Add an option to disable VST3 content scaling

This might be necessary when using a HiDPI screen as plugin GUIs often
don't scale correctly under Wine.

src/common/configuration.cpp

@@ -113,6 +113,12 @@ Configuration::Configuration(const fs::path& config_path,
                 } else {
                     invalid_options.push_back(key);
                 }
+            } else if (key == "vst3_no_scaling") {
+                if (const auto parsed_value = value.as_boolean()) {
+                    vst3_no_scaling = parsed_value->get();
+                } else {
+                    invalid_options.push_back(key);
+                }
             } else {
                 unknown_options.push_back(key);
             }

src/common/configuration.h

@@ -122,6 +122,15 @@ class Configuration {
      */
     std::optional<float> frame_rate;
 
+    /**
+     * Disable `IPlugViewContentScaleSupport::setContentScaleFactor()`. Wine
+     * does not properly implement DPI scaling, so without this option plugins
+     * using GDI+ would draw their editor GUIs at the normal size even though
+     * their window would actually be scaled. That would result in giant black
+     * borders at the top and the right of the window.
+     */
+    bool vst3_no_scaling = false;
+
     /**
      * The name of the plugin group that should be used for the plugin this
      * configuration object was created for. If not set, then the plugin should
@@ -165,6 +174,7 @@ class Configuration {
         s.value1b(editor_xembed);
         s.ext(frame_rate, bitsery::ext::StdOptional(),
               [](S& s, auto& v) { s.value4b(v); });
+        s.value1b(vst3_no_scaling);
         s.ext(group, bitsery::ext::StdOptional(),
               [](S& s, auto& v) { s.text1b(v, 4096); });
 

src/plugin/bridges/common.h

@@ -171,6 +171,9 @@ class PluginBridge {
                    << *config.frame_rate << " fps";
             other_options.push_back(option.str());
         }
+        if (config.vst3_no_scaling) {
+            other_options.push_back("vst3: no GUI scaling");
+        }
         if (!other_options.empty()) {
             init_msg << join_quoted_strings(other_options) << std::endl;
         } else {

src/wine-host/bridges/vst3.cpp

@@ -742,15 +742,26 @@ void Vst3Bridge::run() {
             [&](YaPlugViewContentScaleSupport::SetContentScaleFactor& request)
                 -> YaPlugViewContentScaleSupport::SetContentScaleFactor::
                     Response {
-                        return main_context
-                            .run_in_context<tresult>([&]() {
-                                return object_instances[request
-                                                            .owner_instance_id]
-                                    .plug_view_instance
-                                    ->plug_view_content_scale_support
-                                    ->setContentScaleFactor(request.factor);
-                            })
-                            .get();
+                        if (config.vst3_no_scaling) {
+                            std::cerr << "The host requested the editor GUI to "
+                                         "be scaled by a factor of "
+                                      << request.factor
+                                      << ", but the 'vst3_no_scale' option is "
+                                         "enabled. Ignoring the request."
+                                      << std::endl;
+                            return Steinberg::kResultFalse;
+                        } else {
+                            return main_context
+                                .run_in_context<tresult>([&]() {
+                                    return object_instances
+                                        [request.owner_instance_id]
+                                            .plug_view_instance
+                                            ->plug_view_content_scale_support
+                                            ->setContentScaleFactor(
+                                                request.factor);
+                                })
+                                .get();
+                        }
                     },
             [&](YaPluginBase::Initialize& request)
                 -> YaPluginBase::Initialize::Response {