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215 lines
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<HTML><BODY>
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<HR break>
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<H2><A name=Fl_Gl_Window>class Fl_Gl_Window</A></H2>
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<HR>
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<H3>Class Hierarchy</H3>
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<UL>
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<PRE>
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<A href=Fl_Widget.html#Fl_Widget>Fl_Widget</A>
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+----<B>Fl_Gl_Window</B>
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+----<A href=Fl_Pack.html#Fl_Pack>Fl_Pack</A>, <A href=Fl_Scroll.html#Fl_Scroll>Fl_Scroll</A>, <A href=Fl_Tabs.html#Fl_Tabs>Fl_Tabs</A>, <A href=Fl_Tile.html#Fl_Tile>Fl_Tile</A>, <A href=Fl_Window.html#Fl_Window>Fl_Window</A>
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</PRE>
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</UL>
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<H3>Include Files</H3>
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<UL>
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<PRE>
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#include <FL/Fl_Gl_Window.H>
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</PRE>
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</UL>
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<H3>Description</H3>
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The <TT>Fl_Gl_Window</TT> widget sets things up so OpenGL works, and
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also keeps an OpenGL "context" for that window, so that changes to the
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lighting and projection may be reused between redraws. Fl_Gl_Window
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also flushes the OpenGL streams and swaps buffers after <TT>draw()</TT>
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returns.
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<P>OpenGL hardware typically provides some overlay bit planes, which
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are very useful for drawing UI controls atop your 3D graphics. If the
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overlay hardware is not provided, FLTK tries to simulate the overlay,
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This works pretty well if your graphics are double buffered, but not
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very well for single-buffered. </P>
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<H3>Methods</H3>
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<CENTER>
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<TABLE width=90% summary="Fl_Gl_Window methods.">
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<TR><TD align=left valign=top>
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<UL>
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<LI><A href=#Fl_Gl_Window.Fl_Gl_Window>Fl_Gl_Window</A></LI>
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<LI><A href=#Fl_Gl_Window.~Fl_Gl_Window>~Fl_Gl_Window</A></LI>
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<LI><A href=#Fl_Gl_Window.can_do>can_do</A></LI>
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<LI><A href=#Fl_Gl_Window.can_do_overlay>can_do_overlay</A></LI>
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</UL>
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</TD><TD align=left valign=top>
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<UL>
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<LI><A href=#Fl_Gl_Window.context>context</A></LI>
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<LI><A href=#Fl_Gl_Window.draw>draw</A></LI>
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<LI><A href=#Fl_Gl_Window.draw_overlay>draw_overlay</A></LI>
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<LI><A href=#Fl_Gl_Window.handle>handle</A></LI>
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</UL>
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</TD><TD align=left valign=top>
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<UL>
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<LI><A href=#Fl_Gl_Window.hide>hide</A></LI>
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<LI><A href=#Fl_Gl_Window.invalidate>invalidate</A></LI>
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<LI><A href=#Fl_Gl_Window.make_current>make_current</A></LI>
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</UL>
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</TD><TD align=left valign=top>
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<UL>
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<LI><A href=#Fl_Gl_Window.make_overlay_current>make_overlay_current</A></LI>
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<LI><A href=#Fl_Gl_Window.mode>mode</A></LI>
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<LI><A href=#Fl_Gl_Window.ortho>ortho</A></LI>
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</UL>
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</TD><TD align=left valign=top>
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<UL>
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<LI><A href=#Fl_Gl_Window.redraw_overlay>redraw_overlay</A></LI>
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<LI><A href=#Fl_Gl_Window.swap_buffers>swap_buffers</A></LI>
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<LI><A href=#Fl_Gl_Window.valid>valid</A></LI>
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</UL>
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</TD></TR>
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</TABLE>
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</CENTER>
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<H4><A name=Fl_Gl_Window.Fl_Gl_Window>Fl_Gl_Window::Fl_Gl_Window(int x,
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int y, int w, int h, const char *label = 0)</A></H4>
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Creates a new <TT>Fl_Gl_Window</TT> widget using the given position,
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size, and label string. The default boxtype is <TT>FL_NO_BOX</TT>. The
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default mode is <TT>FL_RGB|FL_DOUBLE|FL_DEPTH</TT>.
