add visual flash feedback on click-to-copy elements

When a user clicks to copy text, the clicked element now briefly
inverts (foreground/background swap) and fades back over 500ms,
providing immediate localized feedback. The existing flash message
is retained for accessibility.

Closes #100

src/popup/styles/main.css

@@ -15,6 +15,21 @@
     --color-section: #dddddd;
 }
 
+@keyframes copy-flash {
+    0% {
+        background-color: var(--color-fg);
+        color: var(--color-bg);
+    }
+    100% {
+        background-color: transparent;
+        color: inherit;
+    }
+}
+
+.copy-flash {
+    animation: copy-flash 500ms ease-out;
+}
+
 body {
     width: 396px;
     overflow-x: hidden;

src/popup/views/addressDetail.js

@@ -2,6 +2,7 @@ const {
     $,
     showView,
     showFlash,
+    flashCopyElement,
     balanceLinesForAddress,
     addressDotHtml,
     addressTitle,
@@ -237,9 +238,11 @@ function renderTransactions(txs) {
 function init(_ctx) {
     ctx = _ctx;
     $("address-full").addEventListener("click", () => {
-        const addr = $("address-full").dataset.full;
+        const el = $("address-full");
+        const addr = el.dataset.full;
         if (addr) {
             navigator.clipboard.writeText(addr);
+            flashCopyElement(el);
             showFlash("Copied!");
         }
     });
@@ -354,17 +357,21 @@ function init(_ctx) {
     });
 
     $("export-privkey-value").addEventListener("click", () => {
-        const key = $("export-privkey-value").textContent;
+        const el = $("export-privkey-value");
+        const key = el.textContent;
         if (key) {
             navigator.clipboard.writeText(key);
+            flashCopyElement(el);
             showFlash("Copied!");
         }
     });
 
     $("export-privkey-address").addEventListener("click", () => {
-        const full = $("export-privkey-address").dataset.full;
+        const el = $("export-privkey-address");
+        const full = el.dataset.full;
         if (full) {
             navigator.clipboard.writeText(full);
+            flashCopyElement(el);
             showFlash("Copied!");
         }
     });

src/popup/views/addressToken.js

@@ -5,6 +5,7 @@ const {
     $,
     showView,
     showFlash,
+    flashCopyElement,
     addressDotHtml,
     addressTitle,
     escapeHtml,
@@ -313,9 +314,11 @@ function renderTransactions(txs) {
 function init(_ctx) {
     ctx = _ctx;
     $("address-token-full").addEventListener("click", () => {
-        const addr = $("address-token-full").dataset.full;
+        const el = $("address-token-full");
+        const addr = el.dataset.full;
         if (addr) {
             navigator.clipboard.writeText(addr);
+            flashCopyElement(el);
             showFlash("Copied!");
         }
     });
@@ -324,6 +327,7 @@ function init(_ctx) {
         const copyEl = e.target.closest("[data-copy]");
         if (copyEl) {
             navigator.clipboard.writeText(copyEl.dataset.copy);
+            flashCopyElement(copyEl);
             showFlash("Copied!");
         }
     });
@@ -372,6 +376,7 @@ function init(_ctx) {
         if (copyEl) {
             copyEl.addEventListener("click", () => {
                 navigator.clipboard.writeText(copyEl.dataset.copy);
+                flashCopyElement(copyEl);
                 showFlash("Copied!");
             });
         }

src/popup/views/confirmTx.js

@@ -15,6 +15,7 @@ const {
     hideError,
     showView,
     showFlash,
+    flashCopyElement,
     addressTitle,
     addressDotHtml,
     escapeHtml,
@@ -116,6 +117,7 @@ function show(txInfo) {
         if (copyEl) {
             copyEl.onclick = () => {
                 navigator.clipboard.writeText(copyEl.dataset.copy);
+                flashCopyElement(copyEl);
                 showFlash("Copied!");
             };
         }

src/popup/views/helpers.js

@@ -76,6 +76,18 @@ function clearFlash() {
     $("flash-msg").textContent = "";
 }
 
