literate: convert org/backend-protocol.org from doc-only to tangle source
Now tangles to: package.lisp, classes.lisp, simple.lisp, tests.lisp All 4 .lisp files deleted and regenerated from org alone — verified GREEN
This commit is contained in:
Hermes Agent
@@ -3,165 +3,177 @@
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#+FILETAGS: :cl-tty:backend:v0.0.1:
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#+OPTIONS: ^:nil
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* Backend Protocol
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* Overview
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The backend protocol is the rendering abstraction layer. Every visual
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operation dispatches through generic functions on a backend class.
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Two implementations exist: =modern-backend= (raw escape sequences,
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truecolor, modern terminal features) and =simple-backend= (ASCII art,
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Two implementations exist: ~modern-backend~ (raw escape sequences,
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truecolor, modern terminal features) and ~simple-backend~ (ASCII art,
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universal compatibility).
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** Contract
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All drawing operations are generic functions dispatched on the backend
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class. Application code never calls terminal escape sequences directly.
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*** Backend Lifecycle
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* Contract
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- =(initialize-backend backend)= → backend
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** Backend Lifecycle
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- ~(initialize-backend backend)~ → backend
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Initialize the terminal, set raw mode, enable features.
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Returns the backend instance.
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- =(shutdown-backend backend)= → nil
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- ~(shutdown-backend backend)~ → nil
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Restore terminal to cooked mode, reset colors, show cursor.
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Must be called on exit regardless of how the image stops.
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- =(backend-size backend)= → (values columns lines integer integer)
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- ~(backend-size backend)~ → (values columns lines)
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Return terminal dimensions. First value = columns, second = lines.
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- =(backend-write backend string)= → integer
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- ~(backend-write backend string)~ → integer
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Write raw string to terminal output. Returns number of bytes written.
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- =(backend-clear backend)= → nil
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- ~(backend-clear backend)~ → nil
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Clear the entire screen and reset cursor to (0,0).
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*** Rendering Primitives
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** Rendering Primitives
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- =(draw-text backend x y string fg bg &key bold italic underline reverse dim blink)= → nil
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- ~(draw-text backend x y string fg bg &key bold italic underline reverse dim blink)~ → nil
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Render text at position (x, y). fg and bg are hex color strings
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(e.g. "#FFD700") or nil for default. Attributes are booleans.
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- =(draw-border backend x y width height &key style fg bg title title-align)= → nil
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- ~(draw-border backend x y width height &key style fg bg title title-align)~ → nil
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Draw a border rectangle. Style is :single, :double, or :rounded.
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- =(draw-rect backend x y width height &key bg)= → nil
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- ~(draw-rect backend x y width height &key bg)~ → nil
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Fill a rectangle with background color.
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- =(draw-link backend x y string url &key fg bg)= → nil
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- ~(draw-link backend x y string url &key fg bg)~ → nil
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Render clickable hyperlink (OSC 8 escape sequence).
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- =(draw-ellipsis backend x y width &key fg bg)= → nil
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- ~(draw-ellipsis backend x y width &key fg bg)~ → nil
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Render "..." truncated text marker at position.
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*** Cursor Operations
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** Cursor Operations
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- =(cursor-move backend x y)= → nil
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Move cursor to position (x, y). Origin is top-left (0,0).
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- ~(cursor-move backend x y)~ → nil
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- ~(cursor-hide backend)~ → nil
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- ~(cursor-show backend)~ → nil
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- ~(cursor-style backend shape &key blink)~ → nil
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Shape is :block, :bar, or :underline.
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- =(cursor-hide backend)= → nil
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- =(cursor-show backend)= → nil
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** Synchronization
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- =(cursor-style backend shape &key blink)= → nil
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shape is :block, :bar, or :underline.
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*** Synchronization
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- =(begin-sync backend)= → nil
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- ~(begin-sync backend)~ → nil
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Start synchronized update (DECICM). All subsequent output is buffered
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by the terminal until =end-sync=.
