export: allow exporting subtitles to sidecar files

app/dialog/export/exportsubtitlestab.cpp

@@ -1,7 +1,6 @@
 #include "exportsubtitlestab.h"
 
 #include <QGridLayout>
-#include <QLabel>
 
 namespace olive {
 
@@ -15,22 +14,46 @@ ExportSubtitlesTab::ExportSubtitlesTab(QWidget *parent) :
 
   int row = 0;
 
+  sidecar_checkbox_ = new QCheckBox(tr("Export to sidecar file"));
+  layout->addWidget(sidecar_checkbox_, row, 0, 1, 2);
+
+  row++;
+
+  sidecar_format_label_ = new QLabel(tr("Sidecar Format:"));
+  sidecar_format_label_->setVisible(false);
+  layout->addWidget(sidecar_format_label_, row, 0);
+
+  sidecar_format_combobox_ = new ExportFormatComboBox(ExportFormatComboBox::kShowSubtitlesOnly);
+  sidecar_format_combobox_->setVisible(false);
+  layout->addWidget(sidecar_format_combobox_, row, 1);
+
+  row++;
+
   layout->addWidget(new QLabel(tr("Codec:")), row, 0);
 
   codec_combobox_ = new QComboBox();
   layout->addWidget(codec_combobox_, row, 1);
 
   outer_layout->addStretch();
+
+  connect(sidecar_checkbox_, &QCheckBox::toggled, sidecar_format_label_, &QWidget::setVisible);
+  connect(sidecar_checkbox_, &QCheckBox::toggled, sidecar_format_combobox_, &QWidget::setVisible);
 }
 
 int ExportSubtitlesTab::SetFormat(ExportFormat::Format format)
 {
   auto scodecs = ExportFormat::GetSubtitleCodecs(format);
-  setEnabled(!scodecs.isEmpty());
+
+  sidecar_checkbox_->setChecked(scodecs.empty());
+  sidecar_checkbox_->setEnabled(!scodecs.empty());
+
+  scodecs = ExportFormat::GetSubtitleCodecs(sidecar_format_combobox_->GetFormat());
+
   codec_combobox_->clear();
   foreach (ExportCodec::Codec scodec, scodecs) {
     codec_combobox_->addItem(ExportCodec::GetCodecName(scodec), scodec);
   }
+
   return scodecs.size();
 }