sw/source/core/access/AccessibilityCheck.cxx | 134 +++++++++++++++++++++++++++
1 file changed, 134 insertions(+)
New commits:
commit cfa594ad0dd7f8e464d8d59f49184a687b1503dc
Author: Tomaž Vajngerl <tomaz.vajng...@collabora.co.uk>
AuthorDate: Sun Dec 15 10:51:39 2019 +0100
Commit: Tomaž Vajngerl <qui...@gmail.com>
CommitDate: Sat Dec 28 12:36:53 2019 +0100
acc. check: text vs. background contrast check
Contrast between text and background shouldn't be too low (under
4.5). The way how to calculate the contrast is defined by the
WCAG21.
Change-Id: Ic52ab68ba0ec6a4ab58e6b01afe74e8e7eeae104
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/85905
Reviewed-by: Tomaž Vajngerl <qui...@gmail.com>
Tested-by: Tomaž Vajngerl <qui...@gmail.com>
diff --git a/sw/source/core/access/AccessibilityCheck.cxx
b/sw/source/core/access/AccessibilityCheck.cxx
index 5608e29dff47..5143ddfb6887 100644
--- a/sw/source/core/access/AccessibilityCheck.cxx
+++ b/sw/source/core/access/AccessibilityCheck.cxx
@@ -23,6 +23,8 @@
#include <tools/urlobj.hxx>
#include <editeng/langitem.hxx>
#include <charatr.hxx>
+#include <svx/xfillit0.hxx>
+#include <svx/xflclit.hxx>
namespace sw
{
@@ -36,6 +38,7 @@ OUString sHyperlinkTextIsLink("Hyperlink text is the same as
the link address '%
OUString sDocumentDefaultLanguage("Document default language is not set");
OUString sStyleNoLanguage("Style '%STYLE_NAME%' has no language set");
OUString sDocumentTitle("Document title is not set");
+OUString sTextContrast("Text contrast is too low.");
class BaseCheck
{
@@ -260,6 +263,136 @@ public:
}
};
+// Based on https://www.w3.org/TR/WCAG21/#dfn-relative-luminance
+double calculateRelativeLuminance(Color const& rColor)
+{
+ // Convert to BColor which has R, G, B colors components
+ // represented by a floating point number from [0.0, 1.0]
+ const basegfx::BColor aBColor = rColor.getBColor();
+
+ double r = aBColor.getRed();
+ double g = aBColor.getGreen();
+ double b = aBColor.getBlue();
+
+ // Calculate the values according to the described algorithm
+ r = (r <= 0.03928) ? r / 12.92 : std::pow((r + 0.055) / 1.055, 2.4);
+ g = (g <= 0.03928) ? g / 12.92 : std::pow((g + 0.055) / 1.055, 2.4);
+ b = (b <= 0.03928) ? b / 12.92 : std::pow((b + 0.055) / 1.055, 2.4);
+
+ return 0.2126 * r + 0.7152 * g + 0.0722 * b;
+}
+
+// TODO move to common color tools (BColorTools maybe)
+// Based on https://www.w3.org/TR/WCAG21/#dfn-contrast-ratio
+double calculateContrastRatio(Color const& rColor1, Color const& rColor2)
+{
+ const double fLuminance1 = calculateRelativeLuminance(rColor1);
+ const double fLuminance2 = calculateRelativeLuminance(rColor2);
+ const std::pair<const double, const double> aMinMax =
std::minmax(fLuminance1, fLuminance2);
+
+ // (L1 + 0.05) / (L2 + 0.05)
+ // L1 is the lighter color (greater luminance value)
+ // L2 is the darker color (smaller luminance value)
+ return (aMinMax.second + 0.05) / (aMinMax.first + 0.05);
+}
+
+class TextContrastCheck : public NodeCheck
+{
+private:
+ void checkTextRange(uno::Reference<text::XTextRange> const& xTextRange,
+ uno::Reference<text::XTextContent> const& xParagraph,
SwTextNode* pTextNode)
+ {
+ sal_Int32 nParaBackColor;
+ uno::Reference<beans::XPropertySet> xParagraphProperties(xParagraph,
uno::UNO_QUERY);