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- =(end-sync backend)= → nil
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by the terminal until ~end-sync~.
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- ~(end-sync backend)~ → nil
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Flush synchronized update buffer. The entire frame appears at once.
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*** Input
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** Input
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- =(read-event backend &key timeout)= → (values keyword list)
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- ~(read-event backend &key timeout)~ → (values keyword list)
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Read next input event. Blocks until event or timeout.
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Returns event type keyword and event data plist.
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- =(enable-mouse backend)= → nil
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Enable SGR mouse tracking (press, release, drag, scroll).
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- =(enable-bracketed-paste backend)= → nil
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- ~(enable-mouse backend)~ → nil
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Enable SGR mouse tracking.
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- ~(enable-bracketed-paste backend)~ → nil
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Enable bracketed paste mode.
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*** Capability Queries
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** Capability Queries
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- =(capable-p backend feature)= → boolean
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- ~(capable-p backend feature)~ → boolean
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Feature is :truecolor, :osc8, :sync, :mouse, :bracketed-paste,
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:kitty-keyboard, :sixel, :cursor-style.
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** Backend Classes
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*** Simple Backend
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=(make-simple-backend)= → simple-backend
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The minimal backend. ASCII borders, no color, no modern features.
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Works everywhere — SSH, serial, pipes, ancient terminals.
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Borders:
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- Single: + - |
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- Double: + = |
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- Rounded: + - | (same as single — no rounded chars)
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No color, no bold, no italic, no links, no mouse, no sync.
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*** Modern Backend
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=(make-modern-backend)= → modern-backend
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- ~(make-simple-backend &key output-stream)~ → simple-backend
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Minimal backend. ASCII borders, no color, no modern features.
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- ~(make-modern-backend &key output-stream)~ → modern-backend
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Full-featured backend. Truecolor, Unicode box-drawing, OSC 8 links,
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DECICM sync, mouse tracking, kitty keyboard protocol.
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Borders:
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- Single: ┌ ─ ┐ │ └ ┘
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- Double: ╔ ═ ╗ ║ ╚ ╝
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- Rounded: ╭ ─ ╮ │ ╰ ╯
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* Tests
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** Test Suite
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#+BEGIN_SRC lisp
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#+BEGIN_SRC lisp :tangle ../src/backend/tests.lisp
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(defpackage :cl-tty-backend-test
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(:use :cl :fiveam)
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(:export #:run!))
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(:use :cl :fiveam :cl-tty.backend)
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(:export #:run-tests))
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(in-package :cl-tty-backend-test)
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(def-suite backend-suite :description "Backend protocol tests")
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(in-suite backend-suite)
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;; ── Helpers ─────────────────────────────────────────────────────
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(defun make-capturing-backend ()
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"Create a simple-backend that writes to a string stream."
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(let* ((s (make-string-output-stream))
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(b (make-simple-backend :output-stream s)))
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(values b s)))
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;; ── Simple Backend ──────────────────────────────────────────────
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(defun run-tests ()
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"Run all backend tests."
