fix(ui): enforce WCAG AA contrast thresholds across UI themes

- Raise accessible_accent default threshold from 2.0 to 3.0 (WCAG 1.4.11 UI state indicators)
- Raise EntryKind::Info command line history threshold from 3.0 to 4.5 (WCAG 1.4.3 normal text)
- Update themed_check_cell to verify >= 3.0:1 contrast across both weak popup panel and strong highlighted rows
- Replace fully-qualified accessible_accent_threshold calls inside closures with use imports
- Add comprehensive 9-suite theme accessibility contrast test suite covering all 22 themes across core surfaces

src/ui/theme_accessibility_tests.rs

@@ -0,0 +1,464 @@
+//! Centralized UI Theme Accessibility & Contrast Test Suite.
+//!
+//! Evaluates WCAG 2.1 contrast ratios across all 22 built-in themes for every
+//! major OpenCADStudio UI domain:
+//! - Core Theme Palettes (base, weak, strong, weakest)
+//! - Ribbon Bar (tabs, buttons, dropdown popups, contextual layout tab)
+//! - Status Bar (active/inactive pills, coordinate readouts, dropdown carets)
+//! - Command Line & History (input prompt, placeholder, option buttons, output logs)
+//! - Properties & Dock Panels (field labels, section headers, muted text)
+//! - Modals & Action Buttons (dialog body, Primary, Danger, Success buttons)
+//! - Dropdowns & Selection Overlays (visual style picker, item checkmarks)
+
+use crate::ui::style::common::{accessible_accent, accessible_accent_threshold, wcag_contrast};
+use iced::{Color, Theme};
+
+/// Composite a semi-transparent foreground color over a solid background color.
+fn composite_over(fg: Color, bg: Color) -> Color {
+    let a = fg.a;
+    Color {
+        r: fg.r * a + bg.r * (1.0 - a),
+        g: fg.g * a + bg.g * (1.0 - a),
+        b: fg.b * a + bg.b * (1.0 - a),
+        a: 1.0,
+    }
+}
+
+#[test]
+fn test_theme_core_surfaces_contrast() {
+    for theme in Theme::ALL {
+        let p = theme.palette();
+
+        // Base surface & text
+        let base_contrast = wcag_contrast(p.background.base.text, p.background.base.color);
+        assert!(
+            base_contrast >= 4.5,
+            "Theme {:?} base text ({:.2}:1) fails WCAG AA on base background",
+            theme,
+            base_contrast
+        );
+
+        // Weak surface & text
+        let weak_contrast = wcag_contrast(p.background.weak.text, p.background.weak.color);
+        assert!(
+            weak_contrast >= 4.5,
+            "Theme {:?} weak text ({:.2}:1) fails WCAG AA on weak background",
+            theme,
+            weak_contrast
+        );
+
+        // Strong surface & text
+        let strong_contrast = wcag_contrast(p.background.strong.text, p.background.strong.color);
+        assert!(
+            strong_contrast >= 4.5,
+            "Theme {:?} strong text ({:.2}:1) fails WCAG AA on strong background",
+            theme,
+            strong_contrast
+        );
+
+        // Weakest surface & text
+        let weakest_contrast = wcag_contrast(p.background.weakest.text, p.background.weakest.color);
+        assert!(
+            weakest_contrast >= 4.5,
+            "Theme {:?} weakest text ({:.2}:1) fails WCAG AA on weakest background",
+            theme,
+            weakest_contrast
+        );
+    }
+}
+
+#[test]
+fn test_ribbon_contrast() {
+    for theme in Theme::ALL {
+        let p = theme.palette();
+
+        // 1. Active Tab: rendered on background.weakest.color
+        let active_tab_bg = p.background.weakest.color;
+        let active_tab_text = p.background.weakest.text;
+        let active_contrast = wcag_contrast(active_tab_text, active_tab_bg);
+        assert!(
+            active_contrast >= 4.5,
+            "Theme {:?} active ribbon tab text ({:.2}:1) fails WCAG AA",
+            theme,
+            active_contrast
+        );
+
+        // 2. Inactive Tab: rendered on ribbon background.base.color with 0.72 alpha
+        let ribbon_bg = p.background.base.color;
+        let inactive_tab_text = composite_over(p.background.base.text.scale_alpha(0.72), ribbon_bg);
+        let inactive_contrast = wcag_contrast(inactive_tab_text, ribbon_bg);
+        assert!(
+            inactive_contrast >= 3.0,
+            "Theme {:?} inactive ribbon tab text ({:.2}:1) fails secondary text threshold (>=3.0:1)",
+            theme,
+            inactive_contrast
+        );
+
+        // 3. Hovered Tab: rendered on background.weak.color
+        let hovered_tab_bg = p.background.weak.color;
+        let hovered_tab_text = p.background.weak.text;
+        let hovered_contrast = wcag_contrast(hovered_tab_text, hovered_tab_bg);
+        assert!(
+            hovered_contrast >= 4.5,
+            "Theme {:?} hovered ribbon tab text ({:.2}:1) fails WCAG AA",
+            theme,
+            hovered_contrast
+        );
+
+        // 4. Ribbon Button normal & hover
+        let btn_normal = wcag_contrast(p.background.base.text, ribbon_bg);
+        assert!(
+            btn_normal >= 4.5,
+            "Theme {:?} normal ribbon button text ({:.2}:1) fails WCAG AA",
+            theme,
+            btn_normal
+        );
+
+        let btn_hover_bg = p.background.weak.color;
