Avoid creating a System instance in she::instance()

This is necessary for tests that don't need a System but call the
instance() function anyway.

src/main/main.cpp

@@ -66,7 +66,7 @@ int app_main(int argc, char* argv[])
     MemLeak memleak;
     base::SystemConsole systemConsole;
     app::AppOptions options(argc, const_cast<const char**>(argv));
-    she::ScopedHandle<she::System> system(she::instance());
+    she::ScopedHandle<she::System> system(she::create_system());
     app::App app;
 
     // Change the name of the memory dump file

src/she/alleg4/she.cpp

@@ -233,7 +233,7 @@ public:
 
 };
 
-System* create_system() {
+System* create_system_impl() {
   return new Alleg4System();
 }
 

src/she/osx/view.mm

@@ -20,7 +20,9 @@
 
 #include <Carbon/Carbon.h>      // For VK codes
 
-using namespace she;
+namespace she {
+
+bool osx_is_key_pressed(KeyScancode scancode);
 
 namespace {
 
@@ -74,7 +76,7 @@ KeyModifiers get_modifiers_from_nsevent(NSEvent* event)
   if (nsFlags & NSControlKeyMask) modifiers |= kKeyCtrlModifier;
   if (nsFlags & NSAlternateKeyMask) modifiers |= kKeyAltModifier;
   if (nsFlags & NSCommandKeyMask) modifiers |= kKeyCmdModifier;
-  if (she::instance()->isKeyPressed(kKeySpace)) modifiers |= kKeySpaceModifier;
+  if (osx_is_key_pressed(kKeySpace)) modifiers |= kKeySpaceModifier;
   return (KeyModifiers)modifiers;
 }
 
@@ -119,8 +121,6 @@ CFStringRef get_unicode_from_key_code(NSEvent* event,
 
 } // anonymous namespace
 
-namespace she {
-
 bool osx_is_key_pressed(KeyScancode scancode)
 {
   if (scancode >= 0 && scancode < kKeyScancodes)
@@ -139,6 +139,8 @@ int osx_get_unicode_from_scancode(KeyScancode scancode)
 
 } // namespace she
 
+using namespace she;
+
 @implementation OSXView
 
 - (id)initWithFrame:(NSRect)frameRect

src/she/skia/she.cpp

@@ -24,7 +24,7 @@
 
 namespace she {
 
-System* create_system() {
+System* create_system_impl() {
   return new SkiaSystem();
 }
 

src/she/system.cpp

@@ -12,12 +12,19 @@
 
 namespace she {
 
+static System* g_system = nullptr;
+
+System* create_system_impl();   // Defined on each back-end
+
+System* create_system()
+{
+  ASSERT(!g_system);
+  return g_system = create_system_impl();
+}
+
 System* instance()
 {
-  static System* sys = nullptr;
-  if (!sys)
-    sys = create_system();
-  return sys;
+  return g_system;
 }
 
 } // namespace she

src/tests/test.h

@@ -38,7 +38,7 @@ int main(int argc, char* argv[])
   #ifdef TEST_GUI
     {
       // Do not create a she::System, as we don't need it for testing purposes.
-      //she::ScopedHandle<she::System> system(she::instance());
+      //she::ScopedHandle<she::System> system(she::create_system());
       ui::UISystem uiSystem;
       ui::Manager uiManager;
   #endif

src/ui/accelerator.cpp

@@ -337,6 +337,9 @@ bool Accelerator::isPressed(KeyModifiers modifiers, KeyScancode scancode, int un
 bool Accelerator::isPressed() const
 {
   she::System* sys = she::instance();
+  if (!sys)
+    return false;
+
   KeyModifiers pressedModifiers = sys->keyModifiers();
 
   // Check if this shortcut is only
@@ -358,6 +361,9 @@ bool Accelerator::isPressed() const
 bool Accelerator::isLooselyPressed() const
 {
   she::System* sys = she::instance();
+  if (!sys)
+    return false;
+
   KeyModifiers pressedModifiers = sys->keyModifiers();
 
   if ((m_modifiers & pressedModifiers) != m_modifiers)