Add cancel with right mouse button

README.md

@@ -49,6 +49,7 @@ pacman -S xcolor
 
 Simply invoke the `xcolor` command to select a color. The selected color will be
 printed to the standard output.
+You can cancel the color picker by clicking right click.
 
 ``` text
 xcolor 0.5.0

src/location.rs

@@ -11,6 +11,7 @@ use crate::util::EnsureOdd;
 
 // Left mouse button
 const SELECTION_BUTTON: xproto::Button = 1;
+const RIGHT_BUTTON: xproto::Button = 3;
 const GRAB_MASK: u16 = (xproto::EVENT_MASK_BUTTON_PRESS | xproto::EVENT_MASK_POINTER_MOTION) as u16;
 
 // Exclusively grabs the pointer so we get all its events
@@ -194,6 +195,9 @@ pub fn wait_for_location(
 
                             break Some(pixels[0]);
                         }
+                        RIGHT_BUTTON => {
+                            return Ok(None);
+                        }
                         _ => {}
                     }
                 }