feat(plot): nice-number ticks, axes, grid, traces, cursors, measurement queries

tests/test_ticks.cpp

@@ -0,0 +1,109 @@
+#include "harness.hpp"
+#include <plot/plot/ticks.hpp>
+#include <cmath>
+#include <cstring>
+#include <limits>
+#include <string>
+#include <vector>
+
+PLOT_TEST(nice_ticks_are_powers_of_ten_times_125) {
+  std::vector<plot::Tick> t;
+  plot::generate_ticks({0.0, 1.0}, /*px=*/500.0f, /*min_px=*/60.0f, t);
+  PLOT_CHECK(!t.empty());
+  for (auto& tick : t) PLOT_CHECK(std::fabs(tick.value * 5.0 - std::round(tick.value * 5.0)) < 1e-9);
+  // spacing of major ticks >= min_px
+  PLOT_CHECK(static_cast<double>(t.size()) <= 500.0 / 60.0 + 2.0);
+}
+PLOT_TEST(ticks_are_monotonic_and_cover_range) {
+  std::vector<plot::Tick> t;
+  plot::generate_ticks({-3.7, 91.2}, 800.0f, 60.0f, t);
+  for (size_t i = 1; i < t.size(); ++i) PLOT_CHECK(t[i].value > t[i-1].value);
+  PLOT_CHECK(t.front().value <= 0.0);
+  PLOT_CHECK(t.back().value >= 90.0);
+}
+PLOT_TEST(si_formatting) {
+  char b[32];
+  plot::format_si(0.0000015, b, sizeof b); PLOT_CHECK(std::string(b) == "1.5\xC2\xB5s" || std::string(b).find("1.5") == 0);
+  plot::format_si(2.5e9, b, sizeof b);     PLOT_CHECK(std::string(b).find("2.5") == 0);
+  plot::format_si(1234.0, b, sizeof b);    PLOT_CHECK(std::string(b).find("1.23") == 0);
+  plot::format_si(0.0, b, sizeof b);       PLOT_CHECK(std::string(b) == "0");
+}
+PLOT_TEST(degenerate_ranges_do_not_hang) {
+  std::vector<plot::Tick> t;
+  plot::generate_ticks({5.0, 5.0}, 500.0f, 60.0f, t);   // must not loop forever
+  PLOT_CHECK(t.size() <= 64);
+  plot::generate_ticks({0.0, 0.0}, 0.0f, 60.0f, t);
+  plot::generate_ticks({1e300, 1e300}, 500.0f, 60.0f, t);
+}
+
+PLOT_TEST(hostile_tick_inputs_clear_the_output) {
+  std::vector<plot::Tick> t{{1.0, true, "stale"}};
+  plot::generate_ticks({10.0, -10.0}, 500.0f, 60.0f, t);        // inverted
+  PLOT_CHECK(t.empty());
+  plot::generate_ticks({0.0, std::nan("")}, 500.0f, 60.0f, t);  // non-finite max
+  PLOT_CHECK(t.empty());
+  plot::generate_ticks({std::nan(""), 1.0}, 500.0f, 60.0f, t);
+  PLOT_CHECK(t.empty());
+  plot::generate_ticks({0.0, 1.0}, 500.0f, 0.0f, t);            // min_px <= 0
+  PLOT_CHECK(t.empty());
+  // Span overflows to infinity: the step would be inf, so nothing is emitted
+  // and, crucially, the loop never runs.
+  plot::generate_ticks({-1e308, 1e308}, 500.0f, 60.0f, t);
+  PLOT_CHECK(t.empty());
+}
+
+PLOT_TEST(minor_ticks_subdivide_and_the_total_is_capped) {
+  std::vector<plot::Tick> t;
+  plot::generate_ticks({0.0, 1.0}, 500.0f, 60.0f, t, /*include_minors=*/true);
+  PLOT_CHECK(t.size() > 10);                                    // minors really added
+  for (size_t i = 1; i < t.size(); ++i) PLOT_CHECK(t[i].value > t[i-1].value);
+  // The major step is 0.2 (leading digit 2), so minors are quartered at 0.05.
+  for (const plot::Tick& tick : t) {
+    const double scale = tick.major ? 5.0 : 20.0;
+    PLOT_CHECK(std::fabs(tick.value * scale - std::round(tick.value * scale)) < 1e-9);
+    PLOT_CHECK(tick.major ? !tick.label.empty() : tick.label.empty());
+  }
+  // A range dense enough to want millions of minors stops at the hard cap.
+  std::vector<plot::Tick> capped;
+  plot::generate_ticks({0.0, 1e9}, 1e6f, 1.0f, capped, /*include_minors=*/true);
+  PLOT_CHECK(capped.size() == plot::kMaxTicks);
+}
+
+PLOT_TEST(si_labels_are_utf8_and_never_overrun) {
+  char b[32];
+  plot::format_si(0.0000015, b, sizeof b);
+  PLOT_CHECK(std::string(b) == "1.5\xC2\xB5");    // U+00B5, not the Greek mu
+  plot::format_si(1234.0, b, sizeof b);
+  PLOT_CHECK(std::string(b) == "1.23k");
+  plot::format_si(-1234.0, b, sizeof b);
+  PLOT_CHECK(std::string(b) == "-1.23k");
+  plot::format_si(2.5e9, b, sizeof b);
+  PLOT_CHECK(std::string(b) == "2.5G");
+  plot::format_si(1.5e-6, b, sizeof b, "s");
+  PLOT_CHECK(std::string(b) == "1.5\xC2\xB5s");   // a caller-supplied unit suffix
+  plot::format_si(std::nan(""), b, sizeof b);     // never silently dropped
+  PLOT_CHECK(std::string(b) == "nan");
+  plot::format_si(std::numeric_limits<double>::infinity(), b, sizeof b);
+  PLOT_CHECK(std::string(b) == "inf");
+
+  // A short buffer truncates; the string is always terminated inside it and
+  // nothing is ever written at or past `n`.
+  for (plot::usize n = 1; n <= 8; ++n) {
+    char small[8];
+    for (char& c : small) c = '#';
+    plot::format_si(-1234.567, small, n);
+    PLOT_CHECK(std::strlen(small) < n);
+    PLOT_CHECK(small[std::strlen(small)] == '\0');
+  }
+}
+
+PLOT_TEST(format_time_shapes) {
+  char b[32];
+  plot::format_time(0.5, b, sizeof b);      PLOT_CHECK(std::string(b) == "500ms");
+  plot::format_time(1.5, b, sizeof b);      PLOT_CHECK(std::string(b) == "1.5s");
+  plot::format_time(90.0, b, sizeof b);     PLOT_CHECK(std::string(b) == "1:30");
+  plot::format_time(3661.0, b, sizeof b);   PLOT_CHECK(std::string(b) == "1:01:01");
+  plot::format_time(-90.0, b, sizeof b);    PLOT_CHECK(std::string(b) == "-1:30");
+  plot::format_time(86400.0, b, sizeof b);  PLOT_CHECK(std::string(b) == "1d");
+  plot::format_time(std::nan(""), b, sizeof b); PLOT_CHECK(std::string(b) == "nan");
+}