XForms: Double-buffering of image data

Thim Kwan (tkwan@earthlink.net)
Sat, 23 Oct 1999 08:23:16 +0000

# To subscribers of the xforms list from Thim Kwan <tkwan@earthlink.net> :

Does anyone know of a way to compose an image and graphics (lines, text,
circles, etc) off-screen and then bit-blit it to an on-screen canvas
window (or a free object window)? I tried freezing and unfreezing the
form, turning on double-buffering for the canvas object, and even using
XUnmapWindow and XMapWindow, but without success.

Currently, the image is displayed by calling flimage_display and then
the graphics are drawn on top of the image. However, this produces a
flickering effect as everything is being drawn into the visible canvas
window. Ideally, there should be a way to draw everything off-screen
and then display it all at once into the visible canvas window. Is this
possible? I know I can do this using Xlib calls by drawing into a
pixmap first and then copying into a window, but I would rather do it
with the Forms library if at all possible.

Thanks,

Thim Kwan
SSR Engineering, Inc

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