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  • garbage collector Issue

    - by Eslam
    this question is like my previous one Given: 3. interface Animal { void makeNoise(); } 4. class Horse implements Animal { 5. Long weight = 1200L; 6. public void makeNoise() { System.out.println("whinny"); } 7. } 8. public class Icelandic extends Horse { 9. public void makeNoise() { System.out.println("vinny"); } 10. public static void main(String[] args) { 11. Icelandic i1 = new Icelandic(); 12. Icelandic i2 = new Icelandic(); 13. Icelandic i3 = new Icelandic(); 14. i3 = i1; i1 = i2; i2 = null; i3 = i1; 15. } 16. } When line 14 is reached, how many objects are eligible for the garbage collector? A. 0 B. 1 C. 2 D. 3 E. 4 F. 6 i choosed A but the right answer is E, but i don't know Why?

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  • Are there any guarantees in JLS about order of execution static initialization blocks?

    - by Roman
    I wonder if it's reliable to use a construction like: private static final Map<String, String> engMessages; private static final Map<String, String> rusMessages; static { engMessages = new HashMap<String, String> () {{ put ("msgname", "value"); }}; rusMessages = new HashMap<String, String> () {{ put ("msgname", "????????"); }}; } private static Map<String, String> msgSource; static { msgSource = engMessages; } public static String msg (String msgName) { return msgSource.get (msgName); } Is there a possibility that I'll get NullPointerException because msgSource initialization block will be executed before the block which initializes engMessages? (about why don't I do msgSource initialization at the end of upper init. block: just the matter of taste; I'll do so if the described construction is unreliable)

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  • Get rid of jfreechart chartpanel unnecessary space

    - by ryvantage
    I am trying to get a JFreeChart ChartPanel to remove unwanted extra space between the edge of the panel and the graph itself. To best illustrate, here's a SSCCE (with JFreeChart installed): public static void main(String[] args) { JPanel panel = new JPanel(new GridBagLayout()); GridBagConstraints gbc = new GridBagConstraints(); gbc.fill = GridBagConstraints.BOTH; gbc.gridwidth = 1; gbc.gridheight = 1; gbc.weightx = 1; gbc.weighty = 1; gbc.gridy = 1; gbc.gridx = 1; panel.add(createChart("Sales", Chart_Type.DOLLARS, 100000, 115000), gbc); gbc.gridx = 2; panel.add(createChart("Quotes", Chart_Type.DOLLARS, 250000, 240000), gbc); gbc.gridx = 3; panel.add(createChart("Profits", Chart_Type.PERCENTAGE, 40.00, 38.00), gbc); JFrame frame = new JFrame(); frame.add(panel); frame.setSize(800, 300); frame.setLocationRelativeTo(null); frame.setVisible(true); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); } private static ChartPanel createChart(String title, Chart_Type type, double goal, double actual) { double maxValue = goal * 2; double yellowToGreenNum = goal; double redToYellowNum = goal * .75; DefaultValueDataset dataset = new DefaultValueDataset(actual); JFreeChart jfreechart = createChart(dataset, Math.max(actual, maxValue), redToYellowNum, yellowToGreenNum, title, type); ChartPanel chartPanel = new ChartPanel(jfreechart); chartPanel.setBorder(new LineBorder(Color.red)); return chartPanel; } private static JFreeChart createChart(ValueDataset valuedataset, Number maxValue, Number redToYellowNum, Number yellowToGreenNum, String title, Chart_Type type) { MeterPlot meterplot = new MeterPlot(valuedataset); meterplot.setRange(new Range(0.0D, maxValue.doubleValue())); meterplot.addInterval(new MeterInterval(" Goal Not Met ", new Range(0.0D, redToYellowNum.doubleValue()), Color.lightGray, new BasicStroke(2.0F), new Color(255, 0, 0, 128))); meterplot.addInterval(new MeterInterval(" Goal Almost Met ", new Range(redToYellowNum.doubleValue(), yellowToGreenNum.doubleValue()), Color.lightGray, new BasicStroke(2.0F), new Color(255, 255, 0, 64))); meterplot.addInterval(new MeterInterval(" Goal Met ", new Range(yellowToGreenNum.doubleValue(), maxValue.doubleValue()), Color.lightGray, new BasicStroke(2.0F), new Color(0, 255, 0, 64))); meterplot.setNeedlePaint(Color.darkGray); meterplot.setDialBackgroundPaint(Color.white); meterplot.setDialOutlinePaint(Color.gray); meterplot.setDialShape(DialShape.CHORD); meterplot.setMeterAngle(260); meterplot.setTickLabelsVisible(false); meterplot.setTickSize(maxValue.doubleValue() / 20); meterplot.setTickPaint(Color.lightGray); meterplot.setValuePaint(Color.black); meterplot.setValueFont(new Font("Dialog", Font.BOLD, 0)); meterplot.setUnits(""); if(type == Chart_Type.DOLLARS) meterplot.setTickLabelFormat(NumberFormat.getCurrencyInstance()); else if(type == Chart_Type.PERCENTAGE) meterplot.setTickLabelFormat(NumberFormat.getPercentInstance()); JFreeChart jfreechart = new JFreeChart(title, JFreeChart.DEFAULT_TITLE_FONT, meterplot, false); return jfreechart; } enum Chart_Type { DOLLARS, PERCENTAGE } If you resize the frame, you can see that you cannot make the edge of the graph go to the edge of the panel (the panels are outlined in red). Especially on the bottom - there is always a gap between the bottom the graph and the bottom of the panel. Is there a way to make the graph fill the entire area? Is there a way to at least guarantee that it is touching one edge of the panel (i.e., it is touching the top and bottom or the left and right) ??

