[chronojump] Webcam preferences show error if cannot playpreview

[Xavier de Blas <xaviblas src gnome org>]

commit a98dafdff62760b69bdd759577a85075855f457c
Author: Xavier de Blas <xaviblas gmail com>
Date:   Tue Jul 16 16:37:59 2019 +0200

    Webcam preferences show error if cannot playpreview

 glade/preferences_win.glade | 14 ++++++++++++--
 src/gui/preferences.cs      | 17 ++++++++++++++++-
 2 files changed, 28 insertions(+), 3 deletions(-)
---
diff --git a/glade/preferences_win.glade b/glade/preferences_win.glade
index 09f28725..b9fd8679 100644
--- a/glade/preferences_win.glade
+++ b/glade/preferences_win.glade
@@ -3943,7 +3943,7 @@ Other</property>
                                             <property name="stock">gtk-missing-image</property>
                                           </widget>
                                           <packing>
-                                            <property name="expand">True</property>
+                                            <property name="expand">False</property>
                                             <property name="fill">True</property>
                                             <property name="position">0</property>
                                           </packing>
@@ -3955,7 +3955,7 @@ Other</property>
                                             <property name="label" translatable="yes">Preview</property>
                                           </widget>
                                           <packing>
-                                            <property name="expand">True</property>
+                                            <property name="expand">False</property>
                                             <property name="fill">True</property>
                                             <property name="position">1</property>
                                           </packing>
@@ -3969,6 +3969,16 @@ Other</property>
                                     <property name="position">0</property>
                                   </packing>
                                 </child>
+                                <child>
+                                  <widget class="GtkLabel" id="label_video_preview_error">
+                                    <property name="can_focus">False</property>
+                                  </widget>
+                                  <packing>
+                                    <property name="expand">False</property>
+                                    <property name="fill">False</property>
+                                    <property name="position">1</property>
+                                  </packing>
+                                </child>
                               </widget>
                               <packing>
                                 <property name="expand">True</property>
diff --git a/src/gui/preferences.cs b/src/gui/preferences.cs
index fe1d0780..9c415cf4 100644
--- a/src/gui/preferences.cs
+++ b/src/gui/preferences.cs
@@ -169,6 +169,7 @@ public class PreferencesWindow
        [Widget] Gtk.Image image_multimedia_video;
        [Widget] Gtk.Image image_video_preview;
        [Widget] Gtk.Button button_video_preview;
+       [Widget] Gtk.Label label_video_preview_error;
        [Widget] Gtk.CheckButton check_camera_stop_after;
        [Widget] Gtk.CheckButton check_camera_advanced;
        [Widget] Gtk.Frame frame_camera_advanced;
@@ -939,14 +940,28 @@ public class PreferencesWindow
        }
 
        private void on_button_video_preview_clicked (object o, EventArgs args)
+       {
+               label_video_preview_error.Visible = false;
+
+               //this allows us to update the previous label, if not we have to end camera play
+               GLib.Timeout.Add(100, new GLib.TimeoutHandler(button_video_preview_do));
+       }
+       private bool button_video_preview_do ()
        {
                string cameraCode = wd_list.GetCodeOfFullname(UtilGtk.ComboGetActive(combo_camera));
                if(cameraCode == "")
-                       return;
+                       return false; //do not call again
 
                Webcam webcamPlay = new WebcamFfmpeg (Webcam.Action.PLAYPREVIEW, UtilAll.GetOSEnum(), 
cameraCode,
                                getSelectedPixelFormat(), getSelectedResolution(), getSelectedFramerate());
+
                Webcam.Result result = webcamPlay.PlayPreviewNoBackground ();
+               if(! result.success) {
+                       label_video_preview_error.Text = result.error;
+                       label_video_preview_error.Visible = true;
+               }
+
+               return false; //do not call again
        }
 
        private string getSelectedPixelFormat()