"""The network cursor's picture, drawn on demand.
 
 The cursor is a hou.NetworkImage stretched over the cells it covers. Houdini
 can only brighten a background image, not tint it, so a configurable colour
 means a differently coloured file. This used to be 144 static PNGs in
 config/hcnetcursor_assets, one per cell size, all the same gold; now the
 picture is painted the first time a (cells, colour) pair is asked for and
 cached in the session's temp dir.
 
 The look is the old asset set's: transparent inside, a BORDER-pixel
 outline. The picture is painted at UNIT_PIXELS per network unit of the rect
 it will be stretched over, so the outline is the same width on every side
 and the same width whatever the cursor's size; the old assets were painted
 per cell, and a box that is not cell-shaped stretched their outline unevenly.
 """
 
 import os
 import tempfile
 
 import hou
 
 UNIT_PIXELS = 100          # image pixels per network unit
 BORDER = 5                 # outline width, in image pixels
 MAX_PIXELS = 2400          # a cursor wider than this reuses the largest picture
 
 _generated = {}
 
 
 def cache_dir():
     base = hou.getenv("HOUDINI_TEMP_DIR") or tempfile.gettempdir()
     return os.path.join(base, "hc_hcnetcursor")
 
 
 def is_cursor_image(path):
     """Whether a background image path is one of ours, from any session.
 
     Matched on the basename only: a hip saved with the cursor showing keeps
     the image in the network's background list, and the directory in that
     path may be an old temp dir or the retired config/hcnetcursor_assets.
     """
     return os.path.basename(path).startswith("hcnetcursor_")
 
 
 def pixel_size(width_units, height_units):
     """Image size for a box this many network units across, as whole pixels."""
     return (max(2 * BORDER, min(int(round(width_units * UNIT_PIXELS)), MAX_PIXELS)),
             max(2 * BORDER, min(int(round(height_units * UNIT_PIXELS)), MAX_PIXELS)))
 
 
 def image_file(width_units, height_units, color_hex):
     """Path of the cursor picture for a box this size in this colour."""
     width, height = pixel_size(width_units, height_units)
     color_hex = color_hex.lstrip("#").lower()
     path = os.path.join(cache_dir(), f"hcnetcursor_{width}x{height}_{color_hex}.png")
     # Asked on every network editor event; paint once per session.
     if _generated.get(path) or os.path.exists(path):
         _generated[path] = True
         return path
     paint(path, width, height, "#" + color_hex)
     _generated[path] = True
     return path
 
 
 def paint(path, width, height, color_hex):
     from PySide6.QtCore import Qt
     from PySide6.QtGui import QColor, QImage, QPainter, QPen
 
     image = QImage(width, height, QImage.Format_ARGB32)
     image.fill(Qt.transparent)
     painter = QPainter(image)
     pen = QPen(QColor(color_hex), BORDER)
     pen.setJoinStyle(Qt.MiterJoin)
     painter.setPen(pen)
     painter.setBrush(Qt.NoBrush)
     # A pen is centred on the path; inset by half so the outline sits fully
     # inside the image, as the old assets did.
     half = BORDER / 2.0
     painter.drawRect(half, half, width - BORDER, height - BORDER)
     painter.end()
 
     os.makedirs(os.path.dirname(path), exist_ok=True)
     if not image.save(path):
         raise RuntimeError(f"could not write cursor image {path}")
     return path