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157 lines
4.4 KiB
C
157 lines
4.4 KiB
C
/*
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u8g_clip.c
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procedures for clipping
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taken over from procs in u8g_pb.c
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Universal 8bit Graphics Library
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Copyright (c) 2012, olikraus@gmail.com
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All rights reserved.
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Redistribution and use in source and binary forms, with or without modification,
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are permitted provided that the following conditions are met:
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* Redistributions of source code must retain the above copyright notice, this list
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of conditions and the following disclaimer.
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* Redistributions in binary form must reproduce the above copyright notice, this
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list of conditions and the following disclaimer in the documentation and/or other
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materials provided with the distribution.
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
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CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
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INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
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MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
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CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
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ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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Notes
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This is one of the most critical parts of u8glib. It must be fast, but still reliable.
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Based on the intersection program (see tools folder), there is minimized version of
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the condition for the intersaction test:
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minimized version
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---1----0 1 b1 <= a2 && b1 > b2
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-----1--0 1 b2 >= a1 && b1 > b2
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---1-1--- 1 b1 <= a2 && b2 >= a1
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It includes the assumption, that a1 <= a2 is always true (correct, because
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a1, a2 are the page dimensions.
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The direct implementation of the above result is done in:
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uint8_t u8g_is_intersection_boolean(u8g_uint_t a0, u8g_uint_t a1, u8g_uint_t v0, u8g_uint_t v1)
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However, this is slower than a decision tree version:
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static uint8_t u8g_is_intersection_decision_tree(u8g_uint_t a0, u8g_uint_t a1, u8g_uint_t v0, u8g_uint_t v1)
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Also suprising is, that he the macro implementation is slower than the inlined version.
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The decision tree is based on the expansion of the truth table.
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*/
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#include "u8g.h"
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#ifdef __GNUC__
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#define U8G_ALWAYS_INLINE __attribute__((always_inline))
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#else
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#define U8G_ALWAYS_INLINE
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#endif
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/*
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intersection assumptions:
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a1 <= a2 is always true
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minimized version
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---1----0 1 b1 <= a2 && b1 > b2
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-----1--0 1 b2 >= a1 && b1 > b2
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---1-1--- 1 b1 <= a2 && b2 >= a1
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*/
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#ifdef OLD_CODE_WHICH_IS_TOO_SLOW
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static uint8_t u8g_is_intersection_boolean(u8g_uint_t a0, u8g_uint_t a1, u8g_uint_t v0, u8g_uint_t v1)
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{
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uint8_t c1, c2, c3, tmp;
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c1 = v0 <= a1;
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c2 = v1 >= a0;
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c3 = v0 > v1;
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tmp = c1;
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c1 &= c2;
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c2 &= c3;
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c3 &= tmp;
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c1 |= c2;
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c1 |= c3;
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return c1 & 1;
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}
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#endif
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#define U8G_IS_INTERSECTION_MACRO(a0,a1,v0,v1) ((uint8_t)( (v0) <= (a1) ) ? ( ( (v1) >= (a0) ) ? ( 1 ) : ( (v0) > (v1) ) ) : ( ( (v1) >= (a0) ) ? ( (v0) > (v1) ) : ( 0 ) ))
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static uint8_t u8g_is_intersection_decision_tree(u8g_uint_t a0, u8g_uint_t a1, u8g_uint_t v0, u8g_uint_t v1) U8G_ALWAYS_INLINE;
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static uint8_t u8g_is_intersection_decision_tree(u8g_uint_t a0, u8g_uint_t a1, u8g_uint_t v0, u8g_uint_t v1)
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{
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/* surprisingly the macro leads to larger code */
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/* return U8G_IS_INTERSECTION_MACRO(a0,a1,v0,v1); */
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if ( v0 <= a1 )
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{
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if ( v1 >= a0 )
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{
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return 1;
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}
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else
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{
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if ( v0 > v1 )
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{
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return 1;
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}
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else
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{
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return 0;
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}
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}
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}
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else
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{
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if ( v1 >= a0 )
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{
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if ( v0 > v1 )
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{
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return 1;
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}
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else
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{
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return 0;
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}
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}
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else
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{
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return 0;
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}
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}
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}
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uint8_t u8g_IsBBXIntersection(u8g_t *u8g, u8g_uint_t x, u8g_uint_t y, u8g_uint_t w, u8g_uint_t h)
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{
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register u8g_uint_t tmp;
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tmp = y;
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tmp += h;
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tmp--;
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if ( u8g_is_intersection_decision_tree(u8g->current_page.y0, u8g->current_page.y1, y, tmp) == 0 )
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return 0;
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tmp = x;
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tmp += w;
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tmp--;
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return u8g_is_intersection_decision_tree(u8g->current_page.x0, u8g->current_page.x1, x, tmp);
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}
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