Added a center method on QMainWindow (#175)

Closes #134

src/cpp/include/nodegui/QtWidgets/QMainWindow/qmainwindow_wrap.h

@@ -20,6 +20,7 @@ public:
   Napi::Value setMenuBar(const Napi::CallbackInfo& info);
   Napi::Value menuBar(const Napi::CallbackInfo& info);
   Napi::Value setMenuWidget(const Napi::CallbackInfo& info);
+  Napi::Value center(const Napi::CallbackInfo &info);
 
   QWIDGET_WRAPPED_METHODS_DECLARATION
 };

src/cpp/lib/QtWidgets/QMainWindow/qmainwindow_wrap.cpp

@@ -1,3 +1,5 @@
+#include <QApplication>
+#include <QDesktopWidget>
 #include "QtWidgets/QMainWindow/qmainwindow_wrap.h"
 #include "QtWidgets/QWidget/qwidget_wrap.h"
 #include "QtWidgets/QMenuBar/qmenubar_wrap.h"
@@ -13,6 +15,7 @@ Napi::Object QMainWindowWrap::init(Napi::Env env, Napi::Object exports) {
     InstanceMethod("setCentralWidget",&QMainWindowWrap::setCentralWidget),
     InstanceMethod("setMenuBar",&QMainWindowWrap::setMenuBar),
     InstanceMethod("setMenuWidget",&QMainWindowWrap::setMenuWidget),
+    InstanceMethod("center",&QMainWindowWrap::center),
   });
   constructor = Napi::Persistent(func);
   exports.Set(CLASSNAME, func);
@@ -84,3 +87,20 @@ Napi::Value QMainWindowWrap::setMenuWidget(const Napi::CallbackInfo& info){
   return env.Null();
 }
 
+Napi::Value QMainWindowWrap::center(const Napi::CallbackInfo &info) {
+  Napi::Env env = info.Env();
+  Napi::HandleScope scope(env);
+
+  auto window = this->getInternalInstance();
+  // https://wiki.qt.io/How_to_Center_a_Window_on_the_Screen
+  window->setGeometry(
+    QStyle::alignedRect(
+      Qt::LeftToRight,
+      Qt::AlignCenter,
+      window->size(),
+      QApplication::desktop()->availableGeometry(window)
+    )
+  );
+
+  return env.Null();
+}

src/demo.ts

@@ -10,6 +10,9 @@ import { QKeySequence } from "./lib/QtGui/QKeySequence";
 import { ShortcutContext } from "./lib/QtEnums";
 import { QMenuBar } from "./lib/QtWidgets/QMenuBar";
 import { QShortcut, QShortcutEvents } from "./lib/QtWidgets/QShortcut";
+import { QPushButton } from "./lib/QtWidgets/QPushButton";
+import { FlexLayout } from "./lib/core/FlexLayout";
+import { QWidget } from "./lib/QtWidgets/QWidget";
 
 const win = new QMainWindow();
 const shortcut = new QShortcut(win);
@@ -93,16 +96,36 @@ quitAction.addEventListener("triggered", () => {
 menu.addAction(quitAction);
 
 menu.setTitle("TestMenu");
-const label = new QLabel();
-label.setOpenExternalLinks(true);
-label.setText(`<a href="https://www.google.com">Google</a>`);
-label.show();
-(global as any).label = label;
-win.setWindowTitle("NodeGUI Demo");
-win.resize(400, 700);
-win.show();
 // menuBar.addMenu(menu);
 
+const button = new QPushButton();
+button.setText("Center");
+button.addEventListener("clicked", () => {
+  win.center();
+});
+
+const rootView = new QWidget();
+
+rootView.setObjectName("root");
+rootView.setLayout(new FlexLayout());
+if (rootView.layout) {
+  rootView.layout.addWidget(button);
+}
+
+win.setCentralWidget(rootView);
+win.setStyleSheet(`
+  #root {
+    flex: 1;
+    height: '100%';
+    align-items: 'center';
+    justify-content: 'center';
+  }
+`);
+
+win.setWindowTitle("NodeGUI Demo");
+win.show();
+win.resize(400, 700);
+
 const qApp = QApplication.instance();
 qApp.setQuitOnLastWindowClosed(false);
 

src/lib/QtWidgets/QMainWindow/index.ts

@@ -56,4 +56,7 @@ export class QMainWindow extends NodeWidget {
       return super.layout;
     }
   }
+  center() {
+    this.native.center();
+  }
 }