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  • Simple but good pattern for EJB

    - by Sara
    What would you suggest as a good and practical but simple pattern for a soloution with: HTML + JSP (as a view/presentation) SERVLETS (controller, request, session-handling) EJB (persistence, businesslogic) MySQL DB And is it necessary to use an own layer of DAO for persistence? I use JPA to persist objects to my DB. Should I withdraw business logic from my EJB? Sources online all tell me different things and confuses me...

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  • ArrayList<Int> Collections.Sort and LineNumberReader Help How to

    - by user1819551
    I have a issue i can't get it to work now let going to the point a explain in the code thanks. This is my class: what I want to do is insert the Integers sort the list and buffer writer in a column with out coma. Now I getting this: [1110018, 1110032, 1110056, 1110059, 1110063, 1110085, 1110096, 1110123, 1110125, 1110185, 1110456, 1110459] I want like this: 111xxxxx 111xxxx xxxx....... I can't do it in single array, have to be in ArrayList. This is my collecting: list.addNumbers(numbers); list.display(); This is my writer: Is buffered coma.write("\n"+list.display()); coma.flush();<br/> Here is my class: public class IdCount {<br/> private ArrayList<Integer> properNumber = new ArrayList<>(); public void addNumbers(Integer numbers) { properNumber.add(numbers); Collections.sort(properNumber); } public String display() { //(I try .toString() Not work) return properNumber.toString(); } My second issue is LineNumberReader: This is my collecting and my writing: try { Reader input = new BufferedReader( new FileReader(inputFile)); try (Scanner in = new Scanner(input)) { while (in.hasNext()) { //(More Code) asp = new LineNumberReader(input); int rom = 0; while (asp.readLine()!=null){ rom++; } System.out.println(rom); coma.write(rom); This one will not write anything an my System Print give me only 12 0 in column.

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  • non-servlet JSP

    - by h2g2java
    I realise there are EL and near EL frameworks like StringTemplate, JUEL, Velocity, etc. However, I am not asking for list of alternatives to JSTL/EL. I came across a package more than a year ago, someone who wrote a util that emulates the functionality of JSP for non-servlet env, i.e., JSP composition which does not need a "servlet container" to function. I ignored it and now I think it would be helpful to me and I need help to recall what it is. My actual motivation is similar to what StringTemplate, JUEL, Velocity would offer to help me compose SQL blocks, HTML blocks but I am thinking that JSPs are precompiled into bytecode and JSPs are more run-time efficient since run-time parsing is done no more than once. So actually, recommendation for alternatives would be acceptable as long as the templates are precompiled into bytecode. But I still prefer the JSP emulator.

