Stackedit/js/extensions/scroll-link.js

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JavaScript
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define([
"jquery",
"underscore",
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"libs/css_browser_selector",
"libs/jquery.mousewheel"
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], function($, _) {
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var scrollLink = {
extensionId: "scrollLink",
extensionName: "Scroll Link",
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optional: true,
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settingsBloc: [
'<p>Binds together editor and preview scrollbars.</p>',
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'<blockquote class="muted"><b>NOTE:</b>',
' The mapping between Markdown and HTML is based on the position of the title elements (h1, h2, ...) in the page.',
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' Therefore, if your document does not contain any title, the mapping will be linear and consequently less accurate.',
'</bloquote>'
].join("")
};
var mdSectionList = [];
var htmlSectionList = [];
function pxToFloat(px) {
return parseFloat(px.substring(0, px.length - 2));
}
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var lastEditorScrollTop = undefined;
var lastPreviewScrollTop = undefined;
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var buildSections = _.debounce(function() {
// Try to find Markdown sections by looking for titles
var editorElt = $("#wmd-input");
mdSectionList = [];
// This textarea is used to measure sections height
var textareaElt = $("#md-section-helper");
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// It has to be the same width as wmd-input
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textareaElt.width(editorElt.width());
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// Consider wmd-input top padding (will be used for 1st and last section)
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var padding = pxToFloat(editorElt.css('padding-top'));
var offset = 0, mdSectionOffset = 0;
function addMdSection(sectionText) {
var sectionHeight = padding;
if(sectionText !== undefined) {
textareaElt.val(sectionText);
sectionHeight += textareaElt.prop('scrollHeight');
}
var newSectionOffset = mdSectionOffset + sectionHeight;
mdSectionList.push({
startOffset: mdSectionOffset,
endOffset: newSectionOffset,
height: sectionHeight
});
mdSectionOffset = newSectionOffset;
padding = 0;
}
// Create MD sections by finding title patterns (excluding gfm blocs)
var text = editorElt.val() + "\n\n";
text.replace(/^```.*\n[\s\S]*?\n```|(^.+[ \t]*\n=+[ \t]*\n+|^.+[ \t]*\n-+[ \t]*\n+|^\#{1,6}[ \t]*.+?[ \t]*\#*\n+)/gm, function(match, title, matchOffset) {
if(title) {
// We just found a title which means end of the previous section
// Exclude last \n of the section
var sectionText = undefined;
if(matchOffset > offset) {
sectionText = text.substring(offset, matchOffset - 1);
}
addMdSection(sectionText);
offset = matchOffset;
}
return "";
});
// Last section
// Consider wmd-input bottom padding and exclude \n\n previously added
padding += pxToFloat(editorElt.css('padding-bottom'));
addMdSection(text.substring(offset, text.length - 2));
// Try to find corresponding sections in the preview
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var previewElt = $(".preview-container");
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htmlSectionList = [];
var htmlSectionOffset = 0;
var previewScrollTop = previewElt.scrollTop();
// Each title element is a section separator
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$("#wmd-preview").children("h1,h2,h3,h4,h5,h6").each(function() {
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// Consider div scroll position and header element top margin
var newSectionOffset = $(this).position().top + previewScrollTop + pxToFloat($(this).css('margin-top'));
htmlSectionList.push({
startOffset: htmlSectionOffset,
endOffset: newSectionOffset,
height: newSectionOffset - htmlSectionOffset
});
htmlSectionOffset = newSectionOffset;
});
// Last section
var scrollHeight = previewElt.prop('scrollHeight');
htmlSectionList.push({
startOffset: htmlSectionOffset,
endOffset: scrollHeight,
height: scrollHeight - htmlSectionOffset
});
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// apply Scroll Link (-10 to have a gap > 9 px)
lastEditorScrollTop = -10;
lastPreviewScrollTop = -10;
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runScrollLink();
}, 500);
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var isScrollEditor = false;
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var isScrollPreview = false;
var runScrollLink = _.debounce(function() {
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if(mdSectionList.length === 0 || mdSectionList.length !== htmlSectionList.length) {
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return;
}
var editorElt = $("#wmd-input");
var editorScrollTop = editorElt.scrollTop();
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var previewElt = $(".preview-container");
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var previewScrollTop = previewElt.scrollTop();
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function animate(srcScrollTop, srcSectionList, destElt, destSectionList, currentDestScrollTop, callback) {
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// Find the section corresponding to the offset
var sectionIndex = undefined;
var srcSection = _.find(srcSectionList, function(section, index) {
sectionIndex = index;
return srcScrollTop < section.endOffset;
});
if(srcSection === undefined) {
// Something wrong in the algorithm...
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return;
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}
var posInSection = (srcScrollTop - srcSection.startOffset) / srcSection.height;
var destSection = destSectionList[sectionIndex];
var destScrollTop = destSection.startOffset + destSection.height * posInSection;
destScrollTop = _.min([
destScrollTop,
destElt.prop('scrollHeight') - destElt.outerHeight()
]);
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if(Math.abs(destScrollTop - currentDestScrollTop) <= 9) {
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// Skip the animation in case it's not necessary
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callback(currentDestScrollTop);
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return;
}
destElt.animate({
scrollTop: destScrollTop
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}, 500, function() {
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callback(destScrollTop);
});
}
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// Perform the animation if diff > 9px
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if(isScrollEditor === true && Math.abs(editorScrollTop - lastEditorScrollTop) > 9) {
isScrollEditor = false;
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// Animate the preview
lastEditorScrollTop = editorScrollTop;
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animate(editorScrollTop, mdSectionList, previewElt, htmlSectionList, previewScrollTop, function(destScrollTop) {
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lastPreviewScrollTop = destScrollTop;
});
}
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else if(isScrollPreview === true && Math.abs(previewScrollTop - lastPreviewScrollTop) > 9) {
isScrollPreview = false;
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// Animate the editor
lastPreviewScrollTop = previewScrollTop;
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animate(previewScrollTop, htmlSectionList, editorElt, mdSectionList, editorScrollTop, function(destScrollTop) {
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lastEditorScrollTop = destScrollTop;
});
}
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}, 500);
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scrollLink.onLayoutConfigure = function(layoutConfig) {
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layoutConfig.onresize = function() {
isScrollEditor = true;
buildSections();
};
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};
scrollLink.onLayoutCreated = function() {
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$(".preview-container").bind("keyup mouseup mousewheel", function() {
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isScrollPreview = true;
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isScrollEditor = false;
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runScrollLink();
});
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$("#wmd-input").bind("keyup mouseup mousewheel", function() {
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isScrollEditor = true;
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isScrollPreview = false;
runScrollLink();
});
};
scrollLink.onEditorConfigure = function(editor) {
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editor.getConverter().hooks.chain("postConversion", function(text) {
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// To avoid losing scrolling position before elements are fully
// loaded
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var previewElt = $("#wmd-preview");
previewElt.height(previewElt.height());
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return text;
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});
};
scrollLink.onPreviewFinished = function() {
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// Now set the correct height
$("#wmd-preview").height("auto");
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isScrollEditor = true;
buildSections();
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};
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return scrollLink;
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});