feat(command-line): adjustable command line opacity

COMMANDLINEOPACITY (20-100 percent, default 100) and a slider under
Options > Display make the floating command line's panels see-through,
so the drawing stays visible behind it. The input field stays opaque
for legibility. The value is an application setting that persists.

Refs #1494

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

locales/ar-SA/opencadstudio.ftl

@@ -294,6 +294,7 @@ command-copy =
     .mode = COPY  أدخل خيار وضع النسخ [Single/Multiple] <Multiple>:
 
 common =
+    .command-line-opacity = شفافية سطر الأوامر
     .txtexp-no-text-selected = TXTEXP: لم يتم تحديد نص.
     .angle-override-shown = تجاوز الزاوية: __ocs_fmt_0__
     .plot-preview-task = معاينة الطباعة

locales/bg-BG/opencadstudio.ftl

@@ -281,6 +281,7 @@ command-copy =
     .displacement = COPY  Задайте преместване:
     .mode = COPY  Въведете режим на копиране [Single/Multiple] <Multiple>:
 common =
+    .command-line-opacity = Непрозрачност на командния ред
     .txtexp-no-text-selected = TXTEXP: няма избран текст.
     .angle-override-shown = Замяна на ъгъла: __ocs_fmt_0__
     .plot-preview-task = Преглед на печата

locales/cs-CZ/opencadstudio.ftl

@@ -281,6 +281,7 @@ command-copy =
     .mode = COPY  Zadejte režim kopírování [Single/Multiple] <Multiple>:
 
 common =
+    .command-line-opacity = Neprůhlednost příkazového řádku
     .txtexp-no-text-selected = TXTEXP: není vybrán žádný text.
     .angle-override-shown = Přepsání úhlu: __ocs_fmt_0__
     .plot-preview-task = Náhled tisku

locales/de-DE/opencadstudio.ftl

@@ -282,6 +282,7 @@ command-copy =
     .mode = COPY  Kopiermodus eingeben [Single/Multiple] <Multiple>:
 
 common =
+    .command-line-opacity = Deckkraft der Befehlszeile
     .txtexp-no-text-selected = TXTEXP: kein Text gewählt.
     .angle-override-shown = Winkelvorgabe: __ocs_fmt_0__
     .plot-preview-task = Plotvorschau

locales/el-GR/opencadstudio.ftl

@@ -281,6 +281,7 @@ command-copy =
     .mode = COPY  Επιλέξτε λειτουργία αντιγραφής [Single/Multiple] <Multiple>:
 
 common =
+    .command-line-opacity = Αδιαφάνεια γραμμής εντολών
     .txtexp-no-text-selected = TXTEXP: δεν επιλέχθηκε κείμενο.
     .angle-override-shown = Παράκαμψη γωνίας: __ocs_fmt_0__
     .plot-preview-task = Προεπισκόπηση εκτύπωσης

locales/en-US/opencadstudio.ftl

@@ -281,6 +281,7 @@ command-copy =
     .mode = COPY  Enter a copy mode option [Single/Multiple] <Multiple>:
 
 common =
+    .command-line-opacity = Command line opacity
     .txtexp-no-text-selected = TXTEXP: no text selected.
     .angle-override-shown = Angle Override: __ocs_fmt_0__
     .browser-cannot-open-typed-path = The browser cannot open a typed path; pick the file instead.

locales/es-ES/opencadstudio.ftl

@@ -282,6 +282,7 @@ command-copy =
     .mode = COPY  Indique modo de copia [Single/Multiple] <Multiple>:
 
 common =
+    .command-line-opacity = Opacidad de la línea de comando
     .txtexp-no-text-selected = TXTEXP: no se ha seleccionado ningún texto.
     .angle-override-shown = Modificación de ángulo: __ocs_fmt_0__
     .plot-preview-task = Vista previa de trazado

locales/fi-FI/opencadstudio.ftl

@@ -281,6 +281,7 @@ command-copy =
     .mode = COPY  Valitse kopiointitila [Single/Multiple] <Multiple>:
 
 common =
+    .command-line-opacity = Komentorivin peittävyys
     .txtexp-no-text-selected = TXTEXP: tekstiä ei ole valittu.
     .angle-override-shown = Kulman ohitus: __ocs_fmt_0__
     .plot-preview-task = Tulostuksen esikatselu

