I'm new to Ractive.js and wondering if there's a lifecycle event I can use to know whenever Ractive is done making DOM updates in response to data changes?
My use-case is that I have a grid of boxes (simple divs) rendering some text from the data model. Whenever my data model updates, Ractive is properly updating the DOM for me. But when it's finished with that, I want to dynamically adjust the font size within each box to make sure the text fits.
This is just the first thing that crossed my mind for sizing my text to fit and it might not be the right solution... but I'm surprised I haven't found such a lifecycle event?
Here's the doc I'm looking at: http://docs.ractivejs.org/latest/lifecycle-events. My application is using magic mode to handle updates.
Unless someone more knowledgeable basically corrects the documentation, it looks like there's no lifecycle event to listen to.
However, I've discovered that Ractive's concept of Decorators give me the functionality I was looking for. By passing a Decorator to my Ractive instance, I get passed the DOM nodes created by RactiveJS and I'm able to do whatever work I need to do (in my case, computing whether the text in the node fits in its container and scaling it down in Javascript).
Related
ok so I have a TitleWindow that I open up... and I have 6 states defined. I am using the Presentation model pattern for all of my views. I have discovered a frustrating nuance. When I tell my window to go to XXX state, the controls have to initialize since the states in flex use lazy loading. so... my PM code that says myTextArea.text bombs out and say "cannot access..." so as a work around, I made some creationComplete events on my controls to register the control with the PM. So when the state changes, the textarea finally initializes and on creationComplete calls PM.registerTextArea() which sets a reference to it. then in that function I run my code... myTextArea.text.. etc.
This seems like such a ugly hack that I hate it. Is there any way to wait until the entire state in created then call code on the PM? I have tried enterstate... but this event seems to fire before the state controls are ready.
I tried to add a comment, but I guess editing is the only way I can do this...
to everyone: thanks for the great feedback. I am doing something slightly off straight PM. Every view has a viewController (as I call them). Its kinda my own hybrid of a delegate / dataprovider. But this is moot. It's the flex component lifecycle when dealing with states that is the pain. if you change state.. there is no event to say "all my components in this state are ready". only event to say "we changed state". so my code that fires on state change is trying to talk to components that aren't ready yet. So from what I see, there seems to be no design pattern or perfect way to ensure that all components are created in a state unless using creationComplete on every component in the state to register it is ready... if you don't, you get a race condition. Regardless of frameworks or design patterns, this seems to be a root issue.
The textarea is an easy PM fix.. just bind it to the pm value. But there are other times I can't.
Specifically, I am trying to attach video to a display once I get to that state. This is done via addchild. regardless of where I do it.. I need to know that the videoDisplay is done loading before I call addchild. I even tried currentStateChange event since docs say that fires last... but alas.. the components in the state are still initializing. So it seems that creationComplete is my only option. Maybe the only sane way to keep to clean code is to create the entire thing (videodisplay and video) using as once the state is entered. I just hoped the flex framework had events to ehlp me here rather than buiilding everything on the fly in as.
Since your PM has a reference to a visual component (myTextArea), this isn't a completely pure form of a presentation model. It appears to be more of a supervising presenter / controller type of setup.
That being said, the way I would fix your problem would be to use a complete presenter outright ( no knowlege of the view at all ) or use a complete controller ( view implements an interface through which the controller communicates ). The advantage of using a presenter in Flex is that you can create a bindable value such as text or selectedItem, and the view will bind to that variable whenever it comes online so the issues dealing with the lifecycle of Flex components go away.
I have a List component from which I'd like to be able to remove items using drag & drop, but without having a specific target. If you use the mac, the behaviour I'm looking for is something like what the Dock uses; when you drag something out of the bounds of the control it should get an icon that indicates that it'll be deleted (OSX uses a cloud or something?) and then if you release it it will be removed from the list.
How can I do this?
(If I need to provide a more clear description, please comment; I'll fill in what I can)
In my experience with drag/drop in Flex, you cannot simply drag something out and handle that. There is no dragOut event (unfortunately), so that would leave you up to the task of writing dragOver and dragDrop listeners on all the containers surrounding your dragInitiator and handling the process accordingly.
It's more time consuming and can become complicated if any of these controls already have specific dragOver and dragDrop event handlers.
Hope this helps.
Having no Flex experience all I can offer is some psuedo code which resembles how I implemented a similar effect in JavaScript, but hopefully it will get you started.
Essentially what you'll want to do is during your drag event measure the current coordinates of the object you're dragging to see if they intersect the original container and when they fall outside of its bounds call the logic to update the icon in order to indicate it will be removed. Then, on the drop event, check the coordinates once more and delete the item if needed.
When I try to access the hidden TABs of my tab navigator control in action script, it returns a null error. But it works OK if I just activate the control in the user interface once. Obviously the control is not created until I use it. How do I make all the tabs automatically created by default ?
<mx:TabNavigator creationPolicy="all"/>
That should do it. Deferred instanciation is a feature, but sometimes it is a hassle.
The Flex framework is optimizing creation be default (creationPolicy="auto") so if you have a configuration dialog with a lot of tabs, for example, and the most useful tab is the first one, your application does not spend time and memory initializing the tabs that the user never sees.
