mainthread: Cause panic when trying to run before initialization

internal/mainthread/mainthread.go

@@ -16,18 +16,23 @@ package mainthread
 
 import (
 	"runtime"
+	"sync/atomic"
 )
 
 func init() {
 	runtime.LockOSThread()
 }
 
-var funcs = make(chan func())
+var (
+	started = int32(0)
+	funcs   = make(chan func())
+)
 
 // Loop starts the main-thread loop.
 //
 // Loop must be called on the main thread.
 func Loop(ch <-chan error) error {
+	atomic.StoreInt32(&started, 1)
 	for {
 		select {
 		case f := <-funcs:
@@ -41,6 +46,10 @@ func Loop(ch <-chan error) error {
 
 // Run calls f on the main thread.
 func Run(f func() error) error {
+	if atomic.LoadInt32(&started) == 0 {
+		panic("mainthread: the mainthread loop is not started yet")
+	}
+
 	ch := make(chan struct{})
 	var err error
 	funcs <- func() {

internal/restorable/image.go

@@ -189,6 +189,13 @@ func (i *Image) ReplacePixels(pixels []byte, x, y, width, height int) {
 	}
 	i.image.ReplacePixels(pixels, x, y, width, height)
 
+	// TODO: We wanted to skip copying pixels, but this can cause reading-pixels before the driver is initialized.
+	//
+	// if !IsRestoringEnabled() {
+	//	i.makeStale()
+	//	return
+	// }
+
 	if x == 0 && y == 0 && width == w && height == h {
 		if pixels != nil {
 			if i.basePixels == nil {