setup app, run works but crashes in OpenGL

src/apprt/gtk.zig

@@ -30,6 +30,16 @@ pub const App = struct {
         )) orelse return error.GtkInitFailed;
         errdefer c.g_object_unref(app);
 
+        // Setup our callbacks
+        _ = c.g_signal_connect_data(
+            app,
+            "activate",
+            c.G_CALLBACK(&activate),
+            null,
+            null,
+            c.G_CONNECT_DEFAULT,
+        );
+
         // We don't use g_application_run, we want to manually control the
         // loop so we have to do the same things the run function does:
         // https://github.com/GNOME/glib/blob/a8e8b742e7926e33eb635a8edceac74cf239d6ed/gio/gapplication.c#L2533
@@ -51,6 +61,9 @@ pub const App = struct {
             return error.GtkApplicationRegisterFailed;
         }
 
+        // This just calls the "activate" signal but its part of the normal
+        // startup routine so we just call it:
+        // https://gitlab.gnome.org/GNOME/glib/-/blob/bd2ccc2f69ecfd78ca3f34ab59e42e2b462bad65/gio/gapplication.c#L2302
         c.g_application_activate(gapp);
 
         return .{ .app = app, .ctx = ctx };
@@ -71,6 +84,12 @@ pub const App = struct {
     pub fn wait(self: App) !void {
         _ = c.g_main_context_iteration(self.ctx, 1);
     }
+
+    fn activate(app: *c.GtkApplication, ud: ?*anyopaque) callconv(.C) void {
+        _ = app;
+        _ = ud;
+        log.debug("application activated", .{});
+    }
 };
 
 pub const Window = struct {

src/main.zig

@@ -101,9 +101,8 @@ pub fn main() !void {
     // Run our app with a single initial window to start.
     var app = try App.create(alloc, .{}, &config);
     defer app.destroy();
-    try app.run();
-    if (build_config.app_runtime == .gtk) return;
     _ = try app.newWindow(.{});
+    try app.run();
 }
 
 // Required by tracy/tracy.zig to enable/disable tracy support.

src/renderer/OpenGL.zig

@@ -420,34 +420,53 @@ pub fn deinitDevMode(self: *const OpenGL) void {
 /// Callback called by renderer.Thread when it begins.
 pub fn threadEnter(self: *const OpenGL, win: apprt.runtime.Window) !void {
     _ = self;
-    if (apprt.runtime == apprt.gtk) @panic("TODO");
 
-    // We need to make the OpenGL context current. OpenGL requires
-    // that a single thread own the a single OpenGL context (if any). This
-    // ensures that the context switches over to our thread. Important:
-    // the prior thread MUST have detached the context prior to calling
-    // this entrypoint.
-    glfw.makeContextCurrent(win.window);
-    errdefer glfw.makeContextCurrent(null);
-    glfw.swapInterval(1);
+    switch (apprt.runtime) {
+        else => @compileError("unsupported app runtime for OpenGL"),
 
-    // Load OpenGL bindings. This API is context-aware so this sets
-    // a threadlocal context for these pointers.
-    const version = try gl.glad.load(&glfw.getProcAddress);
-    errdefer gl.glad.unload();
-    log.info("loaded OpenGL {}.{}", .{
-        gl.glad.versionMajor(@intCast(c_uint, version)),
-        gl.glad.versionMinor(@intCast(c_uint, version)),
-    });
+        apprt.gtk => {
+            // GTK doesn't support threaded OpenGL operations as far as I can
+            // tell, so we use the renderer thread to setup all the state
+            // but then do the actual draws and texture syncs and all that
+            // on the main thread. As such, we don't do anything here.
+        },
+
+        apprt.glfw => {
+            // We need to make the OpenGL context current. OpenGL requires
+            // that a single thread own the a single OpenGL context (if any). This
+            // ensures that the context switches over to our thread. Important:
+            // the prior thread MUST have detached the context prior to calling
+            // this entrypoint.
+            glfw.makeContextCurrent(win.window);
+            errdefer glfw.makeContextCurrent(null);
+            glfw.swapInterval(1);
+
+            // Load OpenGL bindings. This API is context-aware so this sets
+            // a threadlocal context for these pointers.
+            const version = try gl.glad.load(&glfw.getProcAddress);
+            errdefer gl.glad.unload();
+            log.info("loaded OpenGL {}.{}", .{
+                gl.glad.versionMajor(@intCast(c_uint, version)),
+                gl.glad.versionMinor(@intCast(c_uint, version)),
+            });
+        },
+    }
 }
 
 /// Callback called by renderer.Thread when it exits.
 pub fn threadExit(self: *const OpenGL) void {
     _ = self;
-    if (apprt.runtime == apprt.gtk) @panic("TODO");
 
-    gl.glad.unload();
-    glfw.makeContextCurrent(null);
+    switch (apprt.runtime) {
+        else => @compileError("unsupported app runtime for OpenGL"),
+
+        apprt.gtk => {},
+
+        apprt.glfw => {
+            gl.glad.unload();
+            glfw.makeContextCurrent(null);
+        },
+    }
 }
 
 /// Callback when the focus changes for the terminal this is rendering.