Fixes DeployUI Freezing app if too much text is displayed

The JavaFX thread would hang when the string being displayed
in the deploy UI became too long.
This ensures that if the string becomes too long it will
stop displaying more data.

Author: JLLeitschuh

ui/src/main/java/edu/wpi/grip/ui/DeployController.java

@@ -10,6 +10,7 @@
 import edu.wpi.grip.core.serialization.Project;
 import edu.wpi.grip.core.settings.ProjectSettings;
 import edu.wpi.grip.core.settings.SettingsProvider;
+import edu.wpi.grip.ui.components.LogTextArea;
 import edu.wpi.grip.ui.util.StringInMemoryFile;
 import javafx.application.Platform;
 import javafx.beans.binding.Bindings;
@@ -18,8 +19,8 @@
 import javafx.fxml.FXML;
 import javafx.scene.control.Label;
 import javafx.scene.control.ProgressIndicator;
-import javafx.scene.control.TextArea;
 import javafx.scene.control.TextField;
+import javafx.scene.control.ToggleButton;
 import net.schmizz.sshj.SSHClient;
 import net.schmizz.sshj.common.StreamCopier;
 import net.schmizz.sshj.connection.channel.direct.Session;
@@ -70,11 +71,13 @@ public class DeployController {
     @FXML
     private Label status;
     @FXML
-    private TextArea console;
+    private LogTextArea console;
     @FXML
     private BooleanProperty deploying;
     @FXML
     private StringProperty command;
+    @FXML
+    private ToggleButton scrollPauseButton;
 
     @Inject
     private EventBus eventBus;
@@ -93,6 +96,10 @@ public void initialize() {
         command.bind(Bindings.concat(javaHome.textProperty(), "/bin/java ", jvmArgs.textProperty(), " -jar '",
                 deployDir.textProperty(), "/", GRIP_JAR, "' '", deployDir.textProperty(), "/", projectFile.textProperty(), "'"));
 
+        scrollPauseButton.selectedProperty().bindBidirectional(console.pausedScrollProperty());
+        console.setOnScroll(event -> {
+            console.setPausedScroll(true);
+        });
         loadSettings(settingsProvider.getProjectSettings());
     }
 
@@ -227,7 +234,7 @@ public StreamCopier.Listener file(String name, long size) {
                             return;
                         }
 
-                        Platform.runLater(() -> console.setText(console.getText() + line + "\n"));
+                        Platform.runLater(() -> console.addLineToLog(line));
                     }
                 }
             }

ui/src/main/java/edu/wpi/grip/ui/components/LogTextArea.java

@@ -0,0 +1,69 @@
+package edu.wpi.grip.ui.components;
+
+import com.google.common.annotations.VisibleForTesting;
+import javafx.beans.property.BooleanProperty;
+import javafx.beans.property.SimpleBooleanProperty;
+import javafx.scene.control.TextArea;
+
+import static com.google.common.base.Preconditions.checkNotNull;
+
+/**
+ * A text area that is used to display a log.
+ * Implements the ability to pause scrolling and the protection of not
+ * causing the JavaFX thread to hang if the string becomes too long.
+ *
+ * @see <a href="http://stackoverflow.com/a/27747004/3708426">Original idea for this class</a>
+ */
+public class LogTextArea extends TextArea {
+    @VisibleForTesting
+    static final int MAX_STRING_LENGTH = 200000;
+    private final BooleanProperty pausedScrollProperty = new SimpleBooleanProperty(false);
+    @SuppressWarnings("PMD.AvoidStringBufferField")
+    private final StringBuilder fullLog = new StringBuilder();
+    private boolean full = false;
+
+
+    /**
+     * Adds a line to the log. This will keep track of the scroll position and maintain
+     * the scroll position if scrolling is paused.
+     *
+     * @param data The line to add to the text area.
+     */
+    public void addLineToLog(String data) {
+        checkNotNull(data, "Data cannot be null");
+        if (fullLog.length() + data.length() >= MAX_STRING_LENGTH && !full) {
+            full = true;
+            fullLog.append("[ERROR] Too much output to display. Discarding the rest.");
+        } else if (!full) {
+            fullLog.append(data + "\n");
+        } else {
+            return;
+        }
+        final double scrollPosition;
+        if (isPausedScroll()) {
+            scrollPosition = this.getScrollTop();
+        } else {
+            scrollPosition = Double.MAX_VALUE;
+        }
+        this.setText(fullLog.toString());
+        this.setScrollTop(scrollPosition);
+    }
+
+    /**
+     * @return True if the scroll has been paused
+     */
+    public final boolean isPausedScroll() {
+        return pausedScrollProperty.getValue();
+    }
+
+    /**
+     * @return A property that can be bound to prevent auto scrolling
+     */
+    public final BooleanProperty pausedScrollProperty() {
+        return pausedScrollProperty;
+    }
+
+    public final void setPausedScroll(boolean value) {
+        pausedScrollProperty.setValue(value);
+    }
+}

