UI: Resize main preview on the widget's resize signal

Fixes a bug where the preview's size calculations wouldn't update if the
widget itself was resizes but the window wasn't resized.

obs/window-basic-main.cpp

@@ -162,12 +162,15 @@ OBSBasic::OBSBasic(QWidget *parent)
 	ui->scenes->setAttribute(Qt::WA_MacShowFocusRect, false);
 	ui->sources->setAttribute(Qt::WA_MacShowFocusRect, false);
 
-	connect(windowHandle(), &QWindow::screenChanged, [this]() {
+	auto displayResize = [this]() {
 		struct obs_video_info ovi;
 
 		if (obs_get_video_info(&ovi))
 			ResizePreview(ovi.base_width, ovi.base_height);
-	});
+	};
+
+	connect(windowHandle(), &QWindow::screenChanged, displayResize);
+	connect(ui->preview, &OBSQTDisplay::DisplayResized, displayResize);
 
 	installEventFilter(CreateShortcutFilter());
 
@@ -2312,16 +2315,6 @@ void OBSBasic::changeEvent(QEvent *event)
 	UNUSED_PARAMETER(event);
 }
 
-void OBSBasic::resizeEvent(QResizeEvent *event)
-{
-	struct obs_video_info ovi;
-
-	if (obs_get_video_info(&ovi))
-		ResizePreview(ovi.base_width, ovi.base_height);
-
-	OBSMainWindow::resizeEvent(event);
-}
-
 void OBSBasic::on_actionShow_Recordings_triggered()
 {
 	const char *mode = config_get_string(basicConfig, "Output", "Mode");

obs/window-basic-main.hpp

@@ -301,7 +301,6 @@ public:
 protected:
 	virtual void closeEvent(QCloseEvent *event) override;
 	virtual void changeEvent(QEvent *event) override;
-	virtual void resizeEvent(QResizeEvent *event) override;
 
 private slots:
 	void on_actionShow_Recordings_triggered();