Project 7: Bare-Metal Windowing Editor

Starting with this project, we will create SWIM (Simple WIndowing Machine), a basic but functional operating system.

For Level 1 credit:

The VGA buffer contains a text editor with the following capabilities:
- There is a cursor denoting where the next text character typed will appear.
- When the user types a viewable character, it appears at the location of the cursor, and the cursor itself moves to the next column.
- At the end of a row, the cursor moves to the start of the next row.
- Typing the Enter key also moves the cursor to the start of the next row.

For Level 2 credit:

The VGA buffer contains four text editing windows, each of approximately equal size.
Each window has an outline of period (.) characters.
Each window has a header with one of F1, F2, F3, or F4 in the center.
Initially, the F1 window is active.
Pressing a function key makes the corresponding window active.
The currently active window should have a color-highlighted outline.
The currently active window is where keystrokes appear.

For Level 3 credit, each window should have the following additional capabilities:

The backspace or delete key removes the character before the cursor, and moves the cursor one column to the left. If the cursor is in column 0 and not at row 0, backspace will move the cursor to the previous row.
A document may contain four times as many rows as a window. If the user types beyond the last visible row (either from going past the last column or typing the Enter key), the window should scroll. That is, the top line of text will disappear, and the remaining lines of text will all move up one row.
The user can move the cursor around using the arrow keys. If the left or right arrow key moves the cursor past the edge of the window, it should wrap around to the other side. If the up or down arrow key moves the cursor past the top or bottom of the window, it should scroll in the appropriate direction.

Here is an image of what the windowing editor should look like:

This can be built atop the pluggable_interrupt_template project, just like the bare metal game.
As with the game, it should have a central struct to represent the user interface as a whole.
Make heavy use of constants for values like the window height and width, document height, starting locations of windows, and so forth. A later assignment might require adjusting the window boundaries.
Create an additional struct to represent an individual document. For Level 1 and Level 2, this struct really only needs to represent the cursor position and window boundaries, as the text itself can be represented exclusively within the VGA buffer. For Level 3, this struct will need to maintain a representation of the entire document, in order to recover text hidden by scrolling.
For Level 2 and Level 3, the central struct should have an array of four document objects.
- It should then have a usize to denote which of these is the active window.

Submission

Create a new GitHub repository for this project. It will also serve as your repository for Project 10.