diff --git a/js/impress.js b/js/impress.js index db10001..7ccf620 100644 --- a/js/impress.js +++ b/js/impress.js @@ -3566,7 +3566,7 @@ } }; - var computeRelativePositions = function( el, prev ) { + var computeRelativePositions = function( el, prev, root ) { var data = el.dataset; if ( !prev ) { @@ -3575,6 +3575,36 @@ prev = { x:0, y:0, z:0, relative: { x:0, y:0, z:0 } }; } + if ( data.relTo ) { + + var ref = root.getElementById( data.relTo ); + if ( ref ) { + + // Test, if it is a previous step that already has some assigned position data + if ( el.compareDocumentPosition( ref ) & Node.DOCUMENT_POSITION_PRECEDING ) { + prev.x = ref.getAttribute( "data-x" ); + prev.y = ref.getAttribute( "data-y" ); + prev.z = ref.getAttribute( "data-z" ); + } else { + window.console.error( + "impress.js rel plugin: Step \"" + data.relTo + "\" is not defined " + + "*before* the current step. Referencing is limited to previously defined " + + "steps. Please check your markup. Ignoring data-rel-to attribute of " + + "this step. Have a look at the documentation for how to create relative " + + "positioning to later shown steps with the help of the goto plugin." + ); + } + } else { + + // Step not found + window.console.warn( + "impress.js rel plugin: \"" + data.relTo + "\" is not a valid step in this " + + "impress.js presentation. Please check your markup. Ignoring data-rel-to " + + "attribute of this step." + ); + } + } + var step = { x: toNumber( data.x, prev.x ), y: toNumber( data.y, prev.y ), @@ -3619,7 +3649,7 @@ y: el.getAttribute( "data-y" ), z: el.getAttribute( "data-z" ) } ); - var step = computeRelativePositions( el, prev ); + var step = computeRelativePositions( el, prev, root ); // Apply relative position (if non-zero) el.setAttribute( "data-x", step.x ); diff --git a/src/plugins/rel/README.md b/src/plugins/rel/README.md index d457185..800fda7 100644 --- a/src/plugins/rel/README.md +++ b/src/plugins/rel/README.md @@ -2,21 +2,25 @@ Relative Positioning Plugin =========================== This plugin provides support for defining the coordinates of a step relative -to the previous step. This is often more convenient when creating presentations, +to previous steps. This is often more convenient when creating presentations, since as you add, remove or move steps, you may not need to edit the positions as much as is the case with the absolute coordinates supported by impress.js core. Example: - -