Diff: u8g_clip.c

Revision:

0:972874f31c98

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/u8g_clip.c	Wed Mar 07 12:49:14 2018 +0000
@@ -0,0 +1,157 @@
+/*
+
+  u8g_clip.c
+  
+  procedures for clipping
+  taken over from procs in u8g_pb.c
+
+  Universal 8bit Graphics Library
+  
+  Copyright (c) 2012, olikraus@gmail.com
+  All rights reserved.
+
+  Redistribution and use in source and binary forms, with or without modification, 
+  are permitted provided that the following conditions are met:
+
+  * Redistributions of source code must retain the above copyright notice, this list 
+    of conditions and the following disclaimer.
+    
+  * Redistributions in binary form must reproduce the above copyright notice, this 
+    list of conditions and the following disclaimer in the documentation and/or other 
+    materials provided with the distribution.
+
+  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND 
+  CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, 
+  INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF 
+  MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE 
+  DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR 
+  CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 
+  SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 
+  NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 
+  LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER 
+  CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, 
+  STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 
+  ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF 
+  ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.  
+  
+  Notes
+  
+  This is one of the most critical parts of u8glib. It must be fast, but still reliable.
+  Based on the intersection program (see tools folder), there is minimized version of
+  the condition for the intersaction test:
+    minimized version
+    ---1----0 1             b1 <= a2 && b1 > b2
+    -----1--0 1             b2 >= a1 && b1 > b2
+    ---1-1--- 1             b1 <= a2 && b2 >= a1
+  It includes the assumption, that a1 <= a2 is always true (correct, because
+  a1, a2 are the page dimensions.
+
+  The direct implementation of the above result is done in:
+  uint8_t u8g_is_intersection_boolean(u8g_uint_t a0, u8g_uint_t a1, u8g_uint_t v0, u8g_uint_t v1)
+  However, this is slower than a decision tree version:  
+  static uint8_t u8g_is_intersection_decision_tree(u8g_uint_t a0, u8g_uint_t a1, u8g_uint_t v0, u8g_uint_t v1) 
+  Also suprising is, that the macro implementation is slower than the inlined version.
+  
+  The decision tree is based on the expansion of the truth table.
+  
+*/
+
+#include "u8g.h"
+
+#ifdef __GNUC__
+#define U8G_ALWAYS_INLINE __inline__ __attribute__((always_inline))
+#else
+#define U8G_ALWAYS_INLINE
+ #endif 
+
+/*
+  intersection assumptions:
+    a1 <= a2 is always true    
+    
+    minimized version
+    ---1----0 1             b1 <= a2 && b1 > b2
+    -----1--0 1             b2 >= a1 && b1 > b2
+    ---1-1--- 1             b1 <= a2 && b2 >= a1
+  */
+
+#ifdef OLD_CODE_WHICH_IS_TOO_SLOW
+static uint8_t u8g_is_intersection_boolean(u8g_uint_t a0, u8g_uint_t a1, u8g_uint_t v0, u8g_uint_t v1)
+{
+  uint8_t c1, c2, c3, tmp;
+  c1 = v0 <= a1;
+  c2 = v1 >= a0;
+  c3 = v0 > v1;
+  
+  tmp = c1;
+  c1 &= c2;
+  c2 &= c3;
+  c3 &= tmp;
+  c1 |= c2;
+  c1 |= c3;
+  return c1 & 1;
+}
+#endif
+
+#define U8G_IS_INTERSECTION_MACRO(a0,a1,v0,v1) ((uint8_t)( (v0) <= (a1) ) ? ( ( (v1) >= (a0) ) ? ( 1 ) : ( (v0) > (v1) ) ) : ( ( (v1) >= (a0) ) ? ( (v0) > (v1) ) : ( 0 ) ))
+
+//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;
+static uint8_t U8G_ALWAYS_INLINE u8g_is_intersection_decision_tree(u8g_uint_t a0, u8g_uint_t a1, u8g_uint_t v0, u8g_uint_t v1) 
+{
+  /* surprisingly the macro leads to larger code */
+  /* return U8G_IS_INTERSECTION_MACRO(a0,a1,v0,v1); */
+  if ( v0 <= a1 )
+  {
+    if ( v1 >= a0 )
+    {
+      return 1;
+    }
+    else
+    {
+      if ( v0 > v1 )
+      {
+	return 1;
+      }
+      else
+      {
+	return 0;
+      }
+    }
+  }
+  else
+  {
+    if ( v1 >= a0 )
+    {
+      if ( v0 > v1 )
+      {
+	return 1;
+      }
+      else
+      {
+	return 0;
+      }
+    }
+    else
+    {
+      return 0;
+    }
+  }
+}
+
+
+uint8_t u8g_IsBBXIntersection(u8g_t *u8g, u8g_uint_t x, u8g_uint_t y, u8g_uint_t w, u8g_uint_t h)
+{
+  register u8g_uint_t tmp;
+  tmp = y;
+  tmp += h;
+  tmp--;
+  if ( u8g_is_intersection_decision_tree(u8g->current_page.y0, u8g->current_page.y1, y, tmp) == 0 )
+    return 0; 
+  
+  tmp = x;
+  tmp += w;
+  tmp--;
+  return u8g_is_intersection_decision_tree(u8g->current_page.x0, u8g->current_page.x1, x, tmp);
+}
+
+
+