From 36195df44a442041185c729010a0c07bd7adead9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jesu=CC=81s=20A=2E=20A=CC=81lvarez?= <zydeco@namedfork.net>
Date: Fri, 25 Oct 2019 23:11:36 +0200
Subject: [PATCH] make window transparent

---
 BasiliskII/src/MacOSX/utils_macosx.mm | 34 +++++++++++++++++++++++++++
 BasiliskII/src/SDL/video_sdl2.cpp     |  5 ++++
 2 files changed, 39 insertions(+)

diff --git a/BasiliskII/src/MacOSX/utils_macosx.mm b/BasiliskII/src/MacOSX/utils_macosx.mm
index c68d2115..71ad1d3b 100644
--- a/BasiliskII/src/MacOSX/utils_macosx.mm
+++ b/BasiliskII/src/MacOSX/utils_macosx.mm
@@ -52,6 +52,40 @@ void disable_SDL2_macosx_menu_bar_keyboard_shortcuts() {
 	}
 }
 
+void make_window_transparent(SDL_Window * window)
+{
+    if (!window) {
+        return;
+    }
+    
+    SDL_SysWMinfo wmInfo;
+    SDL_VERSION(&wmInfo.version);
+    if (!SDL_GetWindowWMInfo(window, &wmInfo)) {
+        return;
+    }
+    
+    CGColorRef clearColor = [NSColor clearColor].CGColor;
+    NSWindow *cocoaWindow = wmInfo.info.cocoa.window;
+    NSView *sdlView = cocoaWindow.contentView;
+    sdlView.layer.backgroundColor = [NSColor clearColor].CGColor;
+    cocoaWindow.backgroundColor = [NSColor clearColor];
+    cocoaWindow.hasShadow = NO;
+    cocoaWindow.opaque = NO;
+    
+    // make metal layer transparent
+    for (NSView *view in sdlView.subviews) {
+        if ([view.className isEqualToString:@"SDL_cocoametalview"]) {
+            view.layer.opaque = NO;
+            view.layer.backgroundColor = clearColor;
+            return;
+        }
+    }
+
+    // make OpenGL surface transparent
+    GLint zero = 0;
+    [[NSOpenGLContext currentContext] setValues:&zero forParameter:NSOpenGLCPSurfaceOpacity];
+}
+
 bool is_fullscreen_osx(SDL_Window * window)
 {
 	if (!window) {
diff --git a/BasiliskII/src/SDL/video_sdl2.cpp b/BasiliskII/src/SDL/video_sdl2.cpp
index 42247b21..86520abf 100644
--- a/BasiliskII/src/SDL/video_sdl2.cpp
+++ b/BasiliskII/src/SDL/video_sdl2.cpp
@@ -751,6 +751,11 @@ static SDL_Surface * init_sdl_video(int width, int height, int bpp, Uint32 flags
 	}
 	if (flags & SDL_WINDOW_FULLSCREEN) SDL_SetWindowGrab(sdl_window, SDL_TRUE);
 	
+#ifdef __MACOSX__
+    extern void make_window_transparent(SDL_Window * window);
+    make_window_transparent(sdl_window);
+#endif
+    
 	// Some SDL events (regarding some native-window events), need processing
 	// as they are generated.  SDL2 has a facility, SDL_AddEventWatch(), which
 	// allows events to be processed as they are generated.