apprt/embedded: add occlusion state callback

src/Surface.zig

@@ -1527,6 +1527,16 @@ pub fn textCallback(self: *Surface, text: []const u8) !void {
     try self.completeClipboardPaste(text, true);
 }
 
+/// Callback for when the surface is fully visible or not, regardless
+/// of focus state. This is used to pause rendering when the surface
+/// is not visible, and also re-render when it becomes visible again.
+pub fn occlusionCallback(self: *Surface, visible: bool) !void {
+    // If we became visible, then we queue a render. This helps scenarios
+    // where the apprt pauses rendering when the surface is not visible,
+    // i.e. macOS with Metal (see issue #1510).
+    if (visible) try self.queueRender();
+}
+
 pub fn focusCallback(self: *Surface, focused: bool) !void {
     // Notify our render thread of the new state
     _ = self.renderer_thread.mailbox.push(.{

src/apprt/embedded.zig

@@ -945,6 +945,13 @@ pub const Surface = struct {
         };
     }
 
+    pub fn occlusionCallback(self: *Surface, visible: bool) void {
+        self.core_surface.occlusionCallback(visible) catch |err| {
+            log.err("error in occlusion callback err={}", .{err});
+            return;
+        };
+    }
+
     pub fn gotoTab(self: *Surface, n: usize) void {
         const func = self.app.opts.goto_tab orelse {
             log.info("runtime embedder does not goto_tab", .{});
@@ -1546,6 +1553,11 @@ pub const CAPI = struct {
         surface.focusCallback(focused);
     }
 
+    /// Update the occlusion state of a surface.
+    export fn ghostty_surface_set_occlusion(surface: *Surface, visible: bool) void {
+        surface.occlusionCallback(visible);
+    }
+
     /// Filter the mods if necessary. This handles settings such as
     /// `macos-option-as-alt`. The filtered mods should be used for
     /// key translation but should NOT be sent back via the `_key`