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The graphics library
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<H1 CLASS="chapter"><A NAME="htoc257">Chapter 25</A> The graphics library</H1>
The <TT>graphics</TT> library provides a set of portable drawing primitives.
Drawing takes place
in a separate window that is created when <TT>open_graph</TT> is called.<BR>
<BR>
<FONT COLOR=purple>Unix:</FONT>
<BLOCKQUOTE CLASS="quote">
This library is implemented under the X11 windows system.
Programs that use the <TT>graphics</TT> library must be linked as follows:
<PRE>
ocamlc <I>other options</I> graphics.cma <I>other files</I>
</PRE>
For interactive use of the <TT>graphics</TT> library, do:
<PRE>
ocamlmktop -o mytop graphics.cma
./mytop
</PRE>
or (if dynamic linking of C libraries is supported on your platform),
start <TT>ocaml</TT> and type <TT>#load "graphics.cma";;</TT>.<BR>
<BR>
Here are the graphics mode specifications supported by <TT>open_graph</TT> on
the X11 implementation of this library:
the argument to <TT>open_graph</TT> has the format
<TT>"</TT><I>display-name geometry</I><TT>"</TT>,
where <I>display-name</I> is the name of the X-windows display to
connect to, and <I>geometry</I> is a standard X-windows geometry
specification. The two components are separated by a space. Either can
be omitted, or both. Examples:
<DL CLASS="description" COMPACT=compact><DT CLASS="dt-description">
<TT><B>open_graph "foo:0"</B></TT><DD CLASS="dd-description">
connects to the display <TT>foo:0</TT> and creates a window with the default geometry
<DT CLASS="dt-description"><TT><B>open_graph "foo:0 300x100+50-0"</B></TT><DD CLASS="dd-description">
connects to the display <TT>foo:0</TT> and creates a window 300 pixels wide
by 100 pixels tall, at location (50,0)
<DT CLASS="dt-description"><TT><B>open_graph " 300x100+50-0"</B></TT><DD CLASS="dd-description">
connects to the default display and creates a window 300 pixels wide
by 100 pixels tall, at location (50,0)
<DT CLASS="dt-description"><TT><B>open_graph ""</B></TT><DD CLASS="dd-description">
connects to the default display and creates a window with the default
geometry.
</DL>
</BLOCKQUOTE>
<FONT COLOR=purple>Windows:</FONT>
<BLOCKQUOTE CLASS="quote">
This library is available both for standalone compiled programs and
under the toplevel application <TT>ocamlwin.exe</TT>. For the latter, this
library must be loaded in-core by typing
<PRE CLASS="verbatim">
#load "graphics.cma";;
</PRE></BLOCKQUOTE>
The screen coordinates are interpreted as shown in the figure below.
Notice that the coordinate system used is the same as in mathematics:
<I>y</I> increases from the bottom of the screen to the top of the screen,
and angles are measured counterclockwise (in degrees).
Drawing is clipped to the screen.
<BR>
<BR>
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<IMG SRC="libgraph.gif">
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<BR>
<BR>
<a HREF="libref/Graphics.html"> Module <tt>Graphics</tt>: machine-independent graphics primitives</a> <img alt="updated" src="updated_tiny.gif">
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