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.You could define an onLoad handler for the BODY element of a document that initiates any animations in the document.The onLoad handler for a BODY element may be invoked before all frames in all animated GIF images have finished loading, but it will not be invoked until at least one frame of every animated GIF image has finished loading.Layers can also have onLoad handlers.However, if a layer contains images, the images may load asynchronously from the rest of the layer's content, and the layer may think it has finished loading and thus fire its onLoad handler (if it has one) before all its images have finished loading.Images can have onLoad handlers also.However, if the image is an animated GIF, its onLoad handler is invoked every time a frame in the image finishes loading.Therefore if your image is an animated GIF, it is better to define an onLoad handler that initiates any animations that use that image in the BODY element rather than directly on the image.However, it the image is a static GIF or JPEG, by all means define the onLoad handler directly on the image.discusses an example, , that has a layer containing a fish that swims back and forth.The fish starts swimming when someone clicks on a button.To ensure that nobody can click the button before the fish image has finished loading, the layer containing the button is initially hidden.When the document has finished loading, its onLoad handler makes the form layer visible.Pre-fetching ImagesOne way to reduce the time required to start an animation is to ensure that the images used in the animation are downloaded to the browser's cache before the animation starts.This approach is known as prefetching the images.You can prefetch an image by embedding it in a layer.When a layer loads, it loads all its content, including all images, regardless of whether the layer is visible or not.If a page has a hidden layer that contains all the images needed in the animation then when the page opens, the source for the images is downloaded into the browser's cache, even though they are not visible.discusses an example, , that illustrates the use of a hidden layer to contain images that are not needed when the page opens but are used in the course of animating the contents of the page.Suppressing the Icon for Images that Have Not Yet LoadedBy default, when a page opens, it shows a placeholder icon for every image in the page that has not finished loading.Animation sequences may sometimes require multiple images.While the images are loading, the user could see lots of placeholder icons that you would prefer they did not see.A new attribute has been introduced for the IMG tag to allow you to suppress the display of placeholder icons.The SUPPRESS attribute for the IMG tag can be set to either true or false.The default value is false.If SUPPRESS is set to true, neither the place-holder icon or frame that appear during image loading will be displayed and tool-tips will be disabled for that image.If SUPPRESS is set to false, the place-holder icon and frame will always be displayed during loading even if the images are transparent images that would not otherwise be displayed.Tool tips will be active.Last Updated: 08/07/97 15:21:59Copyright © 1997Netscape Communications Corporation [ Pobierz caÅ‚ość w formacie PDF ]
