From 3eec60fae6803cda80077eea63336d363f874684 Mon Sep 17 00:00:00 2001
From: Hans-Christian Ebke <ebke@cs.rwth-aachen.de>
Date: Mon, 14 Mar 2022 21:08:35 +0100
Subject: [PATCH 1/2] Add option -di to specify display by screen ID

---
 src/ddcctl.m | 33 +++++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/src/ddcctl.m b/src/ddcctl.m
index 2a258d5..05746d2 100644
--- a/src/ddcctl.m
+++ b/src/ddcctl.m
@@ -214,11 +214,13 @@ int main(int argc, const char * argv[])
         // Defaults
         NSString *screenName = @"";
         NSUInteger displayId = -1;
+        const char *displayUid = NULL;
         NSUInteger command_interval = 100000;
         BOOL dump_values = NO;
 
         NSString *HelpString = @"Usage:\n"
         @"ddcctl \t-d <1-..>  [display#]\n"
+        @"\t-di <0-..> [display id (overrides -d if specified)]\n"
         @"\t-w <0-..>  [delay in usecs between settings]\n"
         @"\t-W <0-..>  [timeout in nanosecs for replies]\n"
         @"\n"
@@ -261,6 +263,12 @@ int main(int argc, const char * argv[])
                 displayId = atoi(argv[i]);
             }
 
+            else if (!strcmp(argv[i], "-di")) {
+                i++;
+                if (i >= argc) break;
+                displayUid = argv[i];
+            }
+
             else if (!strcmp(argv[i], "-b")) {
                 i++;
                 if (i >= argc) break;
@@ -400,6 +408,31 @@ int main(int argc, const char * argv[])
             }
         }
 
+        if (displayUid != NULL) {
+            char *endptr;
+            uint uid = strtol(displayUid, &endptr, 10);
+            if (endptr == displayUid) {
+                NSLog(@"Display ID needs to be numeric");
+                exit(1);
+            }
+            int i = 1;
+            bool found = false;
+            for (NSNumber *dispId in _displayIDs)
+            {
+                if (uid == dispId.unsignedIntegerValue) {
+                    NSLog(@"UID Match: %d", i);
+                    displayId = i;
+                    found = true;
+                    break;
+                }
+                ++i;
+            }
+            if (!found) {
+                NSLog(@"Display ID %d not found", uid);
+                exit(1);
+            }
+        }
+
         if (0 >= displayId || displayId > [_displayIDs count]) {
             // no display id given, nothing left to do!
             NSLog(@"%@", HelpString);

From c3fc29d9c53820d14afcd416adf6cc53baad444d Mon Sep 17 00:00:00 2001
From: Hans-Christian Ebke <ebke@cs.rwth-aachen.de>
Date: Mon, 14 Mar 2022 21:15:50 +0100
Subject: [PATCH 2/2] Remove debug log msg

---
 src/ddcctl.m | 1 -
 1 file changed, 1 deletion(-)

diff --git a/src/ddcctl.m b/src/ddcctl.m
index 05746d2..b9f5907 100644
--- a/src/ddcctl.m
+++ b/src/ddcctl.m
@@ -420,7 +420,6 @@ int main(int argc, const char * argv[])
             for (NSNumber *dispId in _displayIDs)
             {
                 if (uid == dispId.unsignedIntegerValue) {
-                    NSLog(@"UID Match: %d", i);
                     displayId = i;
                     found = true;
                     break;