Merge pull request #2405 from daiyam/fix-scroll

Better scroll sync between the editor and the preview in the SplitEditor

browser/components/CodeEditor.js

@@ -170,6 +170,10 @@ export default class CodeEditor extends React.Component {
   }
 
   handleEditorActivity() {
+    if (this.props.onCursorActivity) {
+      this.props.onCursorActivity(this.editor)
+    }
+
     if (!this.textEditorInterface.transaction) {
       this.updateTableEditorState()
     }
@@ -380,6 +384,7 @@ export default class CodeEditor extends React.Component {
 
     eventEmitter.emit('code:init')
     this.editor.on('scroll', this.scrollHandler)
+    this.editor.on('cursorActivity', this.editorActivityHandler)
 
     const editorTheme = document.getElementById('editorTheme')
     editorTheme.addEventListener('load', this.loadStyleHandler)
@@ -517,7 +522,6 @@ export default class CodeEditor extends React.Component {
     })
 
     if (this.props.enableTableEditor) {
-      this.editor.on('cursorActivity', this.editorActivityHandler)
       this.editor.on('changes', this.editorActivityHandler)
     }
 
@@ -576,12 +580,18 @@ export default class CodeEditor extends React.Component {
     this.editor.off('paste', this.pasteHandler)
     eventEmitter.off('top:search', this.searchHandler)
     this.editor.off('scroll', this.scrollHandler)
+    this.editor.off('cursorActivity', this.editorActivityHandler)
     this.editor.off('contextmenu', this.contextMenuHandler)
+
     const editorTheme = document.getElementById('editorTheme')
     editorTheme.removeEventListener('load', this.loadStyleHandler)
 
     spellcheck.setLanguage(null, spellcheck.SPELLCHECK_DISABLED)
     eventEmitter.off('code:format-table', this.formatTable)
+
+    if (this.props.enableTableEditor) {
+      this.editor.off('changes', this.editorActivityHandler)
+    }
   }
 
   componentDidUpdate(prevProps, prevState) {

browser/components/MarkdownEditor.js

@@ -139,7 +139,7 @@ class MarkdownEditor extends React.Component {
         },
         () => {
           this.previewRef.current.focus()
-          this.previewRef.current.scrollToRow(cursorPosition.line)
+          this.previewRef.current.scrollToLine(cursorPosition.line)
         }
       )
       eventEmitter.emit('topbar:togglelockbutton', this.state.status)

browser/components/MarkdownPreview.js

@@ -1145,17 +1145,18 @@ class MarkdownPreview extends React.Component {
 
   /**
    * @public
-   * @param {Number} targetRow
+   * @param {Number} targetLine
    */
-  scrollToRow(targetRow) {
+  scrollToLine(targetLine) {
     const blocks = this.getWindow().document.querySelectorAll(
-      'body>[data-line]'
+      'body [data-line]'
     )
 
     for (let index = 0; index < blocks.length; index++) {
       let block = blocks[index]
-      const row = parseInt(block.getAttribute('data-line'))
-      if (row > targetRow || index === blocks.length - 1) {
+      const line = parseInt(block.getAttribute('data-line'))
+
+      if (line > targetLine || index === blocks.length - 1) {
         block = blocks[index - 1]
         block != null && this.scrollTo(0, block.offsetTop)
         break

browser/components/MarkdownSplitEditor.js

@@ -13,14 +13,80 @@ class MarkdownSplitEditor extends React.Component {
     this.value = props.value
     this.focus = () => this.refs.code.focus()
     this.reload = () => this.refs.code.reload()
-    this.userScroll = true
+    this.userScroll = props.config.preview.scrollSync
     this.state = {
       isSliderFocused: false,
       codeEditorWidthInPercent: 50,
       codeEditorHeightInPercent: 50
     }
   }
 