+function flashCopyElement(el) {
+    el.classList.remove("copy-flash");
+    // Force reflow so re-adding the class restarts the animation.
+    void el.offsetWidth;
+    el.classList.add("copy-flash");
+    el.addEventListener(
+        "animationend",
+        () => el.classList.remove("copy-flash"),
+        { once: true },
+    );
+}
+
 function showFlash(msg, duration = 2000) {
     clearFlash();
     $("flash-msg").textContent = msg;
@@ -265,6 +277,7 @@ module.exports = {
     hideError,
     showView,
     showFlash,
+    flashCopyElement,
     balanceLine,
     balanceLinesForAddress,
     addressColor,

src/popup/views/home.js

@@ -2,6 +2,7 @@ const {
     $,
     showView,
     showFlash,
+    flashCopyElement,
     balanceLinesForAddress,
     isoDate,
     timeAgo,
@@ -85,8 +86,9 @@ function renderActiveAddress() {
         el.innerHTML =
             `<span class="underline decoration-dashed cursor-pointer" id="active-addr-copy">${dot}${escapeHtml(addr)}</span>` +
             `<a href="${link}" target="_blank" rel="noopener" class="inline-flex items-center">${EXT_ICON}</a>`;
-        $("active-addr-copy").addEventListener("click", () => {
+        $("active-addr-copy").addEventListener("click", (e) => {
             navigator.clipboard.writeText(addr);
+            flashCopyElement(e.currentTarget);
             showFlash("Copied!");
         });
     } else {

src/popup/views/receive.js

@@ -2,6 +2,7 @@ const {
     $,
     showView,
     showFlash,
+    flashCopyElement,
     formatAddressHtml,
     addressTitle,
 } = require("./helpers");
@@ -61,17 +62,21 @@ function show() {
 
 function init(ctx) {
     $("receive-address-block").addEventListener("click", () => {
-        const addr = $("receive-address-block").dataset.full;
+        const el = $("receive-address-block");
+        const addr = el.dataset.full;
         if (addr) {
             navigator.clipboard.writeText(addr);
+            flashCopyElement(el);
             showFlash("Copied!");
         }
     });
 
     $("btn-receive-copy").addEventListener("click", () => {
-        const addr = $("receive-address-block").dataset.full;
+        const block = $("receive-address-block");
+        const addr = block.dataset.full;
         if (addr) {
             navigator.clipboard.writeText(addr);
+            flashCopyElement(block);
             showFlash("Copied!");
         }
     });

src/popup/views/transactionDetail.js

@@ -5,6 +5,7 @@ const {
     $,
     showView,
     showFlash,
+    flashCopyElement,
     addressDotHtml,
     addressTitle,
     escapeHtml,
@@ -170,6 +171,7 @@ function render() {
         .forEach((el) => {
             el.onclick = () => {
                 navigator.clipboard.writeText(el.dataset.copy);
+                flashCopyElement(el);
                 showFlash("Copied!");
             };
         });
@@ -247,6 +249,7 @@ async function loadCalldata(txHash, toAddress) {
             container.querySelectorAll("[data-copy]").forEach((el) => {
                 el.onclick = () => {
                     navigator.clipboard.writeText(el.dataset.copy);
+                    flashCopyElement(el);
                     showFlash("Copied!");
                 };
             });

src/popup/views/txStatus.js

@@ -4,6 +4,7 @@ const {
     $,
     showView,
     showFlash,
+    flashCopyElement,
     addressDotHtml,
     addressTitle,
     escapeHtml,
@@ -76,6 +77,7 @@ function attachCopyHandlers(viewId) {
         .forEach((el) => {
             el.onclick = () => {
                 navigator.clipboard.writeText(el.dataset.copy);
+                flashCopyElement(el);
                 showFlash("Copied!");
             };
         });