use field names and id for stable parameter state serialization

Author: bandithedoge

src/clap/extensions/parameters.zig

@@ -86,7 +86,7 @@ pub fn extension(comptime Plugin: type) *const c.clap_plugin_params_t {
 
             switch (param) {
                 inline else => |p| p.format(writer, @TypeOf(p).fromFloat(value)) catch {
-                    log.err("failed to format parameter '{s}': {}", .{ p.options.name, value });
+                    log.err("failed to format parameter '{s}': {}", .{ p.options.id.?, value });
                     return false;
                 },
             }
@@ -119,7 +119,7 @@ pub fn extension(comptime Plugin: type) *const c.clap_plugin_params_t {
 
             out.?.* = switch (param) {
                 inline else => |p| @TypeOf(p).toFloat(p.parse(text) catch {
-                    log.err("failed to parse parameter '{s}': {s}", .{ p.options.name, value_text });
+                    log.err("failed to parse parameter '{s}': '{s}'", .{ p.options.id.?, value_text });
                     return false;
                 }),
             };

src/clap/extensions/state.zig

@@ -70,7 +70,7 @@ const Reader = struct {
     }
 };
 
-pub fn extension(comptime Plugin: type) *const c.clap_plugin_state {
+pub fn extension(comptime _: type) *const c.clap_plugin_state {
     const state = struct {
         pub fn save(clap_plugin: [*c]const c.clap_plugin, stream: [*c]const c.clap_ostream) callconv(.c) bool {
             const data = clap.Data.fromClap(clap_plugin);
@@ -84,8 +84,12 @@ pub fn extension(comptime Plugin: type) *const c.clap_plugin_state {
             var map = msgpack.Payload.mapPayload(data.plugin.allocator);
             defer map.free(data.plugin.allocator);
 
-            inline for (data.plugin.parameters.?.slice, std.meta.fields(Plugin.Parameters)) |parameter, field| {
-                map.mapPut(field.name, switch (parameter.*) {
+            for (data.plugin.parameters.?.slice) |parameter| {
+                const id = switch (parameter.*) {
+                    inline else => |*p| p.options.id.?,
+                };
+
+                map.mapPut(id, switch (parameter.*) {
                     .bool => |p| .boolToPayload(p.get()),
                     .float => |p| .floatToPayload(p.get()),
                     .int => |p| .intToPayload(p.get()),
@@ -100,7 +104,7 @@ pub fn extension(comptime Plugin: type) *const c.clap_plugin_state {
                 };
 
                 switch (parameter.*) {
-                    inline else => |p| log.debug("saved parameter '{s}' = {any}", .{ field.name, p.get() }),
+                    inline else => |p| log.debug("saved parameter '{s}' = {any}", .{ id, p.get() }),
                 }
             }
 
@@ -126,9 +130,13 @@ pub fn extension(comptime Plugin: type) *const c.clap_plugin_state {
             };
             defer decoded.free(data.plugin.allocator);
 
-            inline for (data.plugin.parameters.?.slice, std.meta.fields(Plugin.Parameters)) |parameter, field| {
-                if (decoded.mapGet(field.name) catch {
-                    log.err("failed to read parameter '{s}'", .{field.name});
+            for (data.plugin.parameters.?.slice) |parameter| {
+                const id = switch (parameter.*) {
+                    inline else => |*p| p.options.id.?,
+                };
+
+                if (decoded.mapGet(id) catch {
+                    log.err("failed to read parameter '{s}'", .{id});
                     return false;
                 }) |value| {
                     switch (parameter.*) {
@@ -140,7 +148,7 @@ pub fn extension(comptime Plugin: type) *const c.clap_plugin_state {
                 }
 
                 switch (parameter.*) {
-                    inline else => |p| log.debug("read parameter '{s}' = {any}", .{ field.name, p.get() }),
+                    inline else => |p| log.debug("read parameter '{s}' = {any}", .{ id, p.get() }),
                 }
             }
 

src/zigplug/parameters.zig

@@ -6,6 +6,9 @@ pub fn Options(comptime T: type) type {
     return struct {
         /// Human-readable, "pretty" name to be displayed by the host or plugin GUI
         name: [:0]const u8,
+        /// Optional stable and unique identifier that will be used when saving parameter state. If null, the parameters
+        /// struct field name will be used.
+        id: ?[]const u8 = null,
         /// Parameter will be initialized with this value
         default: T,
         // TODO: this should automatically be set for booleans and enums
@@ -150,7 +153,8 @@ pub const Parameter = union(ParameterType) {
         };
     }
 
-    /// Wrap an enum into an integer parameter with automatic formatting
+    /// Wrap an enum into an integer parameter with automatic formatting. The order of enum values should remain stable
+    /// between plugin versions.
     pub fn choice(comptime T: type, comptime options: ChoiceOptions(T)) Parameter {
         switch (@typeInfo(T)) {
             .@"enum" => |info| {

src/zigplug/zigplug.zig

@@ -132,7 +132,7 @@ pub const Plugin = struct {
                                 @compileError("`Parameters` struct field '" ++ field.name ++ "' has no default value");
                         }
                     },
-                    else => @compileError("`Parameters` type is not a struct"),
+                    else => @compileError("`Parameters` is not a struct"),
                 }
 
                 const parameters_context = try allocator.create(Parameters);
@@ -142,12 +142,11 @@ pub const Plugin = struct {
                 var parameters_slice = try allocator.alloc(*Parameter, fields.len);
 
                 inline for (fields, 0..) |field, i| {
-                    if (field.type != Parameter)
-                        @compileError("Parameter '" ++ field.name ++ "' is not of type 'zigplug.Parameter'");
-                    if (field.default_value_ptr == null)
-                        @compileError("Parameter '" ++ field.name ++ "' has no default value");
-
-                    parameters_slice[i] = &@field(parameters_context, field.name);
+                    const param = &@field(parameters_context, field.name);
+                    switch (param.*) {
+                        inline else => |*p| p.options.id = p.options.id orelse field.name,
+                    }
+                    parameters_slice[i] = param;
                 }
 
                 break :blk .{