Added instructions for Windows OS users to resolve a common error by importing the OCCT DLL directory.

[farleyrunkel]

Summary by Sourcery

This pull request updates the INSTALL.md file to include a troubleshooting guide for Windows OS users, addressing a specific DLL import error and providing steps to resolve it.

• Documentation:
  • Added a troubleshooting guide for Windows OS users to resolve the 'DLL load failed while importing _gp' error in the INSTALL.md file.

[sourcery-ai[bot]]

Reviewer's Guide by Sourcery

This pull request updates the INSTALL.md file to include a new section specifically for Windows OS users. It addresses a common ImportError related to DLL loading and provides a code snippet to resolve the issue by importing the OCCT DLL directory.

File-Level Changes

Files	Changes
INSTALL.md	Added instructions for Windows OS users to resolve a DLL load error by importing the OCCT DLL directory.

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[Andrej730]

Is this all that was required? In my case I also was needed to provide paths to occt dependecies.

import os
os.add_dll_directory(r'occt-7.8.0-vc143-64\win64\vc14\bin')
os.add_dll_directory(r'occt-7.8.0-vc143-64\3rdparty-vc14-64\tbb2021.5-vc14-x64\bin')
os.add_dll_directory(r'occt-7.8.0-vc143-64\3rdparty-vc14-64\jemalloc-vc14-64\bin')
os.add_dll_directory(r'occt-7.8.0-vc143-64\3rdparty-vc14-64\freeimage-3.17.0-vc14-64\bin')
os.add_dll_directory(r'occt-7.8.0-vc143-64\3rdparty-vc14-64\openvr-1.14.15-64\bin\win64')
os.add_dll_directory(r'occt-7.8.0-vc143-64\3rdparty-vc14-64\ffmpeg-3.3.4-64\bin')
os.add_dll_directory(r'occt-7.8.0-vc143-64\3rdparty-vc14-64\freetype-2.5.5-vc14-64\bin')

# Test dependencies:
# requires: tbb, jemalloc
from OCC.Core import gp
# requires: freeimage, openvr, ffmpeg, freetype
from OCC.Core import V3d

from OCC.Core.gp import gp_Pnt
p = gp_Pnt(1.0, 2.0, 3.0)
print(p.X())

[farleyrunkel]

@Andrej730 you are right.adding occt dependencies is also required if not adding them to system path.but in my case，adding occt bin directory to system path does not work.i don't know if you meet the same issue？

[Andrej730]

@farleyrunkel yes, that's the same issue I've met 😁

Here's a very insightful issue about it this - https://bugs.python.org/issue43173

Basically Python is checking these places when it's trying to find a dll:

* the loaded extension module's directory
* the application directory (e.g. that of python.exe)
* the user DLL search directories that get added by 
  SetDllDirectory() and AddDllDirectory(), such as with 
  os.add_dll_directory()
* %SystemRoot%\System32
Note that the above list does not include the current working directory or %PATH% directories.

It used to work with the system path before Python 3.8 but then they decided it should work in more safe manner - https://docs.python.org/3/library/os.html#os.add_dll_directory

So, I guess the best way is to either add binaries next to .pyd files or add them using os.add_dll_directory. If you still have issues enabling OCC, you can use procmon to see what exact dlls are missing for you (in procmon you case see every path python is trying to look up and the status whether it found something by that path or not).

PS It would be nice if pythonocc would do any of these things automatically when you're trying to install it on Windows.

[farleyrunkel]

@Andrej730 Yes, I think so too.

PS It would be nice if pythonocc would do any of these things automatically when you're trying to install it on Windows.

[Andrej730]

I'm thinking maybe simple test should also be extended to include some imports that will require dll-dependencies to be successfully located by Python? I've updated my first post in this PR with an example.

[tpaviot]

It's been a long time I stopped building occt/pythonocc on Windows. I'm now working on Linux, I only take care that the conda-build pass on Windows and OSX, but my experience with building pythonocc from scratch on Windows is quite outdated. I will welcome a PR that fixes this dll issue.

[Bill-XU]

@farleyrunkel @Andrej730

I wrote this, maybe more convenient.

def initialize_occt_libraries() -> None:
    """
    Initializes the OCCT libraries by setting the OCCT_ESSENTIALS_PATH environment variable and adding all DLL directories to the DLL search path.

    Raises:
        AssertionError: If the OCCT_ESSENTIALS_PATH environment variable is not set.

    """
    import os
    
    assert "OCCT_ESSENTIALS_PATH" in os.environ, "OCCT_ESSENTIALS_PATH is not set. e.x., export OCCT_ESSENTIALS_PATH=\"C:/Program Files (x86)/OpenCASCADE-7.8.1-vc14-64\""
    _occt_essentials_path = os.environ["OCCT_ESSENTIALS_PATH"]
    assert os.path.exists(_occt_essentials_path), f'OCCT_ESSENTIALS_PATH({_occt_essentials_path}) is not set correctly.'
    
    def __add_all_dll_directories(directory:str) -> None:
        """
        Recursively adds all directories containing DLL files to the DLL search path.
        Exclude path with "debug" in it.

        Args:
            directory (str): The directory to start searching from.

        """
        for root, dirs, files in os.walk(directory):
            if "debug" in root.lower():
                continue
            for file in files:
                if file.endswith(".dll"):
                    os.add_dll_directory(root)
                    break
                pass
        pass
    
    __add_all_dll_directories(_occt_essentials_path)
    pass

try:
    from OCC.Core.AIS import AIS_Shape
except ImportError:
    initialize_occt_libraries()

[Andrej730]

I wrote this, maybe more convenient.

@Bill-XU Looks good! Do you plan to submit it as a PR? Would be nice to have it as OCC.initialize_occt_libraries. It can also have something like if platform.system() != "Windows": return at the start, so it will be safe to include to cross-platform scripts.

[Bill-XU]

I wrote this, maybe more convenient.

@Bill-XU Looks good! Do you plan to submit it as a PR? Would be nice to have it as OCC.initialize_occt_libraries. It can also have something like if platform.system() != "Windows": return at the start, so it will be safe to include to cross-platform scripts.

@Andrej730 I have little knowledge of progamming such a project mixed with C and Python, but will have a try. (I suppose that the initialization process shall be included in PkgBase/init.py.)

[tpaviot]

Superseded by #1384

[tpaviot]

Fixed by #1384