Keep Linux WebViews on one persistent GTK UI thread

internal/webview/goprovider/mainthread_linux.go

@@ -0,0 +1,47 @@
+//go:build linux && cgo
+
+package goprovider
+
+/*
+#cgo pkg-config: gtk+-3.0
+#include <gtk/gtk.h>
+static void pumpGTK(void) {
+  // Bound each batch so Go creation/removal requests cannot be starved.
+  for (int i = 0; i < 64 && g_main_context_pending(NULL); ++i)
+    g_main_context_iteration(NULL, FALSE);
+}
+*/
+import "C"
+
+import (
+	"runtime"
+	"sync"
+	"time"
+)
+
+var gtkThreadOnce sync.Once
+var gtkThreadTasks = make(chan func())
+
+func RunMainThreadLoop(run func() int) int { return run() }
+
+func postMainThreadTask(task func()) bool {
+	gtkThreadOnce.Do(func() {
+		go func() {
+			runtime.LockOSThread()
+			// WebKit must always use its original UI thread, including after
+			// the last page closes. A page cannot stop this shared event loop.
+			ticker := time.NewTicker(10 * time.Millisecond)
+			defer ticker.Stop()
+			for {
+				select {
+				case task := <-gtkThreadTasks:
+					task()
+				case <-ticker.C:
+				}
+				C.pumpGTK()
+			}
+		}()
+	})
+	gtkThreadTasks <- task
+	return true
+}

internal/webview/goprovider/mainthread_other.go

@@ -1,4 +1,4 @@
-//go:build !darwin
+//go:build !darwin && (!linux || !cgo)
 
 package goprovider
 

internal/webview/goprovider/provider.go

@@ -135,12 +135,18 @@ func (p *pageWrapper) start() error {
 		if err := w.Bind(p.callbackName, func(payload string) error {
 			return p.handleCallback(payload)
 		}); err != nil {
+			w.Destroy()
 			p.ready <- err
+			close(p.done)
 			return
 		}
 
 		applyWindowOptions(w, p.opts)
 		w.SetHtml(buildBootstrapHTML(p.callbackName, p.readyID))
+		if runtimepkg.GOOS == "linux" {
+			// All GTK pages share the process-wide event loop below.
+			return
+		}
 		w.Run()
 		w.Destroy()
 		close(p.done)
@@ -326,7 +332,12 @@ func (p *pageWrapper) Close() error {
 		// the quit message lands on the correct queue.
 		terminateDone := make(chan struct{})
 		w.Dispatch(func() {
-			w.Terminate()
+			if runtimepkg.GOOS == "linux" {
+				w.Destroy()
+				close(p.done)
+			} else {
+				w.Terminate()
+			}
 			close(terminateDone)
 		})
 		<-terminateDone