feat: add PRINTER_A4 landscape option for A4 printers

Dot-matrix printers have no hardware page-rotation, so when PRINTER_A4
is enabled in the new printer.conf, txt2printr.sh rotates the ascii art
90 degrees in software before sending it, and photobooth.py caps its
live-preview viewfinder to an A4-landscape character grid (sized from
configurable PRINTER_CPI/PRINTER_LPI) instead of just filling the
terminal, so the preview matches what actually gets printed.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

photobooth.py

@@ -55,6 +55,7 @@ class Config:
         webcam = load_conf("webcam.conf")
         ascii_ = load_conf("ascii.conf")
         keys = load_conf("keybinds.conf")
+        printer = load_conf("printer.conf")
 
         self.device = webcam.get("DEVICE", "/dev/video0")
         w, _, h = webcam.get("RESOLUTION", "640x480").partition("x")
@@ -79,6 +80,10 @@ class Config:
         self.flip_x = as_bool(ascii_.get("FLIP_X"))
         self.flip_y = as_bool(ascii_.get("FLIP_Y"))
 
+        self.printer_a4 = as_bool(printer.get("PRINTER_A4"))
+        self.printer_cpi = float(printer.get("PRINTER_CPI", "10") or 10)
+        self.printer_lpi = float(printer.get("PRINTER_LPI", "6") or 6)
+
         self.key_capture = keys.get("KEY_CAPTURE", " ")
         self.key_brightness_up = keys.get("KEY_BRIGHTNESS_UP", "+")
         self.key_brightness_down = keys.get("KEY_BRIGHTNESS_DOWN", "-")
@@ -168,9 +173,37 @@ def capture_label(cfg):
     return "space" if cfg.key_capture == " " else cfg.key_capture
 
 
+_A4_LONG_MM = 297.0
+_A4_SHORT_MM = 210.0
+_MM_PER_IN = 25.4
+_PRINT_MARGIN_IN = 0.5
+
+
+def a4_landscape_chars(cpi, lpi):
+    """(cols, rows) of an A4 sheet printed sideways, at the given pitch."""
+    long_in = _A4_LONG_MM / _MM_PER_IN
+    short_in = _A4_SHORT_MM / _MM_PER_IN
+    cols = max(1, round((long_in - 2 * _PRINT_MARGIN_IN) * cpi))
+    rows = max(1, round((short_in - 2 * _PRINT_MARGIN_IN) * lpi))
+    return cols, rows
+
+
+def box_dims_for(term_rows, term_cols, a4_target):
+    box_rows, box_cols = max(term_rows - 2, 3), max(term_cols, 10)
+    if a4_target:
+        a4_cols, a4_rows = a4_target
+        box_rows = min(box_rows, a4_rows + 2)
+        box_cols = min(box_cols, a4_cols + 2)
+    return box_rows, box_cols
+
+
 def main(stdscr):
     cfg = Config()
     conv_flags = cfg.converter_flags()
+    a4_target = (
+        a4_landscape_chars(cfg.printer_cpi, cfg.printer_lpi)
+        if cfg.printer_a4 else None
+    )
 
     curses.curs_set(0)
     stdscr.nodelay(True)
@@ -190,7 +223,7 @@ def main(stdscr):
     frame_times = []
     message, message_until = "", 0.0
     rows, cols = stdscr.getmaxyx()
-    box_dims = (max(rows - 2, 3), max(cols, 10))
+    box_dims = box_dims_for(rows, cols, a4_target)
     box_win = curses.newwin(box_dims[0], box_dims[1], 0, 0)
 
     try:
@@ -210,7 +243,7 @@ def main(stdscr):
             jpg_bytes = buf.tobytes()
 
             rows, cols = stdscr.getmaxyx()
-            box_rows, box_cols = max(rows - 2, 3), max(cols, 10)
+            box_rows, box_cols = box_dims_for(rows, cols, a4_target)
             inner_rows, inner_cols = max(box_rows - 2, 1), max(box_cols - 2, 1)
 
             if (box_rows, box_cols) != box_dims:

printer.conf

@@ -0,0 +1,19 @@
+# ASCII Photobooth printer configuration
+# Sourced by txt2printr.sh and photobooth.py.
+
+# Is the printer loaded with A4 paper for a landscape printout? (true/false)
+# Needle/dot-matrix printers have no hardware page-rotation command: the
+# print head only scans across a fixed carriage width while the paper feeds
+# in one fixed direction, so there is no way to make the physical page
+# itself "landscape". Instead, when this is true:
+#  - txt2printr.sh rotates the ascii art 90 degrees in software before
+#    sending it to the printer (turn the printed page 90 degrees to read it)
+#  - photobooth.py sizes its live-preview viewfinder to an A4-landscape
+#    character grid instead of just following the terminal size, so what you
+#    see in the preview matches the shape of what gets printed
+PRINTER_A4=false
+
+# Printer pitch, used only to size the A4 viewfinder above (characters per
+# inch / lines per inch). Defaults match common Epson ESC/P draft settings.
+PRINTER_CPI=10
+PRINTER_LPI=6

txt2printr.sh

@@ -4,6 +4,11 @@
 #
 # Usage: ./txt2printr.sh [ascii-art.txt]
 # Env:   PRINTER_DEV - printer device node (default: /dev/lp0)
+# Reads printer.conf for PRINTER_A4 (landscape rotation).
+
+dir="$(dirname "$0")"
+[ -f "$dir/printer.conf" ] && source "$dir/printer.conf"
+: "${PRINTER_A4:=false}"
 
 infile="${1:-ascii-img.txt}"
 # Source - https://stackoverflow.com/a/638980
@@ -31,8 +36,33 @@ if [ ! -w "$dev" ]; then
     exit 1
 fi
 
+# Rotates the ascii art 90 degrees clockwise so it reads correctly once the
+# printed page itself is turned 90 degrees counter-clockwise - the printer's
+# scan/feed directions are fixed, so this is the only way to get a landscape
+# reading orientation out of it.
+rotate90() {
+    awk '
+        { if (length($0) > maxlen) maxlen = length($0); lines[NR] = $0 }
+        END {
+            for (c = 1; c <= maxlen; c++) {
+                row = ""
+                for (r = NR; r >= 1; r--) {
+                    ch = substr(lines[r], c, 1)
+                    if (ch == "") ch = " "
+                    row = row ch
+                }
+                print row
+            }
+        }
+    ' "$infile"
+}
+
 {
-    printf '\x1b\x40'        # ESC @ - reset printer (ESC/P and IBM Proprinter compatible)
-    sed 's/$/\r/' "$infile"  # CRLF line endings, needed for raw writes to avoid staircasing
-    printf '\x0c'            # form feed - eject the page
+    printf '\x1b\x40'  # ESC @ - reset printer (ESC/P and IBM Proprinter compatible)
+    if [ "$PRINTER_A4" = "true" ]; then
+        rotate90 | sed 's/$/\r/'  # CRLF line endings, needed for raw writes to avoid staircasing
+    else
+        sed 's/$/\r/' "$infile"
+    fi
+    printf '\x0c'  # form feed - eject the page
 } > "$dev"