use combobox to select v4l2loopback video device

src/v4l2sinkproperties.cpp

@@ -18,6 +18,12 @@
 #include <obs-frontend-api.h>
 #include <util/config-file.h>
 
+#include <linux/videodev2.h>
+#include <sys/ioctl.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <QDir>
+
 V4l2sinkProperties::V4l2sinkProperties(QWidget *parent) :
 	QDialog(parent),
 	ui(new Ui::V4l2sinkProperties)
@@ -35,9 +41,17 @@ V4l2sinkProperties::V4l2sinkProperties(QWidget *parent) :
 	const char* device = config_get_string(config, "V4l2sink", "DevicePath");
 	const char* format = config_get_string(config, "V4l2sink", "Format");
 
+	init_devices(device);
+
 	ui->checkBox_auto->setChecked(autostart);
-	ui->lineEdit_dev->setText(device);
-
+
+	QMapIterator<QString, QString> i(devices);
+	while (i.hasNext()) {
+		i.next();
+		ui->comboBox_device->addItem(i.value(), i.key());
+	}
+	ui->comboBox_device->setCurrentIndex(ui->comboBox_device->findData(device));
+
 	ui->comboBox_format->addItem(V4L2SINK_YUV420, V4L2SINK_YUV420);
 	ui->comboBox_format->addItem(V4L2SINK_NV12, V4L2SINK_NV12);
 	ui->comboBox_format->addItem(V4L2SINK_YUY2, V4L2SINK_YUY2);
@@ -60,6 +74,63 @@ V4l2sinkProperties::~V4l2sinkProperties()
 	delete ui;
 }
 
+void V4l2sinkProperties::init_devices(const char* device)
+{
+	QDir dir("/sys/class/video4linux");
+	dir.setFilter(QDir::Dirs | QDir::NoDotAndDotDot);
+	dir.setSorting(QDir::Name);
+	QFileInfoList list = dir.entryInfoList();
+
+	for (int i = 0; i < list.size(); ++i) {
+		int fd;
+		uint32_t caps;
+		struct v4l2_capability video_cap;
+
+		QFileInfo fileInfo = list.at(i);
+		QString fileName = fileInfo.fileName();
+
+		if (!fileName.startsWith("video"))
+			continue;
+		QString devPath = QString("/dev/%1").arg(fileName);
+
+		if ((fd = ::open(devPath.toLatin1(), O_RDWR | O_NONBLOCK)) == -1) {
+			continue;
+		}
+
+		if (::ioctl(fd, VIDIOC_QUERYCAP, &video_cap) == -1) {
+			::close(fd);
+			continue;
+		}
+
+		if (video_cap.capabilities & V4L2_CAP_DEVICE_CAPS) {
+			caps = video_cap.device_caps;
+		} else {
+			caps = video_cap.capabilities;
+		}
+
+		if (!(caps & V4L2_CAP_VIDEO_CAPTURE)) {
+			::close(fd);
+			continue;
+		}
+
+		if (strcmp((char*) video_cap.driver, "v4l2 loopback") != 0) {
+			::close(fd);
+			continue;
+		}
+
+		/* make sure device names are unique */
+		char dev_name[68];
+		sprintf(dev_name, "%s (%s)", video_cap.card, video_cap.bus_info);
+		devices.insert(devPath, QString::fromLocal8Bit(dev_name));
+		::close(fd);
+	}
+
+	QString cur_device = QString::fromLocal8Bit(device);
+	if (!devices.contains(cur_device)) {
+		devices.remove(cur_device);
+	}
+}
+
 void V4l2sinkProperties::closeEvent(QCloseEvent *event)
 {
 	saveSettings();	
@@ -68,7 +139,7 @@ void V4l2sinkProperties::closeEvent(QCloseEvent *event)
 void V4l2sinkProperties::saveSettings()
 {
 	bool autostart = ui->checkBox_auto->isChecked();
-	QByteArray ba_dev_name = ui->lineEdit_dev->text().toUtf8();
+	QByteArray ba_dev_name = ui->comboBox_device->currentData().toString().toUtf8();
 	QByteArray ba_format = ui->comboBox_format->currentData().toString().
 		toUtf8();
 	config_t* config = obs_frontend_get_global_config();
@@ -85,7 +156,7 @@ void V4l2sinkProperties::onStart()
 {
 	QByteArray ba_format = ui->comboBox_format->currentData().toString()
 		.toUtf8();
-	QByteArray ba_dev_name = ui->lineEdit_dev->text().toUtf8();
+	QByteArray ba_dev_name = ui->comboBox_device->currentData().toString().toUtf8();
 	signal_handler_t *handler = v4l2sink_get_signal_handler();
 	signal_handler_connect(handler, "v4l2close", output_stopped , this);
 	enableStart(false);

src/v4l2sinkproperties.h

@@ -17,6 +17,8 @@
 #define V4L2SINKPROPERTIES_H
 
 #include <QDialog>
+#include <QMap>
+#include <QString>
 #include "v4l2sink.h"
 
 #define V4L2SINK_NV12   "NV12"
@@ -46,7 +48,9 @@ private Q_SLOTS:
 	void onStop();
 
 private:
+	void init_devices(const char* device);
 	Ui::V4l2sinkProperties *ui;
+	QMap<QString, QString> devices;
 };
 
 static void output_started(void *data, calldata_t *cd);

src/v4l2sinkproperties.ui

@@ -79,11 +79,7 @@
       <item>
        <layout class="QVBoxLayout" name="verticalLayout">
         <item>
-         <widget class="QLineEdit" name="lineEdit_dev">
-          <property name="placeholderText">
-           <string>/dev/video0</string>
-          </property>
-         </widget>
+         <widget class="QComboBox" name="comboBox_device"/>
         </item>
         <item>
          <widget class="QComboBox" name="comboBox_format"/>