locales/fr-FR/opencadstudio.ftl

@@ -282,6 +282,7 @@ command-copy =
     .mode = COPY  Entrez le mode de copie [Single/Multiple] <Multiple> :
 
 common =
+    .command-line-opacity = Opacité de la ligne de commande
     .txtexp-no-text-selected = TXTEXP : aucun texte sélectionné.
     .angle-override-shown = Remplacement d’angle : __ocs_fmt_0__
     .plot-preview-task = Aperçu du tracé

locales/hi-IN/opencadstudio.ftl

@@ -270,6 +270,7 @@ command-copy =
     .mode = COPY  कॉपी मोड विकल्प दर्ज करें [Single/Multiple] <Multiple>:
 
 common =
+    .command-line-opacity = कमांड लाइन अपारदर्शिता
     .txtexp-no-text-selected = TXTEXP: कोई टेक्स्ट चयनित नहीं।
     .angle-override-shown = कोण ओवरराइड: __ocs_fmt_0__
     .plot-preview-task = प्लॉट पूर्वावलोकन

locales/hu-HU/opencadstudio.ftl

@@ -280,6 +280,7 @@ command-copy =
     .mode = COPY  Adja meg a másolási módot [Single/Multiple] <Multiple>:
 
 common =
+    .command-line-opacity = Parancssor átlátszatlansága
     .txtexp-no-text-selected = TXTEXP: nincs kijelölt szöveg.
     .angle-override-shown = Szög felülbírálása: __ocs_fmt_0__
     .parametric-coincident = Egybeeső

locales/it-IT/opencadstudio.ftl

@@ -281,6 +281,7 @@ command-copy =
     .mode = COPY  Specificare modalità di copia [Single/Multiple] <Multiple>:
 
 common =
+    .command-line-opacity = Opacità della riga di comando
     .txtexp-no-text-selected = TXTEXP: nessun testo selezionato.
     .angle-override-shown = Sostituzione angolo: __ocs_fmt_0__
     .plot-preview-task = Anteprima di stampa

locales/ja-JP/opencadstudio.ftl

@@ -272,6 +272,7 @@ command-copy =
     .mode = COPY  コピーモードを入力 [Single/Multiple] <Multiple>:
 
 common =
+    .command-line-opacity = コマンドラインの不透明度
     .txtexp-no-text-selected = TXTEXP: 文字が選択されていません。
     .angle-override-shown = 角度の優先: __ocs_fmt_0__
     .plot-preview-task = 印刷プレビュー

locales/ko-KR/opencadstudio.ftl

@@ -281,6 +281,7 @@ command-copy =
     .mode = COPY  복사 모드 옵션 입력 [Single/Multiple] <Multiple>:
 
 common =
+    .command-line-opacity = 명령행 불투명도
     .txtexp-no-text-selected = TXTEXP: 선택된 문자가 없습니다.
     .angle-override-shown = 각도 재지정: __ocs_fmt_0__
     .plot-preview-task = 플롯 미리 보기

locales/lo-LA/opencadstudio.ftl

@@ -281,6 +281,7 @@ command-copy =
     .mode = COPY  ປ້ອນຕົວເລືອກໂໝດການຄັດລອກ [Single/Multiple] <Multiple>:
 
 common =
+    .command-line-opacity = ຄວາມທຶບຂອງແຖວຄຳສັ່ງ
     .txtexp-no-text-selected = TXTEXP: ບໍ່ໄດ້ເລືອກຂໍ້ຄວາມ.
     .angle-override-shown = ກຳນົດມຸມແທນ: __ocs_fmt_0__
     .remote-image-url-could-not-be-fetched-the-request-timed-out = ບໍ່ສາມາດດຶງຮູບພາບທາງໄກ "__ocs_fmt_0__" ໄດ້: ການຮ້ອງຂໍໝົດເວລາ.

