# Editor

The source editor is based on [CodeMirror 6](https://codemirror.net/).
Syntax highlighting is chosen from the toolchain that handles the file's
extension, so a `.c` file opens as C, a `.ca65` file as 6502 assembly,
and so on. Every edit triggers a rebuild; see the
[IDE overview](index.md).

## File windows

The sidebar lists one entry per file in the project:

- **Source files** — the main file and any file reached by an
  `#include` or `//#link` directive. These open in the editable source
  editor. See [Build Directives](build-directives.md).
- **Listings** — compiler/assembler listings (for example `.lst` or
  symbol listings) generated by the build. These open read-only. The
  view follows the program counter while debugging and supports **Go To
  Address**.
- **Toolchain headers** — clicking the badge next to an `#include` line
  opens the referenced header from the toolchain's bundled include
  filesystem in a read-only viewer.
- **Binary files** — binary files open in a read-only hex dump.

## Gutter

For some platforms, the gutter shows additional information next to source lines:

- **Hex offset** -- The offset of a given source line.
- **Code bytes** -- The bytes for a given assembly instruction.
- **CPU Cycles** -- The number of CPU cycles for a given assembly instruction.
- Click the hex offset (or the yellow arrow) to run and break on that line.
- Click the red circle to toggle a breakpoint — see [Breakpoints](breakpoints.md).

## Editor keyboard shortcuts

### Editing

| Shortcut | Action |
| --- | --- |
| `Tab` | Insert spaces or a tab character (per settings) or indent selection |
| `Shift+Tab` | Unindent the current line or selection |
| `mod+Z` | Undo |
| `mod+Shift+Z` | Redo |
| `mod+F` | Find |
| `mod+G` | Find next match |
| `mod+D` | Select the next occurrence of the selection |
| `mod+Shift+Backspace` | Delete the current line |

The editor also inherits the standard [CodeMirror 6](https://codemirror.net/) keymap,
including cursor/word movement and selection with the arrow keys, and cut/
copy/paste (`mod+X`, `mod+C`, `mod+V`).