fix #868 Scroll loading does not work when browser zoom is not 100%

Author: vegegoku

domino-ui/src/main/java/org/dominokit/domino/ui/datatable/plugins/pagination/BodyScrollPlugin.java

@@ -21,13 +21,17 @@
 import org.dominokit.domino.ui.datatable.DataTable;
 import org.dominokit.domino.ui.datatable.events.BodyScrollEvent;
 import org.dominokit.domino.ui.datatable.plugins.DataTablePlugin;
+import org.dominokit.domino.ui.datatable.plugins.HasPluginConfig;
 
 /**
  * A plugin for handling body scroll events in a DataTable.
  *
  * @param <T> The type of data in the DataTable.
  */
-public class BodyScrollPlugin<T> implements DataTablePlugin<T> {
+public class BodyScrollPlugin<T>
+    implements DataTablePlugin<T>, HasPluginConfig<T, BodyScrollPlugin<T>, BodyScrollPluginConfig> {
+
+  private BodyScrollPluginConfig config = new BodyScrollPluginConfig(0);
 
   /**
    * Initializes the plugin and adds scroll event listeners to the DataTable's body.
@@ -49,12 +53,30 @@ public void onBodyAdded(DataTable<T> dataTable) {
           int clientHeight = new Double(scrollElement.clientHeight).intValue();
 
           if (JsMath.abs(offsetHeight) + JsMath.abs(scrollTop)
-              == new Double(scrollHeight + (offsetHeight - clientHeight)).intValue()) {
+              >= new Double(scrollHeight + (offsetHeight - clientHeight)).intValue()
+                  - config.getOffset()) {
             dataTable.fireTableEvent(new BodyScrollEvent(ScrollPosition.BOTTOM));
           }
         });
   }
 
+  /**
+   * Sets up the plugin configuration.
+   *
+   * @param config The plugin configuration.
+   */
+  @Override
+  public BodyScrollPlugin<T> setConfig(BodyScrollPluginConfig config) {
+    this.config = config;
+    return this;
+  }
+
+  /** @return the plugin configuration */
+  @Override
+  public BodyScrollPluginConfig getConfig() {
+    return this.config;
+  }
+
   /** An enum representing the scroll position in the DataTable's body. */
   public enum ScrollPosition {
     /** Represents the top scroll position. */

domino-ui/src/main/java/org/dominokit/domino/ui/datatable/plugins/pagination/BodyScrollPluginConfig.java

@@ -0,0 +1,51 @@
+/*
+ * Copyright © 2019 Dominokit
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.dominokit.domino.ui.datatable.plugins.pagination;
+
+import org.dominokit.domino.ui.datatable.plugins.PluginConfig;
+
+/**
+ * Configuration class for {@link BodyScrollPlugin} Allow the user to define the offset of pixels
+ * the plugin will use to fire the event before it reach the bottom of the scroll.
+ */
+public class BodyScrollPluginConfig implements PluginConfig {
+
+  private int offset;
+
+  /**
+   * creates a new instance with the specified scroll offset.
+   *
+   * @param offset number of pixels to be used as scroll offset.
+   */
+  public BodyScrollPluginConfig(int offset) {
+    this.offset = offset;
+  }
+
+  /** @return int number of pixels to use as an offset for reaching the scroll bottom. */
+  public int getOffset() {
+    return offset;
+  }
+
+  /**
+   * sets the number of pixels to use as an offset for reaching the scroll bottom.
+   *
+   * @return same configuration instance
+   */
+  public BodyScrollPluginConfig setOffset(int offset) {
+    this.offset = offset;
+    return this;
+  }
+}