Add public method for setting screen contrast (brightness)

CHANGELOG.md

@@ -8,6 +8,10 @@ with the [embedded-hal](crates.io/crates/embedded-hal) traits for maximum portab
 
 ## [Unreleased] - ReleaseDate
 
+### Added
+
+- [#20](https://github.com/jamwaffles/sh1106/pull/20) Add `set_contrast` method to set the display contrast/brightness.
+
 ## [0.3.1] - 2020-03-21
 
 ### Fixed

src/mode/graphics.rs

@@ -160,6 +160,11 @@ where
     pub fn set_rotation(&mut self, rot: DisplayRotation) -> Result<(), DI::Error> {
         self.properties.set_rotation(rot)
     }
+
+    /// Set the display contrast
+    pub fn set_contrast(&mut self, contrast: u8) -> Result<(), DI::Error> {
+        self.properties.set_contrast(contrast)
+    }
 }
 
 #[cfg(feature = "graphics")]

src/properties.rs

@@ -187,4 +187,9 @@ where
             }
         }
     }
+
+    /// Set the display contrast
+    pub fn set_contrast(&mut self, contrast: u8) -> Result<(), DI::Error> {
+        Command::Contrast(contrast).send(&mut self.iface)
+    }
 }