Problem appending to very large text list in ScrollPan about zebkit

[barmalei]

Your HTTP reading strategy is quite aggressive :) Think it can make browser busy. From the zebra point of view there are number of things that you don't have to do:

• don't call event listener methods directly (textUpdated). This is only text model who knows how to fire events.
• Don't touch setExtraChar. That is one of weird thing I want to remove. Now it is supposed to be used for internal cache that keeps measured line width. The result of the method calling with label is unpredictable.
• You also should not call parse method, since it is just parse and update text without triggering any text model events. There are three methods in text model that are supposed to be used for text updaing: setValue, write, remove

One more thing I suggest is replace label with text field (in read only mode). It allows user to copy paste desired parts. So, try the code snippet below (it is simplified comparatively to your code, but think you can easily modify for your needs):

zebra.ready(function() {
    eval(zebra.Import("ui", "layout"));

    var canvas = new zCanvas(400, 400);
    canvas.fullScreen();
    var root = canvas.root;
    var log = new zebra.ui.TextField(new zebra.data.Text("Internal Log"));
    log.setEditable(false);
    log.setFont(new zebra.ui.Font("Courier New", 14));

    root.properties({
        layout : new BorderLayout(8,8),
        border : new Border(),
        padding: 8,
        kids: {
           CENTER: new zebra.ui.ScrollPan(log),
        }
    });

    // read log every 1.5 second
    zebra.util.task(function(ctx) {
        zebra.io.GET("http://localhost:8090/tests/server.log", function(r) {
            var model = log.view.target;
            // add text to the end of text field
            model.write(r.responseText, model.textLength);
            log.repaint();
        });
    }).run(1000, 1500);
});

[williame]

Your HTTP reading strategy is quite aggressive :) Think it can make browser busy.

Its a 'long poll' so it stalls if there's no update.

replace label with text field (in read only mode)

Thanks, this is much nicer! I can get it to tail by putting the cursor at the end, and I don't have the mess with scroll bars any more.

model.write(r.responseText, model.textLength);

This works nicely. The reason I had avoided it before and done my own calls to parse() is that I want to syntax-highlight and the write() destroys the last Line each time, overwriting whatever I set with setExtraChar.

As an alternative to using setExtraChar to track my own attributes-per-line, I've changed my code to have its own shadow array of attributes. This is fine for read-only scenarios but might need rethinking if I enable edit.

[barmalei]

As an alternative of "setExtraChar" method to keep meta information about a line you can consider of usage internal line structure." zebra.data.Text" keeps lines as the following structure:

function Line(s) {
    this.s = s;
    this.l = 0;
}

You can iterate through the structures by accessing "lines" field (array) of the text model class and add desired attribute to it.

[williame]

Yes, I tried that before settling on a separate array showing the model's lines.

The problem seems to be that when write is called, it recreates the last line's Line() so any attributes I put in there get lost.