1 files changed, 88 insertions, 0 deletions
diff --git a/devtools/client/debugger/src/components/Editor/EmptyLines.js b/devtools/client/debugger/src/components/Editor/EmptyLines.js
new file mode 100644
index 0000000000..70a8c9c0a7
--- /dev/null
+++ b/devtools/client/debugger/src/components/Editor/EmptyLines.js
@@ -0,0 +1,88 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at <http://mozilla.org/MPL/2.0/>. */
+
+import { connect } from "../../utils/connect";
+import { Component } from "react";
+import PropTypes from "prop-types";
+import { getSelectedSource, getSelectedBreakableLines } from "../../selectors";
+import { fromEditorLine } from "../../utils/editor";
+import { isWasm } from "../../utils/wasm";
+
+class EmptyLines extends Component {
+  static get propTypes() {
+    return {
+      breakableLines: PropTypes.object.isRequired,
+      editor: PropTypes.object.isRequired,
+      selectedSource: PropTypes.object.isRequired,
+    };
+  }
+
+  componentDidMount() {
+    this.disableEmptyLines();
+  }
+
+  componentDidUpdate() {
+    this.disableEmptyLines();
+  }
+
+  componentWillUnmount() {
+    const { editor } = this.props;
+
+    editor.codeMirror.operation(() => {
+      editor.codeMirror.eachLine(lineHandle => {
+        editor.codeMirror.removeLineClass(lineHandle, "wrap", "empty-line");
+      });
+    });
+  }
+
+  shouldComponentUpdate(nextProps) {
+    const { breakableLines, selectedSource } = this.props;
+    return (
+      // Breakable lines are something that evolves over time,
+      // but we either have them loaded or not. So only compare the size
+      // as sometimes we always get a blank new empty Set instance.
+      breakableLines.size != nextProps.breakableLines.size ||
+      selectedSource.id != nextProps.selectedSource.id
+    );
+  }
+
+  disableEmptyLines() {
+    const { breakableLines, selectedSource, editor } = this.props;
+
+    const { codeMirror } = editor;
+    const isSourceWasm = isWasm(selectedSource.id);
+
+    codeMirror.operation(() => {
+      const lineCount = codeMirror.lineCount();
+      for (let i = 0; i < lineCount; i++) {
+        const line = fromEditorLine(selectedSource.id, i, isSourceWasm);
+
+        if (breakableLines.has(line)) {
+          codeMirror.removeLineClass(i, "wrap", "empty-line");
+        } else {
+          codeMirror.addLineClass(i, "wrap", "empty-line");
+        }
+      }
+    });
+  }
+
+  render() {
+    return null;
+  }
+}
+
+const mapStateToProps = state => {
+  const selectedSource = getSelectedSource(state);
+  if (!selectedSource) {
+    throw new Error("no selectedSource");
+  }
+  const breakableLines = getSelectedBreakableLines(state);
+
+  return {
+    selectedSource,
+    breakableLines,
+  };
+};
+
+export default connect(mapStateToProps)(EmptyLines);