test_gradient.py fails for i586

[pgajdos]

[  114s] /home/abuild/rpmbuild/BUILD/WeasyPrint-48/weasyprint/tests/test_draw/__init__.py:60: in assert_pixels
[  114s]     name, expected_width, expected_height, pixels, expected_raw)
[  114s] _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
[  114s] 
[  114s] name = 'linear_gradient', width = 9, height = 5
[  114s] raw = b'\x7f\x00\x7f\xff\x7f\x00\x7f\xff\x7f\x00\x7f\xff\x7f\x00\x7f\xff\x7f\x00\x7f\xff\x7f\x00\x7f\xff\x7f\x00\x7f\xff\x7f...7f\xff\x7f\x00\x7f\xff\x7f\x00\x7f\xff\x7f\x00\x7f\xff\x7f\x00\x7f\xff\x7f\x00\x7f\xff\x7f\x00\x7f\xff\x7f\x00\x7f\xff'
[  114s] expected_raw = b'\x80\x00\x80\xff\x80\x00\x80\xff\x80\x00\x80\xff\x80\x00\x80\xff\x80\x00\x80\xff\x80\x00\x80\xff\x80\x00\x80\xff\x80...80\xff\x80\x00\x80\xff\x80\x00\x80\xff\x80\x00\x80\xff\x80\x00\x80\xff\x80\x00\x80\xff\x80\x00\x80\xff\x80\x00\x80\xff'
[  114s] tolerance = 0
[  114s] 
[  114s]     def assert_pixels_equal(name, width, height, raw, expected_raw, tolerance=0):
[  114s]         """Take 2 matrices of pixels and assert that they are the same."""
[  114s]         if raw != expected_raw:  # pragma: no cover
[  114s]             for i, (value, expected) in enumerate(zip(raw, expected_raw)):
[  114s]                 if abs(value - expected) > tolerance:
[  114s]                     write_png(name, raw, width, height)
[  114s]                     write_png(name + '.expected', expected_raw,
[  114s]                               width, height)
[  114s]                     pixel_n = i // 4
[  114s]                     x = pixel_n // width
[  114s]                     y = pixel_n % width
[  114s]                     i % 4
[  114s]                     pixel = tuple(list(raw[i:i + 4]))
[  114s]                     expected_pixel = tuple(list(
[  114s]                         expected_raw[i:i + 4]))
[  114s]                     assert 0, (
[  114s]                         'Pixel (%i, %i) in %s: expected rgba%s, got rgba%s'
[  114s] >                       % (x, y, name, expected_pixel, pixel))
[  114s] E                   AssertionError: Pixel (0, 0) in linear_gradient: expected rgba(128, 0, 128, 255), got rgba(127, 0, 127, 255)
[  114s] 
[  114s] /home/abuild/rpmbuild/BUILD/WeasyPrint-48/weasyprint/tests/test_draw/__init__.py:164: AssertionError
[  114s] ------------------------------ Captured log call -------------------------------
[  114s] INFO     weasyprint.progress:__init__.py:109 Step 1 - Fetching and parsing HTML - HTML string
[  114s] INFO     weasyprint.progress:__init__.py:317 Step 2 - Fetching and parsing CSS - CSS string
[  114s] INFO     weasyprint.progress:__init__.py:66 Step 3 - Applying CSS
[  114s] INFO     weasyprint.progress:document.py:369 Step 4 - Creating formatting structure
[  114s] INFO     weasyprint.progress:pages.py:791 Step 5 - Creating layout - Page 1
[  114s] INFO     weasyprint.progress:document.py:734 Step 6 - Drawing
[  114s] =============================== warnings summary ===============================

Tested with 46, 47 and 48.

Let me know if I can help somehow.

[pgajdos]

(it is test_linear_gradients_7)

[pgajdos]

This is with python 3.7.

[liZe]

Thank you for this issue.

What's your version of Cairo?

[pgajdos]

Cairo version is 1.16.0. Here is full build log.

[liZe]

It's a test that should return a square with one color: a mix of red and blue. The test on the platforms I use give #800080 (on Windows, MacOS and Linux, I suppose i686), while on your platform it gives #7F007F.

There's probably a difference in Cairo about optimizations depending on the platform, and the output is so close that it's tolerated. You can safely ignore this failing test.

If it's important for you to have this test passing (I don't know why you launch tests on i586 😄), we can try to find a solution.

[Tontyna]

My platform, too, gives #7f007f
Windows 7 64bit, Cairo 1.16.0

[liZe]

If it's important for you to have this test passing (I don't know why you launch tests on i586), we can try to find a solution.

@pgajdos Is there a way for you to ignore that test?

[pgajdos]

Sure.

[liZe]

This test is useful, I'd like to keep it. We can try to find other values that work the same way everywhere.

@pgajdos @Tontyna Does this test pass for you?

