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Merged
ThisIs-Developer merged 1 commit into from
May 31, 2026
Merged

perf: cache editor layout geometry and preload styles to eliminate forced reflows #136

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6 changes: 4 additions & 2 deletions desktop-app/resources/index.html
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Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -16,8 +16,10 @@
<title>Markdown Viewer</title>
<link href="/assets/icon.jpg" rel="icon" type="image/jpg">
<!-- Updated libraries to latest versions with Subresource Integrity (SRI) -->
<link rel="stylesheet" href="/libs/bootstrap.min.css" integrity="sha384-T3c6CoIi6uLrA9TneNEoa7RxnatzjcDSCmG1MXxSR1GAsXEV/Dwwykc2MPK8M2HN" crossorigin="anonymous">
<link rel="stylesheet" href="/libs/github-markdown.min.css" integrity="sha384-hZuxRjC/Dsr4zEx1JlUhDQqkvqBPp2VLHsgXfnxPq1ULDy1eIdWCiux7nvO1RIZP" crossorigin="anonymous">
<link rel="preload" href="/libs/bootstrap.min.css" as="style" integrity="sha384-T3c6CoIi6uLrA9TneNEoa7RxnatzjcDSCmG1MXxSR1GAsXEV/Dwwykc2MPK8M2HN" crossorigin="anonymous" onload="this.onload=null;this.rel='stylesheet'">
<noscript><link rel="stylesheet" href="/libs/bootstrap.min.css" integrity="sha384-T3c6CoIi6uLrA9TneNEoa7RxnatzjcDSCmG1MXxSR1GAsXEV/Dwwykc2MPK8M2HN" crossorigin="anonymous"></noscript>
<link rel="preload" href="/libs/github-markdown.min.css" as="style" integrity="sha384-hZuxRjC/Dsr4zEx1JlUhDQqkvqBPp2VLHsgXfnxPq1ULDy1eIdWCiux7nvO1RIZP" crossorigin="anonymous" onload="this.onload=null;this.rel='stylesheet'">
<noscript><link rel="stylesheet" href="/libs/github-markdown.min.css" integrity="sha384-hZuxRjC/Dsr4zEx1JlUhDQqkvqBPp2VLHsgXfnxPq1ULDy1eIdWCiux7nvO1RIZP" crossorigin="anonymous"></noscript>
<link rel="preload" href="/libs/bootstrap-icons.min.css" as="style" integrity="sha384-XGjxtQfXaH2tnPFa9x+ruJTuLE3Aa6LhHSWRr1XeTyhezb4abCG4ccI5AkVDxqC+" crossorigin="anonymous" onload="this.onload=null;this.rel='stylesheet'">
<noscript><link rel="stylesheet" href="/libs/bootstrap-icons.min.css" integrity="sha384-XGjxtQfXaH2tnPFa9x+ruJTuLE3Aa6LhHSWRr1XeTyhezb4abCG4ccI5AkVDxqC+" crossorigin="anonymous"></noscript>
<link rel="stylesheet" href="/styles.css">
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104 changes: 71 additions & 33 deletions desktop-app/resources/js/script.js
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Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -3680,8 +3680,8 @@ document.addEventListener("DOMContentLoaded", function () {
return;
}
const text = markdownEditor.value || '';
const scrollTop = markdownEditor.scrollTop;
const scrollLeft = markdownEditor.scrollLeft;
const scrollTop = cachedScrollTop;
const scrollLeft = cachedScrollLeft;
const fragment = document.createDocumentFragment();
let lastIndex = 0;
findMatches.forEach(function(match, index) {
Expand All @@ -3701,8 +3701,8 @@ document.addEventListener("DOMContentLoaded", function () {

function syncHighlightScroll() {
if (!editorHighlightLayer) return;
editorHighlightLayer.scrollTop = markdownEditor.scrollTop;
editorHighlightLayer.scrollLeft = markdownEditor.scrollLeft;
editorHighlightLayer.scrollTop = cachedScrollTop;
editorHighlightLayer.scrollLeft = cachedScrollLeft;
}

function updateLineNumberGutter(lineCount) {
Expand Down Expand Up @@ -3765,42 +3765,71 @@ document.addEventListener("DOMContentLoaded", function () {
}

const lineCache = new Map();
let lastEditorWidth = 0;
let charWidth = 0;
let maxCharsPerLine = 0;
let cachedPaddingLeft = 10;
let cachedPaddingRight = 10;
let cachedCharWidth = 0;
let cachedLineHeight = 21;
let cachedEditorWidth = 0;
let cachedMaxCharsPerLine = 80;
let cachedScrollTop = 0;
let cachedScrollLeft = 0;
let isGeometryInitialized = false;

function initEditorGeometry() {
if (!markdownEditor) return;
const styles = window.getComputedStyle(markdownEditor);
cachedPaddingLeft = parseFloat(styles.paddingLeft) || 10;
cachedPaddingRight = parseFloat(styles.paddingRight) || 10;

