Harden icon cache concurrency (T-606)

app-modern/ui/gio/shell_test.go

@@ -61,6 +61,8 @@ func TestAppShellKeepsRowControlsByAppID(t *testing.T) {
 	}
 	shell := NewAppShell("Modern", items...)
 	original := shell.rows["app-two"]
+	shell.ApplyIcon("app-one", image.NewNRGBA(image.Rect(0, 0, 16, 16)))
+	shell.ApplyIcon("app-two", image.NewNRGBA(image.Rect(0, 0, 24, 24)))
 
 	shell.model.SetCategory("图像")
 	shell.Layout(testContext(image.Pt(1080, 720)), NewTheme())
@@ -77,6 +79,16 @@ func TestAppShellKeepsRowControlsByAppID(t *testing.T) {
 	if _, exists := shell.rows["app-one"]; exists {
 		t.Fatal("removed app retained row controls")
 	}
+	if _, exists := shell.icons["app-one"]; exists {
+		t.Fatal("removed app retained prepared icon")
+	}
+	icon, exists := shell.icons["app-two"]
+	if !exists {
+		t.Fatal("retained app lost its prepared icon")
+	}
+	if icon.Size() != image.Pt(24, 24) {
+		t.Fatalf("retained app icon size = %v", icon.Size())
+	}
 }
 
 func TestAppShellRendersSelectedDetailAndAppliedIcon(t *testing.T) {