Sequencer - Improved point d'n'd

TODO

@@ -33,6 +33,7 @@ Sync / inputs:
 * Moving tracks
 * Moving segments
 * Add curve display
+* CLEAN UP THAT FUCKING SPAGHETTI MESS!
 
 Misc:
 * General overhaul (e.g. use tabs)

ui-sequencer.cc

@@ -367,7 +367,8 @@ struct T_SyncViewImpl_
 			const float time ) noexcept;
 	bool handlePointDrag(
 			const float mPixels ,
-			bool mouseDown ) noexcept;
+			bool mouseDown ,
+			bool shiftPressed ) noexcept;
 
 	T_MousePos getMousePos( ) const noexcept;
 
@@ -858,7 +859,8 @@ void T_SyncViewImpl_::sequencerWidget( ) noexcept
 				zoomLevel = ( ppu - BarWidth ) / ( BarWidth - width / u ) + 1;
 			}
 		}
-	} else if ( dnd == E_DNDType::POINT && handlePointDrag( mPixels , io.MouseDown[ 0 ] ) ) {
+	} else if ( dnd == E_DNDType::POINT
+			&& handlePointDrag( mPixels , io.MouseDown[ 0 ] , io.KeyShift ) ) {
 		return;
 	} else if ( dnd == E_DNDType::CLICK && ( io.MouseDown[ 0 ] || io.MouseDown[ 1 ] ) ) {
 		return;
@@ -911,7 +913,8 @@ void T_SyncViewImpl_::sequencerWidget( ) noexcept
 			selId = dTrack.id;
 			selSegment = dSeg.seg;
 			selPoint = dPoint.index;
-			const bool pdnd{ io.MouseDown[ 0 ] && dPoint.index != 0 };
+			const bool pdnd{ io.MouseDown[ 0 ]
+				&& ( dPoint.index != 0 || dSeg.seg != 0 ) };
 			if ( pdnd ) {
 				assert( selUpdate == E_ChangeType::NONE );
 				selPointDnDStart = selPointDnDCur = mPixels;
@@ -1400,7 +1403,8 @@ void T_SyncViewImpl_::displayTooltips(
 
 bool T_SyncViewImpl_::handlePointDrag(
 		const float mPixels ,
-		bool mouseDown ) noexcept
+		bool mouseDown ,
+		bool shiftPressed ) noexcept
 {
 	auto& sync( Common::Sync( ) );
 
@@ -1409,32 +1413,51 @@ bool T_SyncViewImpl_::handlePointDrag(
 	const int32_t diffUnits{ int32_t( round( diff * sync.durationUnits( ) / totalPixels ) ) };
 	const bool moved{ fabsf( diff ) >= 2 && abs( diffUnits ) > 0 };
 	const auto ni{ selUpdatingCopies.size( ) };
+	const auto sid{ *selSegment };
+	const auto pid{ *selPoint };
+	assert( pid > 0 || sid > 0 );
+	const bool isLastPoint{ [&](){
+		auto const& s{ selUpdatingOriginals[ 0 ].segments };
+		return sid == s.size( ) - 1 && pid == s[ sid ].durations.size( );
+	}( ) };
 
-	// Update the point as necessary
+	if ( moved && ( shiftPressed || isLastPoint ) ) {
-	if ( moved ) {
+		// Increase/decrease duration
 		selUpdatingCopies = selUpdatingOriginals;
 		for ( auto i = 0u ; i < ni ; i ++ ) {
 			auto& copy{ selUpdatingCopies[ i ] };
-			auto& seg{ copy.segments[ *selSegment ] };
+			auto& seg{ copy.segments[ sid ] };
-			if ( *selPoint == seg.durations.size( ) ) {
+			auto& d{ pid == 0
-				// We're dragging the end point
+				? copy.segments[ sid - 1 ].durations.last( )
-				// XXX make it work "normally"
+				: seg.durations[ pid - 1 ] };
-				seg.durations.last( ) = std::max( 1 ,
+			d = std::max( 1 , diffUnits + int32_t( d ) );
-						diffUnits + int32_t( seg.durations.last( ) ) );
-			} else {
-				// We're dragging some other point, move units
-				// from one side to the other
-				assert( *selPoint > 0 );
-				auto& d0{ seg.durations[ *selPoint - 1 ] };
-				auto& d1{ seg.durations[ *selPoint ] };
-				const int32_t mmNeg( 1 - d0 ) , mmPos( d1 - 1 );
-				const int32_t diff{ diffUnits < mmNeg ? mmNeg
-					: ( diffUnits > mmPos ? mmPos : diffUnits ) };
-				d0 += diff;
-				d1 -= diff;
-			}
 			sync.setCurve( copy );
 		}
+
+	} else if ( moved ) {
+		// Move the point but keep the sum of before/after durations
+		// a constant
+		selUpdatingCopies = selUpdatingOriginals;
+		for ( auto i = 0u ; i < ni ; i ++ ) {
+			auto& copy{ selUpdatingCopies[ i ] };
+			auto& seg{ copy.segments[ sid ] };
+
+			auto& d0{ pid == 0
+				? copy.segments[ sid - 1 ].durations.last( )
+				: seg.durations[ pid - 1 ] };
+			auto& d1{ pid == seg.durations.size( )
+				? copy.segments[ sid + 1 ].durations[ 0 ]
+				: seg.durations[ pid ]
+			};
+
+			const int32_t mmNeg( 1 - d0 ) , mmPos( d1 - 1 );
+			const int32_t diff{ diffUnits < mmNeg ? mmNeg
+				: ( diffUnits > mmPos ? mmPos : diffUnits ) };
+			d0 += diff;
+			d1 -= diff;
+			sync.setCurve( copy );
+		}
+
 	} else {
 		selUpdatingCopies.clear( );
 		for ( auto i = 0u ; i < ni ; i ++ ) {