Asqatasun v4 - AccessiWeb 2.2 - Rule 3.4.2
Summary
This test consists in checking whether the contrast ratio between text and its background is at least 7:1 for the bold under 14px sized textual elements
Business description
Criterion : 3.4
Test : 3.4.2
Test description :
On each Web page, until 120% of the default font size (or 1.2em), do bold text and image of text pass one of the conditions below(except in special cases)?
- the contrast ratio between text and its background is at least 7:1
- a mechanism allows the user to display text with a contrast ratio of at least 7:1
Level : Gold
Technical description
Scope : page
Decision level : semidecidable
Algorithm
Selection
Set1
All the textual elements from the DOM with a font-size inferior or equals to 14px and bold
Set2
All the hidden textual elements from the DOM with a font-size inferior or equals to 14px and bold
Set3
All the img tags
Process
Test1
For each element of Set1, the contrast ratio is computed (regarding the contrast ratio definition) to check whether it is superior to 7.
For each element returning false in Test1, if the "ALTERNATIVE_CONTRAST_MECHANISM" is set to true by the user, raise a Message1, raise a Message2 instead.
If an element has a contrast ratio that cannot be determined (background defined with an image or a gradient), raise a Message3
Test2
For each element of Set2, the contrast ratio is computed (regarding the contrast ratio definition) to check whether it is superior to 7.
For each element returning false in Test2, raise a Message4
Message1 : Bad Contrast
- code : BadContrast
- status: Failed
- parameter : foreground color, background color, contrast ratio, Snippet
- present in source : yes
Message2 : Bad Contrast But Alternative Contrast Mechanism Present On Page
- code : BadContrastButAlternativeContrastMechanismOnPage
- status: NMI
- parameter : foreground color, background color, contrast ratio, Snippet
- present in source : yes
Message3 : Not Treated Background Color
- code : NotTreatedBackgroundColor
- status: NMI
- parameter : none
- present in source : no
Message4 : Bad Contrast on Hidden Element
- code : BadContrastHiddenElement
- status: NMI
- parameter : foreground color, background color, contrast ratio, Snippet
- present in source : yes
Analysis
Not Applicable
- Set1 AND Set2 are empty
Passed
- Test1 returns true for all elements AND Set2 AND Set3 are empty
Failed
- Test1 returns false for at least one element
Pre-qualified
- In all other cases
Notes
- By approximation, we consider that 1.2em of the default font size is equivalent to 14 px.
- The background color ("background" css property), the font color ("color" css property), the font size ("font-size" css property) and the font weight ("font-weight css property) are determined while fetching the page, through the javacript script. Each html element is analyzed to extract these info, as well as whether it is displayed ("display" css property equals to "none" or "visibility" css property equals to "hidden") and whether it is a textual node.