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Terms, Icons, and Labels

Many classes have shortcut names used when creating (instantiating) a class with a configuration object. The shortcut name is referred to as an alias (or xtype if the class extends Ext.Component). The alias/xtype is listed next to the class name of applicable classes for quick reference.

Access Levels

Framework classes or their members may be specified as private or protected. Else, the class / member is public. Public, protected, and private are access descriptors used to convey how and when the class or class member should be used.

Member Types

Member Syntax

Below is an example class member that we can disect to show the syntax of a class member (the lookupComponent method as viewed from the Ext.button.Button class in this case).

lookupComponent ( item ) : Ext.Component

Called when a raw config object is added to this container either during initialization of the items config, or when new items are added), or {@link #insert inserted.

This method converts the passed object into an instanced child component.

This may be overridden in subclasses when special processing needs to be applied to child creation.


item :  Object

The config object being added.


The component to be added.

Let's look at each part of the member row:

Member Flags

The API documentation uses a number of flags to further commnicate the class member's function and intent. The label may be represented by a text label, an abbreviation, or an icon.

Class Icons

- Indicates a framework class

- A singleton framework class. *See the singleton flag for more information

- A component-type framework class (any class within the Ext JS framework that extends Ext.Component)

- Indicates that the class, member, or guide is new in the currently viewed version

Member Icons

- Indicates a class member of type config

- Indicates a class member of type property

- Indicates a class member of type method

- Indicates a class member of type event

- Indicates a class member of type theme variable

- Indicates a class member of type theme mixin

- Indicates that the class, member, or guide is new in the currently viewed version

Class Member Quick-Nav Menu

Just below the class name on an API doc page is a row of buttons corresponding to the types of members owned by the current class. Each button shows a count of members by type (this count is updated as filters are applied). Clicking the button will navigate you to that member section. Hovering over the member-type button will reveal a popup menu of all members of that type for quick navigation.

Getter and Setter Methods

Getting and setter methods that correlate to a class config option will show up in the methods section as well as in the configs section of both the API doc and the member-type menus just beneath the config they work with. The getter and setter method documentation will be found in the config row for easy reference.

History Bar

Your page history is kept in localstorage and displayed (using the available real estate) just below the top title bar. By default, the only search results shown are the pages matching the product / version you're currently viewing. You can expand what is displayed by clicking on the button on the right-hand side of the history bar and choosing the "All" radio option. This will show all recent pages in the history bar for all products / versions.

Within the history config menu you will also see a listing of your recent page visits. The results are filtered by the "Current Product / Version" and "All" radio options. Clicking on the button will clear the history bar as well as the history kept in local storage.

If "All" is selected in the history config menu the checkbox option for "Show product details in the history bar" will be enabled. When checked, the product/version for each historic page will show alongside the page name in the history bar. Hovering the cursor over the page names in the history bar will also show the product/version as a tooltip.

Search and Filters

Both API docs and guides can be searched for using the search field at the top of the page.

On API doc pages there is also a filter input field that filters the member rows using the filter string. In addition to filtering by string you can filter the class members by access level, inheritance, and read only. This is done using the checkboxes at the top of the page.

The checkbox at the bottom of the API class navigation tree filters the class list to include or exclude private classes.

Clicking on an empty search field will show your last 10 searches for quick navigation.

API Doc Class Metadata

Each API doc page (with the exception of Javascript primitives pages) has a menu view of metadata relating to that class. This metadata view will have one or more of the following:

Expanding and Collapsing Examples and Class Members

Runnable examples (Fiddles) are expanded on a page by default. You can collapse and expand example code blocks individually using the arrow on the top-left of the code block. You can also toggle the collapse state of all examples using the toggle button on the top-right of the page. The toggle-all state will be remembered between page loads.

Class members are collapsed on a page by default. You can expand and collapse members using the arrow icon on the left of the member row or globally using the expand / collapse all toggle button top-right.

Desktop -vs- Mobile View

Viewing the docs on narrower screens or browsers will result in a view optimized for a smaller form factor. The primary differences between the desktop and "mobile" view are:

Viewing the Class Source

The class source can be viewed by clicking on the class name at the top of an API doc page. The source for class members can be viewed by clicking on the "view source" link on the right-hand side of the member row.

Ext JS 6.0.1 - Classic Toolkit


Ext.grid.plugin.BufferedRenderer alias: plugin.bufferedrenderer private


NOTE: This is a private utility class for internal use by the framework. Don't rely on its existence.


