Move caching implementation to Python

Less code, more performant since the cache is used from Python.
And we can make the Go code a pure image format conversion filter.

kitty/utils.py

@@ -34,7 +34,6 @@ from typing import (
 
 from .constants import (
     appname,
-    cache_dir,
     clear_handled_signals,
     config_dir,
     is_macos,
@@ -1227,33 +1226,15 @@ def timed_debug_print(*a: Any, sep: str = ' ', end: str = '\n') -> None:
     _timed_debug_print(sep.join(map(str, a)) + end)
 
 
-def cached_rgba_file_descriptor_for_image_path(path: str) -> Tuple[int, int, int]:
-    from hashlib import sha256
-    try:
-        path = os.path.realpath(path, strict=True)
-    except TypeError:
-        path = os.path.realpath(path)
-    src_info = os.stat(path)
-    output_name = sha256(path.encode()).hexdigest() + '.rgba'
-    output_path = os.path.join(cache_dir(), 'rgba', output_name)
+def lock_file(f: BinaryIO) -> None:
+    if not f.writable():
+        raise ValueError('Cannot lock files not opened in writable mode')
+    import fcntl
+    fcntl.lockf(f, fcntl.LOCK_EX)
 
-    def read_data(f: BinaryIO) -> Tuple[int, int, int]:
-        header = f.read(8)
-        import struct
-        width, height = struct.unpack('<II', header)
-        return width, height, os.dup(f.fileno())
 
-    with suppress(OSError), open(output_path, 'rb') as f:
-        dest_info = os.stat(f.fileno())
-        if dest_info.st_size == src_info.st_size and dest_info.st_mtime >= src_info.st_mtime:
-            return read_data(f)
-
-    import subprocess
-    cp = subprocess.run([kitten_exe(), '__render_image__', path], capture_output=True)
-    if cp.returncode != 0:
-        raise ValueError(f'Failed to convert path to RGBA data with error: {cp.stderr.decode("utf-8", "replace")}')
-    ans = cp.stdout.decode().strip()
-    if ans != output_path:
-        raise ValueError(f'The two cache name algorithms dont agree for path: {path}\n{output_path} != {ans}')
-    with open(ans, 'rb') as f:
-        return read_data(f)
+def unlock_file(f: BinaryIO) -> None:
+    if not f.writable():
+        raise ValueError('Cannot unlock files not opened in writable mode')
+    import fcntl
+    fcntl.lockf(f, fcntl.LOCK_UN)