On Mon, 21 Mar 2011, Mattias Gaertner wrote:
On Mon, 21 Mar 2011 11:53:52 +1000
Alexander Klenin <[email protected]> wrote:
On Mon, Mar 21, 2011 at 08:41, Mattias Gaertner
<[email protected]> wrote:
On Mon, 21 Mar 2011 04:58:18 +1000
Alexander Klenin <[email protected]> wrote:
Hm. For me GUI means "graphical user interface" -- that is, windows (aka forms),
interacting with mouse, etc.
I have just committed a demo which does not have any of this,
and yet successfully draws TChart to a file -- see previous mail.
Maybe for you GUI means a different thing?
Yes. The GUI of the screen.
By accessing the LCL canvas you access the widgetset (gtk2) which
accesses the current screen. For example the gtk2 asks for
theme, fonts, screen color depths and sub pixel rendering parameters.
A cgi program has no screen.
It is ok to ask for all these things since thay are necessary to
render the chart.
However, the fact they are unconditionally taken from the screen is IMO
a deficiency of either GTK or LCL-GTK.
The display error comes from the gtk.
As you can see in this thread, as soon as this deficiency is worked around,
(in this case, by using Xvfb utility), the problem is solved.
I wonder how much overhead it is for a cgi program to start gtk on xvfb
compared to a fpcanvas program.
A lot. A connection to the X server must be established, and the whole
of GTK must be set up. This is an expensive operation.
I can't believe people even consider this approach. It's like PHP devels
would suddenly say that "well, from now on you must run your web apps with
an X server". They would be the laughing stock of the whole PHP programmer's
community.
Yet, in lazarus, no-one seems to mind this kind of statements. It's even
encouraged.
None of "theme, screen color depths and sub pixel rendering parameters" are
necessary to create a bitmap. A bitmap is a matrix of pixels with a certain
color. No more, no less. Some of these parameters are needed when the bitmap is
being displayed, but definitely not when it is created.
When making a picture with a digital camera, the camera also has no knowledge
of the screen you'll be displaying the picture on. Nevertheless, it makes pictures.
Michael.
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