Wintertree Spell Check Applet
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Memory consumption in Internet Explorer

When Wintertree Spell Check Applet is used with Internet Explorer using Microsoft's JVM, memory consumed by Internet Explorer increases each time the user goes to another page then returns to the page into which Spell Check Applet is embedded. For example, if the user works on a form which uses Wintertree Spell Check Applet, then switches to some other page, then returns to the form, the memory used by Internet Explorer will increase. After many such switches, the amount of memory consumed by Internet Explorer becomes large, and system sluggishness may result.

The problem is reproducible with any applet that allocates memory. In tests run by Wintertree Software using Internet Explorer 5.5 with Microsoft's JVM, Internet Explorer calls the applet's "destroy" method whenever the user switches to another page. Even if the applet explicitly "frees" memory in the destroy method (by setting the allocated object to "null" and calling System.gc), memory continues to be consumed by Internet Explorer. One possible explanation for this behavior is that IE creates a new instance of the applet each time the page containing the applet is visited, but does not release memory allocated by previous instances. Possibly at some point IE will eventually release the allocated memory, but in tests conducted by Wintertree Software this did not happen.

This problem does not occur when Internet Explorer uses Sun's JVM, so the simplest solution is to upgrade the browser.

Another solution is to use HTML frames. Place Spell Check Applet in a separate frame which remains static, and modify the JavaScript code which supports the applet to access the applet in that frame (instead of the local window). Any changeable pages appear in other frames. Because Spell Check Applet appears in a frame that never changes, it is not destroyed and so memory it allocates is not lost. If you don't want to use frames in your site's user interface, you can place Spell Check Applet in a very small frame that is essentially invisible.

The only other known solution to the problem is close all running copies of Internet Explorer when memory allocation becomes high, then start Internet Explorer again. Closing IE frees the memory it has allocated.