feat(settings): polish the import-key dialog + paste verify preview

Design pass on the Import Private/Viewing Key dialog:

- Group the optional scan-from-height section (label, slider, field, hint) in a
  subtle glass panel via a draw-list splitter so it reads as one distinct,
  clearly-optional block.
- Replace the boxed reveal / Paste / Clear buttons with frameless Material icon
  buttons: the eye toggle sits flush at the Key field's right edge (rounded to
  match the input frame), Paste / Clear are faint icon pills with tooltips.
- Add a centered %-of-chain label to the slider (mirrors the send-tab amount bar).

New: hovering Paste peeks at the clipboard and verifies it before pasting —
a tooltip classifies the clipboard the same way the field indicator does
(✓ valid type for this dialog / ⚠ a key for the other button / ✗ not a key),
with a preview line masked with '*' unless the key is currently revealed (then a
truncated peek). Empty clipboard shows "Clipboard is empty".

i18n: added paste_clip_empty (en + 8 langs); the preview reuses the field
indicator's type / wrong-type keys.

Reviewed via three adversarial multi-agent passes (splitter/panel, icon buttons,
slider math, and the paste preview's correctness/security + i18n); the confirmed
findings (eye hover-pill rounding, unrecognized-state color) are addressed here.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

res/lang/de.json

@@ -785,6 +785,7 @@
     "output_filename": "Ausgabedateiname:",
     "overview": "Übersicht",
     "paste": "Einfügen",
+    "paste_clip_empty": "Zwischenablage ist leer",
     "paste_from_clipboard": "Aus Zwischenablage einfügen",
     "pay_from": "Zahlen von",
     "payment_request": "ZAHLUNGSANFRAGE",

res/lang/es.json

@@ -785,6 +785,7 @@
     "output_filename": "Nombre del archivo:",
     "overview": "Resumen",
     "paste": "Pegar",
+    "paste_clip_empty": "El portapapeles está vacío",
     "paste_from_clipboard": "Pegar del Portapapeles",
     "pay_from": "Pagar desde",
     "payment_request": "SOLICITUD DE PAGO",

res/lang/fr.json

@@ -785,6 +785,7 @@
     "output_filename": "Nom du fichier de sortie :",
     "overview": "Aperçu",
     "paste": "Coller",
+    "paste_clip_empty": "Le presse-papiers est vide",
     "paste_from_clipboard": "Coller depuis le presse-papiers",
     "pay_from": "Payer depuis",
     "payment_request": "DEMANDE DE PAIEMENT",

res/lang/ja.json

@@ -785,6 +785,7 @@
     "output_filename": "出力ファイル名：",
     "overview": "概要",
     "paste": "貼り付け",
+    "paste_clip_empty": "クリップボードは空です",
     "paste_from_clipboard": "クリップボードから貼り付け",
     "pay_from": "支払い元",
     "payment_request": "支払い請求",

res/lang/ko.json

@@ -785,6 +785,7 @@
     "output_filename": "출력 파일명:",
     "overview": "개요",
     "paste": "붙여넣기",
+    "paste_clip_empty": "클립보드가 비어 있습니다",
     "paste_from_clipboard": "클립보드에서 붙여넣기",
     "pay_from": "보낼 곳",
     "payment_request": "결제 요청",

res/lang/pt.json

@@ -785,6 +785,7 @@
     "output_filename": "Nome do arquivo de saída:",
     "overview": "Resumo",
     "paste": "Colar",
+    "paste_clip_empty": "A área de transferência está vazia",
     "paste_from_clipboard": "Colar da Área de Transferência",
     "pay_from": "Pagar de",
     "payment_request": "SOLICITAÇÃO DE PAGAMENTO",

res/lang/ru.json

@@ -785,6 +785,7 @@
     "output_filename": "Имя выходного файла:",
     "overview": "Обзор",
     "paste": "Вставить",
+    "paste_clip_empty": "Буфер обмена пуст",
     "paste_from_clipboard": "Вставить из буфера обмена",
     "pay_from": "Оплатить с",
     "payment_request": "ЗАПРОС НА ОПЛАТУ",

res/lang/zh.json

@@ -785,6 +785,7 @@
     "output_filename": "输出文件名：",
     "overview": "概览",
     "paste": "粘贴",
+    "paste_clip_empty": "剪贴板为空",
     "paste_from_clipboard": "从剪贴板粘贴",
     "pay_from": "付款来源",
     "payment_request": "付款请求",

src/app.cpp

@@ -2761,12 +2761,13 @@ static std::string formatIntWithCommas(long long v)
     return s;
 }
 
