ui/video-presets: Fix locked preset not activating reliably

Fixes a few bugs associated with locked presets. Restoring the selected
preset index is no longer dependent on the order of the presets in the
GUI, the output window's title bar is now updated with the title of the
locked preset when VCS starts up, and locked presets now apply correctly
when VCS is started while there's no capture signal.

src/capture/video_presets.cpp

@@ -95,8 +95,10 @@ void kvideopreset_lock(const bool isLocked)
 
 void kvideopreset_activate_preset(const video_preset_s *const preset)
 {
-    if (LOCKED || !kc_has_signal() || !preset)
-    {
+    if (
+        !preset ||
+        (LOCKED && (preset != MOST_RECENT_ACTIVE_PRESET))
+    ){
         return;
     }
 
@@ -150,12 +152,12 @@ void kvideopreset_remove_all_presets(void)
 
 void kvideopreset_apply_current_active_preset(void)
 {
-    if (LOCKED || !kc_has_signal())
+    if (!kc_has_signal())
     {
         return;
     }
 
-    const video_preset_s *activePreset = strongest_activating_preset();
+    const video_preset_s *activePreset = (LOCKED? MOST_RECENT_ACTIVE_PRESET : strongest_activating_preset());
 
     if (activePreset)
     {
@@ -266,6 +268,16 @@ void video_properties_s::to_capture_device_properties(
     const std::string &nameSpace
 )
 {
+#if defined(CAPTURE_BACKEND_VISION_V4L) || defined(CAPTURE_BACKEND_GENERIC_V4L)
+    // If the namespace is empty, the values would modify the current capture
+    // parameters. But if there's no signal, the parameters won't be available
+    // for modification via V4L and we'd be wasting time trying to change them.
+    if (!kc_has_signal() && nameSpace.empty())
+    {
+        return;
+    }
+#endif
+
     for (const auto &[propName, value]: properties)
     {
         kc_set_device_property((propName + nameSpace), value);

src/capture/vision_v4l/ic_v4l_video_parameters.cpp

@@ -29,7 +29,7 @@ bool ic_v4l_controls_c::set_value(const int newValue, const ic_v4l_controls_c::t
 {
     if (this->v4l_id(control) < 0)
     {
-        DEBUG(("Asked to modify an unrecognized V4L control. Ignoring it."));
+        DEBUG(("Asked to modify a V4L control that isn't available. Ignoring this."));
         return false;
     }
 

src/display/qt/widgets/VideoPresetList.cpp

@@ -129,6 +129,21 @@ int VideoPresetList::find_preset_idx_in_list(const int presetId)
     return -1;
 }
 
+int VideoPresetList::find_preset_idx_in_list(const QString &targetLabel)
+{
+    for (int i = 0; i < this->count(); i++)
+    {
+        const auto *preset = kvideopreset_get_preset_ptr(this->itemData(i).toUInt());
+        const auto label = this->make_preset_item_label(preset);
+        if (label == targetLabel)
+        {
+            return i;
+        }
+    }
+
+    return -1;
+}
+
 void VideoPresetList::update_preset_item_label(const unsigned presetId)
 {
     const auto *const preset = kvideopreset_get_preset_ptr(presetId);

src/display/qt/widgets/VideoPresetList.h

@@ -22,8 +22,7 @@ class VideoPresetList : public QComboBox
 
     ~VideoPresetList(void);
 
-    void add_preset(const unsigned presetId,
-                    const bool blockSignal = false);
+    void add_preset(const unsigned presetId, const bool blockSignal = false);
 
     // Removes the given present from the list, and sets the list's index
     // to the one given. If the given preset doesn't exist in the list, no
@@ -40,6 +39,15 @@ class VideoPresetList : public QComboBox
     // no preset is selected.
     video_preset_s* current_preset(void) const;
 
+    // Creates and returns a string to be displayed as the list item label for
+    // the given present should the preset be added.
+    QString make_preset_item_label(const video_preset_s *const preset);
+
+    // Returns the list index of the given preset; or -1 if the list doesn't
+    // contain the preset.
+    int find_preset_idx_in_list(const int presetId);
+    int find_preset_idx_in_list(const QString &targetLabel);
+
 signals:
     void preset_added(const unsigned presetId);
 
@@ -51,17 +59,9 @@ class VideoPresetList : public QComboBox
 
     void preset_selected(const unsigned presetId);
 
-    void preset_label_changed(const unsigned presetId,
-                              const QString &newLabel);
+    void preset_label_changed(const unsigned presetId, const QString &newLabel);
 
 private:
-    // Returns the list index of the given preset; or -1 if the list doesn't
-    // contain the preset.
-    int find_preset_idx_in_list(const int presetId);
-
-    // Creates and returns a string to be displayed as the list item label for
-    // the given present should the preset be added.
-    QString make_preset_item_label(const video_preset_s *const preset);
 };
 
 #endif

src/display/qt/windows/ControlPanel/VideoPresets.cpp

@@ -167,7 +167,7 @@ control_panel::VideoPresets::VideoPresets(QWidget *parent) :
 
         connect(ui->comboBox_presetList, QOverload<int>::of(&QComboBox::currentIndexChanged), this, [this](const int index)
         {
-            kpers_set_value(INI_GROUP_VIDEO_PRESETS, "SelectedPresetIndex", std::max(index, 0));
+            kpers_set_value(INI_GROUP_VIDEO_PRESETS, "SelectedPreset", ui->comboBox_presetList->make_preset_item_label(ui->comboBox_presetList->current_preset()));
         });
 
         connect(ui->comboBox_presetList, &VideoPresetList::preset_selected, this, [this]
@@ -532,7 +532,7 @@ void control_panel::VideoPresets::update_active_preset_indicator(void)
 
 void control_panel::VideoPresets::assign_presets(const std::vector<video_preset_s*> &presets)
 {
-    const unsigned idx = kpers_value_of(INI_GROUP_VIDEO_PRESETS, "SelectedPresetIndex", 0).toUInt();
+    const QString selectedLabel = kpers_value_of(INI_GROUP_VIDEO_PRESETS, "SelectedPreset", "").toString();
 
     ui->comboBox_presetList->clear();
 
@@ -544,8 +544,9 @@ void control_panel::VideoPresets::assign_presets(const std::vector<video_preset_
     /// TODO: It would be better to sort the items by (numeric) resolution.
     ui->comboBox_presetList->sort_alphabetically();
 
-    ui->comboBox_presetList->setCurrentIndex(-1);
-    ui->comboBox_presetList->setCurrentIndex(std::min(int(idx), (ui->comboBox_presetList->count() - 1)));
+    const int idx = ui->comboBox_presetList->find_preset_idx_in_list(selectedLabel);
+    ui->comboBox_presetList->setCurrentIndex(std::max(idx, 0));
+    emit ui->comboBox_presetList->preset_selected(ui->comboBox_presetList->current_preset()->id);
 
     return;
 }