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 <[email protected]>

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,