feat(shield): pick the mining address from a dropdown + show a confirm preview

Shield-coinbase replaced its free-text "*"-wildcard address box with a dropdown
of the wallet's mining (transparent) addresses and their balances ("All mining
addresses" default), and the confirm step now previews "Shield up to X DRGX from
N mining address(es)… to <label>? Network fee: Y" instead of only relabeling the
button. Also blocks submitting from an empty source or one with no funds. The
z_shieldcoinbase call (args/fee/limit/destination) is unchanged.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/ui/windows/shield_dialog.cpp

@@ -204,6 +204,25 @@ static double srcAmount() { return s_src == 0 ? s_t_amount : s_src == 1 ? s_z_am
 
 static std::string fmtAmt(double v) { char b[48]; std::snprintf(b, sizeof(b), "%.4f", v); return b; }
 
+// Shield-coinbase source helpers. "*" = all spendable mining (transparent) addresses; else one address.
+// Balances are DISPLAY totals (may include immature/non-coinbase), so the UI wording says "up to".
+static double miningBalance(const WalletState& st, const char* from) {
+    if (std::strcmp(from, "*") == 0) {
+        double sum = 0.0;
+        for (const auto& a : st.t_addresses) if (a.isSpendable()) sum += a.balance;
+        return sum;
+    }
+    const int i = addressIndexByString(st.t_addresses, from);
+    return i >= 0 ? st.t_addresses[i].balance : 0.0;
+}
+static int miningAddrCount(const WalletState& st, const char* from) {
+    if (std::strcmp(from, "*") == 0) {
+        int n = 0; for (const auto& a : st.t_addresses) if (a.isSpendable() && a.balance > 0.0) ++n; return n;
+    }
+    const int i = addressIndexByString(st.t_addresses, from);
+    return (i >= 0 && st.t_addresses[i].balance > 0.0) ? 1 : 0;
+}
+
 // A caption-style line that wraps at the dialog edge (Type().textColored doesn't wrap).
 static void wrappedCaption(ImU32 color, const char* text)
 {
@@ -567,8 +586,32 @@ void ShieldDialog::render(App* app)
 
     // ── Shield coinbase: from address ───────────────────────────────────────────────────────────
     if (!isMerge && !opInFlight) {
-        material::LabeledInput(TR("shield_from_address"), "##FromAddr", s_from_address, sizeof(s_from_address));
-        ImGui::TextDisabled("%s", TR("shield_wildcard_hint"));
+        // Pick the mining (transparent) address to shield from a dropdown with balances, instead of a
+        // free-text box with a "*" wildcard. "*" shields all of them.
+        ImGui::TextUnformatted(TR("shield_from_address"));
+        const bool allFrom = std::strcmp(s_from_address, "*") == 0;
+        const std::string fromLbl = allFrom ? std::string(TR("shield_all_mining_addrs"))
+            : (app->getAddressLabel(s_from_address).empty() ? shortAddr(s_from_address)
+                                                            : app->getAddressLabel(s_from_address));
+        ImGui::SetNextItemWidth(-1);
+        if (ImGui::BeginCombo("##FromAddr", fromLbl.c_str())) {
+            if (ImGui::Selectable(TR("shield_all_mining_addrs"), allFrom))
+                strncpy(s_from_address, "*", sizeof(s_from_address));
+            for (const auto& a : state.t_addresses) {
+                if (!a.isSpendable()) continue;
+                const std::string lbl = app->getAddressLabel(a.address);
+                char item[192];
+                std::snprintf(item, sizeof(item), "%s  (%s DRGX)",
+                              lbl.empty() ? shortAddr(a.address).c_str() : lbl.c_str(),
+                              fmtAmt(a.balance).c_str());
+                const bool sel = std::strcmp(s_from_address, a.address.c_str()) == 0;
+                if (ImGui::Selectable(item, sel)) {
+                    strncpy(s_from_address, a.address.c_str(), sizeof(s_from_address) - 1);
+                    s_from_address[sizeof(s_from_address) - 1] = '\0';
+                }
+            }
+            ImGui::EndCombo();
+        }
         ImGui::Spacing();
     }
 
@@ -833,9 +876,24 @@ void ShieldDialog::render(App* app)
                       fmtAmt(srcAmount()).c_str(), srcCount(), shortAddr(s_to_address).c_str());
         ImGui::TextWrapped("%s", cb);
         ImGui::Spacing();
+    } else if (s_confirm && !isMerge) {
+        // Shield-coinbase preview: amount / address count / fee / destination (no amount/count was shown before).
+        const bool allFrom = std::strcmp(s_from_address, "*") == 0;
+        const std::string toLbl = app->getAddressLabel(s_to_address);
+        char cb[360];
+        std::snprintf(cb, sizeof(cb), TR("shield_confirm_fmt"),
+                      fmtAmt(miningBalance(state, s_from_address)).c_str(),
+                      allFrom ? miningAddrCount(state, s_from_address) : 1,
+                      s_utxo_limit,
+                      toLbl.empty() ? shortAddr(s_to_address).c_str() : toLbl.c_str(),
+                      fmtAmt(s_fee).c_str());
+        ImGui::TextWrapped("%s", cb);
+        ImGui::Spacing();
     }
 
     bool can_submit = haveDest && connected && !syncing;
+    // Block a shield from an empty source or one with no funds (the free-text box allowed both).
+    if (!isMerge && (s_from_address[0] == '\0' || miningBalance(state, s_from_address) <= 0.0)) can_submit = false;
     const bool scopeLoaded = s_scan.phase == services::ScopePhase::Loaded;
     if (isMerge && scopeLoaded && srcCount() == 0) can_submit = false;
     if (perAddress) can_submit = connected && !syncing && scopeLoaded && !selectedGroups().empty();

src/util/i18n.cpp

@@ -2621,7 +2621,9 @@ void I18n::loadBuiltinEnglish()
         strings_["shield_check_status"] = "Check Status";
         strings_["shield_completed"] = "Operation completed successfully!";
         strings_["shield_description"] = "Shield your mining rewards by sending coinbase outputs from transparent addresses to a shielded address. This improves privacy by hiding your mining income.";
-        strings_["shield_from_address"] = "From Address:";
+        strings_["shield_from_address"] = "From mining address:";
+        strings_["shield_all_mining_addrs"] = "All mining addresses";
+        strings_["shield_confirm_fmt"] = "Shield up to %s DRGX from %d mining address(es) (at most %d rewards per run) to %s? Network fee: %s DRGX.";
         strings_["shield_funds"] = "Shield Funds";
         strings_["shield_in_progress"] = "Operation in progress...";
         strings_["shield_max_utxos"] = "Max UTXOs per operation";