// Measure character width
const testSpan = document.createElement('span');
testSpan.style.fontFamily = styles.fontFamily;
testSpan.style.fontSize = styles.fontSize;
testSpan.style.visibility = 'hidden';
testSpan.style.position = 'absolute';
testSpan.style.whiteSpace = 'pre';
testSpan.textContent = 'a'.repeat(100);
document.body.appendChild(testSpan);
cachedCharWidth = testSpan.getBoundingClientRect().width / 100;
document.body.removeChild(testSpan);

// Calculate line height
const computed = parseFloat(styles.lineHeight);
if (!Number.isNaN(computed)) {
cachedLineHeight = computed;
} else {
const fontSize = parseFloat(styles.fontSize) || 14;
cachedLineHeight = fontSize * 1.5;
}

isGeometryInitialized = true;
lineCache.clear();
}

function refreshEditorWidth() {
if (!markdownEditor) return;
if (!isGeometryInitialized) {
initEditorGeometry();
}
cachedEditorWidth = markdownEditor.clientWidth;
const availableWidth = cachedEditorWidth - cachedPaddingLeft - cachedPaddingRight;
cachedMaxCharsPerLine = Math.max(1, Math.floor(availableWidth / cachedCharWidth));

cachedScrollTop = markdownEditor.scrollTop;
cachedScrollLeft = markdownEditor.scrollLeft;
}

function updateLineNumbers() {
if (!lineNumbers || !markdownEditor) return;
const lines = (markdownEditor.value || '').split('\n');
const lineCount = Math.max(1, lines.length);

const currentWidth = markdownEditor.clientWidth;
const styles = window.getComputedStyle(markdownEditor);
const paddingLeft = parseFloat(styles.paddingLeft) || 10;
const paddingRight = parseFloat(styles.paddingRight) || 10;
const availableWidth = currentWidth - paddingLeft - paddingRight;

// Measure character width exactly once per resize / layout width change
if (currentWidth !== lastEditorWidth || charWidth === 0) {
lineCache.clear();
lastEditorWidth = currentWidth;

const testSpan = document.createElement('span');
testSpan.style.fontFamily = styles.fontFamily;
testSpan.style.fontSize = styles.fontSize;
testSpan.style.visibility = 'hidden';
testSpan.style.position = 'absolute';
testSpan.style.whiteSpace = 'pre';
testSpan.textContent = 'a'.repeat(100);
document.body.appendChild(testSpan);
charWidth = testSpan.getBoundingClientRect().width / 100;
document.body.removeChild(testSpan);

maxCharsPerLine = Math.max(1, Math.floor(availableWidth / charWidth));
if (cachedEditorWidth === 0) {
refreshEditorWidth();
}

updateLineNumberGutter(lineCount);
const lineHeight = getLineHeight(styles);
const lineHeight = cachedLineHeight;

const existingItems = lineNumbers.children;
const existingCount = existingItems.length;
Expand All @@ -3825,7 +3854,7 @@ document.addEventListener("DOMContentLoaded", function () {
const lineText = lines[i];
let wrapHeight = lineCache.get(lineText);
if (wrapHeight === undefined) {
const wrapCount = getWrappedLineCountMonospace(lineText, maxCharsPerLine);
const wrapCount = getWrappedLineCountMonospace(lineText, cachedMaxCharsPerLine);
wrapHeight = wrapCount * lineHeight;
lineCache.set(lineText, wrapHeight);
}
Expand Down Expand Up @@ -3855,7 +3884,7 @@ document.addEventListener("DOMContentLoaded", function () {

function syncLineNumberScroll() {
if (!lineNumbers) return;
lineNumbers.scrollTop = markdownEditor.scrollTop;
lineNumbers.scrollTop = cachedScrollTop;
}

