• RichEditableText
• Label (Spark only)
• TextInput (both MX and Spark)
• TextArea (both MX and Spark)
• RichTextEditor and all controls that have a TextArea as a subcomponent

   This list does not include RichText component, but luckily with a new Text Layout Framework (TLF) available starting from Flash player 10, it is quite easy to "simulate" dynamic selection of the text with some ActionScript 3 code.

   In the following example, try to drag the slider to the left and to the right to control the dynamic selection of the text of RichText component:

Code listing:

<?xml version="1.0" encoding="utf-8"?>
<s:Application xmlns:fx="http://ns.adobe.com/mxml/2009"
               xmlns:s="library://ns.adobe.com/flex/spark"
               xmlns:mx="library://ns.adobe.com/flex/halo"
               width="200"
               height="75">
    <s:layout>
        <s:HorizontalLayout paddingLeft="25"
                            paddingTop="25"
                            paddingRight="25"/>
    </s:layout>
    <fx:Script>
        <![CDATA[
            import flashx.textLayout.edit.EditManager;
            import flashx.textLayout.edit.SelectionState;
            import flashx.textLayout.formats.TextLayoutFormat;            

            protected function highlightItem(endSelectionCharIndex : int):void
            {
                var containerFormat:TextLayoutFormat = new TextLayoutFormat();
                var paragraphFormat:TextLayoutFormat = new TextLayoutFormat();
                var characterFormat:TextLayoutFormat = new TextLayoutFormat();

                characterFormat = _selectedTextFormat;

                var selectionState : SelectionState = new SelectionState(rt.textFlow, 0, endSelectionCharIndex, _selectedTextFormat);                

                // apply format to the selection
                _textEditManager.applyFormat(
                    characterFormat,
                    paragraphFormat,
                    containerFormat,
                    selectionState);                                

                characterFormat = _notSelectedTextFormat;                

                // apply format to the rest of the text
                var notSelectionState : SelectionState = new SelectionState(rt.textFlow, endSelectionCharIndex, rt.text.length, _notSelectedTextFormat);
                _textEditManager.applyFormat(
                    characterFormat, paragraphFormat, containerFormat, notSelectionState);
            }

            protected function onRichTextCreationComplete():void
            {
                _textEditManager = new EditManager();
                rt.textFlow.interactionManager = _textEditManager;

                _selectedTextFormat = new TextLayoutFormat();
                _selectedTextFormat.backgroundColor = 0xFF99CC;
                _selectedTextFormat.color = 0x000000;

                _notSelectedTextFormat = new TextLayoutFormat();
                _notSelectedTextFormat.backgroundColor = 0xFFFFFF;
                _notSelectedTextFormat.color = 0x000000;
            }

            private var _textEditManager : EditManager;

            private var _selectedTextFormat : TextLayoutFormat;

            private var _notSelectedTextFormat : TextLayoutFormat;            

        ]]>
    </fx:Script>
    <s:RichText id="rt" text="Sample text"
                creationComplete="onRichTextCreationComplete()"/>
    <s:HSlider id="slider"
              minimum="0"
              maximum="10"
              change="highlightItem(slider.value)">
    </s:HSlider>
</s:Application>

   One of such a dirty flags used internally in Flex invalidation mechanism is invalidatePropertiesFlag flag.

   This particular flag is reset in validateProperties() method from mx.core.UIComponent class from Flex 3 SDK:

public function validateProperties():void
{
    if (invalidatePropertiesFlag)
    {
        commitProperties();
        invalidatePropertiesFlag = false;
    }
}

Inside commitProperties() function the actual changes occur to the invalidated property's value, for example, it can be "width" property.

My question is:

   Why dirty flag invalidatePropertiesFlag is reset after commitProperties() call, but not before this call?

I speculate this happens because:

• It is just a matter of life == code convention to put the dirty flag at the end of IF block;
• If code within commitProperties() raises RTE, we will still have a chance to execute the code in commitProperties() during playing next frame in Flash Player and this time maybe the code will not throw RTE.

   At this point, you may start to wonder why the exact location (at the very beginning or at the very end of IF sequence) of the dirty flag can be important?