@assert_no_logs
@requires('cairo', (1, 14, 0))
def test_linear_gradients_7():
    assert_pixels('linear_gradient', 9, 5, '''
        ggggggggg
        ggggggggg
        ggggggggg
        ggggggggg
        ggggggggg
    ''', '''<style>@page { size: 9px 5px; background: repeating-linear-gradient(
      to right, black 3px, black 3px, lime 3px, lime 3px
    )''')

[pgajdos]

With the above, I get for i586:

[   64s] =================================== FAILURES ===================================
[   64s] ___________________________ test_linear_gradients_7 ____________________________
[   64s] 
[   64s]     @assert_no_logs
[   64s]     @requires('cairo', (1, 14, 0))
[   64s]     def test_linear_gradients_7():
[   64s]         assert_pixels('linear_gradient', 9, 5, '''
[   64s]             ggggggggg
[   64s]             ggggggggg
[   64s]             ggggggggg
[   64s]             ggggggggg
[   64s]             ggggggggg
[   64s]         ''', '''<style>@page { size: 9px 5px; background: repeating-linear-gradient(
[   64s]           to right, black 3px, black 3px, lime 3px, lime 3px
[   64s] >       )''')
[   64s] 
[   64s] /home/abuild/rpmbuild/BUILD/WeasyPrint-48/weasyprint/tests/test_draw/test_gradient.py:119: 
[   64s] _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
[   64s] /home/abuild/rpmbuild/BUILD/WeasyPrint-48/weasyprint/tests/test_draw/__init__.py:60: in assert_pixels
[   64s]     name, expected_width, expected_height, pixels, expected_raw)
[   64s] _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
[   64s] 
[   64s] name = 'linear_gradient', width = 9, height = 5
[   64s] raw = b'\x00\x7f\x00\xff\x00\x7f\x00\xff\x00\x7f\x00\xff\x00\x7f\x00\xff\x00\x7f\x00\xff\x00\x7f\x00\xff\x00\x7f\x00\xff\x00...00\xff\x00\x7f\x00\xff\x00\x7f\x00\xff\x00\x7f\x00\xff\x00\x7f\x00\xff\x00\x7f\x00\xff\x00\x7f\x00\xff\x00\x7f\x00\xff'
[   64s] expected_raw = b'\x00\x80\x00\xff\x00\x80\x00\xff\x00\x80\x00\xff\x00\x80\x00\xff\x00\x80\x00\xff\x00\x80\x00\xff\x00\x80\x00\xff\x00...00\xff\x00\x80\x00\xff\x00\x80\x00\xff\x00\x80\x00\xff\x00\x80\x00\xff\x00\x80\x00\xff\x00\x80\x00\xff\x00\x80\x00\xff'
[   64s] tolerance = 0
[   64s] 
[   64s]     def assert_pixels_equal(name, width, height, raw, expected_raw, tolerance=0):
[   64s]         """Take 2 matrices of pixels and assert that they are the same."""
[   64s]         if raw != expected_raw:  # pragma: no cover
[   64s]             for i, (value, expected) in enumerate(zip(raw, expected_raw)):
[   64s]                 if abs(value - expected) > tolerance:
[   64s]                     write_png(name, raw, width, height)
[   64s]                     write_png(name + '.expected', expected_raw,
[   64s]                               width, height)
[   64s]                     pixel_n = i // 4
[   64s]                     x = pixel_n // width
[   64s]                     y = pixel_n % width
[   64s]                     i % 4
[   64s]                     pixel = tuple(list(raw[i:i + 4]))
[   64s]                     expected_pixel = tuple(list(
[   64s]                         expected_raw[i:i + 4]))
[   64s]                     assert 0, (
[   64s]                         'Pixel (%i, %i) in %s: expected rgba%s, got rgba%s'
[   64s] >                       % (x, y, name, expected_pixel, pixel))
[   64s] E                   AssertionError: Pixel (0, 0) in linear_gradient: expected rgba(128, 0, 255, 0), got rgba(127, 0, 255, 0)
[   64s] 
[   64s] /home/abuild/rpmbuild/BUILD/WeasyPrint-48/weasyprint/tests/test_draw/__init__.py:164: AssertionError
[   64s] ------------------------------ Captured log call -------------------------------
[   64s] INFO     weasyprint.progress:__init__.py:109 Step 1 - Fetching and parsing HTML - HTML string
[   64s] INFO     weasyprint.progress:__init__.py:317 Step 2 - Fetching and parsing CSS - CSS string
[   64s] INFO     weasyprint.progress:__init__.py:66 Step 3 - Applying CSS
[   64s] INFO     weasyprint.progress:document.py:369 Step 4 - Creating formatting structure
[   64s] INFO     weasyprint.progress:pages.py:791 Step 5 - Creating layout - Page 1
[   64s] INFO     weasyprint.progress:document.py:734 Step 6 - Drawing
[   64s] =============================== warnings summary ===============================
[   64s] /usr/lib/python3.7/site-packages/html5lib/_trie/_base.py:3
[   64s]   /usr/lib/python3.7/site-packages/html5lib/_trie/_base.py:3: DeprecationWarning: Using or importing the ABCs from 'collections' instead of from 'collections.abc' is deprecated, and in 3.8 it will stop working
[   64s]     from collections import Mapping
[   64s] 
[   64s] -- Docs: https://docs.pytest.org/en/latest/warnings.html
[   64s] ========= 1 failed, 949 passed, 7 xfailed, 1 warnings in 26.69 seconds =========

[pgajdos]

It succeedes for x86_64.

[liZe]

Then I'm afraid I can't do anything. If you can find a value that works with both i586 and x86_64, I'll be happy to use it, but otherwise you'll have to skip this test 😢.

[Tontyna]

The truth (and the mystery) is:

• when rendered as PDF my platform produces #7f007f
• when rendered as PNG my platform produces #800080. That's why the gradient unit tests succeed

Yes, I know, these are different Cairo surfaces. Cannot detect a/the relationship between the processor architecture and the cairo_image_surface in the Cairo source.
Maybe this time it's not Cairo but ... the Cairo PNG functionality depends afaik on libpng

[liZe]

It's hard to decide if the color between #ff00ff and #000000 is #800080 or #7f007f. It's actually between, isn't it? The problem is not technical, it's just logical.

We can solve this by using a color whose hexadecimal components are even. For example, using #800080 and #000000 would give #400040.