Fix macOS hosts providing windowless views on init

Like FLStudio VST3 hosting

dgl/src/pugl.cpp

@@ -237,10 +237,20 @@ double puglGetScaleFactorFromParent(const PuglView* const view)
 {
     const PuglNativeView parent = view->parent ? view->parent : view->transientParent ? view->transientParent : 0;
 #if defined(DISTRHO_OS_MAC)
-    NSWindow* const window = parent != 0 ? [(NSView*)parent window]
-                                         : view->impl->window ? view->impl->window : [view->impl->wrapperView window];
-    NSScreen* const screen = window != nullptr ? [window screen] : [NSScreen mainScreen];
-    return [screen backingScaleFactor];
+    // some of these can return 0 as backingScaleFactor, pick the most relevant valid one
+    const NSWindow* possibleWindows[] = {
+        parent != 0 ? [(NSView*)parent window] : nullptr,
+        view->impl->window,
+        [view->impl->wrapperView window]
+    };
+    for (size_t i=0; i<ARRAY_SIZE(possibleWindows); ++i)
+    {
+        if (possibleWindows[i] == nullptr)
+            continue;
+        if (const double scaleFactor = [[possibleWindows[i] screen] backingScaleFactor])
+            return scaleFactor;
+    }
+    return [[NSScreen mainScreen] backingScaleFactor];
 #elif defined(DISTRHO_OS_WINDOWS)
     const HWND hwnd = parent != 0 ? (HWND)parent : view->impl->hwnd;
     return puglWinGetViewScaleFactor(hwnd);

distrho/src/DistrhoUIVST3.cpp

@@ -306,6 +306,7 @@ public:
         }
         else if (fNeedsResizeFromPlugin)
         {
+            d_stdout("postInit forcely sets size from plugin as %u %u", fUI.getWidth(), fUI.getHeight());
             setSize(fUI.getWidth(), fUI.getHeight());
         }
 
@@ -1478,6 +1479,7 @@ struct dpf_plugin_view : v3_plugin_view_cpp {
             return uivst3->getSize(rect);
 
         d_stdout("dpf_plugin_view::get_size => %p | V3_NOT_INITIALIZED", self);
+        std::memset(rect, 0, sizeof(v3_view_rect));
         view->sizeRequestedBeforeBeingAttached = true;
         return V3_NOT_INITIALIZED;
     }