adding support for initial centered Windows

examples/helloworld/go.mod

@@ -3,5 +3,3 @@ module helloworld
 go 1.12
 
 replace github.com/mojbro/gocoa => ../../
-
-require github.com/mojbro/gocoa v0.0.0-00010101000000-000000000000 // indirect

examples/helloworld/helloworld.go

@@ -18,8 +18,9 @@ func main() {
 	gocoa.OnApplicationDidFinishLaunching(func() {
 		fmt.Println("App running!")
 	})
-	wnd = gocoa.NewWindow(windowTitle, 150, 150, 300, 200)
-
+	wnd = gocoa.NewCenteredWindow(windowTitle, 300, 200)
+	fmt.Printf("created window: %v\n", wnd)
+	fmt.Printf("screen size %v\n", wnd.GetScreen())
 	wnd.OnDidMove(func(uwnd *gocoa.Window) {
 		fmt.Printf("old: %v\nnew: %v\n", wnd, uwnd)
 	})

window.go

@@ -30,6 +30,12 @@ type Window struct {
 	winPtr    unsafe.Pointer
 }
 
+// Screen the screen of the window.
+type Screen struct {
+	X int
+	Y int
+}
+
 var windows []*Window
 
 // NewWindow constructs and returns a new window.
@@ -49,6 +55,30 @@ func NewWindow(title string, x int, y int, w int, h int) *Window {
 	return wnd
 }
 
+// NewCenteredWindow constructs and returns a new window.
+func NewCenteredWindow(title string, w int, h int) *Window {
+	windowID := len(windows)
+	cTitle := C.CString(title)
+	defer C.free(unsafe.Pointer(cTitle))
+	wnd := &Window{
+		title:     title,
+		w:         w,
+		h:         h,
+		callbacks: make(map[WindowEvent]EventHandler),
+		winPtr:    C.Centered_Window_New(C.int(windowID), C.int(w), C.int(h), cTitle)}
+	wnd.x = int(C.Screen_Center_X(wnd.winPtr))
+	wnd.y = int(C.Screen_Center_Y(wnd.winPtr))
+	windows = append(windows, wnd)
+	return wnd
+}
+
+// GetScreen - returns the screen dimensions
+func (wnd *Window) GetScreen() *Screen {
+	return &Screen{
+		X: int(C.Screen_X(wnd.winPtr)),
+		Y: int(C.Screen_Y(wnd.winPtr))}
+}
+
 // MakeKeyAndOrderFront moves the window to the front of the screen list, within its
 // level and it shows the window.
 func (wnd *Window) MakeKeyAndOrderFront() {

window.h

@@ -6,6 +6,11 @@
 #include "progressIndicator.h"
 
 void* Window_New(int goWindowID, int x, int y, int width, int height, const char* title);
+void* Centered_Window_New(int goWindowID, int width, int height, const char* title);
+int Screen_Center_X(void *wndPtr);
+int Screen_Center_Y(void *wndPtr);
+int Screen_X(void *wndPtr);
+int Screen_Y(void *wndPtr);
 void Window_MakeKeyAndOrderFront(void *wndPtr);
 void Window_AddButton(void *wndPtr, ButtonPtr btnPtr);
 void Window_AddTextView(void *wndPtr, TextViewPtr tvPtr);

window.m

@@ -20,6 +20,52 @@
     return window;
 }
 
+void* Centered_Window_New(int goWindowID, int width, int height, const char* title) 
+{
+    NSRect windowRect = NSMakeRect(0, 0, width, height);
+    id window = [[NSWindow alloc] initWithContentRect:windowRect 
+        styleMask:(NSWindowStyleMaskTitled | NSWindowStyleMaskClosable | NSWindowStyleMaskResizable | NSWindowStyleMaskMiniaturizable)
+        backing:NSBackingStoreBuffered
+        defer:NO];
+    [window setTitle:[NSString stringWithUTF8String:title]];
+    [window autorelease];
+    CGFloat xPos = NSWidth([[window screen] frame])/2 - NSWidth([window frame])/2;
+    CGFloat yPos = NSHeight([[window screen] frame])/2 - NSHeight([window frame])/2;
+    gocoa_windowDelegate = [[WindowDelegate alloc] init];
+    [gocoa_windowDelegate setGoWindowID:goWindowID];
+    [window setDelegate:gocoa_windowDelegate];
+    [window setFrame:NSMakeRect(xPos, yPos, NSWidth([window frame]), NSHeight([window frame])) display:YES];
+    return window;
+}
+
+int Screen_Center_X(void *wndPtr)
+{
+    NSWindow* window = (NSWindow*)wndPtr;
+    CGFloat xPos = NSWidth([[window screen] frame])/2 - NSWidth([window frame])/2;
+    return (int)(xPos);
+}
+
+int Screen_Center_Y(void *wndPtr)
+{
+    NSWindow* window = (NSWindow*)wndPtr;
+    CGFloat yPos = NSHeight([[window screen] frame])/2 - NSHeight([window frame])/2;
+    return (int)(yPos);
+}
+
+int Screen_X(void *wndPtr)
+{
+    NSWindow* window = (NSWindow*)wndPtr;
+    CGFloat xPos = NSWidth([[window screen] frame]);
+    return (int)(xPos);
+}
+
+int Screen_Y(void *wndPtr)
+{
+    NSWindow* window = (NSWindow*)wndPtr;
+    CGFloat yPos = NSHeight([[window screen] frame]);
+    return (int)(yPos);
+}
+
 void Window_MakeKeyAndOrderFront(void *wndPtr)
 {
     NSWindow* window = (NSWindow*)wndPtr;