Prevent missing images from breaking the app

Author: Philip-Scott

src/Services/Utils.vala

@@ -21,6 +21,32 @@
 
 public class Spice.Utils {
 
+    private const string[] ACCEPTED_TYPES = {
+        "image/jpeg",
+        "image/png",
+        "image/tiff",
+        "image/svg+xml",
+        "image/gif"
+    };
+
+    // Check if the filename has a picture file extension.
+    public static bool is_valid_image (GLib.File file) {
+        var file_info = file.query_info ("standard::*", 0);
+
+        // Check for correct file type, don't try to load directories and such
+        if (file_info.get_file_type () != GLib.FileType.REGULAR) {
+            return false;
+        }
+
+        foreach (var type in ACCEPTED_TYPES) {
+            if (GLib.ContentType.equals (file_info.get_content_type (), type)) {
+                return true;
+            }
+        }
+
+        return false;
+    }
+
     public static void set_style (Gtk.Widget widget, string css) {
         try {
             var provider = new Gtk.CssProvider ();

src/Widgets/CanvasItems/ImageItem.vala

@@ -20,9 +20,6 @@
 */
 
 public class Spice.ImageItem : Spice.CanvasItem {
-
-    public string uri = "";
-
     const string IMAGE_STYLE_CSS = """
         .colored {
             background-color: transparent;
@@ -32,6 +29,24 @@ public class Spice.ImageItem : Spice.CanvasItem {
             background-repeat: no-repeat;
         }
     """;
+    const string IMAGE_MISSING_CSS = """
+        .colored {
+           border: 4px dashed #000000;
+           border-color: #c92e34;
+        }""";
+
+    private bool valid = false;
+
+    private string uri_ = "";
+    public string uri {
+        get {
+            return uri_;
+        } set {
+            uri_ = value;
+            var file = File.new_for_uri (value);
+            valid = (file.query_exists () && Utils.is_valid_image (file));
+        }
+    }
 
     public ImageItem (Canvas canvas, Json.Object? save_data = null) {
         base (canvas);
@@ -57,6 +72,10 @@ public class Spice.ImageItem : Spice.CanvasItem {
     }
 
     public override void style () {
-        Utils.set_style (this, IMAGE_STYLE_CSS.printf (uri));
+        if (valid) {
+            Utils.set_style (this, IMAGE_STYLE_CSS.printf (uri));
+        } else {
+            Utils.set_style (this, IMAGE_MISSING_CSS);
+        }
     }
 }