feat: change event system

this fixes a common use-after-free footgun and removes the need for a
global allocator

README.md

@@ -22,7 +22,9 @@ pub fn init() void {
     // do initialization stuff
 }
 
-pub fn update(ev: zz.Event) void {
+pub fn update() void {
+    var event = zz.getEvent(my_allocator) catch return;
+    defer event.deinit();
     // handle events
 }
 

example/src/main.zig

@@ -16,10 +16,6 @@ var mode: ?zz.types.InputMode = null;
 
 // called on startup
 pub fn init() void {
-    // set zellzig's allocator
-    // This is required to receive events.
-    zz.allocator = gpa.allocator();
-
     // This is required to make zellij close once everything but our plugin is gone.
     zz.api.setSelectable(false);
 
@@ -28,8 +24,11 @@ pub fn init() void {
 }
 
 // called on every event
-pub fn update(ev: zz.Event) void {
+pub fn update() void {
-    switch (ev) {
+    var ev = zz.getEvent(gpa.allocator()) catch return;
+    defer ev.deinit();
+
+    switch (ev.data) {
         .ModeUpdate => |mode_info| mode = mode_info.mode,
         else => {},
     }

src/api.zig

@@ -15,17 +15,17 @@ pub fn sendObj(data: anytype) !void {
 }
 
 /// Receives a JSON object from zellij
-pub fn recvObj(comptime T: type) !zz.OwnedDeserData(T) {
+pub fn recvObj(comptime T: type, alloc: std.mem.Allocator) !zz.OwnedDeserData(T) {
     var stdin = std.io.getStdIn();
 
     const data = (try stdin.reader().readUntilDelimiterOrEofAlloc(
-        zz.allocator.?,
+        alloc,
         '\n',
         std.math.maxInt(usize),
     )) orelse unreachable;
-    defer zz.allocator.?.free(data);
+    defer alloc.free(data);
 
-    return zz.OwnedDeserData(T).deserialize(zz.allocator.?, data);
+    return zz.OwnedDeserData(T).deserialize(alloc, data);
 }
 
 /// Subscribes to the given events.
@@ -49,15 +49,15 @@ pub fn setSelectable(selectable: bool) void {
 }
 
 /// Returns the ID of this plugin, and zellij's PID.
-pub fn getPluginIds() !zz.OwnedDeserData(types.PluginIds) {
+pub fn getPluginIds(alloc: std.mem.Allocator) !zz.OwnedDeserData(types.PluginIds) {
     zapi.host_get_plugin_ids();
-    return try recvObj(types.PluginIds);
+    return try recvObj(types.PluginIds, alloc);
 }
 
 /// Returns zellij's version string.
-pub fn getZellijVersion() !zz.OwnedDeserData([]const u8) {
+pub fn getZellijVersion(alloc: std.mem.Allocator) !zz.OwnedDeserData([]const u8) {
     zapi.host_get_zellij_version();
-    return try recvObj([]const u8);
+    return try recvObj([]const u8, alloc);
 }
 
 pub fn openFile(path: []const u8) !void {

src/main.zig

@@ -19,22 +19,26 @@ test {
 /// ```zig
 /// // main.zig
 /// const zz = @import("zellzig");
+///
+/// const gpa = std.heap.GeneralPurposeAllocator(.{}){};
+///
 /// comptime {
 ///     zz.createPlugin(@This());
 /// }
 ///
-/// pub fn init() void {
+/// pub fn init() void {}
-///     const alloc = std.heap.GeneralPurposeAllocator(.{}){};
+/// pub fn update(event: zz.Event) void {
-///     zz.allocator = alloc.allocator();
+///     var event = zz.getEvent(gpa.allocator()) catch return;
+///     defer event.deinit();
+///     // use event
 /// }
-/// pub fn update(event: zz.Event) void {}
 /// pub fn render(rows: i32, cols: i32) void {}
 /// ```
 pub fn createPlugin(comptime Plugin: type) void {
     if (@TypeOf(Plugin.init) != fn () void)
         @compileError("Function 'init' has invalid signature!");
 
-    if (@TypeOf(Plugin.update) != fn (Event) void)
+    if (@TypeOf(Plugin.update) != fn () void)
         @compileError("Function 'update' has invalid signature!");
 
     if (@TypeOf(Plugin.render) != fn (i32, i32) void)
@@ -50,17 +54,11 @@ pub fn createPlugin(comptime Plugin: type) void {
         }
 
         export fn update() void {
-            if (allocator == null) {
+            Plugin.update();
-                @panic("Got event while allocator is null! Did you forget to set it?");
-            }
-
-            var ev = api.recvObj(types.Event) catch |err| {
-                std.log.err("Deserialize error: {}", .{err});
-                return;
-            };
-            defer ev.deinit();
-
-            Plugin.update(ev.data);
         }
     };
 }
+
+pub fn getEvent(alloc: std.mem.Allocator) !OwnedDeserData(types.Event) {
+    return try api.recvObj(types.Event, alloc);
+}