locales/nl-NL/opencadstudio.ftl

@@ -282,6 +282,7 @@ command-copy =
     .mode = COPY  Geef kopieermodus op [Single/Multiple] <Multiple>:
 
 common =
+    .command-line-opacity = Dekking van de opdrachtregel
     .txtexp-no-text-selected = TXTEXP: geen tekst geselecteerd.
     .angle-override-shown = Hoekoverschrijving: __ocs_fmt_0__
     .plot-preview-task = Plotvoorbeeld

locales/pl-PL/opencadstudio.ftl

@@ -281,6 +281,7 @@ command-copy =
     .mode = COPY  Podaj tryb kopiowania [Single/Multiple] <Multiple>:
 
 common =
+    .command-line-opacity = Krycie wiersza poleceń
     .txtexp-no-text-selected = TXTEXP: nie wybrano tekstu.
     .angle-override-shown = Zastąpienie kąta: __ocs_fmt_0__
     .plot-preview-task = Podgląd wydruku

locales/pt-BR/opencadstudio.ftl

@@ -282,6 +282,7 @@ command-copy =
     .mode = COPY  Informe o modo de cópia [Single/Multiple] <Multiple>:
 
 common =
+    .command-line-opacity = Opacidade da linha de comando
     .txtexp-no-text-selected = TXTEXP: nenhum texto selecionado.
     .angle-override-shown = Substituição de ângulo: __ocs_fmt_0__
     .plot-preview-task = Visualização da plotagem

locales/ru-RU/opencadstudio.ftl

@@ -285,6 +285,7 @@ command-copy =
     .mode = COPY  Задайте режим копирования [Single/Multiple] <Multiple>:
 
 common =
+    .command-line-opacity = Непрозрачность командной строки
     .txtexp-no-text-selected = TXTEXP: текст не выбран.
     .angle-override-shown = Переопределение угла: __ocs_fmt_0__
     .plot-preview-task = Предварительный просмотр печати

locales/tr-TR/opencadstudio.ftl

@@ -267,6 +267,7 @@ command-copy =
     .mode = COPY  Kopyalama modu seçin [Single/Multiple] <Multiple>:
 
 common =
+    .command-line-opacity = Komut satırı opaklığı
     .txtexp-no-text-selected = TXTEXP: metin seçilmedi.
     .angle-override-shown = Açı geçersiz kılma: __ocs_fmt_0__
     .plot-preview-task = Çizim önizleme

locales/zh-CN/opencadstudio.ftl

@@ -269,6 +269,7 @@ command-copy =
     .mode = COPY  输入复制模式选项 [Single/Multiple] <Multiple>:
 
 common =
+    .command-line-opacity = 命令行不透明度
     .txtexp-no-text-selected = TXTEXP: 未选择文字。
     .angle-override-shown = 角度替代：__ocs_fmt_0__
     .plot-preview-task = 打印预览

locales/zh-TW/opencadstudio.ftl

@@ -281,6 +281,7 @@ command-copy =
     .mode = COPY  輸入複製模式選項 [Single/Multiple] <Multiple>:
 
 common =
+    .command-line-opacity = 命令列不透明度
     .txtexp-no-text-selected = TXTEXP: 未選擇文字。
     .angle-override-shown = 角度取代：__ocs_fmt_0__
     .plot-preview-task = 出圖預覽

src/app/commands/mod.rs

@@ -754,6 +754,7 @@ inventory::submit!(crate::command::CommandRegistration {
         "SKTOLERANCE",
         "CLIPROMPTLINES",
         "COMMANDLINEFADETIME",
+        "COMMANDLINEOPACITY",
         "COLORTHEME",
         "SELECTIONAREA",
         "SELECTIONAREAOPACITY",

src/app/commands/styleprops.rs

@@ -1149,6 +1149,7 @@ impl OpenCADStudio {
                     | "CURSORSIZE"
                     | "PICKBOX"
                     | "HPASSOC"
+                    | "COMMANDLINEOPACITY"
                     | "CURSORTYPE"
                     | "SNAPANG"
                     | "TEXTFILL"
@@ -2537,6 +2538,22 @@ impl OpenCADStudio {
                                     false,
                                 )),
                             },
+                            "COMMANDLINEOPACITY" => match &value {
+                                Some(v) => match v.parse::<u8>() {
+                                    Ok(n) if (20..=100).contains(&n) => {
+                                        self.command_line.set_opacity_percent(n);
+                                        Ok((format!("COMMANDLINEOPACITY = {n}"), true))
+                                    }
+                                    _ => Err("SETVAR: integer from 20 to 100 required.".into()),
+                                },
+                                None => Ok((
+                                    format!(
+                                        "COMMANDLINEOPACITY = {}",
+                                        self.command_line.opacity_percent()
+                                    ),
+                                    false,
+                                )),
+                            },
                             "COMMANDLINEFADETIME" => match &value {
                                 Some(v) => match v.parse::<i32>() {
                                     Ok(n) if (0..=60000).contains(&n) => {
@@ -3147,6 +3164,7 @@ impl OpenCADStudio {
                                         | "CURSORSIZE"
                                         | "PICKBOX"
                                         | "HPASSOC"
+                                        | "COMMANDLINEOPACITY"
                                         | "CURSORTYPE"
                                         | "SNAPANG"
                                         | "CLIPROMPTLINES"