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  • JavaME - LWUIT images eat up all the memory

    - by Marko
    Hi, I'm writing a MIDlet using LWUIT and images seem to eat up incredible amounts of memory. All the images I use are PNGs and are packed inside the JAR file. I load them using the standard Image.createImage(URL) method. The application has a number of forms and each has a couple of labels an buttons, however I am fairly certain that only the active form is kept in memory (I know it isn't very trustworthy, but Runtime.freeMemory() seems to confirm this). The application has worked well in 240x320 resolution, but moving it to 480x640 and using appropriately larger images for UI started causing out of memory errors to show up. What the application does, among other things, is download remote images. The application seems to work fine until it gets to this point. After downloading a couple of PNGs and returning to the main menu, the out of memory error is encountered. Naturally, I looked into the amount of memory the main menu uses and it was pretty shocking. It's just two labels with images and four buttons. Each button has three images used for style.setIcon, setPressedIcon and setRolloverIcon. Images range in size from 15 to 25KB but removing two of the three images used for every button (so 8 images in total), Runtime.freeMemory() showed a stunning 1MB decrease in memory usage. The way I see it, I either have a whole lot of memory leaks (which I don't think I do, but memory leaks aren't exactly known to be easily tracked down), I am doing something terribly wrong with image handling or there's really no problem involved and I just need to scale down. If anyone has any insight to offer, I would greatly appreciate it.

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  • Where about should my main class be created in a project?

    - by Dan
    The problem is where a class should be created in my code. An example is I have a UI class and a main logic class that controls other objects. Should the main logic class create the UI object, or should the UI object create the instance of the main logic class? An explanation of which method is best and why would be ideal. Thanks.

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  • Where do I put javaassist code?

    - by DutrowLLC
    I have an application running on google app engine. I'm using restlets and I have a couple of layers set up including the restlet layer, the model layer, the business layer, and the data layer. I'm attempting to use javaassist to modify some classes, but I'm unsure where to actually put the code. I tried to put the code in the static initialization block: public class Person { String firstName; String getFirstName(){return null;} static{ ClassPool pool = ClassPool.getDefault(); try { CtClass CtPerson = pool.get("Person"); CtMethod CtGetFirstName = CtPerson.getDeclaredMethod("GetFirstName"); CtGetFirstName.setBody("return firstName;"); CtPerson.toClass(); } catch (Exception e) { e.printStackTrace(); } } } ...but that resulted in this error: javassist.CannotCompileException:.....attempted duplicate class definition...". I guess it makes sense that I can't edit the class file in the middle of its generation. I know the code works because I was able to run it correctly by simply putting it in a location that would run when I sent the program a command. (accessed a Restlet resource). The code ran fine if an instance of the class had not already been instantiated, however once I instantiated an instance of the affected class, the javaassist code failed. I assume I need to put this code somewhere that it will only run either: once after the program starts, directly before a class is instantiated for the first time, or even better, during compile time.

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  • Need help make these classes use Visitor Pattern and generics