-// A send-tab-style slider (mirrors RenderAmountBar in send_tab.cpp: rounded track, accent fill, glass
+// A send-tab-style slider (mirrors RenderAmountBar in send_tab.cpp: rounded track, accent fill,
-// thumb) for the optional rescan start height, stacked above a full-width numeric field for exact
+// centered % label, glass thumb) for the optional rescan start height, stacked above a full-width
-// entry. Both share `buf` — the height as a decimal string — so it's the single source of truth.
+// numeric field for exact entry. Both share `buf` — the height as a decimal string — so it's the
-// `tipHeight` is the chain tip = the slider's max; when <= 0 (height unknown) the slider is omitted
+// single source of truth. `tipHeight` is the chain tip = the slider's max; when <= 0 (height unknown)
-// and only the field shows.
+// the slider is omitted and only the field shows. `availW` is the interior width (bar + field span it).
-static void RenderScanHeightControl(char* buf, size_t bufSize, int tipHeight, bool enabled, float dp)
+static void RenderScanHeightControl(char* buf, size_t bufSize, int tipHeight, bool enabled,
+                                    float dp, float availW)
 {
     namespace m = ui::material;
     int cur = buf[0] ? std::atoi(buf) : 0;
@@ -2775,8 +2776,8 @@ static void RenderScanHeightControl(char* buf, size_t bufSize, int tipHeight, bo
     ImGui::BeginDisabled(!enabled);
 
     if (tipHeight > 0) {
-        const float barW = ImGui::GetContentRegionAvail().x;   // slider spans the full row, stacked above the field
+        const float barW = availW;                    // slider spans the panel interior, stacked above the field
-        const float barH = ImGui::GetFrameHeight();            // match the numeric field's height (already dp-scaled)
+        const float barH = ImGui::GetFrameHeight();   // match the numeric field's height (already dp-scaled)
         const float barRound = barH * 0.5f;
         const float thumbR = barH * 0.5f;
 
@@ -2804,7 +2805,18 @@ static void RenderScanHeightControl(char* buf, size_t bufSize, int tipHeight, bo
             dl->AddRectFilled(barMin, ImVec2(fillRight, barMax.y),
                               m::WithAlpha(m::Primary(), enabled ? 150 : 55), barRound);
 
-        // Glass thumb.
+        // Percentage-of-chain label centered on the bar (mirrors the send-tab amount bar).
+        {
+            ImFont* cap = m::Type().caption();
+            char pctBuf[16];
+            snprintf(pctBuf, sizeof(pctBuf), "%.0f%%", pct * 100.0f);
+            const ImVec2 tsz = cap->CalcTextSizeA(cap->LegacySize, 10000.0f, 0.0f, pctBuf);
+            dl->AddText(cap, cap->LegacySize,
+                        ImVec2(barMin.x + (barW - tsz.x) * 0.5f, barMin.y + (barH - tsz.y) * 0.5f),
+                        IM_COL32(255, 255, 255, enabled ? 190 : 80), pctBuf);
+        }
+
+        // Glass thumb (drawn last so it sits above the fill + label).
         const float thumbY = barMin.y + barH * 0.5f;
         dl->AddCircleFilled(ImVec2(thumbCenterX, thumbY), thumbR, IM_COL32(255, 255, 255, enabled ? 205 : 90), 24);
         dl->AddCircle(ImVec2(thumbCenterX, thumbY), thumbR, IM_COL32(255, 255, 255, enabled ? 120 : 50), 24, 1.4f * dp);
@@ -2816,13 +2828,76 @@ static void RenderScanHeightControl(char* buf, size_t bufSize, int tipHeight, bo
         }
     }
 
-    // Exact numeric entry — full-width row beneath the slider.
+    // Exact numeric entry — full-width beneath the slider.
-    ImGui::SetNextItemWidth(ImGui::GetContentRegionAvail().x);
+    ImGui::SetNextItemWidth(availW);
     ImGui::InputText("##importscanheight", buf, bufSize, ImGuiInputTextFlags_CharsDecimal);
 