src/app/mod.rs

@@ -2607,6 +2607,8 @@ pub enum Message {
     ClipromptLinesChanged(i32),
     /// Change how long command-line history lines stay visible (COMMANDLINEFADETIME).
     CommandLineFadeChanged(i32),
+    /// Change the command line's panel opacity (COMMANDLINEOPACITY).
+    CommandLineOpacityChanged(u8),
     /// Toggle reversing the mouse-wheel zoom direction (ZOOMWHEEL).
     ZoomWheelReversedChanged(bool),
     TouchpadPanChanged(bool),

src/app/settings.rs

@@ -587,6 +587,8 @@ pub struct UserSettings {
         deserialize_with = "deserialize_commandline_fade_ms"
     )]
     pub commandline_fade_ms: i32,
+    /// COMMANDLINEOPACITY: command-line panel opacity in percent (20–100).
+    pub command_line_opacity: u8,
     /// SNAPUNIT X/Y spacing used by grid snap. 10 matches the Drafting
     /// Settings dialog defaults; older configs without these keys fall
     /// back via `default_snap_spacing`.
@@ -896,6 +898,7 @@ impl Default for UserSettings {
             language: crate::i18n::Language::default(),
             cliprompt_lines: 3,
             commandline_fade_ms: 3000,
+            command_line_opacity: 100,
             snap_spacing_x: 10.0,
             snap_spacing_y: 10.0,
             grid_spacing_x: 10.0,

src/app/update/file.rs

@@ -847,6 +847,7 @@ impl OpenCADStudio {
             quick_properties: self.quick_properties,
             language: self.language,
             cliprompt_lines: crate::app::settings::clamp_clipromptlines(self.cliprompt_lines),
+            command_line_opacity: self.command_line.opacity_percent(),
             commandline_fade_ms: crate::app::settings::clamp_commandline_fade_ms(
                 self.commandline_fade_ms,
             ),
@@ -999,6 +1000,7 @@ impl OpenCADStudio {
         self.cliprompt_lines = crate::app::settings::clamp_clipromptlines(s.cliprompt_lines);
         self.command_line
             .set_cliprompt_lines(self.cliprompt_lines.clamp(0, 50) as u8);
+        self.command_line.set_opacity_percent(s.command_line_opacity);
         self.commandline_fade_ms =
             crate::app::settings::clamp_commandline_fade_ms(s.commandline_fade_ms);
         self.command_line

src/app/update/mod.rs

@@ -9057,6 +9057,12 @@ impl OpenCADStudio {
                 Task::none()
             }
 
+            Message::CommandLineOpacityChanged(percent) => {
+                self.command_line.set_opacity_percent(percent);
+                self.persist_settings_if_changed();
+                Task::none()
+            }
+
             Message::CommandLineFadeChanged(ms) => {
                 let ms = crate::app::settings::clamp_commandline_fade_ms(ms);
                 self.commandline_fade_ms = ms;

src/app/view/modal.rs

@@ -299,6 +299,7 @@ impl OpenCADStudio {
                             textfill: crate::scene::text::sdf_atlas::textfill(),
                             cliprompt_lines: self.cliprompt_lines,
                             commandline_fade_ms: self.commandline_fade_ms,
+                            command_line_opacity: self.command_line.opacity_percent(),
                             zoom_wheel_reversed: self.zoom_wheel_reversed,
                             touchpad_pan: self.touchpad_pan,
                             ui_scale_percent: self.ui_scale_percent,

src/locale_catalog.rs

@@ -3697,6 +3697,7 @@ pub(super) fn message_attribute(source: &str) -> Option<(&'static str, &'static
         "Width factor" => Some(("common", "width-factor-sentence-case")),
         "Width: %{value}" => Some(("ui", "width-value")),
         "Window" => Some(("common", "window")),
+        "Command line opacity" => Some(("common", "command-line-opacity")),
         "TXTEXP: no text selected." => Some(("common", "txtexp-no-text-selected")),
         "Windows desktop" => Some(("styles", "windows-desktop")),
         "Wipeout" => Some(("common", "wipeout")),

