[Zope] temporary images

[Robin Becker]

My Zen has vanished. I want to calculate some images and have them
displayed. I tried some simple experiments with external methods.

ImageClock(self) computes the bytes for a Gif image of the current time.
UniqueId(self) returns a unique identifier. ChartClock is defined thusly
def ChartClock(self):
    return self.REQUEST['ChartClock']

when this is displayed I see the first image, but not the second.

<dtml-var standard_html_header>
<p>This works <img src=ImageClock?_,<dtml-var UniqueId> ></p>
<dtml-call "REQUEST.set('ChartClock',ImageClock(_))">
<p>This doesn't <img src=ChartClock?_,<dtml-var UniqueId> ></p>
<dtml-var standard_html_footer>

Firstly why don't I get an error with too many arguments.
Secondly why/how do these two processes differ.

The reason for the <dtml-var UniqueId> is to make each view of the clock
different.
-- 
Robin Becker