[jira] [Updated] (TRINIDAD-1442) Aggregate single image to send to client

["Scott O'Bryan (Updated) (JIRA)" <de...@myfaces.apache.org>]

     [ https://issues.apache.org/jira/browse/TRINIDAD-1442?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Scott O'Bryan updated TRINIDAD-1442:
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    Status: Open  (was: Patch Available)
    
> Aggregate single image to send to client
> ----------------------------------------
>
>                 Key: TRINIDAD-1442
>                 URL: https://issues.apache.org/jira/browse/TRINIDAD-1442
>             Project: MyFaces Trinidad
>          Issue Type: New Feature
>          Components: Skinning
>            Reporter: Korhan Bircan
>            Priority: Minor
>         Attachments: 1.2.12.2_imageStripPrototype.patch
>
>
> Instead of sending Trinidad specific and application dependent images one by one, aggregate them into one big image strip and send this strip to the client at one time. Benefits will be twofold. First, there will be fewer HTTP requests and the cold browser page load time will be faster. Second, when png or gif images are combined, they take less space than the sum of individual images.
> This feature would only improve the cold browser load times. There would be no performance improvement for the warm browsers. There should be no change in the look-and-feel of any page.
> In my current implementation I'm using a temporary private context parameter, "org.apache.myfaces.trinidadinternal.ENABLE_IMAGE_AGGREGATION", to turn the feature on and off in case there are any bugs early on. It can be removed once the feature is fully tested. If the feature works properly it should always be on.
> The code starts in trinidadinternal.style.cache.FileSystemStyleCache::_createEntry(). This method creates and caches a style sheet. All the StyleNode's are iterated and if a StyleNode has background-image, an ImageStripIcon is created with the background-image, background-position, width, and height properties of that StyleNode. This ImageStripIcon is appended to an icon map.
> The same selector may appear in multiple places and may define different properties (eg. background-image in one place, background-position in another). In order to match the selectors with background-images, we keep track of the selector names that contain background-images. If a selector is associated with a background-image, we add it to the corresponding ImageStripIcon's selector vector.
> Once we have collected all the background-images and background-positions, width, height information associated with them, we create the image strips. Because there may be multiple image formats (right now gif and png) we store the image strips in an imageStripVec (Vector< ImageStrip >).
> The CSS file is written out in trinidadinternal.style.util.CSSGenerationUtils, we pass imageStripVec and selectorMap to _createStyleSheetFiles(), which calls CSSGenerationUtils.writeCSS() passing along these two arguments.
> In writeCSS() the StyleNodes are converted to CSS. When the StyleNodes are written out we tap in when we see a "background-image" property and insert the image strip name instead of the actual image name, and the image's strip coordinates as background-position, and width/height properties.
> Relevant files:
> trunk_1.2.10.1-branch_imageStripping\trinidad-impl\src\main\java\org\apache\myfaces\trinidadinternal\style\cache\FileSystemStyleCache.java
> trunk_1.2.10.1-branch_imageStripping\trinidad-impl\src\main\java\org\apache\myfaces\trinidadinternal\style\cache\ImageStrip.java
> trunk_1.2.10.1-branch_imageStripping\trinidad-impl\src\main\java\org\apache\myfaces\trinidadinternal\style\cache\ImageStripIcon.java
> trunk_1.2.10.1-branch_imageStripping\trinidad-impl\src\main\java\org\apache\myfaces\trinidadinternal\style\cache\ImageStripUtils.java
> trunk_1.2.10.1-branch_imageStripping\trinidad-impl\src\main\java\org\apache\myfaces\trinidadinternal\style\util\CSSGenerationUtils.java
> Possible issues:
> * All css images would be loaded in memory while creating the image strip which is additional memory utilization.
> * All css images need to be followed by background-position property, which would make css file size larger. This could be offset by replacement of image names. Images names are arbitrarily long, they will be replaced with a fixed length image strip name (could be as short as possible), thus making the file size smaller.
> * Images that have background-repeat:repeat-x property would have to go to a separate image strip file.

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