+ xParagraphProperties->getPropertyValue("ParaBackColor") >>=
nParaBackColor;
+
+ uno::Reference<beans::XPropertySet> xProperties(xTextRange,
uno::UNO_QUERY);
+ if (xProperties.is())
+ {
+ // Forground color
+ sal_Int32 nCharColor;
+ xProperties->getPropertyValue("CharColor") >>= nCharColor;
+ Color aForegroundColor(nCharColor);
+ if (aForegroundColor == COL_AUTO)
+ return;
+
+ const SwPageDesc* pPageDescription = pTextNode->FindPageDesc();
+ const SwFrameFormat& rPageFormat = pPageDescription->GetMaster();
+ const SwAttrSet& rPageSet = rPageFormat.GetAttrSet();
+
+ const XFillStyleItem* pXFillStyleItem(
+ rPageSet.GetItem<XFillStyleItem>(XATTR_FILLSTYLE, false));
+ Color aPageBackground;
+
+ if (pXFillStyleItem->GetValue() == css::drawing::FillStyle_SOLID)
+ {
+ const XFillColorItem* rXFillColorItem
+ = rPageSet.GetItem<XFillColorItem>(XATTR_FILLCOLOR, false);
+ aPageBackground = rXFillColorItem->GetColorValue();
+ }
+
+ sal_Int32 nCharBackColor;
+ sal_Int16 eRelief;
+
+ xProperties->getPropertyValue("CharBackColor") >>= nCharBackColor;
+ xProperties->getPropertyValue("CharRelief") >>= eRelief;
+
+ // Determine the background color
+ // Try Character background (highlight)
+ Color aBackgroundColor(nCharBackColor);
+
+ // If not character background color, try paragraph background
color
+ if (aBackgroundColor == COL_AUTO)
+ aBackgroundColor = Color(nParaBackColor);
+
+ // If not paragraph background color, try page color
+ if (aBackgroundColor == COL_AUTO)
+ aBackgroundColor = aPageBackground;
+
+ // If not page color, assume white background color
+ if (aBackgroundColor == COL_AUTO)
+ aBackgroundColor = COL_WHITE;
+
+ double fContrastRatio = calculateContrastRatio(aForegroundColor,
aBackgroundColor);
+ if (fContrastRatio < 4.5)
+ {
+ svx::AccessibilityIssue aIssue;
+ aIssue.m_aIssueText = sTextContrast;
+ m_rIssueCollection.push_back(aIssue);
+ }
+ }
+ }
+
+public:
+ TextContrastCheck(std::vector<svx::AccessibilityIssue>& rIssueCollection)
+ : NodeCheck(rIssueCollection)
+ {
+ }
+
+ void check(SwNode* pCurrent) override
+ {
+ if (pCurrent->IsTextNode())
+ {
+ SwTextNode* pTextNode = pCurrent->GetTextNode();
+ uno::Reference<text::XTextContent> xParagraph;
+ xParagraph = SwXParagraph::CreateXParagraph(*pTextNode->GetDoc(),
pTextNode);
+ if (xParagraph.is())
+ {
+ uno::Reference<container::XEnumerationAccess>
xRunEnumAccess(xParagraph,
+
uno::UNO_QUERY);
+ uno::Reference<container::XEnumeration> xRunEnum
+ = xRunEnumAccess->createEnumeration();
+ while (xRunEnum->hasMoreElements())
+ {
+ uno::Reference<text::XTextRange>
xRun(xRunEnum->nextElement(), uno::UNO_QUERY);
+ if (xRun.is())
+ checkTextRange(xRun, xParagraph, pTextNode);
+ }
+ }
+ }
+ }
+};
+
class DocumentCheck : public BaseCheck
{
public:
@@ -376,6 +509,7 @@ void AccessibilityCheck::check()
aNodeChecks.push_back(std::make_unique<TableNodeMergeSplitCheck>(m_aIssueCollection));
aNodeChecks.push_back(std::make_unique<NumberingCheck>(m_aIssueCollection));
aNodeChecks.push_back(std::make_unique<HyperlinkCheck>(m_aIssueCollection));
+
aNodeChecks.push_back(std::make_unique<TextContrastCheck>(m_aIssueCollection));
auto const& pNodes = m_pDoc->GetNodes();
SwNode* pNode = nullptr;
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