Make screen width and height constant

src/writers/graphics_320x200x256.rs

@@ -37,20 +37,9 @@ const SIZE: usize = WIDTH * HEIGHT;
 pub struct Graphics320x200x256;
 
 impl Screen for Graphics320x200x256 {
-    #[inline]
-    fn get_width(&self) -> usize {
-        WIDTH
-    }
-
-    #[inline]
-    fn get_height(&self) -> usize {
-        HEIGHT
-    }
-
-    #[inline]
-    fn get_size(&self) -> usize {
-        SIZE
-    }
+    const WIDTH: usize = WIDTH;
+    const HEIGHT: usize = HEIGHT;
+    const SIZE: usize = SIZE;
 }
 
 impl GraphicsWriter<u8> for Graphics320x200x256 {

src/writers/graphics_640x480x16.rs

@@ -40,15 +40,9 @@ const WIDTH_IN_BYTES: usize = WIDTH / 8;
 pub struct Graphics640x480x16;
 
 impl Screen for Graphics640x480x16 {
-    fn get_width(&self) -> usize {
-        WIDTH
-    }
-    fn get_height(&self) -> usize {
-        HEIGHT
-    }
-    fn get_size(&self) -> usize {
-        SIZE
-    }
+    const WIDTH: usize = WIDTH;
+    const HEIGHT: usize = HEIGHT;
+    const SIZE: usize = SIZE;
 }
 
 impl GraphicsWriter<Color16> for Graphics640x480x16 {

src/writers/mod.rs

@@ -51,12 +51,12 @@ static BLANK_CHARACTER: ScreenCharacter = ScreenCharacter {
 
 /// A helper trait used to interact with various vga screens.
 pub trait Screen {
-    /// Returns the width of the `Screen`.
-    fn get_width(&self) -> usize;
-    /// Returns the height of the `Screen`.
-    fn get_height(&self) -> usize;
-    /// Returns the size of the `Screen`.
-    fn get_size(&self) -> usize;
+    /// The width of the `Screen`.
+    const WIDTH: usize;
+    /// The height of the `Screen`.
+    const HEIGHT: usize;
+    /// The size (total area) of the `Screen`.
+    const SIZE: usize;
 }
 
 /// A helper trait used to interact with various vga text modes.
@@ -79,8 +79,7 @@ pub trait TextWriter: Screen {
     /// color of `Color16::Yellow`.
     fn clear_screen(&self) {
         let (_vga, frame_buffer) = self.get_frame_buffer();
-        let screen_size = self.get_width() * self.get_height();
-        for i in 0..screen_size {
+        for i in 0..Self::SIZE {
             unsafe {
                 frame_buffer.add(i).write_volatile(BLANK_CHARACTER);
             }
@@ -94,8 +93,7 @@ pub trait TextWriter: Screen {
             character: b' ',
             color,
         };
-        let screen_size = self.get_width() * self.get_height();
-        for i in 0..screen_size {
+        for i in 0..Self::SIZE {
             unsafe {
                 frame_buffer.add(i).write_volatile(character);
             }
@@ -133,7 +131,7 @@ pub trait TextWriter: Screen {
     /// Returns the `ScreenCharacter` at the given `(x, y)` position.
     fn read_character(&self, x: usize, y: usize) -> ScreenCharacter {
         let (_vga, frame_buffer) = self.get_frame_buffer();
-        let offset = self.get_width() * y + x;
+        let offset = Self::WIDTH * y + x;
         unsafe { frame_buffer.add(offset).read_volatile() }
     }
 
@@ -169,7 +167,7 @@ pub trait TextWriter: Screen {
     /// Sets the current text cursor to the position specified by
     /// `x` and `y`.
     fn set_cursor_position(&self, x: usize, y: usize) {
-        let offset = self.get_width() * y + x;
+        let offset = Self::WIDTH * y + x;
         let (mut vga, _frame_buffer) = self.get_frame_buffer();
         let emulation_mode = vga.get_emulation_mode();
         let cursor_start = offset & 0xFF;
@@ -189,7 +187,7 @@ pub trait TextWriter: Screen {
     /// Prints the given `character` and `color` at `(x, y)`.
     fn write_character(&self, x: usize, y: usize, screen_character: ScreenCharacter) {
         let (_vga, frame_buffer) = self.get_frame_buffer();
-        let offset = self.get_width() * y + x;
+        let offset = Self::WIDTH * y + x;
         unsafe {
             frame_buffer.add(offset).write_volatile(screen_character);
         }

src/writers/text_40x25.rs

@@ -7,6 +7,7 @@ use crate::{
 
 const WIDTH: usize = 40;
 const HEIGHT: usize = 25;
+const SIZE: usize = WIDTH * HEIGHT;
 
 /// A basic interface for interacting with vga text mode 40x25
 ///
@@ -30,17 +31,9 @@ const HEIGHT: usize = 25;
 pub struct Text40x25;
 
 impl Screen for Text40x25 {
-    fn get_width(&self) -> usize {
-        WIDTH
-    }
-
-    fn get_height(&self) -> usize {
-        HEIGHT
-    }
-
-    fn get_size(&self) -> usize {
-        WIDTH * HEIGHT
-    }
+    const WIDTH: usize = WIDTH;
+    const HEIGHT: usize = HEIGHT;
+    const SIZE: usize = SIZE;
 }
 
 impl TextWriter for Text40x25 {

src/writers/text_40x50.rs

@@ -7,6 +7,7 @@ use crate::{
 
 const WIDTH: usize = 40;
 const HEIGHT: usize = 50;
+const SIZE: usize = WIDTH * HEIGHT;
 
 /// A basic interface for interacting with vga text mode 40x50
 ///
@@ -30,17 +31,9 @@ const HEIGHT: usize = 50;
 pub struct Text40x50;
 
 impl Screen for Text40x50 {
-    fn get_width(&self) -> usize {
-        WIDTH
-    }
-
-    fn get_height(&self) -> usize {
-        HEIGHT
-    }
-
-    fn get_size(&self) -> usize {
-        WIDTH * HEIGHT
-    }
+    const WIDTH: usize = WIDTH;
+    const HEIGHT: usize = HEIGHT;
+    const SIZE: usize = SIZE;
 }
 
 impl TextWriter for Text40x50 {

src/writers/text_80x25.rs

@@ -7,6 +7,7 @@ use crate::{
 
 const WIDTH: usize = 80;
 const HEIGHT: usize = 25;
+const SIZE: usize = WIDTH * HEIGHT;
 
 /// A basic interface for interacting with vga text mode 80x25
 ///
@@ -30,17 +31,9 @@ const HEIGHT: usize = 25;
 pub struct Text80x25;
 
 impl Screen for Text80x25 {
-    fn get_width(&self) -> usize {
-        WIDTH
-    }
-
-    fn get_height(&self) -> usize {
-        HEIGHT
-    }
-
-    fn get_size(&self) -> usize {
-        WIDTH * HEIGHT
-    }
+    const WIDTH: usize = WIDTH;
+    const HEIGHT: usize = HEIGHT;
+    const SIZE: usize = SIZE;
 }
 
 impl TextWriter for Text80x25 {