fakelab 0.1.2
Fake FontLab Studio 5 for automated tests and external scripting
Requires Python: >=3.10
Keywords: vfb, fonttools

# FakeLab

Test-driven development for FontLab Studio 5 Python macros and modules.

FakeLab is a FontLab Studio 5 replacement for testing Python code.

Everything is only implemented so far as to make FontLab objects importable
outside of FontLab Studio 5, and run tests.

It is suggested to install FakeLab in a virtual environment so FontLab won't
accidentally import the fake module when running the scripts in actual FontLab
Studio 5. If you can live with the incompatibilites between Python 2.7 and 3,
you can also run FakeLab in Python 3.

Saving VFBs is not supported, as the VFB format is not public, but you can save
`Font` objects as JSON.

The implementation of FakeLab is based on the invaluable
[Unofficial FontLab/Python API Reference](http://www.e-font.de/flpydoc/), and
from running scripts in FontLab Studio and checking what they do, apart from
crashing the application.

## Installation

When you have activated your virtual environment:

```bash
$ pip install -e .
```

FL is then importable outside of FontLab Studio:

```python
from FL import fl, Font

# Make an empty font
f = Font()

# Add the font to the mock app
fl.Add(f)

# Close the font
fl.Close()
```

If your are running in a virtual environment, and need to make your FontLab
modules importable, add a `.pth` file in your virtual environment's site-packages
directory:

```
# fl5modules.pth
/Users/<yourname>/Code/FLMacros/System/Modules
```

## A word of caution

FakeLab is a work in progress, and only implemented as far as I needed it in my
own scripts. I have to admit that the bulk of them still has no tests.

If you encounter a `NotImplementedError` while writing tests, this is where you
can excel at helping to improve this project ;) I'll be happy to accept your
[pull requests](https://github.com/jenskutilek/fakelab/pulls). Alternatively,
[open an issue](https://github.com/jenskutilek/fakelab/issues),
[buy me a coffee](https://ko-fi.com/jenskutilek), and hope that my kids leave
me alone so I can find some time to work on your issue.

## Writing tests

Developing scripts without automated testing is really only for very small
projects. To be sure of the outcomes of a module or script, you should always
write tests. This is usually done using
[pytest](https://docs.pytest.org/en/stable/).

### Tests example

Let's assume you have a FontLab script to select glyphs containing components.
If you have your own tools collection for FontLab, this script may consist of
two parts: One script that is listed in FontLab's macro toolbar, and one Python
module implementing the logic, which is called by the toolbar script.

```
Studio 5
+- Macros
   +- Selection
      +- Select Composites.py
   +- System
      +- Modules
         +- fakeLabDemo
            +- selection
               +- __init__.py
               +- composites.py
```

The `Select Composites.py` script looks like this:

```python
#FLM: Select composites
# Studio 5/Macros/Selection/Select Composites.py
from fakeLabDemo.selection.composites import selectComposites
selectComposites(fl.font)
```

And the module:
```python
# Studio 5/Macros/System/Modules/fakeLabDemo/selection/composites.py
from __future__ import absolute_import, division, print_function

from FL import fl


def getFontIndex(font):
    """
    Get the index of the supplied font.
    We must iterate through the open fonts and compare file names,
    because the == operator can not compare the font objects directly.
    (FL font objects get a different id() each time they are called)

    :param font: A title for the dialog.
    :type font:  :py:class:`FL.Font`
    """
    for i in range(len(fl)):
        cf = fl[i]
        if cf.file_name == font.file_name:
            if font.file_name is None:
                if (
                    cf.family_name == font.family_name
                    and cf.style_name == font.style_name
                ):
                    return (cf, i)
            else:
                return (cf, i)
    # Font was not found, probably there are no open fonts
    return (None, -1)


def setSelection(font, glyph_names):
    """
    Set glyphs from the glyph_names list as selected in the font window.
    """
    f, i = getFontIndex(font)
    if i > -1:
        fl.ifont = i
        fl.Unselect()
        for n in glyph_names:
            fl.Select(n)


def selectComposites(font):
    """
    Select composites in font.
    """
    setSelection(
        font,
        [
            glyph.name
            for glyph in font.glyphs
            if glyph.components
        ]
    )
```

How can we be sure this script does what it is supposed to do? For pytest, we
add another parallel folder structure to the existing structure:

```
Studio 5
+- Macros
   +- Selection
      +- Select Composites.py
   +- System
      +- Modules
         +- fakeLabDemo
            +- selection
               +- __init__.py
               +- composites.py
         +- tests
            +- fakeLabDemo
               +- selection
                  +- composites_test.py
```

The file `composites_test.py`, which is named analogous to the module file it
relates to, is where we will implement our tests:

```python
# Studio 5/Macros/System/Modules/tests/fakeLabDemo/selection/composites_test.py
import pytest

from FL import fl, Component, Font, Glyph, Point
from fakeLabDemo.selection.composites import selectComposites


def test_selectComposites():
    # Construct a fake FontLab font object
    font = Font()
    g = Glyph(1)
    g.name = "A"
    g.width = 500
    g.unicode = 0x41
    font.glyphs.append(g)

    g = Glyph(1)
    g.name = "dieresis"
    g.width = 500
    g.unicode = 0xA8
    font.glyphs.append(g)

    g = Glyph(1)
    g.name = "Adieresis"
    g.width = 500
    g.unicode = 0xC4
    g.components.append(Component(0))
    g.components.append(Component(1, Point(0, 300)))
    font.glyphs.append(g)

    # Add the font to the FL object
    fl.Add(font)
    fl.UpdateFont()

    # Run our script to be tested on the font
    selectComposites(fl.font)

    # You could save the fake font to JSON instead of VFB.
    # fl.font.Save("test_composites.vfb.json")

    # Test if the correct glyphs have been selected
    assert fl.Selected(0) == 0
    assert fl.Selected(1) == 0
    assert fl.Selected(2) == 1

    # Close the fake font
    fl.Close()
```

As you see, you can use the objects just as you would inside FontLab. You just
can not open a font from an existing VFB, which would be much easier. But the
VFB file format is not public.

Instead, you have to construct a test font using the
[FL Python API](http://www.e-font.de/flpydoc/).

Invoke the test script in a Terminal window while your virtual environment is
active:

```bash
cd "Studio 5/Macros/System/Modules"
python -m pytest tests/fakeLabDemo/selection/composites_test.py
```

If everything works out, you will see some output like this:

```
============================ test session starts ===============================
platform darwin -- Python 3.8.7, pytest-6.0.1, py-1.9.0, pluggy-0.13.1
rootdir: /Users/jens/Code/fakelab
collected 1 item

tests/fakeLabDemo/selection/composites_test.py .                          [100%]

============================= 1 passed in 0.02s ================================
```