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<H4><A name=Fl_Gl_Window.~Fl_Gl_Window>virtual
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Fl_Gl_Window::~Fl_Gl_Window()</A></H4>
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The destructor removes the widget and destroys the OpenGL context
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associated with it.
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<H4><A name=Fl_Gl_Window.draw>virtual void Fl_Gl_Window::draw(void)</A></H4>
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<TT>Fl_Gl_Window::draw()</TT> is a pure virtual method. You must
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subclass <TT>Fl_Gl_Window</TT> and provide an implementation for <TT>
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draw()</TT>. You may also provide an implementation of draw_overlay()
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if you want to draw into the overlay planes. You can avoid
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reinitializing the viewport and lights and other things by checking <TT>
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valid()</TT> at the start of <TT>draw()</TT> and only doing the
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initialization if it is false.
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<P>The <TT>draw()</TT> method can <I>only</I> use OpenGL calls. Do not
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attempt to call X, any of the functions in <FL/fl_draw.H>, or <TT>glX</TT>
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directly. Do not call <TT>gl_start()</TT> or <TT>gl_finish()</TT>. </P>
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<P>If double-buffering is enabled in the window, the back and front
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buffers are swapped after this function is completed. </P>
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<H4><A name=Fl_Gl_Window.mode>const int Fl_Gl_Window::mode() const
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<BR> int Fl_Gl_Window::mode(int m)</A></H4>
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Set or change the OpenGL capabilites of the window. The value can be
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any of the following OR'd together:
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<UL>
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<LI><TT>FL_RGB</TT> - RGB color (not indexed) </LI>
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<LI><TT>FL_RGB8</TT> - RGB color with at least 8 bits of each color </LI>
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<LI><TT>FL_INDEX</TT> - Indexed mode </LI>
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<LI><TT>FL_SINGLE</TT> - not double buffered </LI>
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<LI><TT>FL_DOUBLE</TT> - double buffered </LI>
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<LI><TT>FL_ACCUM</TT> - accumulation buffer </LI>
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<LI><TT>FL_ALPHA</TT> - alpha channel in color </LI>
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<LI><TT>FL_DEPTH</TT> - depth buffer </LI>
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<LI><TT>FL_STENCIL</TT> - stencil buffer </LI>
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<LI><TT>FL_MULTISAMPLE</TT> - multisample antialiasing </LI>
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</UL>
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<TT>FL_RGB</TT> and <TT>FL_SINGLE</TT> have a value of zero, so they
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are "on" unless you give <TT>FL_INDEX</TT> or <TT>FL_DOUBLE</TT>.
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<P>If the desired combination cannot be done, FLTK will try turning off <TT>
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FL_MULTISAMPLE</TT>. If this also fails the <TT>show()</TT> will call <TT>
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Fl::error()</TT> and not show the window. </P>
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<P>You can change the mode while the window is displayed. This is most
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useful for turning double-buffering on and off. Under X this will
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cause the old X window to be destroyed and a new one to be created. If
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this is a top-level window this will unfortunately also cause the
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window to blink, raise to the top, and be de-iconized, and the <TT>xid()</TT>
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will change, possibly breaking other code. It is best to make the GL
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window a child of another window if you wish to do this! </P>
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<H4><A name=Fl_Gl_Window.can_do>static int Fl_Gl_Window::can_do(int)
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<BR> int Fl_Gl_Window::can_do() const</A></H4>
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Returns non-zero if the hardware supports the given or current OpenGL
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mode.
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<h4><a name=Fl_Gl_Window.context>void* Fl_Gl_Window::context() const;
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<br>void Fl_Gl_Window::context(void*, int destroy_flag = false);</a></h4>
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Return or set a pointer to the GLContext that this window is
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using. This is a system-dependent structure, but it is portable to copy
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the context from one window to another. You can also set it to NULL,
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which will force FLTK to recreate the context the next time <a
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href=#make_current><tt>make_current()</tt></a> is called, this is
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useful for getting around bugs in OpenGL implementations.
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<p>If <i>destroy_flag</i> is true the context will be destroyed by
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fltk when the window is destroyed, or when the <a
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href=#mode><tt>mode()</tt></a> is changed, or the next time
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<tt>context(x)</tt> is called.
