Bug 578178 – Show large previews for image files

Use the actual image from the file for expanded mode previews for image files. Use the pixbuf loader to set the appropriate image size as soon as the image is prepared, but before it is loaded, to avoid loading large images. Apply the pixbuf orientation setting so that the image is properly rotated. Preserve the original size of the image if its dimensions are smaller than the space available.

Make sure we provide the accurate available width for the details actor. This
width has to exclude the padding and border width. Also provide the available height for the details actor.

js/ui/docDisplay.js

@@ -88,7 +88,7 @@ DocDisplayItem.prototype = {
 
     // Ensures the preview icon is created.
     _ensurePreviewIconCreated : function() {
-        if (!this._showPreview || this._previewIcon)
+        if (this._previewIcon)
             return; 
 
         this._previewIcon = new Clutter.Texture();
@@ -100,6 +100,24 @@ DocDisplayItem.prototype = {
         } else {
             Shell.clutter_texture_set_from_pixbuf(this._previewIcon, this._docInfo.get_icon(GenericDisplay.PREVIEW_ICON_SIZE));
         }
+    },
+
+    // Creates and returns a large preview icon, but only if this._docInfo is an image file
+    // and we were able to generate a pixbuf from it successfully.
+    _createLargePreviewIcon : function(availableWidth, availableHeight) {
+        if (this._docInfo.get_mime_type() == null || this._docInfo.get_mime_type().indexOf("image/") != 0)
+            return null;
+
+        let largePreviewPixbuf = Shell.create_pixbuf_from_image_file(this._docInfo.get_uri(), availableWidth, availableHeight);
+        
+        if (largePreviewPixbuf == null)
+            return null;
+
+        let largePreviewIcon = new Clutter.Texture();
+
+        Shell.clutter_texture_set_from_pixbuf(largePreviewIcon, largePreviewPixbuf); 
+
+        return largePreviewIcon;
     }
 };