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libraries/FastLED/tests/test_traverse_grid.cpp

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+#include "fl/namespace.h"
+#include "fl/time_alpha.h"
+#include "fl/traverse_grid.h"
+#include "test.h"
+
+#include <set>
+#include <utility>
+#include <iostream>
+
+using namespace fl;
+
+struct CollectingVisitor {
+    std::set<std::pair<int, int>> visited;
+
+    void visit(int x, int y) {
+        visited.insert({x, y});
+    }
+};
+
+TEST_CASE("Traverse grid") {
+    SUBCASE("Horizontal line") {
+        vec2f start{1.2f, 2.5f};
+        vec2f end{5.7f, 2.5f};
+
+        CollectingVisitor visitor;
+        traverseGridSegment(start, end, visitor);
+
+        CHECK(visitor.visited.size() == 5);
+        for (int x = 1; x <= 5; ++x) {
+            CHECK(visitor.visited.count({x, 2}) == 1);
+        }
+    }
+
+    SUBCASE("Vertical line") {
+        vec2f start{3.4f, 1.1f};
+        vec2f end{3.4f, 4.9f};
+
+        CollectingVisitor visitor;
+        traverseGridSegment(start, end, visitor);
+
+        CHECK(visitor.visited.size() == 4);
+        for (int y = 1; y <= 4; ++y) {
+            CHECK(visitor.visited.count({3, y}) == 1);
+        }
+    }
+
+
+    SUBCASE("Forward diagonal") {
+        vec2f start{1.1f, 1.1f};
+        vec2f end{4.9f, 4.9f};
+
+        CollectingVisitor visitor;
+        traverseGridSegment(start, end, visitor);
+
+        std::set<std::pair<int, int>> expected = {
+            {1,1}, {1,2}, {2,2}, {2,3}, {3,3}, {3,4}, {4,4}
+        };
+
+        CHECK(visitor.visited.size() == expected.size());
+        for (const auto& cell : expected) {
+            CHECK(visitor.visited.count(cell) == 1);
+        }
+    }
+
+    SUBCASE("Backward diagonal") {
+        vec2f start{4.9f, 1.1f};
+        vec2f end{1.1f, 4.9f};
+
+        CollectingVisitor visitor;
+        traverseGridSegment(start, end, visitor);
+
+        std::set<std::pair<int, int>> expected = {
+            {4,1}, {4,2}, {3,2}, {3,3}, {2,3}, {2,4}, {1,4}
+        };
+
+        CHECK(visitor.visited.size() == expected.size());
+        for (const auto& cell : expected) {
+            CHECK(visitor.visited.count(cell) == 1);
+        }
+    }
+
+    SUBCASE("Single cell") {
+        vec2f start{2.2f, 3.3f};
+        vec2f end{2.2f, 3.3f};
+
+        CollectingVisitor visitor;
+        traverseGridSegment(start, end, visitor);
+
+        CHECK(visitor.visited.size() == 1);
+        CHECK(visitor.visited.count({2, 3}) == 1);
+    }
+}