Bresenham line drawing code added, as posted by Björn Stenberg

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@89 a1c6a512-1295-4272-9138-f99709370657

firmware/lcd.c

@@ -413,6 +413,78 @@ void lcd_invertrect (int x, int y, int nx, int ny)
     lcd_bitmap (ones, x+i, y, 1, ny, FALSE);
 }
 
+#define DRAW_PIXEL(x,y) display[x][y/8] |= (1<<(y%7))
+
+void lcd_drawline( int x1, int y1, int x2, int y2 )
+{
+    int numpixels;
+    int i;
+    int deltax, deltay;
+    int d, dinc1, dinc2;
+    int x, xinc1, xinc2;
+    int y, yinc1, yinc2;
+
+    deltax = abs(x2 - x1);
+    deltay = abs(y2 - y1);
+
+    if(deltax >= deltay)
+    {
+        numpixels = deltax;
+        d = 2 * deltay - deltax;
+        dinc1 = deltay * 2;
+        dinc2 = (deltay - deltax) * 2;
+        xinc1 = 1;
+        xinc2 = 1;
+        yinc1 = 0;
+        yinc2 = 1;
+    }
+    else
+    {
+        numpixels = deltay;
+        d = 2 * deltax - deltay;
+        dinc1 = deltax * 2;
+        dinc2 = (deltax - deltay) * 2;
+        xinc1 = 0;
+        xinc2 = 1;
+        yinc1 = 1;
+        yinc2 = 1;
+    }
+    numpixels++; /* include endpoints */
+
+    if(x1 > x2)
+    {
+        xinc1 = -xinc1;
+        xinc2 = -xinc2;
+    }
+
+    if(y1 > y2)
+    {
+        yinc1 = -yinc1;
+        yinc2 = -yinc2;
+    }
+
+    x = x1;
+    y = y1;
+
+    for(i=0; i<numpixels; i++)
+    {
+        DRAW_PIXEL(x,y);
+
+        if(d < 0)
+        {
+            d += dinc1;
+            x += xinc1;
+            y += yinc1;
+        }
+        else
+        {
+            d += dinc2;
+            x += xinc2;
+            y += yinc2;
+        }
+    }
+}
+
 #else
 /* no LCD defined, no code to use */
 #endif