    - by Shervin
    Hi. I need help to generify and implement the visitor pattern. We are using tons of instanceof and it is a pain. I am sure it can be modified, but I am not sure how to do it. Basically we have an interface ProcessData public interface ProcessData { public setDelegate(Object delegate); public Object getDelegate(); //I am sure these delegate methods can use generics somehow } Now we have a class ProcessDataGeneric that implements ProcessData public class ProcessDataGeneric implements ProcessData { private Object delegate; public ProcessDataGeneric(Object delegate) { this.delegate = delegate; } } Now a new interface that retrieves the ProcessData interface ProcessDataWrapper { public ProcessData unwrap(); } Now a common abstract class that implements the wrapper so ProcessData can be retrieved @XmlSeeAlso( { ProcessDataMotorferdsel.class,ProcessDataTilskudd.class }) public abstract class ProcessDataCommon implements ProcessDataWrapper { protected ProcessData unwrapped; public ProcessData unwrap() { return unwrapped; } } Now the implementation public class ProcessDataMotorferdsel extends ProcessDataCommon { public ProcessDataMotorferdsel() { unwrapped = new ProcessDataGeneric(this); } } similarly public class ProcessDataTilskudd extends ProcessDataCommon { public ProcessDataTilskudd() { unwrapped = new ProcessDataGeneric(this); } } Now when I use these classes, I always need to do instanceof ProcessDataCommon pdc = null; if(processData.getDelegate() instanceof ProcessDataMotorferdsel) { pdc = (ProcessDataMotorferdsel) processData.getDelegate(); } else if(processData.getDelegate() instanceof ProcessDataTilskudd) { pdc = (ProcessDataTilskudd) processData.getDelegate(); } I know there is a better way to do this, but I have no idea how I can utilize Generics and the Visitor Pattern. Any help is GREATLY appreciated.

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  • Trouble adding Image to a JPanel

    - by user1276078
    I'm making a video game, and I need to add an image to a JPanel and then add that JPanel to a JFrame. All of the tutorials I've seen say to add it to a JLabel, but the image needs to be able to move around. Unless you can move a JLabel around, I can't do that. How would I be able to add an Image directly to a JPanel. This is what I have so far, but it is just like it was on a JApplet class Penguin extends JPanel { public Image image; public void paintComponent( Graphics g ) { image = getImage( getDocumentBase(), "Penguins.jpg" ); g.drawImage( image, 0, 0, this ); } }

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  • GF 3.0.1 + Virtual Server: www.myhost.com:8080/projectname-war => www.myhost.com. How?

    - by Harry Pham
    EDIT I need to change www.myhost.com:8080/myproject-war to www.myhost.com. Here is what I've been trying: I configurate the Virtual Server: server. I have still have default Network Listeners to be http-listener-1 and http-listner-2. I change the Default Web Module to ScholarActive#ScholarActive-war.war (The only option in the drop down list, since I only deploy 1 application). For the docroot, I try this ${com.sun.aas.instanceRoot}/applications/ScholarActive/ScholarActive-war_war or this ${com.sun.aas.instanceRoot}/applications/ScholarActive/ Both does not work. What does docroot need to point to, for this to work? what I try to do is: when I type localhost:8080/ScholarActive-war, then my application load, I want to make so that if I type locahost:8080, it will load the app as well, then what left is changed the port to 80. But no luck. Any Idea?

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  • JDO in Google App Engine: order of keys in unowned one-to-many relationship

    - by Kel
    I'm implementing web application with JDO in Google App Engine. According to documentation, in owned one-to-many relationships, order of elements in "owner" object collection is determined either by automatically created index field, or by information given in explicit ordering clause. For example: @PersistenceCapable public class Person { // ... @Order(extensions = @Extension(vendorName="datanucleus", key="list-ordering", value="country asc, city asc")) private List<ContactInfo> contacts = new List<ContactInfo>(); In unowned relationships, "owner" object contains collection of keys of "nested" objects, for example: @PersistenceCapable public class Author { // ... @Persistent private List<Key> books; Is order of keys preserved, if I use List<Key> collection in "owner" object for storing keys of "nested" elements? I could not find answer neither in JDO relationships article, nor in Data Classes article :(

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  • Relation many-to-many with attributes : how ?

    - by mada
    Hi, Excuse me for my poor english in advance as it is not my mother tongue. Like in this example: http://www.xylax.net/hibernate/manytomany.html But i have in the table foo-bar 2 attributes which are not part of the primary or foreign keys.: one boolean(A) & one string(B). I know how to map it without attributes but not in this case. I have not found an answer in the documentation. I need to know please how to map it & what kind of collection i have to declare in my class Foo. Thanks in advance for your answer. I really appreciate the time given by you.

