Show warnings if avfilter, especially avfilter.subtitles was not found

Also add it as dependency for mlt to the dev-docs build instructions

dev-docs/build.md

@@ -86,7 +86,7 @@ And if you want to build MLT manually:
 git clone https://github.com/mltframework/mlt.git
 
 # Install MLT dependencies
-sudo apt install libxml++2.6-dev libavformat-dev libswscale-dev libavutil-dev librtaudio-dev
+sudo apt install libxml++2.6-dev libavformat-dev libswscale-dev libavfilter-dev libavutil-dev libsdl1.2-dev librtaudio-dev
 ```
 
 #### Build and install the projects

src/dialogs/wizard.cpp

@@ -404,21 +404,59 @@ void Wizard::checkMltComponents()
         // Check that we have the frei0r effects installed
         Mlt::Properties *filters = pCore->getMltRepository()->filters();
         bool hasFrei0r = false;
-        QString filterName;
         for (int i = 0; i < filters->count(); ++i) {
-            filterName = filters->get_name(i);
+            QString filterName = filters->get_name(i);
             if (filterName.startsWith(QStringLiteral("frei0r."))) {
                 hasFrei0r = true;
                 break;
             }
         }
-        delete filters;
         if (!hasFrei0r) {
             // Frei0r effects not found
             qDebug() << "Missing Frei0r module";
             m_warnings.append(
                 i18n("<li>Missing package: <b>Frei0r</b> effects (frei0r-plugins)<br/>provides many effects and transitions. Install recommended</li>"));
         }
+        if (!hasFrei0r) {
+            // Frei0r effects not found
+            qDebug() << "Missing Frei0r module";
+            m_warnings.append(
+                i18n("<li>Missing package: <b>Frei0r</b> effects (frei0r-plugins)<br/>provides many effects and transitions. Install recommended</li>"));
+        }
+
+        // Check that we have the avfilter effects installed
+        bool hasAvfilter = false;
+        for (int i = 0; i < filters->count(); ++i) {
+            QString filterName = filters->get_name(i);
+            if (filterName.startsWith(QStringLiteral("avfilter."))) {
+                hasAvfilter = true;
+                break;
+            }
+        }
+        if (!hasAvfilter) {
+            // Frei0r effects not found
+            qDebug() << "Missing AVFilter module";
+            m_warnings.append(
+                i18n("<li>Missing package: <b>AVFilter</b><br/>provides many effects. Install recommended</li>"));
+        } else {
+            // Check that we have the avfilter.subtitles effects installed
+            bool hasSubtitle = false;
+            for (int i = 0; i < filters->count(); ++i) {
+                QString filterName = filters->get_name(i);
+                if (filterName == QStringLiteral("avfilter.subtitles")) {
+                    hasSubtitle = true;
+                    break;
+                }
+            }
+            if (!hasAvfilter) {
+                // Frei0r effects not found
+                qDebug() << "Missing avfilter.subtitles module";
+                m_warnings.append(
+                    i18n("<li>Missing filter: <b>avfilter.subtitles</b><br/>required for subtitle feature. Install recommended</li>"));
+            }
+        }
+        delete filters;
+
 
 #if(!(defined(Q_OS_WIN)||defined(Q_OS_MAC)))
         // Check that we have the breeze icon theme installed

src/timeline2/view/qml/timeline.qml

@@ -428,6 +428,7 @@ Rectangle {
     property bool paletteUnchanged: true
     property int maxLabelWidth: 20 * root.baseUnit * Math.sqrt(root.timeScale)
     property bool showSubtitles: false
+    property bool subtitlesWarning: timeline.subtitlesWarning
     property bool subtitlesLocked: timeline.subtitlesLocked
     property bool subtitlesDisabled: timeline.subtitlesDisabled
     property int trackTagWidth: fontMetrics.boundingRect("M").width * ((getAudioTracksCount() > 9) || (trackHeaderRepeater.count - getAudioTracksCount() > 9)  ? 3 : 2)
@@ -944,6 +945,37 @@ Rectangle {
                         width: childrenRect.width
                         x: Math.max(2 * root.collapsedHeight + 2, parent.width - width - 4)
                         spacing: 0
+                        ToolButton {
+                            id: warningButton
+                            visible: subtitlesWarning
+                            focusPolicy: Qt.NoFocus
+                            contentItem: Item {
+                                Image {
+                                    source: "image://icon/data-warning"
+                                    anchors.centerIn: parent
+                                    width: root.collapsedHeight - 4
+                                    height: root.collapsedHeight - 4
+                                    cache: root.paletteUnchanged
+                                }
+                            }
+                            width: root.collapsedHeight
+                            height: root.collapsedHeight
+                            onClicked: timeline.subtitlesWarningDetails()
+                            ToolTip {
+                                visible: warningButton.hovered
+                                font: miniFont
+                                delay: 1500
+                                timeout: 5000
+                                background: Rectangle {
+                                    color: activePalette.alternateBase
+                                    border.color: activePalette.light
+                                }
+                                contentItem: Label {
+                                    color: activePalette.text
+                                    text: i18n("Click to see details")
+                                }
+                            }
+                        }
                         ToolButton {
                             id: analyseButton
                             focusPolicy: Qt.NoFocus

src/timeline2/view/timelinecontroller.cpp

@@ -4806,6 +4806,18 @@ void TimelineController::subtitleSpeechRecognition()
     d.exec();
 }
 
+bool TimelineController::subtitlesWarning() const
+{
+    return !EffectsRepository::get()->hasInternalEffect("avfilter.subtitles");
+}
+
+void TimelineController::subtitlesWarningDetails()
+{
+    KMessageBox::error(nullptr, i18n("The avfilter.subtitles filter is required, but was not found."
+                                     " The subtitles feature will probably not work as expected."));
+    emit regainFocus();
+}
+
 void TimelineController::deleteSubtitle(int startframe, int endframe, const QString &text)
 {
     auto subtitleModel = pCore->getSubtitleModel();

src/timeline2/view/timelinecontroller.h

@@ -71,6 +71,7 @@ class TimelineController : public QObject
     Q_PROPERTY(QColor lockedColor READ lockedColor NOTIFY colorsChanged)
     Q_PROPERTY(QColor selectionColor READ selectionColor NOTIFY colorsChanged)
     Q_PROPERTY(QColor groupColor READ groupColor NOTIFY colorsChanged)
+    Q_PROPERTY(bool subtitlesWarning READ subtitlesWarning)
     Q_PROPERTY(bool subtitlesDisabled READ subtitlesDisabled NOTIFY subtitlesDisabledChanged)
     Q_PROPERTY(bool subtitlesLocked READ subtitlesLocked NOTIFY subtitlesLockedChanged)
     Q_PROPERTY(bool guidesLocked READ guidesLocked NOTIFY guidesLockedChanged)
@@ -177,6 +178,9 @@ public:
     Q_INVOKABLE void showToolTip(const QString &info = QString()) const;
     Q_INVOKABLE void showKeyBinding(const QString &info = QString()) const;
     Q_INVOKABLE void showTimelineToolInfo(bool show) const;
+    /** @brief Returns true if the avfilter.subtiles filter is not found */
+    bool subtitlesWarning() const;
+    Q_INVOKABLE void subtitlesWarningDetails();
     void switchSubtitleDisable();
     bool subtitlesDisabled() const;
     void switchSubtitleLock();