I've customised the style of a ListBox in order to register for the VirtualizingStackPanel.CleanUpVirtualizedItemEvent. I need to free up some memory when the item is re-virtualized, and then re-load the memory when it is un-virtualized. Whenever I check to see if the item is virtualized, it always returns false:
const bool isVirtualizing = VirtualizingStackPanel::GetIsVirtualizing(e->UIElement); // Always returns false
How do I work with this event? I can change the ListBox to use VirtualizingStackPanel.VirtualizationMode="Standard" but that causes the UI to be created and deleted constantly, which can lead to performance issues. I'd rather recycle the UI controls if possible.
Related
In order to optimize createjs code, I cannot find info on this matter.
Case:
I have a scrollbar component, and each time I move the scrollbar stage is updated to reflect changes in scrollbar visual. Also a scroll event is triggered.
Application listens to the event, and updates some visual in scrolled content, therefore another Stage.update() is triggered.
My question is: does stage get updated only at each "tick", or the above situation will cause stage to update twice in the same instant degrading performance?
In code, will:
stage.update();
stage.update();
stage.update();
Cause stage to update 3 times in a row? Or only once at next tick?
Thank you
There is no debouncing on the stage update, so each time you call it, the stage will be rendered. Additionally, internal counters like tick-based frame advances will be fired.
It is not advisable to run it more times than you need to. Usually apps either have a continuous Ticker, or are updated only when content changes.
If you want to create a hybrid, I recommend checking an update property that you set yourself. Then you can toggle it any time, and it will run once per tick max.
createjs.Ticker.on("tick", function(e) {
if (shouldUpdate) { stage.update(e); }
shouldUpdate = false;
});
Hope that helps!
From the manual:
The latter four events have some overhead associated with them, so you
need to enable them with stage.enableMouseOver(frequency). The
frequency parameter indicates how many times per second EaselJS should
calculate what is currently under the pointer. A higher number is more
responsive, but also more computationally expensive.
I need to enable a mouseover functionality only on a certain class of objects on my otherwise crowded stage. Is there a way to enable the mouseover checking only for certain objects as opposed for the whole stage? Or is EaselJS only checking objects with a "mouseover / mouseout, and rollover / rollout" listener? What about the pointer property - it works only if enableMouseOver is enabled - is that checked for all objects or only for those with pointer property other than default?
Is EaselJS internally doing some space partitioning like k d trees to boost the performance?
You can prevent any object from receiving a mouse event by setting mouseEnabled=false.
myBitmap.mouseEnabled = false;
If you have a large amount of items (such as particles), make sure they are in a container, and set mouseEnabled AND mouseChildren=false on the container, and the Stage will not check any of the container's children.
myContainer.mouseEnabled = myContainer.mouseChildren = false;
If you still want to know when a container's general area is clicked, you can swap out the default mouse behaviour with a hitArea, which is used in place of its actual contents.
var hitArea = new createjs.Shape();
hitArea.graphics.drawRect(0, 0, 500, 500);
myContainer.hitArea = hitArea;
Hope that helps!
For improving the performance i used cache if any object is static
I used mouseEnabled =false;
I did not render any text or images inside the canvas i used mix of
angular or plain javascript to render the dom element
Fairly new to developing for Windows 8, I'm working on an app that has a rather flat model. I have looked and looked, but can't seem to find a clear answer on how to set a WinJS page to prevent backward navigation. I have tried digging into the API, but it doesn't say anything on the matter.
The code I'm attempting to use is
WinJS.Navigation.canGoBack = false;
No luck, it keeps complaining about the property being read only, however, there are no setter methods to change it.
Thanks ahead of time,
~Sean
canGoBack does only have a getter (defined in base.js), and it reflects the absence or presence of the backstack; namely nav.history.backstack.
The appearance of the button itself is controlled by the disabled attribute on the associated button DOM object, which in turn is part of a CSS selector controlling visibility. So if you do tinker with the display of the Back button yourself be aware that the navigation plumbing is doing the same.
Setting the backstack explicitly is possible; there's a sample the Navigation and Navigation History Sample that includes restoring a history as well as preventing navigation using beforenavigate, with the following code:
// in ready
WinJS.Navigation.addEventListener("beforenavigate", this.beforenavigate);
//
beforenavigate: function (eventObject) {
// This function gives you a chance to veto navigation. This demonstrates that capability
if (this.shouldPreventNavigation) {
WinJS.log && WinJS.log("Navigation to " + eventObject.detail.location + " was prevented", "sample", "status");
eventObject.preventDefault();
}
},
You can't change canGoBack, but you can disable the button to hide it and free the history stack.
