\version "2.18.2"

enterStrictTime = {
      \set Score.proportionalNotationDuration = #(ly:make-moment 1/20)
      \override Score.SpacingSpanner.uniform-stretching = ##t
      \override Score.SpacingSpanner.strict-note-spacing = ##t
}

leaveStrictTime = {
      \set Score.proportionalNotationDuration = #(ly:make-moment 1/4)
      \override Score.SpacingSpanner.uniform-stretching = ##f
      \override Score.SpacingSpanner.strict-note-spacing = ##f
}

first = \drummode {
<<
  {
   \voiceOne
    cymr8 cymr8
    \tuplet3/2{hh16 hh hh}
    hh8
    \tuplet3/2{tomh16 tomh tomh}
    \tuplet3/2{tomh16 tomh tomh}
    \tuplet3/2{tomh16 tomh tomh}
    tomh8
  }
  \\
  { \voiceTwo
	\repeat unfold 8 bd8
  }
>>
}

second = \drummode {
<<
  \voiceOne \repeat unfold 8 tomh8
  \\
  \voiceTwo \repeat unfold 8 bd8
>>
}

\score {
  \new DrumStaff {
    <<
      \new DrumVoice {
        \drummode {

% Note: Manual breaks used instead of bars-per-line-engraver.

% Strict time was turned on in the layout block and the output looks good.
% Note that there are only 3 measures.
          \mark "Case 1"
	  \first \first \first \break
          \second \second \first \break

% strict time is still on and the output looks bad.
% Note that there are 4 measures and not enough room so space is being
% condensed within the measure to accommodate.
          \mark "Case 2"
	  \first \first \first \first \break
          \second \second \second \second \break

% Strict time is still on and the output looks bad.
          \mark "Case 3"
          \repeat percent 4 { \first } \break
          \repeat percent 4 { \second } \break

% Strict time is still on and the output looks good.
          \mark "Case 4"
          \repeat percent 4 {\enterStrictTime \first  \leaveStrictTime} \break
          \repeat percent 4 {\enterStrictTime \second \leaveStrictTime} \break
% In case \leaveStrict time still applies
          \enterStrictTime

          \mark "Case 5"
          \leaveStrictTime
% Strict time is off and the output looks bad.
          \repeat percent 4 { \first } \break
          \repeat percent 4 { \second } \break
          \enterStrictTime

          \mark "Case 6"
          \leaveStrictTime
% Strict time is off and the output looks good.
          \repeat percent 4 {\enterStrictTime \first  \leaveStrictTime} \break
          \repeat percent 4 {\enterStrictTime \second \leaveStrictTime} \break
          \enterStrictTime
        }
      }
    >>
  }
  \layout {
    \context {
      \DrumStaff
      \remove Time_signature_engraver
    }
    \context {
      \DrumVoice
    }
    \context {
      \Score
% Turn on strict time for the whole score
      \enterStrictTime

      \override NonMusicalPaperColumn.line-break-permission = ##f
    }
  }
}

\paper {
  indent = 0
  left-margin = 5\mm
  line-width=#200
  ragged-right = ##f
  ragged-bottom = ##t
}