From 0e936872094ab8b86a2428bc6d46f35d907667de Mon Sep 17 00:00:00 2001
From: Ryan Kennedy <rkennedy9064@gmail.com>
Date: Wed, 18 Mar 2020 20:45:30 -0500
Subject: [PATCH] Initial code for #4

---
 src/colors.rs             | 24 ++++++++++++++++++++++++
 src/writers/mod.rs        | 23 +++++++++++++++++++----
 src/writers/text_40x25.rs |  5 +++--
 src/writers/text_40x50.rs |  5 +++--
 src/writers/text_80x25.rs |  5 +++--
 5 files changed, 52 insertions(+), 10 deletions(-)

diff --git a/src/colors.rs b/src/colors.rs
index e6bd956..33e5f89 100644
--- a/src/colors.rs
+++ b/src/colors.rs
@@ -52,6 +52,16 @@ impl TextModeColor {
     pub const fn new(foreground: Color16Bit, background: Color16Bit) -> TextModeColor {
         TextModeColor((background as u8) << 4 | (foreground as u8))
     }
+
+    /// Sets the background color given the specified `background`;
+    pub fn set_background(&mut self, background: Color16Bit) {
+        self.0 = (background as u8) << 4 | (self.0 & 0x0F);
+    }
+
+    /// Sets the foreground color given the specified `foreground`.
+    pub fn set_foreground(&mut self, foreground: Color16Bit) {
+        self.0 = foreground as u8;
+    }
 }
 
 /// Represents the default vga 256 color palette.
@@ -105,3 +115,17 @@ pub const DEFAULT_PALETTE: [u8; PALETTE_SIZE] = [
     0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F,
     0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F,
 ];
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn test_set_foreground() {
+        let mut color = TextModeColor::new(Color16Bit::Yellow, Color16Bit::Black);
+        color.set_foreground(Color16Bit::Red);
+        color.set_background(Color16Bit::DarkGrey);
+        assert_eq!(color.0 & 0x0F, Color16Bit::Red as u8);
+        assert_eq!(color.0 >> 4, Color16Bit::DarkGrey as u8);
+    }
+}
diff --git a/src/writers/mod.rs b/src/writers/mod.rs
index f68050a..b2f497b 100644
--- a/src/writers/mod.rs
+++ b/src/writers/mod.rs
@@ -25,12 +25,20 @@ pub struct ScreenCharacter {
 }
 
 impl ScreenCharacter {
-    /// Creates a new `ScreenCharacter` with the specified `character`
-    /// and a `TextModeColor` with the specified `foreground` and `background`.
-    pub fn new(character: u8, foreground: Color16Bit, background: Color16Bit) -> ScreenCharacter {
-        let color = TextModeColor::new(foreground, background);
+    /// Creates a new `ScreenCharacter` with the specified `character` and `TextModeColor`.
+    pub fn new(character: u8, color: TextModeColor) -> ScreenCharacter {
         ScreenCharacter { character, color }
     }
+
+    /// Returns the `character` associated with the `ScreenCharacter`.
+    pub fn get_character(&self) -> u8 {
+        self.character
+    }
+
+    /// Returns the `color` associated with the `ScreenCharacter`.
+    pub fn get_color(&self) -> TextModeColor {
+        self.color
+    }
 }
 
 static BLANK_CHARACTER: ScreenCharacter = ScreenCharacter {
@@ -98,6 +106,13 @@ pub trait TextWriter {
         );
     }
 
+    /// 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;
+        unsafe { frame_buffer.add(offset).read_volatile() }
+    }
+
     /// Sets the size of the cursor, as specified by `scan_line_start` and `scan_line_end`.
     ///
     /// This field controls the appearance of the text mode cursor by specifying the scan
diff --git a/src/writers/text_40x25.rs b/src/writers/text_40x25.rs
index 3ce2328..5eb92f2 100644
--- a/src/writers/text_40x25.rs
+++ b/src/writers/text_40x25.rs
@@ -15,11 +15,12 @@ const HEIGHT: usize = 25;
 /// Basic usage:
 ///
 /// ```no_run
-/// use vga::colors::Color16Bit;
+/// use vga::colors::{Color16Bit, TextModeColor};
 /// use vga::writers::{ScreenCharacter, TextWriter, Text40x25};
 ///
 /// let text_mode = Text40x25::new();
-/// let screen_character = ScreenCharacter::new(b'T', Color16Bit::Yellow, Color16Bit::Black);
+/// let color = TextModeColor::new(Color16Bit::Yellow, Color16Bit::Black);
+/// let screen_character = ScreenCharacter::new(b'T', color);
 ///
 /// text_mode.set_mode();
 /// text_mode.clear_screen();
diff --git a/src/writers/text_40x50.rs b/src/writers/text_40x50.rs
index 0e0397b..ac604f4 100644
--- a/src/writers/text_40x50.rs
+++ b/src/writers/text_40x50.rs
@@ -15,11 +15,12 @@ const HEIGHT: usize = 50;
 /// Basic usage:
 ///
 /// ```no_run
-/// use vga::colors::Color16Bit;
+/// use vga::colors::{Color16Bit, TextModeColor};
 /// use vga::writers::{ScreenCharacter, TextWriter, Text40x50};
 ///
 /// let text_mode = Text40x50::new();
-/// let screen_character = ScreenCharacter::new(b'T', Color16Bit::Yellow, Color16Bit::Black);
+/// let color = TextModeColor::new(Color16Bit::Yellow, Color16Bit::Black);
+/// let screen_character = ScreenCharacter::new(b'T', color);
 ///
 /// text_mode.set_mode();
 /// text_mode.clear_screen();
diff --git a/src/writers/text_80x25.rs b/src/writers/text_80x25.rs
index 5dcf524..aadb975 100644
--- a/src/writers/text_80x25.rs
+++ b/src/writers/text_80x25.rs
@@ -15,11 +15,12 @@ const HEIGHT: usize = 25;
 /// Basic usage:
 ///
 /// ```no_run
-/// use vga::colors::Color16Bit;
+/// use vga::colors::{Color16Bit, TextModeColor};
 /// use vga::writers::{ScreenCharacter, TextWriter, Text80x25};
 ///
 /// let text_mode = Text80x25::new();
-/// let screen_character = ScreenCharacter::new(b'T', Color16Bit::Yellow, Color16Bit::Black);
+/// let color = TextModeColor::new(Color16Bit::Yellow, Color16Bit::Black);
+/// let screen_character = ScreenCharacter::new(b'T', color);
 ///
 /// text_mode.set_mode();
 /// text_mode.clear_screen();