Start work on helper process for windows file dialogs

setup/installer/windows/file_dialogs.cpp

@@ -0,0 +1,79 @@
+/*
+ * file_dialogs.c
+ * Copyright (C) 2016 Kovid Goyal <kovid at kovidgoyal.net>
+ *
+ * Distributed under terms of the GPL3 license.
+ */
+
+#include <Windows.h>
+#include <Shobjidl.h>
+#include <stdio.h>
+#include <string.h>
+
+#define PRINTERR(x) fprintf(stderr, x); fflush(stderr);
+#define REPORTERR(x) { PRINTERR(x); ret = 1; goto error; }
+#define CALLCOM(x, err) hr = x; if(FAILED(hr)) REPORTERR(err)
+
+int show_dialog(HWND parent, bool save_dialog) {
+	int ret = 0;
+	IFileDialog *pfd = NULL;
+	IShellItem *psiResult = NULL;
+	DWORD dwFlags;
+	HRESULT hr = S_OK;
+	hr = CoInitialize(NULL);
+	if (FAILED(hr)) { PRINTERR("Failed to initialize COM"); return 1; }
+
+	CALLCOM(CoCreateInstance(CLSID_FileOpenDialog, NULL, CLSCTX_INPROC_SERVER, (save_dialog ? IID_IFileSaveDialog : IID_IFileOpenDialog), reinterpret_cast<LPVOID*>(&pfd)), "Failed to create COM object for file dialog")
+	CALLCOM(pfd->GetOptions(&dwFlags), "Failed to get options")
+	dwFlags |= FOS_FORCEFILESYSTEM;
+	CALLCOM(pfd->SetOptions(dwFlags), "Failed to set options")
+	hr = pfd->Show(parent);
+	if (hr == HRESULT_FROM_WIN32(ERROR_CANCELLED)) goto error;
+	if (FAILED(hr)) REPORTERR("Failed to show dialog")
+
+	CALLCOM(pfd->GetResult(&psiResult), "Failed to get dialog result")
+
+error:
+	if(pfd) pfd->Release();
+	CoUninitialize();
+	return ret;
+}
+
+bool read_bytes(size_t sz, char* buf, bool allow_incomplete=false) {
+	char *ptr = buf, *limit = buf + sz;
+	while(limit > ptr && !feof(stdin) && !ferror(stdin)) {
+		ptr += fread(ptr, 1, limit - ptr, stdin);
+	}
+	if (ferror(stdin)) { PRINTERR("Failed to read from stdin!"); return false; }
+	if (ptr - buf != sz) { if (!allow_incomplete) PRINTERR("Truncated input!"); return false; }
+	return true;
+}
+
+#define READ(x, y) if (!read_bytes((x), (y))) return 1;
+
+int WINAPI wWinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, PWSTR pCmdLine, int nCmdShow) {
+	char buf[257];
+	size_t key_size = 0;
+	HWND parent = NULL;
+	bool save_dialog = false;
+
+	while(!feof(stdin)) {
+		memset(buf, 0, sizeof(buf));
+		if(!read_bytes(1, buf, true)) { if (feof(stdin)) break; return 1;}
+		key_size = (size_t)buf[0];
+		READ(key_size, buf);
+		if (key_size == 4 && memcmp(buf, "HWND", 4) == 0) {
+			READ(sizeof(HWND), buf);
+			if (sizeof(HWND) == 8) parent = (HWND)*((__int64*)buf);
+			else if (sizeof(HWND) == 4) parent = (HWND)*((__int32*)buf);
+			else { fprintf(stderr, "Unknown pointer size: %d", sizeof(HWND)); return 1;}
+		}
+
+		else {
+			PRINTERR("Unknown key");
+			return 1;
+		}
+	}
+
+	return show_dialog(parent, save_dialog);
+}

src/calibre/gui2/win_file_dialogs.py

@@ -0,0 +1,90 @@
+#!/usr/bin/env python2
+# vim:fileencoding=utf-8
+# License: GPLv3 Copyright: 2016, Kovid Goyal <kovid at kovidgoyal.net>
+
+from __future__ import (unicode_literals, division, absolute_import,
+                        print_function)
+import sys, subprocess, struct, os
+from threading import Thread
+
+from PyQt5.Qt import QMainWindow, QApplication, QPushButton, pyqtSignal, QEventLoop, Qt
+
+is64bit = sys.maxsize > (1 << 32)
+base = sys.extensions_location if hasattr(sys, 'new_app_layout') else os.path.dirname(sys.executable)
+HELPER = os.path.join(base, 'calibre-file-dialogs.exe')
+
+def get_hwnd(widget=None):
+    ewid = None
+    if widget is not None:
+        ewid = widget.effectiveWinId()
+    if ewid is None:
+        return None
+    return int(ewid)
+
+def serialize_hwnd(hwnd):
+    if hwnd is None:
+        return b''
+    return struct.pack(b'=' + (b'B4sQ' if is64bit else b'I'), 4, b'HWND', int(hwnd))
+
+def serialize_string(key, val):
+    key = key.encode('ascii') if not isinstance(key, bytes) else key
+    val = type('')(val).encode('utf-8')
+    if len(val) > 2**16 - 1:
+        raise ValueError('%s is too long' % key)
+    return struct.pack(b'=B%dsH%ds' % (len(key), len(val)), len(key), key, len(val), val)
+
+class Helper(Thread):
+
+    def __init__(self, process, data, callback):
+        Thread.__init__(self, name='FileDialogHelper')
+        self.process = process
+        self.callback = callback
+        self.data = data
+        self.daemon = True
+        self.rc = 0
+        self.stdoutdata = None
+
+    def run(self):
+        self.stdoutdata, self.stderrdata = self.process.communicate(b''.join(self.data))
+        self.rc = self.process.wait()
+        self.callback()
+
+class Loop(QEventLoop):
+
+    dialog_closed = pyqtSignal()
+
+    def __init__(self):
+        QEventLoop.__init__(self)
+        self.dialog_closed.connect(self.exit, type=Qt.QueuedConnection)
+
+def run_file_dialog(parent=None, title=None):
+    data = []
+    if parent is not None:
+        data.append(serialize_hwnd(get_hwnd(parent)))
+    if title is not None:
+        data.append(serialize_string('TITLE', title))
+    loop = Loop()
+    h = Helper(subprocess.Popen(
+        [HELPER], stdout=subprocess.PIPE, stdin=subprocess.PIPE, stderr=subprocess.PIPE),
+               data, loop.dialog_closed.emit)
+    h.start()
+    loop.exec_(QEventLoop.ExcludeUserInputEvents)
+    if h.rc != 0:
+        raise Exception('File dialog failed: ' + h.stderrdata.decode('utf-8'))
+    if not h.stdoutdata:
+        return ()
+    return tuple(x.decode('utf-8') for x in h.stdoutdata.split(b'\0'))
+
+if __name__ == '__main__':
+    HELPER = sys.argv[-1]
+    app = QApplication([])
+    q = QMainWindow()
+
+    def clicked():
+        print(run_file_dialog(b)), sys.stdout.flush()
+
+    b = QPushButton('click me')
+    b.clicked.connect(clicked)
+    q.setCentralWidget(b)
+    q.show()
+    app.exec_()