fix: sheet dismiss no-op

gova.go

@@ -50,12 +50,35 @@ func provideOverlays(s *Scope, a fyne.App, w fyne.Window, bridge *fyneBridge.Fyn
 				fyneBridge.ShowAlert(w, title, message, specs)
 			})
 		},
-		showSheet: func(content View, onDismiss func()) {
+		showSheet: func(content View, onDismiss func()) func() {
 			spec := toSpec(content.viewNode())
+			var (
+				mu       sync.Mutex
+				hideFn   func()
+				canceled bool
+			)
 			fyne.Do(func() {
 				mounted := bridge.Mount(spec)
-				fyneBridge.ShowSheet(w, mounted.Object, onDismiss)
+				hide := fyneBridge.ShowSheet(w, mounted.Object, onDismiss)
+				mu.Lock()
+				if canceled {
+					mu.Unlock()
+					hide()
+					return
+				}
+				hideFn = hide
+				mu.Unlock()
 			})
+			return func() {
+				mu.Lock()
+				canceled = true
+				h := hideFn
+				hideFn = nil
+				mu.Unlock()
+				if h != nil {
+					fyne.Do(h)
+				}
+			}
 		},
 		setTheme: func(t *Theme) {
 			tc := fyneBridge.ThemeConfig{

internal/fyne/overlay.go

@@ -43,12 +43,13 @@ func ShowAlert(win fyne.Window, title, message string, actions []AlertActionSpec
 	d.Show()
 }
 
-func ShowSheet(win fyne.Window, content fyne.CanvasObject, onDismiss func()) {
+func ShowSheet(win fyne.Window, content fyne.CanvasObject, onDismiss func()) func() {
 	wrapped := container.New(layout.NewCustomPaddedLayout(10, 10, 10, 10), content)
 	d := dialog.NewCustom("", "Close", wrapped, win)
 	d.SetOnClosed(onDismiss)
 	d.Resize(fyne.NewSize(400, 300))
 	d.Show()
+	return d.Hide
 }
 
 type AlertActionSpec struct {

overlay.go

@@ -1,9 +1,11 @@
 package gova
 
+import "sync"
+
 type ActionStyle int
 
 const (
-	ActionDefault     ActionStyle = iota
+	ActionDefault ActionStyle = iota
 	ActionCancel
 	ActionDestructive
 )
@@ -20,7 +22,7 @@ var overlayStoreKey = &StoreKey[*overlayFuncs]{Default: nil}
 
 type overlayFuncs struct {
 	showAlert func(title, message string, actions []AlertAction)
-	showSheet func(content View, onDismiss func())
+	showSheet func(content View, onDismiss func()) func()
 	setTheme  func(theme *Theme)
 }
 
@@ -37,19 +39,40 @@ func UseAlert(s *Scope) func(title, message string, actions ...AlertAction) {
 }
 
 // UseSheet returns (show, dismiss) functions for presenting a sheet overlay.
+// dismiss programmatically closes the most recently shown sheet; it is a
+// no-op if no sheet is currently presented (either never shown, already
+// dismissed by the user, or already dismissed programmatically).
 func UseSheet(s *Scope) (show func(content View), dismiss func()) {
 	store := UseStore(s, overlayStoreKey)
 	fns := store.Get()
 
-	var dismissFn func()
+	var (
+		mu     sync.Mutex
+		cancel func()
+	)
 	show = func(content View) {
-		if fns != nil && fns.showSheet != nil {
-			fns.showSheet(content, func() { dismissFn = nil })
+		if fns == nil || fns.showSheet == nil {
+			return
 		}
+		// onDismiss fires when the sheet is closed by any path
+		// (user-driven Close button or programmatic cancel) so the
+		// next dismiss() call doesn't try to cancel a dead sheet.
+		c := fns.showSheet(content, func() {
+			mu.Lock()
+			cancel = nil
+			mu.Unlock()
+		})
+		mu.Lock()
+		cancel = c
+		mu.Unlock()
 	}
 	dismiss = func() {
-		if dismissFn != nil {
-			dismissFn()
+		mu.Lock()
+		c := cancel
+		cancel = nil
+		mu.Unlock()
+		if c != nil {
+			c()
 		}
 	}
 	return show, dismiss

