From 50417ee5528762a9a793023c1c78af2eeec78eb0 Mon Sep 17 00:00:00 2001
From: Sergey Fedorov <barracuda@macos-powerpc.org>
Date: Sun, 19 Jul 2026 09:09:50 +0000
Subject: [PATCH 09/71] debug(macos): probe build fingerprint + first-row cell
 dump
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Two diagnostics:
- Print "render_probe rev<N> built <date> <time>" on startup. The rev is bumped
  on logic changes and __DATE__/__TIME__ change when the TU recompiles, so a run
  identifies the exact code that produced its output without needing a full
  rebuild (incremental builds can otherwise leave doubt about which binary ran).
- Dump the first grid row's cell codepoints after rendering, to attribute a
  missing glyph in the image to the engine (cell absent) vs the compositor (cell
  present but not drawn). The image shows line 1 rendering as "ontour" — the
  leading 'c' (column 0) is absent; this pinpoints where.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AeG2jwYMX5gdvvtUnx3PJa
---
 src/contour_macos/render_probe.cpp | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/src/contour_macos/render_probe.cpp b/src/contour_macos/render_probe.cpp
index e3ed0eea..42598f82 100644
--- a/src/contour_macos/render_probe.cpp
+++ b/src/contour_macos/render_probe.cpp
@@ -55,11 +55,20 @@ void writePpm(std::string const& path, contour_macos::PixelBuffer const& buf)
 
 } // namespace
 
+// Bump whenever the probe's behavior changes, so a run's output identifies the code that
+// produced it. __DATE__/__TIME__ update whenever THIS translation unit is recompiled, so the
+// printed line is a reliable "is the running binary built from the current source?" signal
+// without needing a full rebuild.
+#define RENDER_PROBE_REVISION 3
+
 int main(int argc, char** argv)
 {
     using namespace vtbackend;
     using namespace vtrasterizer;
 
+    std::printf("render_probe rev%d built %s %s\n", RENDER_PROBE_REVISION, __DATE__, __TIME__);
+    std::fflush(stdout);
+
     std::string const outputPath = argc > 1 ? argv[1] : "render_probe.ppm";
 
     auto const pageSize = PageSize { LineCount { 10 }, ColumnCount { 40 } };
@@ -141,6 +150,22 @@ int main(int argc, char** argv)
     target.beginFrame();
     (void) renderer.render(terminal, /* pressureHint */ false);
 
+    // Diagnostic: dump the first row's grid cells so a missing glyph in the image can be
+    // attributed to the engine (cell absent from the grid) vs the compositor (cell present
+    // but not drawn).
+    {
+        auto& screen = terminal.primaryScreen();
+        std::printf("row 0 cells:");
+        for (int col = 0; col < 24; ++col)
+        {
+            auto cell = screen.at(LineOffset { 0 }, ColumnOffset { col });
+            char32_t const cp = cell.codepoint(0);
+            std::printf(" [%d]=U+%04X('%c')", col, (unsigned) cp, (cp >= 32 && cp < 127) ? (char) cp : '?');
+        }
+        std::printf("\n");
+        std::fflush(stdout);
+    }
+
     writePpm(outputPath, target.outputBuffer());
     std::printf("render_probe: wrote %s (%ux%u)\n",
                 outputPath.c_str(),