SizeInput: better handle input focus effect for mouse and touch

The input slider handle now animates in response to
mousedown/touchstart, and returns to its initial state on
mouseup/touchend. This does not break existing behaviour when navigating
via keyboard.

src/components/SizeInput/SizeInput.css

@@ -38,6 +38,7 @@
   appearance: none;
   width: 14px; /* Set a specific slider handle width */
   height: 14px; /* Slider handle height */
+  padding: 6px;
   border-radius: 50%;
   background: white; /* Green background */
   cursor: pointer; /* Cursor on hover */
@@ -47,6 +48,7 @@
 .size-bar input::-moz-range-thumb {
   width: 14px; /* Set a specific slider handle width */
   height: 14px; /* Slider handle height */
+  padding: 6px;
   background: black; /* Green background */
   cursor: pointer; /* Cursor on hover */
   transition: height 0.1s, width 0.1s;
@@ -56,7 +58,6 @@
   outline: none;
   width: 20px; /* Set a specific slider handle width */
   height: 20px; /* Slider handle height */
-  transition: height 0.1s, width 0.1s;
   box-shadow: 0 0 0 6px rgba(255, 255, 255, 0.2);
 }
 
@@ -64,6 +65,5 @@
   outline: none;
   width: 20px; /* Set a specific slider handle width */
   height: 20px; /* Slider handle height */
-  transition: height 0.1s, width 0.1s;
   box-shadow: 0 0 0 6px rgba(255, 255, 255, 0.2);
 }

src/components/SizeInput/SizeInput.tsx

@@ -1,4 +1,4 @@
-import React from "react";
+import React, { useCallback } from "react";
 import { useRecoilState } from "recoil";
 
 import { iconSizeAtom } from "../../state/atoms";
@@ -6,17 +6,29 @@ import "./SizeInput.css";
 
 type SizeInputProps = {};
 
+const handleFocus = (event: React.UIEvent<HTMLInputElement>) => {
+  const { currentTarget } = event;
+  currentTarget.focus();
+};
+
+const handleBlur = (event: React.UIEvent<HTMLInputElement>) => {
+  event.currentTarget.blur();
+};
+
 const SizeInput: React.FC<SizeInputProps> = () => {
   const [size, setSize] = useRecoilState(iconSizeAtom);
 
-  const handleSizeChange = (event: React.ChangeEvent<HTMLInputElement>) => {
+  const handleSizeChange = useCallback(
+    (event: React.ChangeEvent<HTMLInputElement>) => {
       const {
         target: { value },
       } = event;
       const sizeInput = parseInt(value);
 
       if (sizeInput > 0) setSize(sizeInput);
-  };
+    },
+    [setSize]
+  );
 
   return (
     <div className="size-bar">
@@ -29,6 +41,9 @@ const SizeInput: React.FC<SizeInputProps> = () => {
         min={16}
         max={96}
         onChange={handleSizeChange}
+        onTouchStart={handleFocus}
+        onTouchEnd={handleBlur}
+        onMouseUp={handleBlur}
         step={4}
       />
     </div>