ui/src/main/resources/edu/wpi/grip/ui/Deploy.fxml

@@ -10,6 +10,7 @@
 <?import javafx.scene.image.Image?>
 <?import javafx.scene.image.ImageView?>
 <?import javafx.scene.layout.*?>
+<?import edu.wpi.grip.ui.components.LogTextArea?>
 <VBox styleClass="deploy-pane" maxWidth="Infinity" xmlns:fx="http://javafx.com/fxml/1"
       onKeyPressed="if (event.code == javafx.scene.input.KeyCode.ENTER) { controller.onDeploy() }"
       xmlns="http://javafx.com/javafx/null" fx:controller="edu.wpi.grip.ui.DeployController" fillWidth="true">
@@ -69,6 +70,7 @@
 
             <ButtonBar GridPane.columnIndex="0" GridPane.rowIndex="3" GridPane.columnSpan="2">
                 <buttons>
+                    <ToggleButton fx:id="scrollPauseButton" text="Pause Scroll" ButtonBar.buttonData="OTHER"/>
                     <Button fx:id="deployButton" defaultButton="true" onMouseClicked="#onDeploy" text="Deploy"
                             ButtonBar.buttonData="APPLY">
                         <fx:script>deployButton.disableProperty().bind(deploying)</fx:script>
@@ -102,6 +104,6 @@
         <Label fx:id="status"/>
     </StackPane>
 
-    <TextArea fx:id="console" editable="false" styleClass="console" prefRowCount="24" prefColumnCount="100"
+    <LogTextArea fx:id="console" editable="false" styleClass="console" prefRowCount="24" prefColumnCount="100"
               VBox.vgrow="ALWAYS"/>
 </VBox>

ui/src/test/java/edu/wpi/grip/ui/components/LogTextAreaTest.java

@@ -0,0 +1,71 @@
+package edu.wpi.grip.ui.components;
+
+
+import autovalue.shaded.org.apache.commons.lang.StringUtils;
+import javafx.scene.Scene;
+import javafx.stage.Stage;
+import org.junit.Test;
+import org.testfx.framework.junit.ApplicationTest;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotEquals;
+
+public class LogTextAreaTest extends ApplicationTest {
+    private LogTextArea logTextArea;
+
+    @Override
+    public void start(Stage stage) {
+        logTextArea = new LogTextArea();
+        stage.setScene(new Scene(logTextArea));
+        stage.show();
+    }
+
+    @Test
+    public void testAddFirstLine() {
+        final String FIRST_LINE = "First Line Of Text";
+        logTextArea.addLineToLog(FIRST_LINE);
+        assertEquals("First line wasn't added", FIRST_LINE + "\n", logTextArea.getText());
+    }
+
+    @Test
+    public void testAddTwoLines() {
+        final String FIRST_LINE = "First Line Of Text";
+        final String SECOND_LINE = "Second line of text";
+        logTextArea.addLineToLog(FIRST_LINE);
+        logTextArea.addLineToLog(SECOND_LINE);
+        assertEquals("Second line wasn't added", FIRST_LINE + "\n" + SECOND_LINE + "\n", logTextArea.getText());
+    }
+
+    @Test
+    public void testAddingReallyLongLineOfText() {
+        final String INITIAL_TEXT = StringUtils.rightPad("Initial string", LogTextArea.MAX_STRING_LENGTH - 3 , "Long\n");
+        logTextArea.addLineToLog(INITIAL_TEXT);
+        assertEquals("Text was not added to logger", INITIAL_TEXT + "\n", logTextArea.getText());
+    }
+
+    @Test
+    public void testAddingStringThatIsTooLong() {
+        final String INITIAL_TEXT = StringUtils.rightPad("Initial string", LogTextArea.MAX_STRING_LENGTH, "Long\n");
+        logTextArea.addLineToLog(INITIAL_TEXT);
+        assertNotEquals("The initial text should not have been appended as it was too long", INITIAL_TEXT + "\n", logTextArea.getText());
+    }
+
+    @Test
+    public void testAddingStringToFullLog() {
+        testAddingStringThatIsTooLong();
+        final String currentText = logTextArea.getText();
+        logTextArea.addLineToLog("More logged text");
+        assertEquals("This text should not be appended as the log is full", currentText, logTextArea.getText());
+    }
+
+    @Test
+    public void testScrollIsMaintainedWhenScrollIsPaused() {
+        logTextArea.setPausedScroll(true);
+        final double INITIAL_SCROLL = logTextArea.getScrollTop();
+        final String LONG_TEXT = StringUtils.rightPad("InitialString", 500, "Text\n");
+        logTextArea.addLineToLog(LONG_TEXT);
+        assertEquals("The log should not have scrolled", INITIAL_SCROLL, logTextArea.getScrollTop(), 0.001);
+    }
+
+
+}