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<H4><A name=Fl_Gl_Window.valid>char Fl_Gl_Window::valid() const
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<BR> void Fl_Gl_Window::valid(char i)</A></H4>
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<TT>Fl_Gl_Window::valid()</TT> is turned off when FLTK creates a new
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context for this window or when the window resizes, and is turned on <I>
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after</I> <TT>draw()</TT> is called. You can use this inside your <TT>
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draw()</TT> method to avoid unneccessarily initializing the OpenGL
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context. Just do this:
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<UL><PRE>
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void mywindow::draw() {
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if (!valid()) {
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glViewport(0,0,w(),h());
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glFrustum(...);
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glLight(...);
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...other initialization...
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}
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... draw your geometry here ...
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}
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</PRE></UL>
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You can turn <TT>valid()</TT> on by calling <TT>valid(1)</TT>. You
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should only do this after fixing the transformation inside a <TT>draw()</TT>
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or after <TT>make_current()</TT>. This is done automatically after <TT>
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draw()</TT> returns.
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<H4><A name=Fl_Gl_Window.invalidate>void Fl_Gl_Window::invalidate()</A></H4>
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The <TT>invalidate()</TT> method turns off <TT>valid()</TT> and is
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equivalent to calling <TT>value(0)</TT>.
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<H4><A name=Fl_Gl_Window.ortho>void Fl_Gl_Window::ortho()</A></H4>
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Set the projection so 0,0 is in the lower left of the window and each
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pixel is 1 unit wide/tall. If you are drawing 2D images, your <TT>
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draw()</TT> method may want to call this if <TT>valid()</TT> is false.
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<H4><A name=Fl_Gl_Window.make_current>void Fl_Gl_Window::make_current()</A>
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</H4>
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The <TT>make_current()</TT> method selects the OpenGL context for the
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widget. It is called automatically prior to the <TT>draw()</TT> method
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being called and can also be used to implement feedback and/or
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selection within the <TT>handle()</TT> method.
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<H4><A name=Fl_Gl_Window.make_overlay_current>void
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Fl_Gl_Window::make_overlay_current()</A></H4>
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The <TT>make_overlay_current()</TT> method selects the OpenGL context
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for the widget's overlay. It is called automatically prior to the <TT>
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draw_overlay()</TT> method being called and can also be used to
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implement feedback and/or selection within the <TT>handle()</TT>
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method.
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<H4><A name=Fl_Gl_Window.swap_buffers>void Fl_Gl_Window::swap_buffers()</A>
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</H4>
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The <TT>swap_buffers()</TT> method swaps the back and front buffers.
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It is called automatically after the <TT>draw()</TT> method is called.
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<H4><A name=Fl_Gl_Window.hide>void Fl_Gl_Window::hide()</A></H4>
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Hides the window and destroys the OpenGL context.
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<H4><A name=Fl_Gl_Window.can_do_overlay>int
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Fl_Gl_Window::can_do_overlay()</A></H4>
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Returns true if the hardware overlay is possible. If this is false,
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FLTK will try to simulate the overlay, with significant loss of update
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speed. Calling this will cause FLTK to open the display.
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<H4><A name=Fl_Gl_Window.redraw_overlay>void
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Fl_Gl_Window::redraw_overlay()</A></H4>
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This method causes <TT>draw_overlay</TT> to be called at a later time.
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Initially the overlay is clear, if you want the window to display
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something in the overlay when it first appears, you must call this
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immediately after you <TT>show()</TT> your window.
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<H4><A name=Fl_Gl_Window.draw_overlay>virtual void
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Fl_Gl_Window::draw_overlay()</A></H4>
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You must implement this virtual function if you want to draw into the
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overlay. The overlay is cleared before this is called. You should
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draw anything that is not clear using OpenGL. You must use <TT>
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gl_color(i)</TT> to choose colors (it allocates them from the colormap
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using system-specific calls), and remember that you are in an indexed
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OpenGL mode and drawing anything other than flat-shaded will probably
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not work.
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<P>Both this function and <TT>Fl_Gl_Window::draw()</TT> should check <TT>
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Fl_Gl_Window::valid()</TT> and set the same transformation. If you
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don't your code may not work on other systems. Depending on the OS,
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and on whether overlays are real or simulated, the OpenGL context may
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be the same or different between the overlay and main window. </P>
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</BODY></HTML>
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