   The reason is:

   If the code within commitProperties() implementation will try to invalidate some another component's property (e.g "height" property) by using dirty flag, then this invalidation call will not be added to mx.managers.LayoutManager.invalidatePropertiesQueue, because dirty flag invalidatePropertiesFlag is still equal to true, see the listing of invalidateProperties method from UIComponent for the explanation:

public function invalidateProperties():void
    {
        if (!invalidatePropertiesFlag)
        {
            invalidatePropertiesFlag = true;

            if (parent && UIComponentGlobals.layoutManager)
                UIComponentGlobals.layoutManager.invalidateProperties(this);
        }
    }

   The following example (source code can be viewed here)
illustrates this problem:

   In this example, Spark's DropDownMenu component selectedItem property is validated with mx:StringValidator validator.

   But the red border highlighting about error (selectedItem is blank) will not go away on the first successfull selection of selectedItem property in DropDownMenu.

   The validation error will only disappear on the second selection run, because DropDownMenu's "errorString" property is changed using invalidation mechanism, which in turn does not start on the first run because dirty flag invalidatePropertiesFlag is not yet reset.

The workaround to this sutuation is to trigger property invalidation mechanism manually by calling validateProperties method, but sometimes it can be not that convenient to call invalidation mechanism manually.

To sum up - I vote for the change in Flex SDK - dirty flag "invalidatePropertiesFlag" should be reset before the execution of commitProperties() method

   Just before submitting the bug issue, I've tested the functionality under the question under the latest Adobe Flex SDK stable build (3.2.0.3794 at the time of writing) - and I was surprised to find out that the bug is already fixed. Joy! Joy!

    I rushed to find the reasoning for this change for UITextFormat class by reading change notes at Flex SDK download section at Adobe open source web-site, but could not find any remarks regarding this change - would be handy to have a better insight behind this change for the community.

   ps If you wonder, the issue was incorrect implementation of an internal function copyFrom from UITextFormat class. UITextField's public getUITextFormat() method relies on this copyFrom function to return UITextFormat object for the UITextField class instance. In a nutshell UITextFormat object is just a wrapper around textFormat class that should contain all the properties from wrapped textFormat class instance + add some additional functionality.

   As it turned out, In Adobe Flex SDK 3.1 and below, 7(!) different properties were not copied into UITextFormat object from existing textFormat format object because of wrong implementation of UITextFormat.copyFrom function.

   Now, we are safe, this particular issue is fixed!

1. use itemUpdated(obj) ArrayCollection's method.
2. use setItemAt(obj, index) ArrayCollection's method.

   ActionScript code sample:

    //Update an existing person in the ArrayCollection via setItemAt

    public function updatePersonViaSetItemAt():void {
        var currentlySelectedItem : Object = dg.selectedItem;
        currentlySelectedItem.first = firstInput.text;
        currentlySelectedItem.last = lastInput.text;
        ac.setItemAt(currentlySelectedItem, dg.selectedIndex);
    }

    // Update an existing person in the ArrayCollection via itemUpdated

    public function updatePersonViaItemUpdated():void {
        var currentlySelectedItem : Object = dg.selectedItem;
        currentlySelectedItem.first =  firstInput.text;
        currentlySelectedItem.last =  lastInput.text;
        ac.itemUpdated(currentlySelectedItem);

    }

   Which one to choose?

   I would strongly advice to always use 'itemUpdated' because of the following reasons:

• Calling setItemAt(x) on your existing data item in ArrayCollection is an equivalent to calling the removeItemAt(x) method and then calling the addItemAt(..., x) method on your data item.
  
     Thus after making the call to setItemAt(x, index) you will loose the current selection in your ArrayCollection dependant UI component (mx:DataGrid, mx:Tree, mx:Combobox.. etc..)
  
  
• If the Sort rule is already applied to your ArrayCollection then you can receive some funky results like unwanted inserting of a new row when partly changing several properties of the existing data item in ArrayCollection.

   Interactive sample with "View source" option enabled to watch the difference:
http://jabbypanda.com/labs/updateArrayCollectionItem/updateArrayCollectionItem.html

You can try the following:

1. First apply sorting to any of the DataGrid's column
2. Select the first row in the Datagrid
3. Rename the surname of the person to something completely new starting with a new letter
4. Press "Update via setItemAt()" button control

Voilà, new unwanted row becomes visible in the Datagrid.

After intoductory meeting of Ukrainian Adobe Flash platform user group(UAFPUG) at February 2008 codenamed UAFPUG-0, the first real seminar UAFPUG-1 had quickly followed at 15th of March, 2008 at Global Logic office premises at Kharkiv, Ukraine.

Speakers list had included 3 (THREE!) talented local Flash profesionals who had presented to the audience of 45 attendees mostly from all major cities in Eastern Ukraine and Kyiv included + 1 international visitor from Russia.

The speech topics were as follows: