From f22a41cb05c5cc1bbe8ce391fa918707138afad3 Mon Sep 17 00:00:00 2001
From: "Steinar H. Gunderson" <sgunderson@bigfoot.com>
Date: Wed, 9 Jan 2019 22:34:09 +0100
Subject: [PATCH] Only enable the preview button if we can actually preview
 something.

---
 futatabi/mainwindow.cpp | 26 ++++++++++++++++++++++++++
 futatabi/mainwindow.h   |  1 +
 2 files changed, 27 insertions(+)

diff --git a/futatabi/mainwindow.cpp b/futatabi/mainwindow.cpp
index a7f6f82..4a4c0d6 100644
--- a/futatabi/mainwindow.cpp
+++ b/futatabi/mainwindow.cpp
@@ -342,6 +342,8 @@ void MainWindow::queue_clicked()
 
 void MainWindow::preview_clicked()
 {
+	// See also enable_or_disable_preview_button().
+
 	if (ui->playlist->hasFocus()) {
 		// Allow the playlist as preview iff it has focus and something is selected.
 		QItemSelectionModel *selected = ui->playlist->selectionModel();
@@ -575,6 +577,10 @@ bool MainWindow::eventFilter(QObject *watched, QEvent *event)
 	int scrub_sensitivity = 100;  // pts units per pixel.
 	int wheel_sensitivity = 100;  // pts units per degree.
 
+	if (event->type() == QEvent::FocusIn || event->type() == QEvent::FocusOut) {
+		enable_or_disable_preview_button();
+	}
+
 	unsigned stream_idx = ui->preview_display->get_stream_idx();
 
 	if (watched == ui->clip_list) {
@@ -809,6 +815,8 @@ void MainWindow::preview_single_frame(int64_t pts, unsigned stream_idx, MainWind
 
 void MainWindow::playlist_selection_changed()
 {
+	enable_or_disable_preview_button();
+
 	QItemSelectionModel *selected = ui->playlist->selectionModel();
 	bool any_selected = selected->hasSelection();
 	ui->playlist_duplicate_btn->setEnabled(any_selected);
@@ -1031,6 +1039,24 @@ void MainWindow::highlight_camera_input(int stream_idx)
 	}
 }
 
+void MainWindow::enable_or_disable_preview_button()
+{
+	// Follows the logic in preview_clicked().
+
+	if (ui->playlist->hasFocus()) {
+		// Allow the playlist as preview iff it has focus and something is selected.
+		// TODO: Is this part really relevant?
+		QItemSelectionModel *selected = ui->playlist->selectionModel();
+		if (selected->hasSelection()) {
+			ui->preview_btn->setEnabled(true);
+			return;
+		}
+	}
+
+	// TODO: Perhaps only enable this if something is actually selected.
+	ui->preview_btn->setEnabled(!cliplist_clips->empty());
+}
+
 void MainWindow::set_output_status(const string &status)
 {
 	ui->live_label->setText(QString::fromStdString("Current output (" + status + ")"));
diff --git a/futatabi/mainwindow.h b/futatabi/mainwindow.h
index 8d28611..d7e037c 100644
--- a/futatabi/mainwindow.h
+++ b/futatabi/mainwindow.h
@@ -138,6 +138,7 @@ private:
 	void padding_toggled(double seconds, bool checked);
 
 	void highlight_camera_input(int stream_idx);
+	void enable_or_disable_preview_button();
 
 	template<class Model>
 	void replace_model(QTableView *view, Model **model, Model *new_model);
-- 
2.39.2