Rule 1.2.5

Summary

This test consists in checking whether the textual alternative of each decorative canvas image is empty.

Business description

Criterion

1.2

Test

1.2.5

Description

Pour chaque image bitmap de décoration (balise canvas), le contenu entre <canvas> et </canvas> doit être dépourvu de contenus textuels, cette règle est-elle respectée ?

Level

A

Technical description

Scope

Page

Decision level

Semi-Decidable

Algorithm

Selection

Set1

All the <canvas> tags of the page not within a link and not identified as captcha (see Notes about captcha detection) (css selector : canvas:not(a canvas))

Set2

All the elements of Set1 identified as decorative image by marker usage (see Notes for details about detection through marker)

Set3

All the elements of Set1 identified neither as informative image, nor as decorative image by marker usage (see Notes for details about detection through marker)

Process

Tests

Test1

For each element of Set1, Check the presence of text between <canvas> tags.

For each occurrence of true-result of Test1, raise a MessageA

Test2

For each element of Set2, Check the presence of text between <canvas> tags.

For each occurrence of true-result of Test2, raise a MessageB

For each occurrence of false-result of Test2, raise a MessageC

Messages

MessageA : Decorative image with not empty alternative
  • code : DecorativeElementWithNotEmptyAltAttribute
  • status: Failed
  • parameter : text, Snippet
  • present in source : yes
MessageB : Check the nature of the image with a not empty alternative
  • code : CheckNatureOfElementWithNotEmptyAltAttribute
  • status: Pre-qualified
  • parameter : text, Snippet
  • present in source : yes
MessageD : Check the nature of the image with a empty alternative
  • code : CheckNatureOfElementWithEmptyAltAttribute
  • status: Pre-qualified
  • parameter : text, Snippet
  • present in source : yes

Analysis

Passed

All the canvas tags are identified as decorative and don't have text between <canvas> tags (Test1 returns false for all elements)

Failed

At least one canvas identified as decorative have text between <canvas> tags (Test1 returns true at least one element)

Not Applicable

The page has no <canvas> tag (Set1 is empty)

Pre-qualified

In all other cases

Notes

Markers

Informative images markers are set through the INFORMATIVE_IMAGE_MARKER parameter.

Decorative images markers are set through the DECORATIVE_IMAGE_MARKER parameter.

The value(s) passed as marker(s) will be checked against the following attributes:

  • class
  • id
  • role

Captcha detection

An element is identified as a CAPTCHA when the "captcha" occurrence is found :

  • on one attribute of the element
  • or within the text of the element
  • or on one attribute of one parent of the element
  • or within the text of one parent of the element
  • or on one attribute of a sibling of the element
  • or within the text of a sibling of the element