Add a Grid

The grid holds the state of the terminal with row-major ordering.
Eventually, the grid::Cell type will hold other attributes such as
color, background color, decorations, and weight.

An initialization list is added for common ASCII symbols.

1 files changed, 95 insertions, 0 deletions

diff --git a/src/grid.rs b/src/grid.rs
new file mode 100644
index 00000000..93d9cd28
--- /dev/null
+++ b/src/grid.rs
@@ -0,0 +1,95 @@
+//! Functions for computing properties of the terminal grid
+
+use std::ops::{Index, IndexMut};
+
+/// Calculate the number of cells for an axis
+pub fn num_cells_axis(cell_width: u32, cell_sep: i32, screen_width: u32) -> u32 {
+    ((screen_width as i32 + cell_sep) as f64 / (cell_width as i32 - cell_sep) as f64) as u32
+}
+
+#[derive(Clone)]
+pub struct Cell {
+    pub character: Option<String>,
+}
+
+impl Cell {
+    pub fn new(c: Option<String>) -> Cell {
+        Cell {
+            character: c,
+        }
+    }
+}
+
+/// Represents the terminal display contents
+pub struct Grid {
+    /// Rows in the grid. Each row holds a list of cells corresponding to the columns in that row.
+    raw: Vec<Row>,
+
+    /// Number of columns
+    _cols: usize,
+
+    /// Number of rows.
+    ///
+    /// Invariant: rows is equivalent to cells.len()
+    rows: usize,
+}
+
+impl Grid {
+    pub fn new(rows: usize, cols: usize) -> Grid {
+        let mut raw = Vec::with_capacity(rows);
+        for _ in 0..raw.capacity() {
+            raw.push(Row::new(cols));
+        }
+
+        Grid {
+            raw: raw,
+            _cols: cols,
+            rows: rows,
+        }
+    }
+
+    pub fn rows(&self) -> usize {
+        self.rows
+    }
+}
+
+impl Index<usize> for Grid {
+    type Output = Row;
+
+    fn index<'a>(&'a self, index: usize) -> &'a Row {
+        &self.raw[index]
+    }
+}
+
+impl IndexMut<usize> for Grid {
+    fn index_mut<'a>(&'a mut self, index: usize) -> &'a mut Row {
+        &mut self.raw[index]
+    }
+}
+
+/// A row in the grid
+pub struct Row(Vec<Cell>);
+
+impl Row {
+    pub fn new(columns: usize) -> Row {
+        Row(vec![Cell::new(None); columns])
+    }
+
+    pub fn cols(&self) -> usize {
+        self.0.len()
+    }
+}
+
+impl Index<usize> for Row {
+    type Output = Cell;
+
+    fn index<'a>(&'a self, index: usize) -> &'a Cell {
+        &self.0[index]
+    }
+}
+
+impl IndexMut<usize> for Row {
+    fn index_mut<'a>(&'a mut self, index: usize) -> &'a mut Cell {
+        &mut self.0[index]
+    }
+}