>>> rescanLibraries main
(DEBUG)>>>>>>>>> rescanLibraries main
(DEBUG)>>>>>>>>> onBoardOrPortChange main
java.lang.Throwable
at processing.app.Base.onBoardOrPortChange(Base.java:1346)
at processing.app.Base$12.actionPerformed(Base.java:1605)
at processing.app.Base.rebuildBoardsMenu(Base.java:1550)
at processing.app.Base.(Base.java:285)
at processing.app.Base.main(Base.java:150)
(DEBUG)>>>>>>>>> rescanLibraries main
(DEBUG)>>>>>>>>> rescanLibraries main
(DEBUG)>>>>>>>>> onBoardOrPortChange main
java.lang.Throwable
at processing.app.Base.onBoardOrPortChange(Base.java:1346)
at processing.app.Base$12.actionPerformed(Base.java:1605)
at processing.app.Base.rebuildBoardsMenu(Base.java:1550)
at processing.app.Base.(Base.java:285)
at processing.app.Base.main(Base.java:150)
(DEBUG)>>>>>>>>> rescanLibraries main
(DEBUG)>>>>>>>>> rescanLibraries main
(DEBUG)>>>>>>>>> onBoardOrPortChange main
java.lang.Throwable
at processing.app.Base.onBoardOrPortChange(Base.java:1346)
at processing.app.Base$12.actionPerformed(Base.java:1605)
at processing.app.Base.rebuildBoardsMenu(Base.java:1550)
at processing.app.Base.(Base.java:285)
at processing.app.Base.main(Base.java:150)
(DEBUG)>>>>>>>>> rescanLibraries main
(DEBUG)>>>>>>>>> rescanLibraries main
(DEBUG)>>>>>>>>> onBoardOrPortChange main
java.lang.Throwable
at processing.app.Base.onBoardOrPortChange(Base.java:1346)
at processing.app.Base$12.actionPerformed(Base.java:1605)
at processing.app.Base.rebuildBoardsMenu(Base.java:1550)
at processing.app.Base.(Base.java:285)
at processing.app.Base.main(Base.java:150)
(DEBUG)>>>>>>>>> rescanLibraries main
(DEBUG)>>>>>>>>> rescanLibraries main
(DEBUG)>>>>>>>>> onBoardOrPortChange main
java.lang.Throwable
at processing.app.Base.onBoardOrPortChange(Base.java:1346)
at processing.app.Base$12.actionPerformed(Base.java:1605)
at processing.app.Base.rebuildBoardsMenu(Base.java:1550)
at processing.app.Base.(Base.java:285)
at processing.app.Base.main(Base.java:150)
(DEBUG)>>>>>>>>> rescanLibraries main
(DEBUG)>>>>>>>>> rescanLibraries main
(DEBUG)>>>>>>>>> onBoardOrPortChange main
java.lang.Throwable
at processing.app.Base.onBoardOrPortChange(Base.java:1346)
at processing.app.Base$12.actionPerformed(Base.java:1605)
at processing.app.Base.rebuildBoardsMenu(Base.java:1550)
at processing.app.Base.(Base.java:285)
at processing.app.Base.main(Base.java:150)
(DEBUG)>>>>>>>>> rescanLibraries main
(DEBUG)>>>>>>>>> rescanLibraries main
(DEBUG)>>>>>>>>> onBoardOrPortChange main
java.lang.Throwable
at processing.app.Base.onBoardOrPortChange(Base.java:1346)
at processing.app.Base$12.actionPerformed(Base.java:1605)
at processing.app.Base.rebuildBoardsMenu(Base.java:1550)
at processing.app.Base.(Base.java:285)
at processing.app.Base.main(Base.java:150)
(DEBUG)>>>>>>>>> rescanLibraries main
(DEBUG)>>>>>>>>> rescanLibraries main
(DEBUG)>>>>>>>>> onBoardOrPortChange main
java.lang.Throwable
at processing.app.Base.onBoardOrPortChange(Base.java:1346)
at processing.app.Base$12.actionPerformed(Base.java:1605)
at processing.app.Base.rebuildBoardsMenu(Base.java:1550)
at processing.app.Base.(Base.java:285)
at processing.app.Base.main(Base.java:150)
(DEBUG)>>>>>>>>> rescanLibraries main
(DEBUG)>>>>>>>>> rescanLibraries main
(DEBUG)>>>>>>>>> onBoardOrPortChange main
java.lang.Throwable
at processing.app.Base.onBoardOrPortChange(Base.java:1346)
at processing.app.Base$12.actionPerformed(Base.java:1605)
at processing.app.Base.rebuildBoardsMenu(Base.java:1550)
at processing.app.Base.(Base.java:285)
at processing.app.Base.main(Base.java:150)
(DEBUG)>>>>>>>>> rescanLibraries main
(DEBUG)>>>>>>>>> rescanLibraries main
(DEBUG)>>>>>>>>> onBoardOrPortChange main
java.lang.Throwable
at processing.app.Base.onBoardOrPortChange(Base.java:1346)
at processing.app.Base$12.actionPerformed(Base.java:1605)
at processing.app.Base.rebuildBoardsMenu(Base.java:1550)
at processing.app.Base.(Base.java:285)
at processing.app.Base.main(Base.java:150)
(DEBUG)>>>>>>>>> rescanLibraries main
(DEBUG)>>>>>>>>> rescanLibraries main
(DEBUG)>>>>>>>>> onBoardOrPortChange main
java.lang.Throwable
at processing.app.Base.onBoardOrPortChange(Base.java:1346)
at processing.app.Base.(Base.java:294)
at processing.app.Base.main(Base.java:150)
(DEBUG)>>>>>>>>> rescanLibraries main
(DEBUG)>>>>>>>>> rescanLibraries main
>>>>> pdeKeywords = processing.app.syntax.PdeKeywords@63a28987
>>>>> pdeKeywords = processing.app.syntax.PdeKeywords@63a28987
>>>>> pdeKeywords = processing.app.syntax.PdeKeywords@63a28987
>>>>> pdeKeywords = processing.app.syntax.PdeKeywords@63a28987

```

Start in Base.java at createBoardMenusAndCustomMenus, rebuildBoardsMenu, and filterVisibilityOfSubsequentBoardMenus, following the stack through onBoardOrPortChange and LibrariesIndexer.rescanLibraries(). Reproduce IDE startup and board selection with the reported debug output; done means the repeated unnecessary library rescans no longer cause the reported slowdown.

Written by the indexing model from the issue text.