Implements buffered rendering of a grid, allowing users to scroll through thousands of records without the performance penalties of rendering all the records into the DOM at once.

The number of rows rendered outside the visible area can be controlled by configuring the plugin.

Users should not instantiate this class. It is instantiated automatically and applied to all grids.

Implementation notes

This class monitors scrolling of the Ext.view.Table within a Ext.grid.Panel to render a small section of the dataset.

No members found using the current filters


Optional Configs

leadingBufferZone : Number

The number of extra rows to render on the leading side of scrolling outside the numFromEdge buffer as scrolling proceeds.

Defaults to:


numFromEdge : Number

The zone which causes new rows to be appended to the view. As soon as the edge of the rendered grid is this number of rows from the edge of the viewport, the view is moved.

Defaults to:


scrollToLoadBuffer : Number

This is the time in milliseconds to buffer load requests when the store is a and a page required for rendering is not present in the store's cache and needs loading.

Defaults to:


synchronousRender : Boolean

By default, on detection of a scroll event which brings the end of the rendered table within numFromEdge rows of the grid viewport, if the required rows are available in the Store, the BufferedRenderer will render rows from the Store immediately before returning from the event handler. This setting helps avoid the impression of whitespace appearing during scrolling.

Set this to false to defer the render until the scroll event handler exits. This allows for faster scrolling, but also allows whitespace to be more easily scrolled into view.

Defaults to:


trailingBufferZone : Number

The number of extra rows to render on the trailing side of scrolling outside the numFromEdge buffer as scrolling proceeds.

Defaults to:



Instance Properties

isBufferedRenderer : Boolean

true in this class to identify an object as an instantiated BufferedRenderer, or subclass thereof.

Defaults to:


position : Number

Current pixel scroll position of the associated Ext.view.Table.

Defaults to:



Instance Methods

afterTableLayout ( ownerContext )
private pri


ownerContext :  Ext.layout.ContextItem

The view's layout context Called when a view's layout run is complete.

beforeTableLayout ( ownerContext )
private pri


ownerContext :  Ext.layout.ContextItem

The view's layout context Called before the start of a view's layout run

getLastVisibleRowIndex ( startRow, endRow, viewportTop, viewportBottom ) : Number
private pri

Returns the index of the last row in your table view deemed to be visible.


startRow :  Object

endRow :  Object

viewportTop :  Object

viewportBottom :  Object



private pri

TableView's getViewRange delegates the operation to this method if buffered rendering is present.

onReplace ( store, startIndex, oldRecords, newRecords )
private pri

Handles the Store replace event, producing a correct buffered view after the replace operation.


store :  Object

startIndex :  Object

oldRecords :  Object

newRecords :  Object

onViewResize ( view, width, height, oldWidth, oldHeight )
private pri

Called directly from Ext.view.Table#onResize. Reacts to View changing height by recalculating the size of the rendered block, and either trimming it or adding to it.


view :  Ext.view.Table

The Table view.

width :  Number

The new Width.

height :  Number

The new height.

oldWidth :  Number

The old width.

oldHeight :  Number

The old height.

refreshView ( startIndex )
private pri

Refreshes the current rendered range if possible. Optionally refreshes starting at the specified index.


startIndex :  Object

scrollTo ( record, [options] )
private pri

Scrolls to and optionally selects the specified row index in the total dataset.

This is a private method for internal usage by the framework.

Use the grid's ensureVisible method to scroll a particular record or record index into view.


record :  Number/

The record, or the zero-based position in the dataset to scroll to.

options :  Object (optional)

An object containing options to modify the operation.

animate :  Boolean (optional)

Pass true to animate the row into view.

highlight :  Boolean (optional)

Pass true to highlight the row with a glow animation when it is in view.

select :  Boolean (optional)

Pass as true to select the specified row.

focus :  Boolean (optional)

Pass as true to focus the specified row.

callback :  Function (optional)

A function to call when the row has been scrolled to.

recordIdx :  Number

The resulting record index (may have changed if the passed index was outside the valid range).

record :

The resulting record from the store.

node :  HTMLElement

The resulting view row element.

scope :  Object (optional)

The scope (this reference) in which to execute the callback. Defaults to this BufferedRenderer.

column :  Ext.grid.column.Column / Number (optional)

The column, or column index to scroll into view.

Ext JS 6.0.1 - Classic Toolkit