Stackedit/js/extensions/scrollLink.js

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JavaScript
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define([
"jquery",
"underscore",
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"classes/Extension",
"text!html/scrollLinkSettingsBlock.html",
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"libs/css_browser_selector",
"libs/jquery.mousewheel"
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], function($, _, Extension, scrollLinkSettingsBlockHTML) {
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var scrollLink = new Extension("scrollLink", "Scroll Link", true);
scrollLink.settingsBlock = scrollLinkSettingsBlockHTML;
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var sectionList = undefined;
scrollLink.onSectionsCreated = function(sectionListParam) {
sectionList = sectionListParam;
};
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var editorElt = undefined;
var previewElt = undefined;
var textareaElt = undefined;
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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
mdSectionList = [];
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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'));
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var mdSectionOffset = 0;
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function addMdSection(sectionText) {
var sectionHeight = padding;
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if(sectionText.length !== 0) {
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textareaElt.val(sectionText);
sectionHeight += textareaElt.prop('scrollHeight');
}
var newSectionOffset = mdSectionOffset + sectionHeight;
mdSectionList.push({
startOffset: mdSectionOffset,
endOffset: newSectionOffset,
height: sectionHeight
});
mdSectionOffset = newSectionOffset;
padding = 0;
}
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_.each(sectionList, function(sectionText, index) {
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if(index !== sectionList.length - 1) {
// Remove the last \n preceding the next title
sectionText = sectionText.substring(0, sectionText.length - 1);
}
else {
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// Last section
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// Consider wmd-input bottom padding and exclude \n\n previously
// added
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padding += pxToFloat(editorElt.css('padding-bottom'));
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}
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addMdSection(sectionText);
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});
// Try to find corresponding sections in the preview
htmlSectionList = [];
var htmlSectionOffset = 0;
var previewScrollTop = previewElt.scrollTop();
// Each title element is a section separator
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previewElt.find(".preview-content > .wmd-title").each(function() {
var titleElt = $(this);
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// Consider div scroll position and header element top margin
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var newSectionOffset = titleElt.position().top + previewScrollTop + pxToFloat(titleElt.css('margin-top'));
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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 editorScrollTop = editorElt.scrollTop();
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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editorElt = $("#wmd-input");
previewElt = $(".preview-container");
// This textarea is used to measure sections height
textareaElt = $("#md-section-helper");
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$(".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();
});
};
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var previewContentsElt = undefined;
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scrollLink.onEditorConfigure = function(editor) {
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previewContentsElt = $("#preview-contents");
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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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previewContentsElt.height(previewContentsElt.height());
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return text;
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});
};
scrollLink.onPreviewFinished = function() {
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// Now set the correct height
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previewContentsElt.height("auto");
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isScrollEditor = true;
buildSections();
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};
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return scrollLink;
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});