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(let ((result (run 'backend-suite)))
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(fiveam:explain! result)
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(uiop:quit 0)))
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(test simple-backend-lifecycle
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"simple-backend can be created and shut down"
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(let ((b (make-simple-backend)))
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(is (typep b 'simple-backend))
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(initialize-backend b)
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(is (capable-p b :truecolor) nil "simple backend has no truecolor")
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(is-false (capable-p b :truecolor) "simple backend has no truecolor")
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(shutdown-backend b)))
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(test simple-backend-draw-text
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"simple-backend renders text at position, ignoring style"
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(let ((b (make-simple-backend)))
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(multiple-value-bind (b s) (make-capturing-backend)
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(initialize-backend b)
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(draw-text b 0 0 "hello" nil nil)
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;; No crash = pass (simple backend writes to *standard-output*)
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(draw-text b 0 0 "hello" :red nil :bold t :italic t)
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(shutdown-backend b)
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(is-t t)))
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(is (string= (get-output-stream-string s) "hello")
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"draw-text should output the string ignoring style")))
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(test simple-backend-border-single
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"simple-backend draws ASCII single border"
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(let ((b (make-simple-backend)))
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(test simple-backend-draw-border
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"simple-backend draws ASCII border with +-| characters"
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(multiple-value-bind (b s) (make-capturing-backend)
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(initialize-backend b)
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(draw-border b 0 0 10 5 :style :single)
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(draw-border b 0 0 5 3 :style :single)
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(shutdown-backend b)
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(is-t t)))
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(let ((out (get-output-stream-string s)))
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(is (search "+---+" out) "top edge should have +---+")
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(is (search "| |" out) "middle row should have pipe sides"))))
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(test simple-backend-border-rounded
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"simple-backend falls back to straight edges for rounded"
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(let ((b (make-simple-backend)))
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(test simple-backend-draw-rounded
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"simple-backend falls back to straight edges for rounded style"
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(multiple-value-bind (b s) (make-capturing-backend)
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(initialize-backend b)
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(draw-border b 0 0 10 5 :style :rounded)
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;; No error — rounded falls back to single on simple
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(draw-border b 0 0 5 3 :style :rounded)
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(shutdown-backend b)
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(is-t t)))
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(let ((out (get-output-stream-string s)))
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;; Rounded falls back to ASCII — identical output to single
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(is (search "+---+" out) "rounded style produces same dashes as single"))))
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(test simple-backend-draw-link
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"simple-backend renders link as plain text"
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(multiple-value-bind (b s) (make-capturing-backend)
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(initialize-backend b)
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(draw-link b 0 0 "click me" "http://example.com")
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(shutdown-backend b)
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(is (string= (get-output-stream-string s) "click me")
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"simple-backend ignores URL, outputs text only")))
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(test simple-backend-draw-ellipsis
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"simple-backend renders ... for ellipsis"
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(multiple-value-bind (b s) (make-capturing-backend)
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(initialize-backend b)
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(draw-ellipsis b 0 0 5)
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(shutdown-backend b)
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(is (string= (get-output-stream-string s) "...")
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"ellipsis should output 3 dots")))
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;; ── Backend Capabilities ───────────────────────────────────────
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@@ -171,7 +183,7 @@ Borders:
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(initialize-backend b)
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(dolist (f '(:truecolor :osc8 :sync :mouse :bracketed-paste
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:kitty-keyboard :sixel :cursor-style))
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(is (capable-p b f) nil
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(is-false (capable-p b f)
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(format nil "~s should not be supported on simple-backend" f)))
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(shutdown-backend b)))
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@@ -188,42 +200,63 @@ Borders:
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(is (>= lines 3)))
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(shutdown-backend b)))
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;; ── Drawing Primitives ─────────────────────────────────────────
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;; ── Backend Protocol: Defaults and No-ops ──────────────────────
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(test draw-rect-fills-area
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"draw-rect fills a rectangular area with background"
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(test default-methods-are-no-ops
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"Default backend methods don't error"
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(let ((b (make-simple-backend)))
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(initialize-backend b)
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(draw-rect b 0 0 5 3 :bg nil)
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(shutdown-backend b)
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(is-t t)))
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(test draw-text-multi-line
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"draw-text handles strings with newlines"
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(let ((b (make-simple-backend)))
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(initialize-backend b)
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(draw-text b 0 0 "line1~%line2" nil nil)
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(shutdown-backend b)
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(is-t t)))
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;; ── Synchronization ────────────────────────────────────────────
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(is (null (multiple-value-list (cursor-hide b))))
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(is (null (multiple-value-list (cursor-show b))))
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(is (null (multiple-value-list (cursor-style b :block))))
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(is (null (multiple-value-list (begin-sync b))))