// Class encapsulating Search & Replace Engine
Expand Down Expand Up @@ -4344,6 +4373,7 @@ document.addEventListener("DOMContentLoaded", function () {
const targetScrollTop = Math.max(0, (lineIndex * lineHeight) - (editorHeight / 2) + (lineHeight / 2));

markdownEditor.scrollTop = targetScrollTop;
cachedScrollTop = targetScrollTop;
syncHighlightScroll();
syncLineNumberScroll();
} catch (e) {
Expand Down Expand Up @@ -4938,12 +4968,14 @@ document.addEventListener("DOMContentLoaded", function () {
const previewPercent = 100 - editorWidthPercent;
editorPaneElement.style.flex = `0 0 calc((100% - var(--dock-width, 0px)) * ${editorWidthPercent / 100} - 4px)`;
previewPaneElement.style.flex = `0 0 calc((100% - var(--dock-width, 0px)) * ${previewPercent / 100} - 4px)`;
refreshEditorWidth();
scheduleLineNumberUpdate();
}

function resetPaneWidths() {
editorPaneElement.style.flex = '';
previewPaneElement.style.flex = '';
refreshEditorWidth();
}

function openMobileMenu() {
Expand Down Expand Up @@ -5035,6 +5067,8 @@ document.addEventListener("DOMContentLoaded", function () {

initTabs();
if (loadGlobalState().syncScrollingEnabled === false) toggleSyncScrolling();
initEditorGeometry();
refreshEditorWidth();
updateMobileStats();
updateFindHighlights();
syncHighlightScroll();
Expand Down Expand Up @@ -5066,6 +5100,8 @@ document.addEventListener("DOMContentLoaded", function () {
}

window.addEventListener('resize', () => {
initEditorGeometry();
refreshEditorWidth();
scheduleLineNumberUpdate();
if (window.innerWidth < 1080 && isFrDocked && isFindModalOpen) {
toggleFrDockMode(true);
Expand Down Expand Up @@ -5136,6 +5172,8 @@ document.addEventListener("DOMContentLoaded", function () {
});

editorPane.addEventListener("scroll", function() {
cachedScrollTop = this.scrollTop;
cachedScrollLeft = this.scrollLeft;
syncEditorToPreview();
syncHighlightScroll();
syncLineNumberScroll();
Expand Down
6 changes: 4 additions & 2 deletions index.html
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Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -78,8 +78,10 @@
<title>Markdown Viewer</title>
<link href="assets/icon.jpg" rel="icon" type="image/jpg">
<!-- Updated libraries to latest versions with Subresource Integrity (SRI) -->
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/bootstrap/5.3.2/css/bootstrap.min.css" integrity="sha384-T3c6CoIi6uLrA9TneNEoa7RxnatzjcDSCmG1MXxSR1GAsXEV/Dwwykc2MPK8M2HN" crossorigin="anonymous">
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/github-markdown-css/5.3.0/github-markdown.min.css" integrity="sha384-hZuxRjC/Dsr4zEx1JlUhDQqkvqBPp2VLHsgXfnxPq1ULDy1eIdWCiux7nvO1RIZP" crossorigin="anonymous">
<link rel="preload" href="https://cdnjs.cloudflare.com/ajax/libs/bootstrap/5.3.2/css/bootstrap.min.css" as="style" integrity="sha384-T3c6CoIi6uLrA9TneNEoa7RxnatzjcDSCmG1MXxSR1GAsXEV/Dwwykc2MPK8M2HN" crossorigin="anonymous" onload="this.onload=null;this.rel='stylesheet'">
<noscript><link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/bootstrap/5.3.2/css/bootstrap.min.css" integrity="sha384-T3c6CoIi6uLrA9TneNEoa7RxnatzjcDSCmG1MXxSR1GAsXEV/Dwwykc2MPK8M2HN" crossorigin="anonymous"></noscript>
<link rel="preload" href="https://cdnjs.cloudflare.com/ajax/libs/github-markdown-css/5.3.0/github-markdown.min.css" as="style" integrity="sha384-hZuxRjC/Dsr4zEx1JlUhDQqkvqBPp2VLHsgXfnxPq1ULDy1eIdWCiux7nvO1RIZP" crossorigin="anonymous" onload="this.onload=null;this.rel='stylesheet'">
<noscript><link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/github-markdown-css/5.3.0/github-markdown.min.css" integrity="sha384-hZuxRjC/Dsr4zEx1JlUhDQqkvqBPp2VLHsgXfnxPq1ULDy1eIdWCiux7nvO1RIZP" crossorigin="anonymous"></noscript>
<link rel="preload" href="https://cdn.jsdelivr.net/npm/bootstrap-icons@1.11.3/font/bootstrap-icons.min.css" as="style" integrity="sha384-XGjxtQfXaH2tnPFa9x+ruJTuLE3Aa6LhHSWRr1XeTyhezb4abCG4ccI5AkVDxqC+" crossorigin="anonymous" onload="this.onload=null;this.rel='stylesheet'">
<noscript><link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/bootstrap-icons@1.11.3/font/bootstrap-icons.min.css" integrity="sha384-XGjxtQfXaH2tnPFa9x+ruJTuLE3Aa6LhHSWRr1XeTyhezb4abCG4ccI5AkVDxqC+" crossorigin="anonymous"></noscript>
<link rel="stylesheet" href="styles.css">
Expand Down
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