1 files changed, 105 insertions, 0 deletions
diff --git a/devtools/client/inspector/fonts/components/LetterSpacing.js b/devtools/client/inspector/fonts/components/LetterSpacing.js
new file mode 100644
index 0000000000..42d6ddfa61
--- /dev/null
+++ b/devtools/client/inspector/fonts/components/LetterSpacing.js
@@ -0,0 +1,105 @@
+/* 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 LetterSpacing extends PureComponent {
+  static get propTypes() {
+    return {
+      disabled: PropTypes.bool.isRequired,
+      onChange: PropTypes.func.isRequired,
+      value: PropTypes.string.isRequired,
+    };
+  }
+
+  constructor(props) {
+    super(props);
+    // Local state for min/max bounds indexed by unit to allow user input that
+    // goes out-of-bounds while still providing a meaningful default range. The indexing
+    // by unit is needed to account for unit conversion (ex: em to px) where the operation
+    // may result in out-of-bounds values. Avoiding React's state and setState() because
+    // `value` is a prop coming from the Redux store while min/max are local. Reconciling
+    // value/unit changes is needlessly complicated and adds unnecessary re-renders.
+    this.historicMin = {};
+    this.historicMax = {};
+  }
+
+  getDefaultMinMax(unit) {
+    let min;
+    let max;
+    switch (unit) {
+      case "px":
+        min = -10;
+        max = 10;
+        break;
+      default:
+        min = -0.2;
+        max = 0.6;
+        break;
+    }
+
+    return { min, max };
+  }
+
+  render() {
+    // For a unitless or a NaN value, default unit to "em".
+    const unit = getUnitFromValue(this.props.value) || "em";
+    // When the initial value of "letter-spacing" is "normal", the parsed value
+    // is not a number (NaN). Guard by setting the default value to 0.
+    const isKeywordValue = this.props.value === "normal";
+    const value = isKeywordValue ? 0 : parseFloat(this.props.value);
+
+    let { min, max } = this.getDefaultMinMax(unit);
+    min = Math.min(min, value);
+    max = Math.max(max, value);
+    // Allow lower and upper bounds to move to accomodate the incoming value.
+    this.historicMin[unit] = this.historicMin[unit]
+      ? Math.min(this.historicMin[unit], min)
+      : min;
+    this.historicMax[unit] = this.historicMax[unit]
+      ? Math.max(this.historicMax[unit], max)
+      : max;
+
+    return FontPropertyValue({
+      allowOverflow: true,
+      allowUnderflow: true,
+      disabled: this.props.disabled,
+      label: getStr("fontinspector.letterSpacingLabel"),
+      min: this.historicMin[unit],
+      max: this.historicMax[unit],
+      name: "letter-spacing",
+      onChange: this.props.onChange,
+      // Increase the increment granularity because letter spacing is very sensitive.
+      step: getStepForUnit(unit) / 100,
+      // Show the value input and unit only when the value is not a keyword.
+      showInput: !isKeywordValue,
+      showUnit: !isKeywordValue,
+      unit,
+      unitOptions: ["em", "rem", "px"],
+      value,
+      // Show the value as a read-only label if it's a keyword.
+      valueLabel: isKeywordValue ? this.props.value : null,
+    });
+  }
+}
+
+module.exports = LetterSpacing;