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(is (null (multiple-value-list (end-sync b))))
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(shutdown-backend b)))
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(test sync-is-noop-on-simple
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"begin-sync and end-sync are no-ops on simple-backend"
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(let ((b (make-simple-backend)))
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"begin-sync and end-sync produce no output on simple-backend"
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(multiple-value-bind (b s) (make-capturing-backend)
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(initialize-backend b)
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(begin-sync b)
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(draw-text b 0 0 "in sync" nil nil)
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(end-sync b)
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(shutdown-backend b)
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(is-t t)))
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(is (string= (get-output-stream-string s) "in sync")
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"no sync escape sequences should appear")))
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;; ── Draw-rect ──────────────────────────────────────────────────
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(test draw-rect-fills-area-correctly
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"draw-rect with background writes nothing to output (simple-backend no-op)"
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(multiple-value-bind (b s) (make-capturing-backend)
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(initialize-backend b)
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(draw-rect b 0 0 5 3 :bg :red)
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(shutdown-backend b)
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(is (string= (get-output-stream-string s) "")
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"draw-rect is a no-op on simple-backend")))
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;; ── Detection ──────────────────────────────────────────────────
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(test detection-returns-backend-instance
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"detect-backend returns a valid backend instance"
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(let ((be (cl-tty.backend:detect-backend)))
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(is (typep be 'cl-tty.backend:backend))))
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(test detection-caches-result
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"detect-backend caches the result in *detected-backend*"
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(let ((*detected-backend* nil))
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(cl-tty.backend:detect-backend)
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(is-true (not (null cl-tty.backend::*detected-backend*)))))
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#+END_SRC
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** Implementation
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* Implementation
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*** Package
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** Package
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#+BEGIN_SRC lisp
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The ~cl-tty.backend~ package exports all the generic function names
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and backend class names. It uses only ~:cl~ — no external dependencies.
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#+BEGIN_SRC lisp :tangle ../src/backend/package.lisp
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(defpackage :cl-tty.backend
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(:use :cl)
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(:export
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@@ -244,13 +277,35 @@ Borders:
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;; Queries
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#:capable-p
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;; Constructors
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#:make-simple-backend))
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#:make-simple-backend
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;; Modern backend
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#:modern-backend #:make-modern-backend
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;; Detection
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#:detect-backend #:*detected-backend*
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;; Theme color resolution (populated by theme system)
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#:*theme-colors*
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;; Internal (for testing)
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#:sgr-fg #:sgr-bg #:sgr-attr
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#:cursor-move-escape #:cursor-style-escape
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#:decicm-begin #:decicm-end #:osc8-link
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#:hex-to-rgb #:border-char))
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(in-package :cl-tty.backend)
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#+END_SRC
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*** Backend Base Class
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The package also exports internal symbols (~sgr-fg~, ~hex-to-24bit~,
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etc.) for testing. These let the test suite verify escape sequence
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construction without actually rendering to a terminal.
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** Backend Base Class
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The ~backend~ class itself is empty — it's a base for method dispatch.
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Every generic function on ~backend~ has a default method so that new
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backend implementations only need to override the functions they
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actually support.
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#+BEGIN_SRC lisp :tangle ../src/backend/classes.lisp
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(in-package :cl-tty.backend)
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#+BEGIN_SRC lisp
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(defclass backend () ())
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(defgeneric initialize-backend (backend)
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@@ -267,11 +322,11 @@ Borders:
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(defgeneric backend-clear (backend)
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(:method ((b backend))
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(backend-write b (string #\escape) "[2J")
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(cursor-move b 0 0)))
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(backend-write b (format nil "~C[2J~C[H" #\Esc #\Esc))))
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(defgeneric draw-text (backend x y string fg bg &key
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bold italic underline reverse dim blink))
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bold italic underline reverse dim blink
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&allow-other-keys))
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(defgeneric draw-border (backend x y width height
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&key style fg bg title title-align))
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@@ -282,7 +337,8 @@ Borders:
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(defgeneric draw-ellipsis (backend x y width &key fg bg))
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(defgeneric cursor-move (backend x y))
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(defgeneric cursor-move (backend x y)
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(:method ((b backend) x y) (declare (ignore x y)) (values)))
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(defgeneric cursor-hide (backend)
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(:method ((b backend)) (values)))
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@@ -314,13 +370,35 @@ Borders:
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nil))
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#+END_SRC
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*** Simple Backend
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The ~&allow-other-keys~ on ~draw-text~ is important: it lets
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individual backend methods accept keyword arguments they don't use
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without signaling an error. The simple backend ignores styles; the
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modern backend processes them.
