Try inverting display colours

Invert the screen colours for as long as the program is active. Only
works on the main display currently.

Inspired by Nikolai Ruhe's
(https://stackoverflow.com/users/104790/nikolai-ruhe) answer on Stack
Overflow about screen colour inversion:
https://stackoverflow.com/questions/14163788/how-does-on-screen-color-inversion-work-in-os-x/14165523#14165523

and this question:
https://stackoverflow.com/questions/32823023/permanently-modifying-rgb-gamma-table

2 files changed, 21 insertions, 0 deletions

diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..b6b403c
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,2 @@
+all:
+	clang -x objective-c -framework Coregraphics -o invert-catalina-invert main.m
diff --git a/main.m b/main.m
new file mode 100644
index 0000000..5cc0ad0
--- /dev/null
+++ b/main.m
@@ -0,0 +1,19 @@
+#import <CoreGraphics/CoreGraphics.h>
+
+int main(int argc, const char * argv[]) {
+    const CGGammaValue gamma[2] = {1, 0};
+    const CGGammaValue two[2] = {1, 0};
+    const CGGammaValue three[2] = {0, 1};
+
+    CGSetDisplayTransferByTable(
+        CGMainDisplayID(),
+        2,
+        gamma,
+        gamma,
+        gamma
+    );
+
+    sleep(5);
+
+    return 0;
+}