1 files changed, 101 insertions, 0 deletions
diff --git a/devtools/client/inspector/fonts/components/LineHeight.js b/devtools/client/inspector/fonts/components/LineHeight.js
new file mode 100644
index 0000000000..34949dc7e8
--- /dev/null
+++ b/devtools/client/inspector/fonts/components/LineHeight.js
@@ -0,0 +1,101 @@
+/* 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/. */
+
+"use strict";
+
+const {
+  createFactory,
+  PureComponent,
+} = require("resource://devtools/client/shared/vendor/react.js");
+const PropTypes = require("resource://devtools/client/shared/vendor/react-prop-types.js");
+
+const FontPropertyValue = createFactory(
+  require("resource://devtools/client/inspector/fonts/components/FontPropertyValue.js")
+);
+
+const {
+  getStr,
+} = require("resource://devtools/client/inspector/fonts/utils/l10n.js");
+const {
+  getUnitFromValue,
+  getStepForUnit,
+} = require("resource://devtools/client/inspector/fonts/utils/font-utils.js");
+
+class LineHeight extends PureComponent {
+  static get propTypes() {
+    return {
+      disabled: PropTypes.bool.isRequired,
+      onChange: PropTypes.func.isRequired,
+      value: PropTypes.string.isRequired,
+    };
+  }
+
+  constructor(props) {
+    super(props);
+    this.historicMax = {};
+  }
+
+  render() {
+    // When the initial value of "line-height" is "normal", the parsed value
+    // is not a number (NaN). Guard by setting the default value to 1.2.
+    // This will be the starting point for changing the value by dragging the slider.
+    // @see https://searchfox.org/mozilla-central/rev/1133b6716d9a8131c09754f3f29288484896b8b6/layout/generic/ReflowInput.cpp#2786
+    const isKeywordValue = this.props.value === "normal";
+    const value = isKeywordValue ? 1.2 : parseFloat(this.props.value);
+
+    // When values for line-height are be unitless, getUnitFromValue() returns null.
+    // In that case, set the unit to an empty string for special treatment in conversion.
+    const unit = getUnitFromValue(this.props.value) || "";
+    let max;
+    switch (unit) {
+      case "":
+      case "em":
+      case "rem":
+        max = 2;
+        break;
+      case "vh":
+      case "vw":
+      case "vmin":
+      case "vmax":
+        max = 15;
+        break;
+      case "%":
+        max = 200;
+        break;
+      default:
+        max = 108;
+        break;
+    }
+
+    // Allow the upper bound to increase so it accomodates the out-of-bounds value.
+    max = Math.max(max, value);
+    // Ensure we store the max value ever reached for this unit type. This will be the
+    // max value of the input and slider. Without this memoization, the value and slider
+    // thumb get clamped at the upper bound while decrementing an out-of-bounds value.
+    this.historicMax[unit] = this.historicMax[unit]
+      ? Math.max(this.historicMax[unit], max)
+      : max;
+
+    return FontPropertyValue({
+      allowOverflow: true,
+      disabled: this.props.disabled,
+      label: getStr("fontinspector.lineHeightLabelCapitalized"),
+      min: 0,
+      max: this.historicMax[unit],
+      name: "line-height",
+      onChange: this.props.onChange,
+      step: getStepForUnit(unit),
+      // Show the value input and unit only when the value is not a keyword.
+      showInput: !isKeywordValue,
+      showUnit: !isKeywordValue,
+      unit,
+      unitOptions: ["", "em", "%", "px"],
+      value,
+      // Show the value as a read-only label if it's a keyword.
+      valueLabel: isKeywordValue ? this.props.value : null,
+    });
+  }
+}
+
+module.exports = LineHeight;