Do not allow zero for size and spacing properties that could lead to

crashes or unexpected behavior

diylc/diylc-core/src/org/diylc/core/annotations/PositiveMeasureValidator.java

@@ -40,7 +40,7 @@ public class PositiveMeasureValidator implements IPropertyValidator {
     if (value instanceof AbstractMeasure) {
       AbstractMeasure<?> measure = (AbstractMeasure<?>) value;
       if (measure.getValue() < 0) {
-        throw new ValidationException("must be greater than zero.");
+        throw new ValidationException("must be greater or equal to zero.");
       }
     } else {
       throw new ValidationException("wrong data type, measure expected.");

diylc/diylc-core/src/org/diylc/core/annotations/PositiveNonZeroMeasureValidator.java

@@ -0,0 +1,49 @@
+/*
+
+    DIY Layout Creator (DIYLC).
+    Copyright (c) 2009-2018 held jointly by the individual authors.
+
+    This file is part of DIYLC.
+
+    DIYLC is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    DIYLC is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with DIYLC.  If not, see <http://www.gnu.org/licenses/>.
+
+*/
+package org.diylc.core.annotations;
+
+import org.diylc.core.IPropertyValidator;
+import org.diylc.core.ValidationException;
+import org.diylc.core.measures.AbstractMeasure;
+
+/**
+ * Validates any generic {@link AbstractMeasure} descendants and makes sure that the value is
+ * positive.
+ * 
+ * @author Branislav Stojkovic
+ */
+public class PositiveNonZeroMeasureValidator implements IPropertyValidator {
+
+  @Override
+  public void validate(Object value) throws ValidationException {
+    if (value == null)
+      return;
+    if (value instanceof AbstractMeasure) {
+      AbstractMeasure<?> measure = (AbstractMeasure<?>) value;
+      if (measure.getValue() <= 0) {
+        throw new ValidationException("must be greater than zero.");
+      }
+    } else {
+      throw new ValidationException("wrong data type, measure expected.");
+    }
+  }
+}