     ImGui::EndDisabled();
 }
 
+// Hover preview for the Paste button: peek at the clipboard, classify it in the dialog's current
+// key-type mode, and show a validity line + a preview masked with '*' unless the key is currently
+// revealed — so the user can verify the clipboard holds a valid key before pasting it.
+static void RenderPasteHoverPreview(bool viewMode, bool reveal, float dp)
+{
+    namespace m = ui::material;
+    const char* clipRaw = ImGui::GetClipboardText();
+    std::string key(clipRaw ? clipRaw : "");
+    while (!key.empty() && (key.front()==' '||key.front()=='\t'||key.front()=='\n'||key.front()=='\r')) key.erase(key.begin());
+    while (!key.empty() && (key.back()==' '||key.back()=='\t'||key.back()=='\n'||key.back()=='\r')) key.pop_back();
+
+    ImGui::BeginTooltip();
+    ImGui::TextUnformatted(TR("paste"));
+
+    if (key.empty()) {
+        ImGui::TextColored(ImGui::ColorConvertU32ToFloat4(m::OnSurfaceDisabled()), "%s", TR("paste_clip_empty"));
+        ImGui::EndTooltip();
+        return;
+    }
+
+    const bool isView   = services::WalletSecurityController::isViewingKey(key);
+    const bool isSpend  = services::WalletSecurityController::isRecognizedPrivateKey(key);
+    const bool shielded = services::WalletSecurityController::classifyPrivateKey(key)
+                          == services::WalletSecurityController::KeyKind::Shielded;
+    const bool recognized = viewMode ? isView : isSpend;   // valid for THIS dialog's mode
+    const bool wrongType  = viewMode ? isSpend : isView;   // a key, but for the other button
+
+    // valid / wrong-type / not-a-key. The field indicator softens the last case to amber+HELP, but this
+    // is a verify-before-paste check, so a truly-unrecognized clipboard gets a deliberately stronger
+    // red ✗ "don't paste" signal (amber ⚠ stays reserved for a real key aimed at the other button).
+    const ImVec4 amber(0.8f, 0.6f, 0.0f, 1.0f);   // matches the field indicator's wrong-type amber
+    const ImVec4 red = m::ErrorVec4();
+    ImGui::PushFont(m::Type().iconSmall());
+    if (recognized)     ImGui::TextColored(m::SuccessVec4(), ICON_MD_CHECK_CIRCLE);
+    else if (wrongType) ImGui::TextColored(amber, ICON_MD_WARNING);
+    else                ImGui::TextColored(red, ICON_MD_CANCEL);
+    ImGui::PopFont();
+    ImGui::SameLine(0, 4.0f * dp);
+    if (recognized) {
+        const char* label = viewMode ? TR("import_key_type_zview")
+                          : shielded  ? TR("import_key_type_zspend")
+                                      : TR("import_key_type_tkey");
+        ImGui::TextColored(m::SuccessVec4(), "%s", label);
+    } else if (wrongType) {
+        ImGui::TextColored(amber, "%s", viewMode ? TR("import_viewkey_wrong_type") : TR("import_key_wrong_type"));
+    } else {
+        ImGui::TextColored(red, "%s", TR("import_key_type_unknown"));
+    }
+
+    // Preview line — masked with '*' unless the key is currently revealed (then a truncated peek).
+    std::string preview;
+    if (reveal) {
+        preview = key.size() > 22 ? key.substr(0, 14) + "..." + key.substr(key.size() - 6) : key;
+    } else {
+        const size_t n = std::min(key.size(), (size_t)32);
+        preview.assign(n, '*');
+        if (key.size() > n) preview += "...";
+    }
+    ImGui::TextColored(ImGui::ColorConvertU32ToFloat4(m::OnSurfaceMedium()), "%s", preview.c_str());
+
+    ImGui::EndTooltip();
+}
+
 void App::renderImportKeyDialog()
 {
     namespace m = ui::material;
@@ -2869,19 +2944,31 @@ void App::renderImportKeyDialog()
         ImGui::Spacing();
     }
 