src/ui/command_line.rs

@@ -191,6 +191,9 @@ pub struct CommandLine {
     /// in milliseconds (0–60000, default 3000). 0 means history never fades;
     /// the pinned step prompt still shows.
     fade_ms: u32,
+    /// COMMANDLINEOPACITY: how opaque the command line's panels are, in
+    /// percent (20–100, default 100), so the drawing shows through.
+    opacity_percent: u8,
 }
 
 impl Default for CommandLine {
@@ -217,6 +220,7 @@ impl Default for CommandLine {
             step_options: Vec::new(),
             cliprompt_lines: 3,
             fade_ms: DEFAULT_COMMANDLINE_FADE_MS,
+            opacity_percent: 100,
         }
     }
 }
@@ -509,6 +513,15 @@ impl CommandLine {
         self.fade_ms
     }
 
+    /// COMMANDLINEOPACITY mirror (percent, 20–100).
+    pub fn set_opacity_percent(&mut self, percent: u8) {
+        self.opacity_percent = percent.clamp(20, 100);
+    }
+
+    pub fn opacity_percent(&self) -> u8 {
+        self.opacity_percent
+    }
+
     fn fade_secs(&self) -> f32 {
         self.fade_ms as f32 / 1000.0
     }
@@ -1127,12 +1140,15 @@ impl CommandLine {
         // The transient recent lines and the full archive are two views of the
         // same history. Showing both while the archive is open creates a fake
         // second history region and visually disconnects the input row (#555).
+        let opacity = f32::from(self.opacity_percent) / 100.0;
         let recent_history: Element<'a, Message> = if self.history_open || !has_recent_history {
             container(column![]).height(0).into()
         } else {
             container(history_rows)
-                .style(|theme: &Theme| container::Style {
+                .style(move |theme: &Theme| container::Style {
-                    background: Some(Background::Color(theme.palette().background.base.color)),
+                    background: Some(Background::Color(
+                        theme.palette().background.base.color.scale_alpha(opacity),
+                    )),
                     ..Default::default()
                 })
                 .width(Length::Fill)
@@ -1153,10 +1169,11 @@ impl CommandLine {
                 recent_history,
                 history_divider,
                 container(input_row)
-                    .style(|theme: &Theme| {
+                    .style(move |theme: &Theme| {
                         let palette = theme.palette();
+                        let color = palette.background.weakest.color.scale_alpha(opacity);
                         container::Style {
-                            background: Some(Background::Color(palette.background.weakest.color)),
+                            background: Some(Background::Color(color)),
                             ..Default::default()
                         }
                     })
@@ -1170,7 +1187,9 @@ impl CommandLine {
         .style(move |theme: &Theme| {
             let palette = theme.palette();
             container::Style {
-                background: Some(Background::Color(palette.background.base.color)),
+                background: Some(Background::Color(
+                    palette.background.base.color.scale_alpha(opacity),
+                )),
                 border: Border {
                     color: palette.background.neutral.color,
                     width: if history_open { 1.0 } else { 0.0 },

src/ui/window/options.rs

@@ -53,6 +53,8 @@ pub struct AppPrefs {
     pub cliprompt_lines: i32,
     /// COMMANDLINEFADETIME: how long overlay history lines stay visible, in ms.
     pub commandline_fade_ms: i32,
+    /// COMMANDLINEOPACITY: command-line panel opacity in percent.
+    pub command_line_opacity: u8,
     /// ZOOMWHEEL: reverse the mouse-wheel zoom direction.
     pub zoom_wheel_reversed: bool,
     /// Scroll pans and Ctrl+scroll zooms (touchpads).
@@ -974,6 +976,22 @@ pub fn view_window<'a>(
             ))
             .size(11)
             .width(sizing.width),
+        )
+        .push(Space::new().height(12))
+        .push(
+            row![
+                text(crate::t!("Command line opacity")).size(12).width(140),
+                slider(
+                    20..=100,
+                    prefs.command_line_opacity.clamp(20, 100),
+                    Message::CommandLineOpacityChanged,
+                )
+                .step(5u8)
+                .width(Fill),
+                text(format!("{}%", prefs.command_line_opacity)).size(11).width(44),
+            ]
+            .spacing(10)
+            .align_y(iced::Center),
         );
 
     let display_element = display.spacing(0).width(sizing.width);