VST3: Map k91_4 and k90_4 to the canonical JUCE 9.1.4 and 9.0.4 layouts

BREAKING-CHANGES.txt

@@ -4,6 +4,38 @@ JUCE breaking changes
 develop
 =======
 
+Change
+------
+The k91_4 and k90_4 VST3 layouts are now mapped to the canonical JUCE 9.1.4 and
+9.0.4 AudioChannelSets. This has a different ChannelType layout than the
+AudioChannelSet previously used with such VST3 SpeakerArrangements.
+
+Possible Issues
+---------------
+VST3 plugins that were prepared to work with the k91_4 and k90_4
+SpeakerArrangements may now have incorrect channel mapping. The channels
+previously accessible through ChannelType::left and right are now accessible
+through ChannelType::wideLeft and wideRight, and channels previously accessible
+through ChannelType::leftCentre and rightCentre are now accessible through
+ChannelType::left and right.
+
+Workaround
+----------
+Code that accesses the channels that correspond to the VST3 Speakers kSpeakerL,
+kSpeakerR, kSpeakerLc and kSpeakerRc needs to be updated. These channels are now
+accessible respectively through ChannelTypes wideLeft, wideRight, left and
+right. Previously they were accessible respectively through left, right,
+leftCentre and rightCentre.
+
+Rationale
+---------
+This change allows developers to handle the 9.1.4 and 9.0.4 surround layouts
+with one codepath across all plugin formats. Previously the
+AudioChannelSet::create9point1point4() and create9point0point4() layouts would
+only be used in CoreAudio and AAX, but a different AudioChannelSet would be used
+in VST3 even though they were functionally equivalent.
+
+
 Change
 ------
 The signatures of the ContentSharer member functions have been updated. The

modules/juce_audio_basics/buffers/juce_AudioChannelSet.h

@@ -258,19 +258,19 @@ public:
 
     /** Creates a set for a 9.0.4 surround setup (left, right, centre, leftSurroundSide, rightSurroundSide, leftSurroundRear, rightSurroundRear, wideLeft, wideRight, topFrontLeft, topFrontRight, topRearLeft, topRearRight).
 
-        Is equivalent to: AAX_eStemFormat_9_0_4 (AAX).
+        Is equivalent to: k90_4 (VST3), AAX_eStemFormat_9_0_4 (AAX).
     */
     static AudioChannelSet JUCE_CALLTYPE create9point0point4();
 
     /** Creates a set for a 9.1.4 surround setup (left, right, centre, LFE, leftSurroundSide, rightSurroundSide, leftSurroundRear, rightSurroundRear, wideLeft, wideRight, topFrontLeft, topFrontRight, topRearLeft, topRearRight).
 
-        Is equivalent to: AAX_eStemFormat_9_1_4 (AAX).
+        Is equivalent to: k91_4 (VST3), AAX_eStemFormat_9_1_4 (AAX).
     */
     static AudioChannelSet JUCE_CALLTYPE create9point1point4();
 
     /** Creates a set for a 9.0.6 surround setup (left, right, centre, LFE, leftSurroundSide, rightSurroundSide, leftSurroundRear, rightSurroundRear, wideLeft, wideRight, topFrontLeft, topFrontRight, topSideLeft, topSideRight, topRearLeft, topRearRight).
 
-        Is equivalent to: AAX_eStemFormat_9_0_6 (AAX).
+        Is equivalent to: k90_6 (VST3), AAX_eStemFormat_9_0_6 (AAX).
     */
     static AudioChannelSet JUCE_CALLTYPE create9point0point6();
 

modules/juce_audio_processors/format_types/juce_VST3Common.h

@@ -416,6 +416,8 @@ namespace detail
         { k70_6,                        { X::left, X::right, X::centre,         X::leftSurroundRear, X::rightSurroundRear, X::leftSurroundSide, X::rightSurroundSide, X::topFrontLeft, X::topFrontRight, X::topRearLeft, X::topRearRight, X::topSideLeft, X::topSideRight } },
 
         // The VST3 layout uses 'left/right' and 'left-of-center/right-of-center', but the JUCE layout uses 'left/right' and 'wide-left/wide-right'.
+        { k91_4,                        { X::wideLeft, X::wideRight, X::centre, X::LFE, X::leftSurroundRear, X::rightSurroundRear, X::left, X::right, X::leftSurroundSide, X::rightSurroundSide, X::topFrontLeft, X::topFrontRight, X::topRearLeft, X::topRearRight } },
+        { k90_4,                        { X::wideLeft, X::wideRight, X::centre,         X::leftSurroundRear, X::rightSurroundRear, X::left, X::right, X::leftSurroundSide, X::rightSurroundSide, X::topFrontLeft, X::topFrontRight, X::topRearLeft, X::topRearRight } },
         { k91_6,                        { X::wideLeft, X::wideRight, X::centre, X::LFE, X::leftSurroundRear, X::rightSurroundRear, X::left, X::right, X::leftSurroundSide, X::rightSurroundSide, X::topFrontLeft, X::topFrontRight, X::topRearLeft, X::topRearRight, X::topSideLeft, X::topSideRight } },
         { k90_6,                        { X::wideLeft, X::wideRight, X::centre,         X::leftSurroundRear, X::rightSurroundRear, X::left, X::right, X::leftSurroundSide, X::rightSurroundSide, X::topFrontLeft, X::topFrontRight, X::topRearLeft, X::topRearRight, X::topSideLeft, X::topSideRight } },
     };