overlay_test.go

@@ -0,0 +1,130 @@
+package gova
+
+import (
+	"context"
+	"testing"
+)
+
+// fakeOverlay records calls and exercises the cancel-handle contract that
+// the real Fyne-backed overlayFuncs implement. Each call to showSheet
+// returns a fresh cancel closure; invoking it counts toward cancelCount
+// and fires the onDismiss callback (mirroring Fyne's CustomDialog, which
+// calls SetOnClosed on programmatic Hide).
+type fakeOverlay struct {
+	showCount   int
+	cancelCount int
+	lastOnDismiss func()
+}
+
+func (f *fakeOverlay) funcs() *overlayFuncs {
+	return &overlayFuncs{
+		showSheet: func(content View, onDismiss func()) func() {
+			f.showCount++
+			f.lastOnDismiss = onDismiss
+			closed := false
+			return func() {
+				if closed {
+					return
+				}
+				closed = true
+				f.cancelCount++
+				if onDismiss != nil {
+					onDismiss()
+				}
+			}
+		},
+	}
+}
+
+func TestUseSheetDismissInvokesCancel(t *testing.T) {
+	scope := newScope(context.Background(), nil)
+	fake := &fakeOverlay{}
+	Provide(scope, overlayStoreKey, fake.funcs())
+
+	show, dismiss := UseSheet(scope)
+
+	show(Text("first"))
+	if fake.showCount != 1 {
+		t.Fatalf("expected 1 showSheet call, got %d", fake.showCount)
+	}
+
+	dismiss()
+	if fake.cancelCount != 1 {
+		t.Fatalf("dismiss did not invoke cancel hook: cancelCount=%d (UseSheet must wire dismiss to the cancel closure returned by showSheet)", fake.cancelCount)
+	}
+}
+
+func TestUseSheetDismissBeforeShowIsNoOp(t *testing.T) {
+	scope := newScope(context.Background(), nil)
+	fake := &fakeOverlay{}
+	Provide(scope, overlayStoreKey, fake.funcs())
+
+	_, dismiss := UseSheet(scope)
+	// Calling dismiss before any show should not panic and should not
+	// invoke any cancel hook (there is nothing to cancel).
+	dismiss()
+	if fake.cancelCount != 0 {
+		t.Fatalf("dismiss before show should be a no-op; cancelCount=%d", fake.cancelCount)
+	}
+}
+
+func TestUseSheetDismissIsIdempotent(t *testing.T) {
+	scope := newScope(context.Background(), nil)
+	fake := &fakeOverlay{}
+	Provide(scope, overlayStoreKey, fake.funcs())
+
+	show, dismiss := UseSheet(scope)
+	show(Text("x"))
+	dismiss()
+	dismiss()
+	dismiss()
+
+	if fake.cancelCount != 1 {
+		t.Fatalf("repeated dismiss should not re-cancel: cancelCount=%d", fake.cancelCount)
+	}
+}
+
+func TestUseSheetUserCloseClearsHandle(t *testing.T) {
+	// Simulates the user clicking the sheet's Close button: Fyne fires
+	// the onDismiss callback directly, without going through the cancel
+	// hook. A subsequent programmatic dismiss() must then be a no-op.
+	scope := newScope(context.Background(), nil)
+	fake := &fakeOverlay{}
+	Provide(scope, overlayStoreKey, fake.funcs())
+
+	show, dismiss := UseSheet(scope)
+	show(Text("x"))
+
+	if fake.lastOnDismiss == nil {
+		t.Fatal("expected showSheet to receive an onDismiss callback")
+	}
+	fake.lastOnDismiss() // user closed the sheet themselves
+
+	dismiss()
+	if fake.cancelCount != 0 {
+		t.Fatalf("dismiss after user-close should be no-op; cancelCount=%d", fake.cancelCount)
+	}
+}
+
+func TestUseSheetReshowGetsFreshCancel(t *testing.T) {
+	scope := newScope(context.Background(), nil)
+	fake := &fakeOverlay{}
+	Provide(scope, overlayStoreKey, fake.funcs())
+
+	show, dismiss := UseSheet(scope)
+
+	show(Text("first"))
+	dismiss()
+	if fake.cancelCount != 1 {
+		t.Fatalf("first dismiss did not cancel: cancelCount=%d", fake.cancelCount)
+	}
+
+	show(Text("second"))
+	if fake.showCount != 2 {
+		t.Fatalf("expected 2 showSheet calls after reshow; got %d", fake.showCount)
+	}
+	dismiss()
+	if fake.cancelCount != 2 {
+		t.Fatalf("dismiss after reshow did not cancel new sheet: cancelCount=%d", fake.cancelCount)
+	}
+}