This works as well as usual with fpc 3.1.1:
/opt/lazarus/ide/sourcefilemanager.pas(6450,29) Error: (5038) identifier idents no member "DesignPPI"
/opt/lazarus/ide/sourcefilemanager.pas(6452,71) Error: (5038) identifier idents no member "DesignPPI"
/opt/lazarus/ide/sourcefilemanager.pas(6454,88) Error: (5038) identifier idents no member "DesignPPI"
/opt/lazarus/ide/sourcefilemanager.pas(6455,88) Error: (5038) identifier idents no member "DesignPPI"
/opt/lazarus/ide/sourcefilemanager.pas(6457,86) Error: (5038) identifier idents no member "DesignPPI"
/opt/lazarus/ide/sourcefilemanager.pas(6458,86) Error: (5038) identifier idents no member "DesignPPI"
/opt/lazarus/ide/sourcefilemanager.pas(6459,27) Error: (5038) identifier idents no member "DesignPPI"
sourcefilemanager.pas(8456) Fatal: (10026) There were 7 errors compiling module, stopping
Fatal: (1018) Compilation aborted
Makefile:3961: recipe for target 'lazarus' failed
And the different icons are gone. In 1.6. some Lazarus windows had differently colored icons, and now they are all blue. How are you supposed to use Alt+TAB, when all the icons are the same?