From cc96e209c645dc53e3bafdaf8d89a3ecda8dfeb8 Mon Sep 17 00:00:00 2001
From: Henner Zeller <h.zeller@acm.org>
Date: Fri, 16 Sep 2016 18:24:34 -0700
Subject: [PATCH] o C-API: Report back options actually used.

---
 include/led-matrix-c.h |  7 ++++++-
 lib/led-matrix-c.cc    | 15 +++++++++++++++
 2 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/include/led-matrix-c.h b/include/led-matrix-c.h
index b7c74ba..e999e6a 100644
--- a/include/led-matrix-c.h
+++ b/include/led-matrix-c.h
@@ -102,12 +102,17 @@ struct RGBLedMatrixOptions {
 
 /**
  * Universal way to create and initialize a matrix.
- * The "options" struct (if not NULL) contains all configuration values
+ * The "options" struct (if not NULL) contains all default configuration values
  * chosen by the programmer to create the matrix.
  *
  * If "argc" and "argv" are provided, this function also reads command line
  * flags provided, that then can override any of the defaults given.
  * The arguments that have been used from the command line are removed from
+ * the argv list (and argc is adjusted) - that way these don't mess with your
+ * own command line handling.
+ *
+ * The actual options used are filled back into the "options" struct if not
+ * NULL.
  *
  * Usage:
  * ----------------
diff --git a/lib/led-matrix-c.cc b/lib/led-matrix-c.cc
index ce0660b..f20c07f 100644
--- a/lib/led-matrix-c.cc
+++ b/lib/led-matrix-c.cc
@@ -75,6 +75,21 @@ struct RGBLedMatrix *led_matrix_create_from_options(
     }
   }
 
+  if (opts) {
+#define ACTUAL_VALUE_BACK_TO_OPT(o) opts->o = default_opts.o
+    ACTUAL_VALUE_BACK_TO_OPT(rows);
+    ACTUAL_VALUE_BACK_TO_OPT(chain_length);
+    ACTUAL_VALUE_BACK_TO_OPT(parallel);
+    ACTUAL_VALUE_BACK_TO_OPT(pwm_bits);
+    ACTUAL_VALUE_BACK_TO_OPT(brightness);
+    ACTUAL_VALUE_BACK_TO_OPT(scan_mode);
+    ACTUAL_VALUE_BACK_TO_OPT(disable_hardware_pulsing);
+    ACTUAL_VALUE_BACK_TO_OPT(show_refresh_rate);
+    ACTUAL_VALUE_BACK_TO_OPT(swap_green_blue);
+    ACTUAL_VALUE_BACK_TO_OPT(inverse_colors);
+#undef ACTUAL_VALUE_BACK_TO_OPT
+  }
+
   rgb_matrix::RGBMatrix *matrix = CreateMatrixFromOptions(matrix_options,
                                                           runtime_opt);
   return from_matrix(matrix);