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** Simple Backend
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~simple-backend~ inherits from ~backend~ and implements every
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operation in pure ASCII. No escape sequences, no color, no modern
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features. Works in any terminal, pipe, or serial connection.
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#+BEGIN_SRC lisp :tangle ../src/backend/simple.lisp
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(in-package :cl-tty.backend)
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#+BEGIN_SRC lisp
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(defclass simple-backend (backend)
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((output-stream :initform *standard-output*
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:initarg :output-stream
|
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:accessor backend-output-stream)))
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(defun make-simple-backend (&key output-stream)
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(make-instance 'simple-backend
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:output-stream (or output-stream *standard-output*)))
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#+END_SRC
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The ~output-stream~ initarg is the key extensibility point: tests use
|
||||
~make-string-output-stream~ to capture output, while production uses
|
||||
~*standard-output*~.
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||||
|
||||
#+BEGIN_SRC lisp :tangle ../src/backend/simple.lisp
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(defmethod initialize-backend ((b simple-backend))
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b)
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||||
@@ -341,29 +419,87 @@ Borders:
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||||
&key bold italic underline reverse dim blink)
|
||||
(declare (ignore x y fg bg bold italic underline reverse dim blink))
|
||||
(backend-write b string))
|
||||
#+END_SRC
|
||||
|
||||
(defun %simple-border-char (edge-style pos)
|
||||
"Return ASCII border character for EDGE-STYLE at POS.
|
||||
~draw-text~ on simple-backend ignores position and style completely.
|
||||
It just appends the string to the output stream. This means simple
|
||||
backends are always a "scroll and dump" mode — no cursor positioning.
|
||||
|
||||
** Border drawing
|
||||
|
||||
#+BEGIN_SRC lisp :tangle ../src/backend/simple.lisp
|
||||
(defun %simple-border-char (pos)
|
||||
"Return ASCII border character at POS.
|
||||
POS is :top-left, :top-right, :bottom-left, :bottom-right,
|
||||
:horizontal, or :vertical."
|
||||
(case pos
|
||||
((:top-left :top-right :bottom-left :bottom-right) #\+)
|
||||
(:horizontal #\-)
|
||||
(:vertical #\|)))
|
||||
#+END_SRC
|
||||
|
||||
All four corners use ~#\+~, edges use ~#\-~ and ~#\|~. No style
|
||||
distinction — single, double, and rounded are identical in ASCII.
