Making Movies: problems

[Sven N. Thommesen]

Swarm 1.3 contains new code (in the Pixmap class) to save snapshots of
screens to disk for the purpose of being able later to view the visual
state of the system at some particular sim time.

The demo code in Heatbugs demonstrates how to save the whole root window,
and this works well. The code also holds out the implicit promise that it
should be possible to save the images of individual widgets, which I have
now tried to do (under X on Linux). 

I *was* able to create snapshots of the different types of widgets we have
(control panel, probes, rasters, EZGraphs (Graphs) and EZBins (Histograms).
But there were some problems:

1. EZBin needs a method -getHisto for access to the underlying histogram
widget, to parallel EZGraph's -getGraph.

2. The resulting bit maps show only the 'contents' of the windows, without
the surrounding border decorations, and without the window title.

3. If the window is overlapped by something else on the screen, the saved
bitmap shows the window with whatever was on top of it, rather than the
unencumbered window.

4. If you use fvwm's window manager's 'virtual desktop' feature, Pixmap is
not able to snapshot widgets that are not on the current pane of the
current desktop.  

5. For curiosity only: if I try to snapshot [widget getParent] instead of
the widget itself, I get the whole window for probe widgets, but not for
raster widgets ... ? And for widgets off the current window, I still get a
snapshot of the root window, not the window the widget is actually on ... ?

6. I won't even ask if the current code allows for making movies from
BatchSwarm, along the lines of Benedikt's earlier efforts ... ?

I believe these shortcomings are not necessarily inherent to or dictated by
X itself, and I'm sure other users would appreciate if our expert
programmers were able to remove these limitations in an upcoming release.

Sven Thommesen


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