From 708e501245fbca9f973a6e4d7ec1d172ca0470a3 Mon Sep 17 00:00:00 2001
From: Simon Bruder <simon.bruder@mailbox.tu-dresden.de>
Date: Sat, 6 May 2023 17:39:18 +0200
Subject: [PATCH] u02: Implement DDA line tool

---
 u02/src/tests.cpp | 58 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 58 insertions(+)

diff --git a/u02/src/tests.cpp b/u02/src/tests.cpp
index a2f7209..dd2eeee 100644
--- a/u02/src/tests.cpp
+++ b/u02/src/tests.cpp
@@ -5,6 +5,8 @@
 #include <catch2/generators/catch_generators_adapters.hpp>
 #include <catch2/generators/catch_generators_random.hpp>
 
+#include "canvas_buffer.h"
+#include "dda_line_tool.h"
 #include "util.h"
 
 TEST_CASE("Transform Mirror") {
@@ -102,3 +104,59 @@ TEST_CASE("Transformation to standard case (prop)") {
   REQUIRE(x0 <= x1);
   REQUIRE(y0 >= y1);
 }
+
+TEST_CASE("DDA line tool (prop: for every row/column, only one pixel is set)") {
+  const int size = 100;
+  canvas_buffer *canvas = new canvas_buffer(size, size);
+  dda_line_tool *tool = new dda_line_tool(*canvas);
+
+  int x0 = GENERATE(take(10, random(0, size - 1)));
+  int y0 = GENERATE(take(10, random(0, size - 1)));
+  int x1 = GENERATE(take(10, random(0, size - 1)));
+  int y1 = GENERATE(take(10, random(0, size - 1)));
+
+  tool->draw(x0, y0, x1, y1);
+
+  int x_min = std::min(x0, x1);
+  int x_max = std::max(x0, x1);
+  int y_min = std::min(y0, y1);
+  int y_max = std::max(y0, y1);
+
+  // Depending on what the direction of the line (rounded to the next 90°) is,
+  // either every row or column has only one pixel set.
+  bool vertical = false;
+  int draw_direction_min;
+  int draw_direction_max;
+  int unique_direction_min;
+  int unique_direction_max;
+  if (abs(y1 - y0) > abs(x1 - x0)) {
+    vertical = true;
+    draw_direction_min = y_min;
+    draw_direction_max = y_max;
+    unique_direction_min = x_min;
+    unique_direction_max = x_max;
+  } else {
+    draw_direction_min = x_min;
+    draw_direction_max = x_max;
+    unique_direction_min = y_min;
+    unique_direction_max = y_max;
+  }
+
+  int sum;
+  for (int dd = draw_direction_min; dd <= draw_direction_max; dd++) {
+    sum = 0;
+    for (int ud = unique_direction_min; ud <= unique_direction_max; ud++) {
+      int x, y;
+      if (vertical) {
+        x = ud;
+        y = dd;
+      } else {
+        x = dd;
+        y = ud;
+      }
+      if (canvas->get_pixel(x, y))
+        sum++;
+    }
+    REQUIRE(sum == 1);
+  }
+}