feat: define initial viewport (pattern-lab#1386)

packages/docs/src/docs/advanced-config-options.md

@@ -47,6 +47,12 @@ Sets whether or not you want the styleguide to load with the pattern info open o
 
 **default**: `false`
 
+## defaultInitialViewportWidth (optional)
+
+Possibility to define whether the initial viewport width on opening pattern lab in the browser should take the default of `100%` (value `true`) or take the (permanently) persisted value after the users have interacted with the viewport resize buttons previously (value `false`). This is especially beneficial in case that you'd expect the pages in full viewport at revisits, and even further if your startpage is defined as a "static" markdown welcome / orientation page.
+
+**default**: `false`
+
 ## defaultPatternInfoPanelCode (optional)
 
 Sets default active pattern info code panel by file extension - if unset, uses the value out of _patternExtension_ config value, or instead use value `html` to display the html code initially, or the value defined for the _patternExtension_.

packages/uikit-workshop/src/scripts/lit-components/pl-viewport/pl-viewport.js

@@ -397,6 +397,7 @@ class IFrame extends BaseLitComponent {
     const url = urlHandler.getFileName(this.getPatternParam());
 
     const initialWidth =
+      !window.config.defaultInitialViewportWidth &&
       store.getState().app.viewportPx &&
       store.getState().app.viewportPx <= this.clientWidth
         ? store.getState().app.viewportPx + 'px;'