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  • hibernate formula with column

    - by coolguy
    I have a table with a column that will be encrypted by a trigger after the record is inserted. When I read the column, I need to apply a decrypt function in the hibernate domain class. While saving the object, the value of the column will be saved as such. While reading the column, apply a database function on the read data. @Formula and @Column annotation cannot be applied to an attribute in the entity class. How do I achieve this functionality without using one attribute for saving and another one with @Formula for reading it?

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  • How a servlet can get the absolute path to a file outside of the servlet?

    - by WolfmanDragon
    We have been using System.getProperties("user.dir") to get the location of a properties file. Now that it has been deployed on Tomcat(via servlet), the System call is giving the location as tomcat and not at the location at where the properties file exist. How can we call the the properties file dynamically? Given: Tomcat is not the only way the app will be deployed We have no control on where the app may be placed. Relative paths will not work as that Vista is being used and Vista breaks relative paths. This must work on all OS, including(but not limited to) Linux, XP and Vista. EDIT I implied this, but in case I was not clear enough, I have no way of knowing the path String.

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  • Put together tiles in android sdk and use as background

    - by Jon
    In a feeble attempt to learn some Android development am I stuck at graphics. My aim here is pretty simple: Take n small images and build a random image, larger than the screen with possibility to scroll around. Have an animated object move around on it I have looked at the SDK examples, Lunar Lander especially but there are a few things I utterly fail to wrap my head around. I've got a birds view plan (which in my head seems reasonably sane): How do I merge the tiles into one large image? The background is static so I figure I should do like this: Make a 2d array with refs to the tiles Make a large Drawable and draw the tiles on it At init draw this big image as the background At each onDraw redraw the background of the previous spot of the moving object, and the moving object at its new location The problem is the hands on things. I load the small images with "Bitmap img1 = BitmapFactory.decodeResource (res, R.drawable.img1)", but then what? Should I make a canvas and draw the images on it with "canvas.drawBitmap (img1, x, y, null);"? If so how to get a Drawable/Bitmap from that? I'm totally lost here, and would really appreciate some hands on help (I would of course be grateful for general hints as well, but I'm primarily trying to understand the Graphics objects). To make you, dear reader, see my level of confusion will I add my last desperate try: Drawable drawable; Canvas canvas = new Canvas (); Bitmap img1 = BitmapFactory.decodeResource (res, R.drawable.img1); // 50 x 100 px image Bitmap img2 = BitmapFactory.decodeResource (res, R.drawable.img2); // 50 x 100 px image canvas.drawBitmap (img1, 0, 0, null); canvas.drawBitmap (img2, 50, 0, null); drawable.draw (canvas); // obviously wrong as draw == null this.setBackground (drawable); Thanks in advance

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  • how to handle result set data

    - by ashwani66476
    Hello All I am getting lacks of records in my Result Set. My concerns are : How Result Set handle these records internally? and How a programmer can handle those records in batches So that memory problem would not occur.? waiting for your answers .. Many Thanks

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  • File Hierarchy system with a web application logic question: List searching

    - by molleman
    I need to search through a list of folders that could have more folders inside it, and add a new folder depending what folder is its parent.(the path is stored as a String for eg = "root/MyCom/home/") Then i fill in a field with a new folder name and add it to the final folder(eg "home/"). Below as you can see , I can navigate to the right location and add the new folder to a current folder, My trouble is that i cannot ensure that currentFolder element is placed back in the list it came from how could i add a folder to a list of folders, that could be within a list of folders,that could be within a list of folders and endless more? YFUser user = (YFUser)getSession().getAttribute(SESSION_USER); Folder newFolder = new Folder(); newFolder.setFolderName(foldername); // this is the path string (root/MyCom/home/) split in the different folder names String folderNames[] = folderLocationString.split("/"); int folderNamesLength = folderNames.length; Folder root = user.getRoot(); Folder currentFolder = root; for(int i=0;i<=folderNamesLength; i++){ // because root is folderNames[i] String folderName = folderNames[i++]; int currentFolderSize = currentFolder.getChildren.getSize(); for(int o=1; o<= currentFolderSize ; o++){ if(currentFolder.getChildren().get(o) instanceof Folder){ if(folderName.equals(currentFolder.getChildren().get(o).getFolderName())){ currentFolder = currentFolder.getChildren().get(o); if (i == counter){ //now i am inside the correct folder and i add it to the list of folders within it //the trouble is knowing how to re add this changed folder back to the list before it currentFolder.getChildren.add(newFolder); } } } } }

