Add a wrapper around the Win32 window API

meson.build

@@ -57,6 +57,7 @@ executable(
     'src/common/serialization.cpp',
     'src/wine-host/plugin-bridge.cpp',
     'src/wine-host/vst-host.cpp',
+    'src/wine-host/win32-editor.cpp',
   ],
   native : false,
   include_directories : include_dir,

src/wine-host/win32-editor.cpp

@@ -0,0 +1,47 @@
+#include "win32-editor.h"
+
+ATOM register_window_class(std::string window_class_name);
+
+Win32Editor::Win32Editor(std::string window_class_name)
+    : window_class(register_window_class(window_class_name)) {}
+
+HWND Win32Editor::open() {
+    window_handle =
+        std::unique_ptr<std::remove_pointer_t<HWND>, decltype(&DestroyWindow)>(
+            CreateWindowEx(WS_EX_TOOLWINDOW,
+                           reinterpret_cast<LPCSTR>(window_class),
+                           "yabridge plugin", 0, 0, 0, 256, 256, nullptr,
+                           nullptr, GetModuleHandle(nullptr), nullptr),
+            &DestroyWindow);
+
+    return window_handle->get();
+}
+
+void Win32Editor::close() {
+    // RAII does the rest for us
+    window_handle = std::nullopt;
+}
+
+std::optional<intptr_t> Win32Editor::get_x11_handle() {
+    if (!window_handle.has_value()) {
+        return std::nullopt;
+    }
+
+    return reinterpret_cast<intptr_t>(
+        GetProp(window_handle.value().get(), "__wine_x11_whole_window"));
+}
+
+ATOM register_window_class(std::string window_class_name) {
+    WNDCLASSEX window_class{};
+
+    window_class.cbSize = sizeof(WNDCLASSEX);
+    window_class.style = CS_DBLCLKS | CS_HREDRAW | CS_VREDRAW;
+    // TODO: Probably do something here to handle resizes
+    window_class.lpfnWndProc = DefWindowProc;
+    window_class.hInstance = GetModuleHandle(nullptr);
+    window_class.hCursor = LoadCursor(nullptr, IDC_ARROW);
+    window_class.hbrBackground = CreateHatchBrush(HS_CROSS, RGB(255, 0, 255));
+    window_class.lpszClassName = window_class_name.c_str();
+
+    return RegisterClassEx(&window_class);
+}

src/wine-host/win32-editor.h

@@ -0,0 +1,47 @@
+#define NOMINMAX
+#define NOSERVICE
+#define NOMCX
+#define NOIMM
+#define WIN32_LEAN_AND_MEAN
+#include <windows.h>
+
+#include <memory>
+#include <optional>
+#include <string>
+
+/**
+ * A wrapper around the win32 windowing API to create and destroy editor
+ * windows. A VST plugin can embed itself in that window, and we can then later
+ * embed the window in a VST host provided X11 window.
+ */
+class Win32Editor {
+   public:
+    /**
+     * @param window_class_name The name for the window class for editor
+     *   windows.
+     */
+    Win32Editor(std::string window_class_name);
+
+    /**
+     * Open a window and return a handle to the new Win32 window that can be
+     * used by the hosted VST plugin.
+     */
+    HWND open();
+    void close();
+
+    /**
+     * Return the X11 window handle for the window if it's currently open.
+     */
+    std::optional<intptr_t> get_x11_handle();
+
+   private:
+    ATOM window_class;
+
+    /**
+     * A pointer to the currently active window. Will be a null pointer if no
+     * window is active.
+     */
+    std::optional<
+        std::unique_ptr<std::remove_pointer_t<HWND>, decltype(&DestroyWindow)>>
+        window_handle;
+};