jfjoch_viewer: Track top-pixels without storing/sorting all valid pixels

tests/TopPixelsTest.cpp

@@ -0,0 +1,28 @@
+// SPDX-FileCopyrightText: 2025 Filip Leonarski, Paul Scherrer Institute <filip.leonarski@psi.ch>
+// SPDX-License-Identifier: GPL-3.0-only
+
+#include <catch2/catch_all.hpp>
+#include "../common/TopPixels.h"
+
+TEST_CASE("TopPixels") {
+    TopPixels tp(5);
+
+    REQUIRE(tp.Empty());
+    REQUIRE(tp.Size() == 0);
+
+    for (int i = 50; i > 0; i--)
+        tp.Add(i*2, i);
+
+    tp.Add(500,245);
+    tp.Add(0,1221);
+
+    REQUIRE(tp.Size() == 5);
+
+    CHECK(tp[0].index == 245);
+    CHECK(tp[0].value == 500);
+    for (int i = 1; i < 4; i++) {
+        CHECK(tp[i].index == (50 - i + 1));
+        CHECK(tp[i].value == (50 - i + 1) * 2);
+    }
+}
+