Added Topmost/Always on Top functionality to MacOS (#154)

* Added a topmost property to WindowOptons and initialized it to false in WindowOption's default method

* Added an mfb_topmost function that sets the window's floating level to NSFloatingWindowLevel so it will be topmost

* Added an extern definition of mfb_topmost and conditionally call it if WindowOptions.topmost is true

* changing mfb_topmost first arg name from win to window to staty consistent with rust extern declaration

src/lib.rs

@@ -185,6 +185,8 @@ pub struct WindowOptions {
     pub scale: Scale,
     /// Adjust how the scaling of the buffer used with update_with_buffer should be done.
     pub scale_mode: ScaleMode,
+    /// Should the window be the topmost window (default: false)
+    pub topmost: bool,
 }
 
 impl Window {
@@ -995,6 +997,7 @@ impl Default for WindowOptions {
             resize: false,
             scale: Scale::X1,
             scale_mode: ScaleMode::Stretch,
+            topmost: false,
         }
     }
 }

src/native/macosx/MacMiniFB.m

@@ -292,6 +292,23 @@ void* mfb_open(const char* name, int width, int height, uint32_t flags, int scal
 
 ///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
 
+// Sets whether window is the topmost window
+void mfb_topmost(void* window, bool topmost)
+{
+
+	OSXWindow* win = (OSXWindow*)window;
+
+	if(topmost)
+	{
+		win.level = NSFloatingWindowLevel; // set level to floating
+	} else 
+	{
+		win.level = 0; // set to default/normal
+	}
+
+}
+///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
+
 static NSString* findAppName(void)
 {
     size_t i;

src/os/macos/mod.rs

@@ -192,6 +192,9 @@ extern "C" {
     fn mfb_create_menu(name: *const c_char) -> *mut c_void;
     fn mfb_remove_menu_at(window: *mut c_void, index: i32);
 
+    /// Sets the whether or not the window is the topmost window
+    fn mfb_topmost(window: *mut c_void, topmost: bool);
+
     fn mfb_add_menu_item(
         menu_item: *mut c_void,
         menu_id: i32,
@@ -288,6 +291,11 @@ impl Window {
                 &mut view_handle,
             );
 
+
+            if opts.topmost { 
+                mfb_topmost(handle, true);
+            }
+
             if handle == ptr::null_mut() {
                 return Err(Error::WindowCreate("Unable to open Window".to_owned()));
             }