The background task detects when elements with the class `tc-dynaview-set-tiddler-when-visible` scroll into view. The first time that they do, the background task assigns the value in the attribute `data-dynaview-set-value` to the tiddler whose title is in the attribute `data-dynaview-set-tiddler`. This assignment can be tied to a reveal widget to cause content to be displayed when it becomes visible. If the class `tc-dynaview-expand-viewport` is set then the viewport is expanded so that the processing occurs when elements move near the viewport.
!! Unset tiddler field when set visible before but then scrolled out of view
The background task detects when elements with the class `tc-dynaview-set-tiddler-when-visible` scroll out view after they have scrolled into view. When scrolling out of view after they have scrolled in, the background task assigns the value in the attribute `data-dynaview-unset-value` to the tiddler whose title is in the attribute `data-dynaview-unset-tiddler`. This assignment can be tied to a reveal widget to cause content to be hidden when it becomes invisible. If the class `tc-dynaview-expand-viewport` is set then the viewport is expanded so that the processing occurs when elements move near the viewport.
The background task can optionally dynamically update a pair of state tiddlers with the dimensions of the browser viewport.
* Set the configuration tiddler $:/config/DynaView/ViewportDimensions to the text "yes" to enable this feature
* The viewport dimensions can be found in $:/state/DynaView/ViewportDimensions/Width and $:/state/DynaView/ViewportDimensions/Height
!! Font "Optisizer"
The background task can optionally dynamically optimise the font size of a passage of text to match a desired line length.
* Set the configuration tiddler $:/config/DynaView/Optisizer to the text "yes" to enable this feature
* Optionally, update the configuration tiddler $:/config/DynaView/Optisizer/Text with the "maquette" -- a character string matchng the desired length (this string should not include spaces).
* Assign the following CSS classes to appropriate elements on the page:
** `.tc-dynaview-optisizer-site` for an HTML element whose `offsetWidth` property gives the desired output width
** `.tc-dynaview-optisizer-maquette` for an HTML element that will contain the maquette
* The computed optimum font size can be found in the tiddler $:/state/DynaView/Optisizer/FontSize
The tiddler $:/plugins/tiddlywiki/dynaview/optisizer-maquette contains an example configuration that can be used to adjust the size of tiddler body text. To use it:
* Set $:/config/DynaView/Optisizer to the text "yes"
* Set $:/themes/tiddlywiki/vanilla/metrics/bodyfontsize to `{{$:/state/DynaView/Optisizer/FontSize}}`
* Set $:/themes/tiddlywiki/vanilla/metrics/bodylineheight to `1.5` to ensure that the line height matches the font size
