Add option to use placeholder icon as custom icon

customattrs/src/main/java/de/mm20/launcher2/customattrs/CustomAttribute.kt

@@ -94,6 +94,7 @@ sealed class CustomIcon : CustomAttribute {
                     )
                 }
                 "force_themed_icon" -> ForceThemedIcon
+                "default_placeholder_icon" -> DefaultPlaceholderIcon
                 else -> null
             }
         }
@@ -172,3 +173,14 @@ object UnmodifiedSystemDefaultIcon: CustomIcon() {
     }
 
 }
+
+/**
+ * Use the default placeholder icon
+ */
+object DefaultPlaceholderIcon: CustomIcon() {
+    override fun toDatabaseValue(): String {
+        return jsonObjectOf(
+            "type" to "default_placeholder_icon"
+        ).toString()
+    }
+}

icons/src/main/java/de/mm20/launcher2/icons/IconRepository.kt

@@ -150,6 +150,9 @@ class IconRepository(
                 )
             )
         }
+        if (customIcon is DefaultPlaceholderIcon) {
+            return placeholderProvider?.let { listOf(it) } ?: emptyList()
+        }
         return emptyList()
     }
 
@@ -263,6 +266,8 @@ class IconRepository(
             )
         }
 
+        providerOptions.add(DefaultPlaceholderIcon)
+
         suggestions.addAll(
             transformationOptions.map {
                 val transformations = getTransformations(it) ?: defaultTransformations