// disabling and hiding backbutton
document.querySelector(".win-backbutton").disabled = true;
// freeing navigation stack
WinJS.Navigation.history.backStack = [];
This will prevent going backward and still allow going forward.
So lots of searching and attempting different methods of disabling the Back Button, finally found a decent solution. It has been adapted from another stackoverflow question.
Original algorithm: How to Get Element By Class in JavaScript?
MY SOLUTION
At the beginning of a fragment page, right as the page definition starts declaring the ready: function, I used an adapted version of the above algorithm and used the resulting element selection to set the disabled attribute.
// Retrieve Generated Back Button
var elems = document.getElementsByTagName('*'), i;
for (i in elems)
{
if((" "+elems[i].className+" ").indexOf("win-backbutton") > -1)
{
var d = elems[i];
}
}
// Disable the back button
d.setAttribute("disabled", "disabled");
The code gets all elements from the page's DOM and filters it for the generated back button. When the proper element is found, it is assigned to a variable and from there we can set the disabled property.
I couldn't find a lot of documentation on working around the default navigation in a WinJS Navigation app, so here are some methods that failed (for reference purposes):
Getting the element by class and setting | May have failed from doing it wrong, as I have little experience with HTML and javascript.
Using the above method, but setting the attribute within the for loop breaks the app and causes it to freeze for unknown reasons.
Setting the attribute in the default.js before the navigation is finished. | The javascript calls would fail to recognize either methods called or DOM elements, presumably due to initialization state of the page.
There were a few others, but I think there must be a better way to go about retrieving the element after a page loads. If anyone can enlighten me, I would be most grateful.
~Sean R.
I have problem in DOJO with DataGrid. I refresh my grid on every 1 sec with this code
window.store_data_log= new dojo.data.ItemFileReadStore({data:{items:temp}});
var grid = dijit.byId("grid_log");
grid.setStore(window.store_data_log);
and it works fine ( put new data ). Problem is that when I have lot off rows and I scroll down, my grid refreshs and my scroll goes on top grid. How to solve this ?
Of course, you are totally clearing the store and resetting it every second from scratch. When you reset the store, you basically reset the grid. I would expect nothing less than the grid resetting the scroll position when you refresh its store.
You may want to learn how to properly use the store rather than just trying to reset it. I answered this here:
How to refresh datagrid
If you use dojo properly, you will get good results, but by just taking a shortcut and trying to refresh the store every second you are going to get an unusable grid.
You need to take a step back and solve your application architecture and not expect the grid refresh to be some kind of magic solution.
After going through (dojo) datagrid.js, I found how to resolve the issue:
//datastore you're using//
var store = new dojox.data.QueryReadStore({
//in the fetch()//
fetch: function (request){
//add the following://
request.isRender = false;
}
});
Important: Only set request.isRender to false when you don't want the grid to scroll back to the top. Just keep in mind that some situations (like sorting on a new column), it's probably best to set it to true. Just add some if/else statements to help with the logic.
I just have a query on deleting displayobject instance. Let me elaborate on this:
I had created a custom component called ‘PanelItem’ (which basically contains a Text Area and a close button in a Panel container)
Then in the main.mxml, I had utilized the above custom component as follows:
var tempPanel: PanelItem = new PanelItem();
Subsequently assigned values for its attributes such as x,y, width, height and id for tempPanel and then added child instances as below
addChild(tempPanel);
The above code displays one instance of the custom displayobject. My problem is that when the ‘close’ button on the panel is clicked, I want the displayobject instance to be removed from the memory.
To do the ‘close’ action, I had added the following to the code
tempPanel.removAllChildren();
tempPanel.visible = false;
But the above only removes the children of displayobject and the doesnot removes the displayobject instance completely from memory. I read somewhere I need to ‘delete’ the displayobject, but could not find any reference to the same in the help file
Any thoughts on how do I go about removing the displayobject completely from memory?
Anther question I have is, if I had invoked multiple instances of tempPanel, how do I get a count of the number of instances.
TempPanel.numChildren() only returns the number of child instance (which got invoked thru addChild method) and not the actual numbers of displayobjects floating around.
Any help on the above will be much appreciated.
Thanks
Srinivasan S
you could extend from CasaSprite (http://as3.casalib.org/docs/org_casalib_display_CasaSprite.html) which has a destroy function.