first blood ... err stripes

src/intersection.h

@@ -0,0 +1,109 @@
+#include <pebble.h>
+
+#define	DONT_INTERSECT    0
+#define	DO_INTERSECT      1
+#define COLLINEAR         2
+
+#define SAME_SIGNS( a, b )	\
+		(((long) ((unsigned long) a ^ (unsigned long) b)) >= 0 )
+
+int lines_intersect(
+  x1, y1,
+  x2, y2,
+  x3, y3,
+  x4, y4,
+  x,
+  y
+)
+  
+long  x1, y1, x2, y2, x3, y3, x4, y4, *x, *y;
+
+{
+  long a1, a2, b1, b2, c1, c2; /* Coefficients of line eqns. */
+  long r1, r2, r3, r4;         /* 'Sign' values */
+  long denom, offset, num;     /* Intermediate values */
+
+  a1 = y2 - y1;
+  b1 = x1 - x2;
+  c1 = x2 * y1 - x1 * y2;
+  
+  r3 = a1 * x3 + b1 * y3 + c1;
+  r4 = a1 * x4 + b1 * y4 + c1;
+  
+  if ( r3 != 0 &&
+      r4 != 0 &&
+      SAME_SIGNS( r3, r4 ))
+    return ( DONT_INTERSECT );
+
+  a2 = y4 - y3;
+  b2 = x3 - x4;
+  c2 = x4 * y3 - x3 * y4;
+
+  r1 = a2 * x1 + b2 * y1 + c2;
+  r2 = a2 * x2 + b2 * y2 + c2;
+
+  if ( r1 != 0 &&
+      r2 != 0 &&
+      SAME_SIGNS( r1, r2 ))
+    return ( DONT_INTERSECT );
+
+  denom = a1 * b2 - a2 * b1;
+  if ( denom == 0 )
+    return ( COLLINEAR );
+  offset = denom < 0 ? - denom / 2 : denom / 2;
+
+  num = b1 * c2 - b2 * c1;
+  *x = ( num < 0 ? num - offset : num + offset ) / denom;
+
+  num = a2 * c1 - a1 * c2;
+  *y = ( num < 0 ? num - offset : num + offset ) / denom;
+
+  return ( DO_INTERSECT );
+}
+
+#define INTERSECTION_NONE 0
+#define INTERSECTION_PARTIAL 1
+#define INTERSECTION_FULL 2
+
+typedef struct {
+  uint8_t success;
+  GPoint p1;
+  GPoint p2;
+} Intersection;
+
+Intersection rectintersect(GPoint p1, GPoint p2, GRect rect) {
+  long x,y;
+  long x1=0,y1=0,x2=0,y2=0;
+  bool intersection = false, final_intersection = false;
+  if (lines_intersect(p1.x, p1.y, p2.x, p2.y, rect.origin.x, rect.origin.y, rect.origin.x, rect.origin.y+rect.size.h, &x, &y) == DO_INTERSECT) {
+    x1 = x; y1 = y; intersection = true;
+  }
+  if (lines_intersect(p1.x, p1.y, p2.x, p2.y, rect.origin.x, rect.origin.y, rect.origin.x+rect.size.w, rect.origin.y, &x, &y) == DO_INTERSECT) {
+    if (!intersection) {
+      x1 = x; y1 = y; intersection = true;
+    } else if (x != x1 && y != y1) {
+      x2 = x; y2 = y; final_intersection = true;
+    }
+  }
+  if (!final_intersection && lines_intersect(p1.x, p1.y, p2.x, p2.y, rect.origin.x, rect.origin.y+rect.size.h, rect.origin.x+rect.size.w, rect.origin.y+rect.size.h, &x, &y) == DO_INTERSECT) {
+    if (!intersection) {
+      x1 = x; y1 = y; intersection = true;
+    } else if (x != x1 && y != y1) {
+      x2 = x; y2 = y; final_intersection = true;
+    }
+  }
+  if (!final_intersection && lines_intersect(p1.x, p1.y, p2.x, p2.y, rect.origin.x+rect.size.w, rect.origin.y, rect.origin.x+rect.size.w, rect.origin.y+rect.size.h, &x, &y) == DO_INTERSECT) {
+    if (!intersection) {
+      x1 = x; y1 = y;
+    } else if (x != x1 && y != y1) {
+      x2 = x; y2 = y; final_intersection = true;
+    }
+  }
+  if(final_intersection) {
+    return (Intersection) { .success = INTERSECTION_FULL, .p1 = (GPoint) { .x = x1, .y = y1 }, .p2 = (GPoint) { .x = x2, .y = y2 } };
+  } else if (intersection) {
+    return (Intersection) { .success = INTERSECTION_PARTIAL, .p1 = (GPoint) { .x = x1, .y = y1 }, .p2 = (GPoint) { .x = x2, .y = y2 } };
+  } else {
+    return (Intersection) { .success = INTERSECTION_NONE, .p1 = (GPoint) { .x = x1, .y = y1 }, .p2 = (GPoint) { .x = x2, .y = y2 } };
+  }
+}

src/squared.c

@@ -6,6 +6,8 @@
  */
 
 #include <pebble.h>
+#include <intersection.h>
+
 
 Window *window;
 
@@ -610,7 +612,10 @@ static void updateSlot(Layer *layer, GContext *ctx) {
     GColor8 newColor = getSlotColor(tx, ty, slot->curDigit, slot->slotIndex, slot->isalpha);
     
 	  graphics_context_set_fill_color(ctx, oldColor);
-    graphics_fill_rect(ctx, GRect((tx*tilesize)-(tx*widthadjust), ty*tilesize-(ty*widthadjust), tilesize-widthadjust, tilesize-widthadjust), 0, GCornerNone);
+    
+    GRect singletile = GRect((tx*tilesize)-(tx*widthadjust), ty*tilesize-(ty*widthadjust), tilesize-widthadjust, tilesize-widthadjust);
+    
+    graphics_fill_rect(ctx, singletile, 0, GCornerNone);
     
     if(!gcolor_equal(oldColor, newColor)) {
       w = (skewedNormTime*TILE_SIZE/ANIMATION_NORMALIZED_MAX)+shift-widthadjust;
@@ -622,6 +627,22 @@ static void updateSlot(Layer *layer, GContext *ctx) {
       graphics_context_set_fill_color(ctx, newColor);
       graphics_fill_rect(ctx, GRect((tx*tilesize)-(tx*widthadjust), ty*tilesize-(ty*widthadjust), w, tilesize-widthadjust), 0, GCornerNone);
     }
+    
+    GPoint line_start = GPoint(0,0);
+    GPoint line_end = GPoint(90,180);
+    
+    graphics_context_set_stroke_width(ctx, 1);
+    graphics_context_set_stroke_color(ctx, GColorRed);
+    //graphics_draw_line(ctx, line_start, line_end);
+    
+    Intersection intersect = rectintersect(line_start, line_end, singletile);
+    
+    if (intersect.success >= INTERSECTION_FULL && !gcolor_equal(newColor, BACKGROUND_COLOR)) {
+      graphics_context_set_stroke_color(ctx, GColorWhite);
+      graphics_context_set_stroke_width(ctx, 2);
+      graphics_draw_line(ctx, intersect.p1, intersect.p2);
+      //APP_LOG(APP_LOG_LEVEL_INFO, "intersection at %d,%d and %d,%d", intersect.p1.x, intersect.p1.y, intersect.p2.x, intersect.p2.y);
+    }
 	}
 }