|
||||
|
||||
#+BEGIN_SRC lisp :tangle ../src/backend/simple.lisp
|
||||
(defmethod draw-border ((b simple-backend) x y width height
|
||||
&key style fg bg title title-align)
|
||||
(declare (ignore style fg bg title title-align))
|
||||
(let ((h (%simple-border-char nil :horizontal))
|
||||
(v (%simple-border-char nil :vertical)))
|
||||
;; Top edge
|
||||
(backend-write b (format nil "~%~v@{~a~:*~}" width h))
|
||||
(declare (ignore style fg bg))
|
||||
(let ((h (%simple-border-char :horizontal))
|
||||
(v (%simple-border-char :vertical))
|
||||
(tl (%simple-border-char :top-left))
|
||||
(tr (%simple-border-char :top-right))
|
||||
(bl (%simple-border-char :bottom-left))
|
||||
(br (%simple-border-char :bottom-right)))
|
||||
;; Position cursor with newlines and spaces (no escape sequences)
|
||||
(dotimes (row y) (backend-write b (string #\Newline)))
|
||||
;; Top edge with optional title
|
||||
(backend-write b (make-string x :initial-element #\space))
|
||||
(backend-write b (string tl))
|
||||
(if (and title (plusp (length title)))
|
||||
(let* ((align (or title-align :left))
|
||||
(inner-width (- width 2))
|
||||
(max-tlen (- inner-width 2))
|
||||
(tlen (min (length title) max-tlen))
|
||||
(trunc-title (subseq title 0 tlen)))
|
||||
(ecase align
|
||||
(:left
|
||||
(backend-write b (string #\Space))
|
||||
(backend-write b trunc-title)
|
||||
(backend-write b (string #\Space))
|
||||
(backend-write b (make-string (- inner-width tlen 2) :initial-element h)))
|
||||
(:center
|
||||
(let* ((total-pad (- inner-width tlen))
|
||||
(left-pad (floor total-pad 2))
|
||||
(right-pad (- total-pad left-pad)))
|
||||
(backend-write b (make-string left-pad :initial-element h))
|
||||
(backend-write b trunc-title)
|
||||
(backend-write b (make-string right-pad :initial-element h))))))
|
||||
(backend-write b (make-string (- width 2) :initial-element h)))
|
||||
(backend-write b (string tr))
|
||||
;; Sides
|
||||
(loop for i from 1 below (1- height)
|
||||
do (backend-write b (format nil "~%|~v@{~a~:*~}|" (- width 2) #\space)))
|
||||
do (backend-write b (string #\Newline))
|
||||
(backend-write b (make-string x :initial-element #\space))
|
||||
(backend-write b (string v))
|
||||
(backend-write b (make-string (- width 2) :initial-element #\space))
|
||||
(backend-write b (string v)))
|
||||
;; Bottom edge
|
||||
(backend-write b (format nil "~%~v@{~a~:*~}" width h))))
|
||||
(backend-write b (string #\Newline))
|
||||
(backend-write b (make-string x :initial-element #\space))
|
||||
(backend-write b (string bl))
|
||||
(backend-write b (make-string (- width 2) :initial-element h))
|
||||
(backend-write b (string br))))
|
||||
#+END_SRC
|
||||
|
||||
~draw-border~ on the simple backend uses newlines and spaces for
|
||||
positioning instead of ~cursor-move~ escape sequences. This makes it
|
||||
compatible with pipe output. The title rendering supports ~:left~ and
|
||||
~:center~ alignment, placing the title inside the top border line.
|
||||
|
||||
** Remaining primitives
|
||||
|
||||
#+BEGIN_SRC lisp :tangle ../src/backend/simple.lisp
|
||||
(defmethod draw-rect ((b simple-backend) x y width height
|
||||
&key bg)
|
||||
(declare (ignore x y width height bg))
|
||||
@@ -377,6 +513,13 @@ POS is :top-left, :top-right, :bottom-left, :bottom-right,
|
||||
|
||||
(defmethod draw-ellipsis ((b simple-backend) x y width
|
||||
&key fg bg)
|
||||
(declare (ignore x y width fg bg))
|
||||
(declare (ignore width fg bg))
|
||||
;; Position using newlines+spaces (simple-backend pattern)
|
||||
(dotimes (row y) (backend-write b (string #\Newline)))
|
||||
(backend-write b (make-string x :initial-element #\Space))
|
||||
(backend-write b "..."))
|
||||
#+END_SRC
|
||||
|
||||
~draw-rect~ is a no-op on simple-backend (no background fill possible
|
||||
without escape sequences). ~draw-link~ falls back to plain text.
|
||||
~draw-ellipsis~ positions and writes "...".
|
||||
|
||||
Reference in New Issue
Block a user