From 338f89679dfadffdab39614c082191b1ca8c3f29 Mon Sep 17 00:00:00 2001
From: Mitchell Hashimoto <mitchell.hashimoto@gmail.com>
Date: Mon, 3 Jul 2023 19:44:06 -0700
Subject: [PATCH] apprt: add C API for detecting background transparency per
 surface

---
 include/ghostty.h                       | 1 +
 macos/Sources/Ghostty/SurfaceView.swift | 9 +++++++++
 src/apprt/embedded.zig                  | 5 +++++
 3 files changed, 15 insertions(+)

diff --git a/include/ghostty.h b/include/ghostty.h
index 43d478ab1..9b3c6b904 100644
--- a/include/ghostty.h
+++ b/include/ghostty.h
@@ -276,6 +276,7 @@ void *ghostty_app_userdata(ghostty_app_t);
 ghostty_surface_t ghostty_surface_new(ghostty_app_t, ghostty_surface_config_s*);
 void ghostty_surface_free(ghostty_surface_t);
 ghostty_app_t ghostty_surface_app(ghostty_surface_t);
+bool ghostty_surface_transparent(ghostty_surface_t);
 void ghostty_surface_refresh(ghostty_surface_t);
 void ghostty_surface_set_content_scale(ghostty_surface_t, double, double);
 void ghostty_surface_set_focus(ghostty_surface_t, bool);
diff --git a/macos/Sources/Ghostty/SurfaceView.swift b/macos/Sources/Ghostty/SurfaceView.swift
index 48467e264..bb3db5fa1 100644
--- a/macos/Sources/Ghostty/SurfaceView.swift
+++ b/macos/Sources/Ghostty/SurfaceView.swift
@@ -197,6 +197,15 @@ extension Ghostty {
             ghostty_surface_set_size(surface, UInt32(scaledSize.width), UInt32(scaledSize.height))
         }
         
+        override func viewDidMoveToWindow() {
+            guard let window = self.window else { return }
+            guard let surface = self.surface else { return }
+            guard ghostty_surface_transparent(surface) else { return }
+            window.isOpaque = false
+            window.hasShadow = false
+            window.backgroundColor = .clear
+        }
+        
         override func resignFirstResponder() -> Bool {
             let result = super.resignFirstResponder()
             
diff --git a/src/apprt/embedded.zig b/src/apprt/embedded.zig
index f5a8f899a..a90cef4e5 100644
--- a/src/apprt/embedded.zig
+++ b/src/apprt/embedded.zig
@@ -470,6 +470,11 @@ pub const CAPI = struct {
         return surface.app;
     }
 
+    /// Returns ture if the surface has transparency set.
+    export fn ghostty_surface_transparent(surface: *Surface) bool {
+        return surface.app.config.@"background-opacity" < 1.0;
+    }
+
     /// Tell the surface that it needs to schedule a render
     export fn ghostty_surface_refresh(surface: *Surface) void {
         surface.refresh();