-    // Masked key field with a reveal (eye) toggle + Paste/Clear.
+    // Masked key field; the reveal (eye) toggle sits frameless flush at its right edge, with frameless
+    // Paste / Clear icon actions beneath — lighter and less cluttered than three boxed buttons.
     ImGui::TextUnformatted(viewMode ? TR("import_viewkey_field") : TR("import_key_field"));
-    float eyeW = ImGui::GetFrameHeight();
+    const float fieldH = ImGui::GetFrameHeight();
-    ImGui::SetNextItemWidth(-(eyeW + ui::Layout::spacingSm()));
+    const ImVec2 iconSz(fieldH, fieldH);
+    ImGui::SetNextItemWidth(ImGui::GetContentRegionAvail().x - fieldH);
     ImGuiInputTextFlags flags = import_key_reveal_ ? 0 : ImGuiInputTextFlags_Password;
     ImGui::InputText("##importkey", import_key_input_, sizeof(import_key_input_), flags);
-    ImGui::SameLine(0, ui::Layout::spacingSm());
+    ImGui::SameLine(0, 0);
-    if (m::TactileButton(import_key_reveal_ ? ICON_MD_VISIBILITY_OFF : ICON_MD_VISIBILITY,
+    m::IconButtonStyle eyeSt;
-                         ImVec2(eyeW, eyeW), m::Type().iconSmall()))
+    eyeSt.hoverBg = m::WithAlpha(m::OnSurface(), 30);
+    eyeSt.bgRounding = 4.0f * dp;   // match the input frame's corners (it sits flush at the field's edge)
+    eyeSt.tooltip = TR("import_key_reveal_tip");
+    if (m::IconButton("##revealkey", import_key_reveal_ ? ICON_MD_VISIBILITY_OFF : ICON_MD_VISIBILITY,
+                      m::Type().iconSmall(), iconSz, eyeSt))
         import_key_reveal_ = !import_key_reveal_;
-    if (ImGui::IsItemHovered()) m::Tooltip("%s", TR("import_key_reveal_tip"));
 
-    if (m::TactileButton(TR("paste"))) {
+    m::IconButtonStyle actSt;
+    actSt.restBg  = m::WithAlpha(m::OnSurface(), 14);   // faint pill so it still reads as a button
+    actSt.hoverBg = m::WithAlpha(m::OnSurface(), 34);
+    // Paste has no static tooltip — hovering shows a live clipboard preview that classifies the key
+    // (masked with '*' when the key isn't revealed) so the user can verify it before pasting.
+    const bool pasteClicked = m::IconButton("##pastekey", ICON_MD_CONTENT_PASTE, m::Type().iconSmall(), iconSz, actSt);
+    if (ImGui::IsItemHovered()) RenderPasteHoverPreview(viewMode, import_key_reveal_, dp);
+    if (pasteClicked) {
         const char* clipboard = ImGui::GetClipboardText();
         if (clipboard) {
             std::string trimmed(clipboard);
@@ -2890,8 +2977,10 @@ void App::renderImportKeyDialog()
             snprintf(import_key_input_, sizeof(import_key_input_), "%s", trimmed.c_str());
         }
     }
-    ImGui::SameLine();
+    ImGui::SameLine(0, ui::Layout::spacingSm());
-    if (m::TactileButton(TR("clear"))) sodium_memzero(import_key_input_, sizeof(import_key_input_));
+    actSt.tooltip = TR("clear");
+    if (m::IconButton("##clearkey", ICON_MD_CLEAR, m::Type().iconSmall(), iconSz, actSt))
+        sodium_memzero(import_key_input_, sizeof(import_key_input_));
 
     // Trimmed view + classification. The indicator and the Import guard share isRecognizedImportKey.
     std::string keyTrim(import_key_input_);
@@ -2931,36 +3020,63 @@ void App::renderImportKeyDialog()
     }
     ImGui::Spacing();
 
