Inform VST2 and JUCE plugins about UI scale factor

Signed-off-by: falkTX <falktx@falktx.com>

source/backend/plugin/CarlaPluginJuce.cpp

@@ -371,17 +371,23 @@ public:
 
         if (yesNo)
         {
-            if (fWindow == nullptr)
+            if (juce::AudioProcessorEditor* const editor = fInstance->createEditorIfNeeded())
             {
-                juce::String uiName(pData->name);
-                uiName += " (GUI)";
+                const EngineOptions& opts(pData->engine->getOptions());
 
-                fWindow = new JucePluginWindow(pData->engine->getOptions().frontendWinId);
-                fWindow->setName(uiName);
-            }
+                editor->setScaleFactor(opts.uiScale);
+
+                if (fWindow == nullptr)
+                {
+                    juce::String uiName(pData->name);
+                    uiName += " (GUI)";
+
+                    fWindow = new JucePluginWindow(opts.frontendWinId);
+                    fWindow->setName(uiName);
+                }
 
-            if (juce::AudioProcessorEditor* const editor = fInstance->createEditorIfNeeded())
                 fWindow->show(editor);
+            }
         }
         else
         {

source/backend/plugin/CarlaPluginVST2.cpp

@@ -497,18 +497,16 @@ public:
             if (fUI.window == nullptr)
             {
                 const char* msg = nullptr;
-                const uintptr_t frontendWinId(pData->engine->getOptions().frontendWinId);
+                const EngineOptions& opts(pData->engine->getOptions());
 
 #if defined(CARLA_OS_MAC)
-                fUI.window = CarlaPluginUI::newCocoa(this, frontendWinId, false);
+                fUI.window = CarlaPluginUI::newCocoa(this, opts.frontendWinId, false);
 #elif defined(CARLA_OS_WIN)
-                fUI.window = CarlaPluginUI::newWindows(this, frontendWinId, false);
+                fUI.window = CarlaPluginUI::newWindows(this, opts.frontendWinId, false);
 #elif defined(HAVE_X11)
-                fUI.window = CarlaPluginUI::newX11(this, frontendWinId, false);
+                fUI.window = CarlaPluginUI::newX11(this, opts.frontendWinId, false);
 #else
                 msg = "Unsupported UI type";
-                // unused
-                (void)frontendWinId;
 #endif
 
                 if (fUI.window == nullptr)
@@ -525,6 +523,13 @@ public:
                 value = (intptr_t)fUI.window->getDisplay();
 #endif
 
+                // inform plugin of what UI scale we use
+                dispatcher(effVendorSpecific,
+                           CCONST('P', 'r', 'e', 'S'),
+                           CCONST('A', 'e', 'C', 's'),
+                           nullptr,
+                           opts.uiScale);
+
                 // NOTE: there are far too many broken VST2 plugins, don't bother checking return value
                 if (dispatcher(effEditOpen, 0, value, fUI.window->getPtr()) != 0 || true)
                 {