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  • JPA entity design / cannot delete entity

    - by timaschew
    I though its simple what I want, but I cannot find any solution for my problem. I'm using playframework 1.2.3 and it's using Hibernate as JPA. So I think playframework has nothing to do with the problem. I have some classes (I omit the nonrelevant fields) public class User { ... } public class Task { public DataContainer dataContainer; } public class DataContainer { public Session session; public User user; } public class Session { ... } So I have association from Task to DataContainer and from DataContainer to Sesssion and the DataContainer belongs to a User. The DataContainers can have always the same User, but the Session have to be different for each instance. And the DataContainer of a Task have also to be different in each instance. A DataContainer can have a Sesesion or not (it's optinal). I use only unidirectional assoc. It should be sufficient. In other words: Every Task must has one DataContainer. Every DataContainer must has one/the same User and can have one Session. To create a DB schema I use JPA annotations: @Entity public class User extends Model { ... } @Entity public class Task extends Model { @OneToOne(optional = false, cascade = CascadeType.ALL) public DataContainer dataContainer; } @Entity public class DataContainer extends Model { @OneToOne(optional = true, cascade = CascadeType.ALL) public Session session; @ManyToOne(optional = false, cascade = CascadeType.ALL) public User user; } @Entity public class Session extends Model { ... } BTW: Model is a play class and provides the primary id as long type. When I create some for each entity a object and 'connect them', I mean the associations, it works fine. But when I try to delete a Session, I get a constraint violation exception, because a DataContainer still refers to the Session I want to delete. I want that the Session (field) of the DataContainer will be set to null respectively the foreign key (session_id) should be unset in the database. This will be okay, because its optional. I don't know, I think I have multiple problems. Am I using the right annotation @OneToOne ? I found on the internet some additional annotation and attributes: @JoinColumn and a mappedBy attribute for the inverse relationship. But I don't have it, because its not bidirectional. Or is a bidirectional assoc. essentially? Another try was to use @OnDelete(action = OnDeleteAction.CASCADE) the the contraint changed from NO ACTIONs when update or delete to: ADD CONSTRAINT fk4745c17e6a46a56 FOREIGN KEY (session_id) REFERENCES annotation_session (id) MATCH SIMPLE ON UPDATE NO ACTION ON DELETE CASCADE; But in this case, when I delete a session, the DataContainer and User is deleted. That's wrong for me. EDIT: I'm using postgresql 9, the jdbc stuff is included in play, my only db config is db=postgres://app:app@localhost:5432/app

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  • Which text margin does SWT Table use when drawing text?

    - by Zordid
    I got a relatively easy question - but I cannot find anything anywhere to answer it. I use a simple SWT table widget in my application that displays only text in the cells. I got an incremental search feature and want to highlight text snippets in all cells if they match. So when typing "a", all "a"s should be highlighted. To get this, I add an SWT.EraseItem listener to interfere with the background drawing. If the current cell's text contains the search string, I find the positions and calculate relative x-coordinates within the text using event.gc.stringExtent - easy. With that I just draw rectangles "behind" the occurrences. Now, there's a flaw in this. The table does not draw the text without a margin, so my x coordinate does not really match - it is slightly off by a few pixels! But how many?? Where do I retrieve the cell's text margins that table's own drawing will use? No clue. Cannot find anything. :-( Bonus question: the table's draw method also shortens text and adds "..." if it does not fit into the cell. Hmm. My occurrence finder takes the TableItem's text and thus also tries to mark occurrences that are actually not visible because they are consumed by the "...". How do I get the shortened text and not the "real" text within the EraseItem draw handler? Thanks!

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