+  componentDidUpdate(prevProps) {
+    if (
+      this.props.config.preview.scrollSync !==
+      prevProps.config.preview.scrollSync
+    ) {
+      this.userScroll = this.props.config.preview.scrollSync
+    }
+  }
+
+  handleCursorActivity(editor) {
+    if (this.userScroll) {
+      const previewDoc = _.get(
+        this,
+        'refs.preview.refs.root.contentWindow.document'
+      )
+      const previewTop = _.get(previewDoc, 'body.scrollTop')
+
+      const line = editor.doc.getCursor().line
+      let top
+      if (line === 0) {
+        top = 0
+      } else {
+        const blockElements = previewDoc.querySelectorAll('body [data-line]')
+        const blocks = []
+        for (const block of blockElements) {
+          const l = parseInt(block.getAttribute('data-line'))
+
+          blocks.push({
+            line: l,
+            top: block.offsetTop
+          })
+
+          if (l > line) {
+            break
+          }
+        }
+
+        if (blocks.length === 1) {
+          const block = blockElements[blockElements.length - 1]
+
+          blocks.push({
+            line: editor.doc.size,
+            top: block.offsetTop + block.offsetHeight
+          })
+        }
+
+        const i = blocks.length - 1
+
+        const ratio =
+          (blocks[i].top - blocks[i - 1].top) /
+          (blocks[i].line - blocks[i - 1].line)
+
+        const delta = Math.floor(_.get(previewDoc, 'body.clientHeight') / 3)
+
+        top =
+          blocks[i - 1].top +
+          Math.floor((line - blocks[i - 1].line) * ratio) -
+          delta
+      }
+
+      this.scrollTo(previewTop, top, y =>
+        _.set(previewDoc, 'body.scrollTop', y)
+      )
+    }
+  }
+
   setValue(value) {
     this.refs.code.setValue(value)
   }
@@ -30,59 +96,125 @@ class MarkdownSplitEditor extends React.Component {
     this.props.onChange(e)
   }
 
-  handleScroll(e) {
-    if (!this.props.config.preview.scrollSync) return
+  handleEditorScroll(e) {
+    if (this.userScroll) {
+      const previewDoc = _.get(
+        this,
+        'refs.preview.refs.root.contentWindow.document'
+      )
+      const codeDoc = _.get(this, 'refs.code.editor.doc')
+
+      const from = codeDoc.cm.coordsChar({ left: 0, top: 0 }).line
+      const to = codeDoc.cm.coordsChar({
+        left: 0,
+        top: codeDoc.cm.display.lastWrapHeight * 1.125
+      }).line
+      const previewTop = _.get(previewDoc, 'body.scrollTop')
+
+      let top
+      if (from === 0) {
+        top = 0
+      } else if (to === codeDoc.lastLine()) {
+        top =
+          _.get(previewDoc, 'body.scrollHeight') -
+          _.get(previewDoc, 'body.clientHeight')
+      } else {
+        const line = from + Math.floor((to - from) / 3)
 
-    const previewDoc = _.get(
-      this,
-      'refs.preview.refs.root.contentWindow.document'
-    )
-    const codeDoc = _.get(this, 'refs.code.editor.doc')
-    let srcTop, srcHeight, targetTop, targetHeight
+        const blockElements = previewDoc.querySelectorAll('body [data-line]')
+        const blocks = []
+        for (const block of blockElements) {
+          const l = parseInt(block.getAttribute('data-line'))
+
+          blocks.push({
+            line: l,
+            top: block.offsetTop
+          })
+
+          if (l > line) {
+            break
+          }
+        }
 
+        if (blocks.length === 1) {
+          const block = blockElements[blockElements.length - 1]
+
+          blocks.push({
+            line: codeDoc.size,
+            top: block.offsetTop + block.offsetHeight
+          })
+        }
+
+        const i = blocks.length - 1
+
+        const ratio =
+          (blocks[i].top - blocks[i - 1].top) /
+          (blocks[i].line - blocks[i - 1].line)
+
+        top =
+          blocks[i - 1].top + Math.floor((line - blocks[i - 1].line) * ratio)
+      }
+
+      this.scrollTo(previewTop, top, y =>
+        _.set(previewDoc, 'body.scrollTop', y)
+      )
+    }
+  }
+
+  handlePreviewScroll(e) {
     if (this.userScroll) {
-      if (e.doc) {
-        srcTop = _.get(e, 'doc.scrollTop')
-        srcHeight = _.get(e, 'doc.height')
-        targetTop = _.get(previewDoc, 'body.scrollTop')
-        targetHeight = _.get(previewDoc, 'body.scrollHeight')
+      const previewDoc = _.get(
+        this,
+        'refs.preview.refs.root.contentWindow.document'
+      )
+      const codeDoc = _.get(this, 'refs.code.editor.doc')
+
+      const srcTop = _.get(previewDoc, 'body.scrollTop')
+      const editorTop = _.get(codeDoc, 'scrollTop')
+
+      let top
+      if (srcTop === 0) {
+        top = 0
       } else {
-        srcTop = _.get(previewDoc, 'body.scrollTop')
-        srcHeight = _.get(previewDoc, 'body.scrollHeight')
-        targetTop = _.get(codeDoc, 'scrollTop')
-        targetHeight = _.get(codeDoc, 'height')
-      }
+        const delta = Math.floor(_.get(previewDoc, 'body.clientHeight') / 3)
+        const previewTop = srcTop + delta
+
+        const blockElements = previewDoc.querySelectorAll('body [data-line]')
+        const blocks = []
+        for (const block of blockElements) {
+          const top = block.offsetTop
+
+          blocks.push({
+            line: parseInt(block.getAttribute('data-line')),
+            top
+          })
 
