feat(test_demo): Add validation for command-line options

Adds error handling for unknown or invalid command-line options:
- Unknown options (e.g., --invalid) print error and help, then exit(1)
- Missing arguments (e.g., --resolution without WxH) print error and help
- Invalid format (e.g., --resolution abc) print error and help

Error handling:
- Prints specific error message to stderr
- Shows full help text for reference
- Exits with status code 1 (error)
- --help still exits with status code 0 (success)

Examples of new behavior:
  $ test_demo --unknown
  Error: Unknown option '--unknown'
  [help text displayed]

  $ test_demo --resolution
  Error: --resolution requires an argument (e.g., 1024x768)
  [help text displayed]

  $ test_demo --resolution abc
  Error: Invalid resolution format 'abc' (expected WxH, e.g., 1024x768)
  [help text displayed]

This prevents silent failures and helps users discover correct usage.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

1 files changed, 29 insertions, 8 deletions

diff --git a/src/test_demo.cc b/src/test_demo.cc
index 4d2d60b..a93b0b1 100644
--- a/src/test_demo.cc
+++ b/src/test_demo.cc
@@ -53,6 +53,7 @@ int main(int argc, char** argv) {
   bool log_peaks_fine = false;
 
 #if !defined(STRIP_ALL)
+  // Early exit for invalid options
   for (int i = 1; i < argc; ++i) {
     if (strcmp(argv[i], "--help") == 0) {
       print_usage(argv[0]);
@@ -61,17 +62,37 @@ int main(int argc, char** argv) {
       fullscreen_enabled = true;
     } else if (strcmp(argv[i], "--tempo") == 0) {
       tempo_test_enabled = true;
-    } else if (strcmp(argv[i], "--resolution") == 0 && i + 1 < argc) {
-      const char* res_str = argv[++i];
-      int w, h;
-      if (sscanf(res_str, "%dx%d", &w, &h) == 2) {
-        width = w;
-        height = h;
+    } else if (strcmp(argv[i], "--resolution") == 0) {
+      if (i + 1 < argc) {
+        const char* res_str = argv[++i];
+        int w, h;
+        if (sscanf(res_str, "%dx%d", &w, &h) == 2) {
+          width = w;
+          height = h;
+        } else {
+          fprintf(stderr, "Error: Invalid resolution format '%s' (expected WxH, e.g., 1024x768)\n\n", res_str);
+          print_usage(argv[0]);
+          return 1;
+        }
+      } else {
+        fprintf(stderr, "Error: --resolution requires an argument (e.g., 1024x768)\n\n");
+        print_usage(argv[0]);
+        return 1;
+      }
+    } else if (strcmp(argv[i], "--log-peaks") == 0) {
+      if (i + 1 < argc) {
+        log_peaks_file = argv[++i];
+      } else {
+        fprintf(stderr, "Error: --log-peaks requires a filename argument\n\n");
+        print_usage(argv[0]);
+        return 1;
       }
-    } else if (strcmp(argv[i], "--log-peaks") == 0 && i + 1 < argc) {
-      log_peaks_file = argv[++i];
     } else if (strcmp(argv[i], "--log-peaks-fine") == 0) {
       log_peaks_fine = true;
+    } else {
+      fprintf(stderr, "Error: Unknown option '%s'\n\n", argv[i]);
+      print_usage(argv[0]);
+      return 1;
     }
   }
 #else