bVisual

Accessibility

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Understanding Visio Navigation Order

Visio defaults to tabbing from shape to shape in the order that the shapes are added to the page. However, this can end up with an illogical order if you are trying to navigate a diagram with the keyboard, which is often an accessibility requirement. Fortunately, Visio provides a Diagram Navigation pane so that the tab order can be changed, but how does it do it? The following short video shows how the navigation order, displayed as numbers in each shape, is assigned a value as soon as the order is edited.



Accessibility is important in my current project, so understanding how this happens was important to understand, and to surface this order to JavaScript, as we want to list the shapes in a logical order too.
I managed this by adding a User.visNavOrder to the master shape of all the significant masters, and a hidden Shape Data row, labelled “Navigation Order“. This has the following formula for its value:

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Ensuring High Contrast Text in Visio Shapes

I am working on a project where I need to ensure high contrast of the text in the Visio shapes for accessibility. At first, I attempted to write my own formula but a colleague pointed my to a website that confirms if the contrast is acceptable ( contrast-ratio.com ), and showed me that a few of my examples failed. So the search was on for a better formula than my own. This lead me to a Stack Exchange answer with just what I was looking for (Formula for Color Contrast between Text and Background). All I needed to do was to convert this into a ShapeSheet formula or two, and then I could apply it to the text inside the shapes.

VisioColorMap



Any text created with Data Graphic Text Callouts cannot have the high contrast formula applied to because they can be moved independent of the background. However any text added with Insert / Field inside the shape changes between black and white with respect to the FillForegnd value in its background.
Following the article above, it is necessary to calculate the lightness, L, of the FillForegnd, and then to check if black or white text is going to provide satisfactory contrast.

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