-    // Optional scan-from height. z_importkey / z_importviewingkey accept a start block, so a shielded
+    // Optional scan-from-height, grouped in a subtle glass panel so it reads as one distinct,
-    // import of a recent key needn't rescan the whole chain. A send-tab-style slider (bounded by the
+    // clearly-optional block. z_importkey / z_importviewingkey accept a start block, so a shielded
-    // chain tip) plus a numeric field set it. Transparent WIF (importprivkey) has no start-height
+    // import of a recent key needn't rescan the whole chain. Transparent WIF (importprivkey) has no
-    // parameter, so the control is disabled + noted once a transparent key is recognized.
+    // start-height parameter, so the control is disabled + noted once a transparent key is recognized.
+    ImGui::Dummy(ImVec2(0, 2.0f * dp));
     {
         const bool transparentKey = !viewMode && isSpend && !shielded;   // recognized transparent WIF
         if (transparentKey && import_key_scan_height_[0])
             sodium_memzero(import_key_scan_height_, sizeof(import_key_scan_height_));  // no stale height
         const int tip = state_.sync.blocks;   // chain tip = slider max; 0 when unknown
 
-        // Label, with the current chain height right-aligned when known.
+        // Render the content on an upper draw channel, then paint the glass panel behind it once the
+        // block's height is known (immediate-mode auto-sized panel via a draw-list splitter).
+        ImDrawList* dl = ImGui::GetWindowDrawList();
+        ImDrawListSplitter splitter;
+        splitter.Split(dl, 2);
+        splitter.SetCurrentChannel(dl, 1);
+
+        const float padX = 12.0f * dp, padY = 10.0f * dp;
+        const float panelW = ImGui::GetContentRegionAvail().x;
+        const ImVec2 panelMin = ImGui::GetCursorScreenPos();
+
+        ImGui::Dummy(ImVec2(0, padY));
+        ImGui::Indent(padX);
+        const float availW = ImGui::GetContentRegionAvail().x - padX;   // interior width (both side paddings)
+
+        // Label + current chain height, right-aligned within the interior.
         const float rowStartX = ImGui::GetCursorPosX();
-        const float rowW = ImGui::GetContentRegionAvail().x;
         ImGui::TextColored(ImGui::ColorConvertU32ToFloat4(m::OnSurfaceMedium()), "%s", TR("import_scan_label"));
         if (tip > 0) {
             char tipBuf[64];
             snprintf(tipBuf, sizeof(tipBuf), "%s %s", TR("import_scan_tip"), formatIntWithCommas(tip).c_str());
-            const float targetX = rowStartX + rowW - ImGui::CalcTextSize(tipBuf).x;
+            const float targetX = rowStartX + availW - ImGui::CalcTextSize(tipBuf).x;
             ImGui::SameLine();
             if (targetX > ImGui::GetCursorPosX()) ImGui::SetCursorPosX(targetX);
             ImGui::TextColored(ImGui::ColorConvertU32ToFloat4(m::OnSurfaceDisabled()), "%s", tipBuf);
         }
 
         RenderScanHeightControl(import_key_scan_height_, sizeof(import_key_scan_height_),
-                                tip, !transparentKey, dp);
+                                tip, !transparentKey, dp, availW);
 
         ImGui::TextColored(ImGui::ColorConvertU32ToFloat4(m::OnSurfaceDisabled()), "%s",
                            transparentKey ? TR("import_scan_transparent") : TR("import_scan_hint"));
-        ImGui::Spacing();
+
+        ImGui::Unindent(padX);
+        ImGui::Dummy(ImVec2(0, padY));
+
+        const ImVec2 panelMax(panelMin.x + panelW, ImGui::GetCursorScreenPos().y);
+        splitter.SetCurrentChannel(dl, 0);
+        m::GlassPanelSpec spec;
+        spec.rounding    = 8.0f * dp;
+        spec.fillAlpha   = 20;
+        spec.borderAlpha = 30;
+        m::DrawGlassPanel(dl, panelMin, panelMax, spec);
+        splitter.Merge(dl);
     }
+    ImGui::Dummy(ImVec2(0, 2.0f * dp));
 
     // Progress / result / error.
     if (import_in_progress_) {

src/util/i18n.cpp

@@ -1370,6 +1370,7 @@ void I18n::loadBuiltinEnglish()
         strings_["import_scan_hint"] = "0 = rescan from the start";
         strings_["import_scan_transparent"] = "Transparent keys always rescan fully";
         strings_["import_scan_tip"] = "current height";
+        strings_["paste_clip_empty"] = "Clipboard is empty";
 
         // --- Key Export Dialog ---
         strings_["key_export_fetching"] = "Fetching key from wallet...";