This makes a lot of difference when dialogs like this never release, and is a good default to go with.
One thing to look at is using a private variable in your dialog/form instead of pushing the data to the control on the hidden page. This style treats the whole form as if it were a component, which it sort of is. To repeat: the MXML form/dialog/canvas is a class, and it can have data and methods in addition to containing other components.
Cheers
On a side note, I've run into the deferred-loading policy in a multi-state application, and circumvented it by forcing all elements to be included and invisible in the initial state. Something to consider, but only as a hack.
What is the best way to render to a UIComponent which hasn't been added to the stage? (I'm using UIComponents as renderers for objects, and want to render new copies for image export, filtering, etc.)
Two strategies I've seen/used so far include realizing the component to ensure it calls all the lifecycle methods:
Add the component to Application.application, render with BitmapData.draw(), remove component. This is similar to what I've seen done for printing unrealized components as well.
Add the component to a pop up window, render with BitmapData.draw(), dismiss popup after rendering complete.
I believe both of these just rely on the UI not refreshing while the current thread/event is executing, though (1) could also rely on the component being realized out of view.
Is there a better way?
What I've used in the past with much success is the following:
Create a new instance of your component
Add an event listener for FlexEvent.CREATION_COMPLETE
Set visible=false on the component
Add the component as a child of the main Application
When the component is created, the event listener function will be invoked. The rest of the logic should be put in / invoked from your event listener function
Remove the event listener you added in step #2.
Use ImageSnapshot.captureImage() or captureBitmapData() to capture the visual representation of the component.
Remove the component from the main Application
Process the image data as you need to.
I've used this to snapshot various Flex charting components for use in PDF's generated on the server side. After getting the BitmapData I use the PNGEncoder or JPEGEncoder classes to compress the data, then encode it in Base64 before uploading to the server.
I'm pretty sure you can use the draw() method in BitmapData without having your component on the DisplayList.
For example is use it when I need to modify images I load with the Loader Class. In the init handler I create a BitmapData instance and draw the Bitmap from the loadInfo.content property, then copyPixels() or whatever I need to modify the loaded image
So much of a UIComponent's layout can be tied to it's context. This is especially true for a lot of its derivatives (e.g. HBox) since the fluidity of the layout is tied to it's parent's size and the number of siblings sharing its parents space.
Additionally Flex can be a real pain to get to visually update. Often critical render functions aren't done synchronously ... there are callLater, callLater2 and other hacky approaches that make dealing with the auto-magical layout properties of UIComponents a major headache. Not even calling validateNow or updateDisplayList can guarantee that the layout will be correct on the current frame (instead of a few frames in the future).
I suggest the best thing you can do is not use a UIComponent and try and use a Sprite or other.
Your approach to attach it but make it invisible (alpha = 0, mouseEnabled = false, mouseChildren = false) is decent. You should listen for the FlexEvent.CREATION_COMPLETE callback before you are certain it is properly laid out. Then you can bitmapData.draw it and then remove it from the stage. If you must use UIComponents then I know of no better way.
You can call the lifecycle function manually before using the BitmapData.draw(). Do the following.
createChildren().
commitProperties().
updateDisplayList().
bmd.draw().
The first 2 steps are not 100% necessary, you can put all codes into updateDisplayList(). Because you invoke the function manually, you don't have to worry this is invoked by Flex framework many times.
I've written a simple calendar control to allow for selecting single days, weeks, months and so on. The simplicity comes from the fact that I don't really do any drawing myself, opting instead to create a bunch of boxes and labels to act as date cells for the calendar.
When a date or a date range is selected, I need to highlight that range. It's easily done by iterating through the cells and switching their style. [edit:] However, this seems to cause a delay during which the cells are first drawn as if the style name was blank, and then re-drawn with the correct style, despite the fact that I never explicitly set the style to null -- I alternate between "CalendarCell" and "CalendarCellSelected".
If this were Windows Forms, I'd call SuspendLayout on the parent container to make sure the controls are repainted only after I've finished the updates. What I'm looking to know is whether or not a similar solution exists for Flex. I'd like to avoid drawing the entire calendar "manually", so to speak, if that's at all possible.
edit: changed the problem description to more accurately reflect what I'm seeing.
Are you using callLater() at all?
If you use callLater() it may impove your visuals as it batches up changes until it needs to draw a frame or you force a frame draw with validateNow() or similar. It might be enough in your case.
Is your calendar control a UIComponent? Is it using the standard invalidation methods like commitProperties(), updateDisplayList(), etc?
What you might want to do is keep a private array of the cells that will have their styles changed, but then do the actual style switching in your commitProperties() override. I'm just not sure if setStyle() fires an validateNow() because the flickering is a bit surprising.
This may not be exactly what you're looking for, but David Coletta at Adobe has posted a video explaining an EventCoalescer that they use in Buzzword for deferring events that update specific areas of the app UI until the user has stopped moving the insertion point in the text, for example.
This blog post by Hans Van de Velde also has a similar solution, and actual code for it as well.