-      const distance = (targetHeight * srcTop) / srcHeight - targetTop
-      const framerate = 1000 / 60
-      const frames = 20
-      const refractory = frames * framerate
-
-      this.userScroll = false
-
-      let frame = 0
-      let scrollPos, time
-      const timer = setInterval(() => {
-        time = frame / frames
-        scrollPos =
-          time < 0.5
-            ? 2 * time * time // ease in
-            : -1 + (4 - 2 * time) * time // ease out
-        if (e.doc)
-          _.set(previewDoc, 'body.scrollTop', targetTop + scrollPos * distance)
-        else
-          _.get(this, 'refs.code.editor').scrollTo(
-            0,
-            targetTop + scrollPos * distance
-          )
-        if (frame >= frames) {
-          clearInterval(timer)
-          setTimeout(() => {
-            this.userScroll = true
-          }, refractory)
+          if (top > previewTop) {
+            break
+          }
+        }
+
+        if (blocks.length === 1) {
+          const block = blockElements[blockElements.length - 1]
+
+          blocks.push({
+            line: codeDoc.size,
+            top: block.offsetTop + block.offsetHeight
+          })
         }
-        frame++
-      }, framerate)
+
+        const i = blocks.length - 1
+
+        const from = codeDoc.cm.heightAtLine(blocks[i - 1].line, 'local')
+        const to = codeDoc.cm.heightAtLine(blocks[i].line, 'local')
+
+        const ratio =
+          (previewTop - blocks[i - 1].top) / (blocks[i].top - blocks[i - 1].top)
+
+        top = from + Math.floor((to - from) * ratio) - delta
+      }
+
+      this.scrollTo(editorTop, top, y => codeDoc.cm.scrollTo(0, y))
     }
   }
 
@@ -168,6 +300,35 @@ class MarkdownSplitEditor extends React.Component {
     })
   }
 
+  scrollTo(from, to, scroller) {
+    const distance = to - from
+    const framerate = 1000 / 60
+    const frames = 20
+    const refractory = frames * framerate
+
+    this.userScroll = false
+
+    let frame = 0
+    let scrollPos, time
+    const timer = setInterval(() => {
+      time = frame / frames
+      scrollPos =
+        time < 0.5
+          ? 2 * time * time // ease in
+          : -1 + (4 - 2 * time) * time // ease out
+
+      scroller(from + scrollPos * distance)
+
+      if (frame >= frames) {
+        clearInterval(timer)
+        setTimeout(() => {
+          this.userScroll = true
+        }, refractory)
+      }
+      frame++
+    }, framerate)
+  }
+
   render() {
     const {
       config,
@@ -280,7 +441,8 @@ class MarkdownSplitEditor extends React.Component {
           noteKey={noteKey}
           linesHighlighted={linesHighlighted}
           onChange={e => this.handleOnChange(e)}
-          onScroll={this.handleScroll.bind(this)}
+          onScroll={e => this.handleEditorScroll(e)}
+          onCursorActivity={e => this.handleCursorActivity(e)}
           spellCheck={config.editor.spellcheck}
           enableSmartPaste={config.editor.enableSmartPaste}
           hotkey={config.hotkey}
@@ -317,7 +479,7 @@ class MarkdownSplitEditor extends React.Component {
           tabInde='0'
           value={value}
           onCheckboxClick={e => this.handleCheckboxClick(e)}
-          onScroll={this.handleScroll.bind(this)}
+          onScroll={e => this.handlePreviewScroll(e)}
           showCopyNotification={config.ui.showCopyNotification}
           storagePath={storage.path}
           noteKey={noteKey}