From e7f5ab3f55402cedb17c136020588f67a9216e54 Mon Sep 17 00:00:00 2001
From: Rangi42 <sylvie.oukaour+rangi42@gmail.com>
Date: Sat, 20 Sep 2025 20:21:37 -0400
Subject: [PATCH] Warn about `rgbgfx -O` without `-o` or any of `-A -T -P -Q`

---
 src/gfx/main.cpp                 | 12 ++++++++++++
 test/gfx/warn_group_output.err   |  2 ++
 test/gfx/warn_group_output.flags |  1 +
 3 files changed, 15 insertions(+)
 create mode 100644 test/gfx/warn_group_output.err
 create mode 100644 test/gfx/warn_group_output.flags

diff --git a/src/gfx/main.cpp b/src/gfx/main.cpp
index 7aa54356..201e4c47 100644
--- a/src/gfx/main.cpp
+++ b/src/gfx/main.cpp
@@ -44,6 +44,8 @@ static struct LocalOptions {
 	bool autoPalmap;
 	bool groupOutputs;
 	bool reverse;
+
+	bool autoAny() const { return autoAttrmap || autoTilemap || autoPalettes || autoPalmap; }
 } localOptions;
 
 // Short options
@@ -846,6 +848,16 @@ int main(int argc, char *argv[]) {
 		);
 	}
 
+	if (localOptions.groupOutputs) {
+		if (!localOptions.autoAny()) {
+			warnx("Grouping outputs ('-O') is enabled, but without any automatic output paths "
+			      "('-A', '-P', '-Q', or '-T')");
+		}
+		if (options.output.empty()) {
+			warnx("Grouping outputs ('-O') is enabled, but without an output tile data file ('-o')"
+			);
+		}
+	}
 	auto autoOutPath = [](bool autoOptEnabled, std::string &path, char const *extension) {
 		if (!autoOptEnabled) {
 			return;
diff --git a/test/gfx/warn_group_output.err b/test/gfx/warn_group_output.err
new file mode 100644
index 00000000..c54b03b8
--- /dev/null
+++ b/test/gfx/warn_group_output.err
@@ -0,0 +1,2 @@
+warning: Grouping outputs ('-O') is enabled, but without any automatic output paths ('-A', '-P', '-Q', or '-T')
+warning: Grouping outputs ('-O') is enabled, but without an output tile data file ('-o')
diff --git a/test/gfx/warn_group_output.flags b/test/gfx/warn_group_output.flags
new file mode 100644
index 00000000..ebc68ab8
--- /dev/null
+++ b/test/gfx/warn_group_output.flags
@@ -0,0 +1 @@
+-O