From fb03164e9f0a5318d1472db2983c4e8c36b38fd9 Mon Sep 17 00:00:00 2001
From: Ross Wilson <rzzzwilson@gmail.com>
Date: Tue, 17 May 2016 09:59:03 +0700
Subject: [PATCH] Implementing 'fake' display.

---
 pymlac/Display.py | 59 ++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 56 insertions(+), 3 deletions(-)

diff --git a/pymlac/Display.py b/pymlac/Display.py
index 530a781..6913b34 100644
--- a/pymlac/Display.py
+++ b/pymlac/Display.py
@@ -126,8 +126,13 @@ class Display(object):
         if self.dirty:
             self.write()
 
-    def bresenham(self, x1, y1, x2, y2):
-        """Draw a straight line on the graphics array."""
+    def bresenham_orig(self, x1, y1, x2, y2):
+        """Draw a straight line on the graphics array.
+
+        Only works for one octant.
+        """
+
+        log('bresenham_orig: (%d,%d) to (%d,%d)' % (x1, y1, x2, y2))
 
 # algorithm from:
 # http://www.idav.ucdavis.edu/education/GraphicsNotes/Bresenhams-Algorithm.pdf
@@ -155,8 +160,56 @@ class Display(object):
 
         for i in range(x1, x2):
             self.array[j*self.ScaleMaxX + i] = 1
+            log('bresenham: setting (%d,%d), sigma=%s, dy=%s' % (i, j, str(sigma), str(dy)))
             if sigma >= 0:
                 j += 1
                 sigma -= dx
-            i += 1
             sigma += dy
+
+    def bresenham(self, x1, y1, x2, y2):
+        log('bresenham: (%d,%d) to (%d,%d)' % (x1, y1, x2, y2))
+
+        dx = x2 - x1
+        dy = y2 - y1
+
+        # Determine how steep the line is
+        is_steep = abs(dy) > abs(dx)
+
+        # Rotate line
+        if is_steep:
+            x1, y1 = y1, x1
+            x2, y2 = y2, x2
+
+        # Swap start and end points if necessary and store swap state
+        swapped = False
+        if x1 > x2:
+            x1, x2 = x2, x1
+            y1, y2 = y2, y1
+            swapped = True
+
+        # Recalculate differentials
+        dx = x2 - x1
+        dy = y2 - y1
+
+        # Calculate error
+        error = int(dx / 2.0)
+        ystep = 1 if y1 < y2 else -1
+
+        # Iterate over bounding box generating points between start and end
+        y = y1
+        for x in range(x1, x2 + 1):
+            (x, y) = (y, x) if is_steep else (x, y)
+            self.array[y*self.ScaleMaxX + x] = 1
+            log('bresenham: setting point (%d, %d)' % (x, y))
+            error -= abs(dy)
+            if error < 0:
+                y += ystep
+                error += dx
+
+
+if __name__ == '__main__':
+    d = Display()
+    for v in range(0, 1024, 10):
+        d.draw(v, 0, v, 1023)
+        d.draw(0, v, 1023, v)
+    d.close()