mirror of https://github.com/BOINC/boinc.git
80 lines
3.0 KiB
C++
80 lines
3.0 KiB
C++
// The contents of this file are subject to the BOINC Public License
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// Version 1.0 (the "License"); you may not use this file except in
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// compliance with the License. You may obtain a copy of the License at
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// http://boinc.berkeley.edu/license_1.0.txt
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//
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// Software distributed under the License is distributed on an "AS IS"
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// basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See the
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// License for the specific language governing rights and limitations
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// under the License.
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//
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// The Original Code is the Berkeley Open Infrastructure for Network Computing.
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//
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// The Initial Developer of the Original Code is the SETI@home project.
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// Portions created by the SETI@home project are Copyright (C) 2002
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// University of California at Berkeley. All Rights Reserved.
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//
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// Contributor(s):
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//
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// The class GRAPHICS_DOUBLE_BUFFER provides a mechanism
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// for synchronizing the generation of graphics information
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// (done by the "science thread")
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// with the graphics rendering (done by the "GUI thread",
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// which periodically calls the application-supplied render() function)
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//
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// We assume that graphics info is generated incrementally
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// and displayed incrementally.
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// The scheme handles mismatches between generation and rendering rates:
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// - if generation is faster than display, data cycles will be skipped
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// - if display is faster than generation, the display will "linger"
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// on a cycle until the next cycle is available in its entirety.
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//
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// Here's what the application programmer does:
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// - subclass GRAPHICS_BUFFER, adding your application-specific data
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// - declare a GRAPHICS_DOUBLE_BUFFER object (call it gdb),
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// initializing it with pointers to two GRAPHICS_BUFFER structures.
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// - when the science thread wants to add an increment of data,
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// it calls gdb->get_generate_buffer(first)
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// ("first" indicates whether this is the first data increment of a cycle).
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// If this returns nonzero, it adds data to the buffer.
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// If this addition causes it to be full, it calls gdb->generate_done();
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// - render() calls gdb->get_render_buffer().
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// If this returns nonzero, it displays some or all the data.
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// If this completes the display of the data, it calls gdb->render_done().
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// Here's how it works:
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// There are two buffers, each with a "state" (see below).
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// In a given state, only one thread can access the data or change the state.
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//
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#define GB_STATE_IDLE 0
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#define GB_STATE_GENERATING 1
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#define GB_STATE_GENERATED 2
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#define GB_STATE_RENDERING 3
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#define GB_STATE_RENDERED 4
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// subclass this for your applications
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//
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class GRAPHICS_BUFFER {
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public:
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virtual void clear();
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int state;
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};
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class GRAPHICS_DOUBLE_BUFFER {
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GRAPHICS_BUFFER* b1, *b2;
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GRAPHICS_BUFFER* get_buffer(int state);
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public:
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void init(GRAPHICS_BUFFER*, GRAPHICS_BUFFER*);
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// the following called by app's render()
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//
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GRAPHICS_BUFFER* get_render_buffer();
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void render_done(GRAPHICS_BUFFER*);
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// the following called by app's science thread
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//
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GRAPHICS_BUFFER* get_generate_buffer(bool first);
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void generate_done(GRAPHICS_BUFFER*);
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};
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