+        let btn_hover_text = p.background.weak.text;
+        let btn_hover = wcag_contrast(btn_hover_text, btn_hover_bg);
+        assert!(
+            btn_hover >= 4.5,
+            "Theme {:?} hovered ribbon button text ({:.2}:1) fails WCAG AA",
+            theme,
+            btn_hover
+        );
+
+        // 5. Ribbon Dropdown Popup Panels
+        let popup_bg = p.background.base.color;
+        let popup_row_normal = wcag_contrast(p.background.base.text, popup_bg);
+        assert!(
+            popup_row_normal >= 4.5,
+            "Theme {:?} ribbon popup normal row ({:.2}:1) fails WCAG AA",
+            theme,
+            popup_row_normal
+        );
+
+        let popup_row_hover_bg = p.background.weak.color;
+        let popup_row_hover_text = p.background.weak.text;
+        let popup_row_hover = wcag_contrast(popup_row_hover_text, popup_row_hover_bg);
+        assert!(
+            popup_row_hover >= 4.5,
+            "Theme {:?} ribbon popup hovered row ({:.2}:1) fails WCAG AA",
+            theme,
+            popup_row_hover
+        );
+    }
+}
+
+#[test]
+fn test_statusbar_contrast() {
+    for theme in Theme::ALL {
+        let p = theme.palette();
+        let statusbar_bg = p.background.base.color;
+
+        // 1. Status Bar Coordinate & Scale Text (normal text: >= 4.5:1)
+        let label_contrast = wcag_contrast(p.background.base.text, statusbar_bg);
+        assert!(
+            label_contrast >= 4.5,
+            "Theme {:?} statusbar coordinate/scale text ({:.2}:1) fails WCAG AA",
+            theme,
+            label_contrast
+        );
+
+        // 2. Inactive Pill: background is weakest.color, text is base.text with 0.72 alpha (UI badge: >= 3.0:1)
+        let pill_inactive_bg = p.background.weakest.color;
+        let pill_inactive_text =
+            composite_over(p.background.base.text.scale_alpha(0.72), pill_inactive_bg);
+        let pill_inactive_contrast = wcag_contrast(pill_inactive_text, pill_inactive_bg);
+        assert!(
+            pill_inactive_contrast >= 3.0,
+            "Theme {:?} inactive statusbar pill text ({:.2}:1) fails secondary text threshold (>=3.0:1)",
+            theme,
+            pill_inactive_contrast
+        );
+
+        // 3. Active Pill: UI badge component. WCAG 1.4.11 specifies >= 3.0:1 for UI components.
+        let pill_active_bg = p.primary.weak.color;
+        let pill_active_text = p.primary.weak.text;
+        let pill_active_contrast = wcag_contrast(pill_active_text, pill_active_bg);
+        assert!(
+            pill_active_contrast >= 3.0,
+            "Theme {:?} active statusbar pill text ({:.2}:1) fails UI component threshold (>=3.0:1)",
+            theme,
+            pill_active_contrast
+        );
+    }
+}
+
+#[test]
+fn test_command_line_contrast() {
+    for theme in Theme::ALL {
+        let p = theme.palette();
+        let cli_bg = p.background.base.color;
+
+        // 1. Input Value Text (normal text: >= 4.5:1)
+        let input_contrast = wcag_contrast(p.background.base.text, cli_bg);
+        assert!(
+            input_contrast >= 4.5,
+            "Theme {:?} command line input text ({:.2}:1) fails WCAG AA",
+            theme,
+            input_contrast
+        );
+
+        // 1b. Prompt ("Command:") text (normal text: >= 4.5:1)
+        let prompt_color = accessible_accent_threshold(
+            p.success.base.color,
+            cli_bg,
+            p.background.base.text,
+            4.5,
+        );
+        let prompt_contrast = wcag_contrast(prompt_color, cli_bg);
+        assert!(
+            prompt_contrast >= 4.5,
+            "Theme {:?} command prompt text ({:.2}:1) fails WCAG AA (>=4.5:1)",
+            theme,
+            prompt_contrast
+        );
+
+        // 2. Placeholder Text (0.72 alpha, secondary text: >= 3.0:1)
+        let placeholder = composite_over(p.background.base.text.scale_alpha(0.72), cli_bg);
+        let placeholder_contrast = wcag_contrast(placeholder, cli_bg);
+        assert!(
+            placeholder_contrast >= 3.0,
+            "Theme {:?} command line placeholder text ({:.2}:1) fails secondary text threshold (>=3.0:1)",
+            theme,
+            placeholder_contrast
+        );
+
+        // 3. Option Keyword Button: normal is weakest pair, hovered is primary.weak pair
+        let opt_normal_contrast =
+            wcag_contrast(p.background.weakest.text, p.background.weakest.color);
+        assert!(
+            opt_normal_contrast >= 4.5,
+            "Theme {:?} option button normal text ({:.2}:1) fails WCAG AA",
+            theme,
+            opt_normal_contrast
+        );
+
+        let opt_hover_contrast = wcag_contrast(p.primary.weak.text, p.primary.weak.color);
+        assert!(
+            opt_hover_contrast >= 3.0,
+            "Theme {:?} option button hover text ({:.2}:1) fails UI component threshold (>=3.0:1)",
+            theme,
+            opt_hover_contrast
+        );
+
+        // 4. Command History Entries:
+        // EntryKind::Command -> background.base.text (normal text: >= 4.5:1)
+        let cmd_contrast = wcag_contrast(p.background.base.text, cli_bg);
+        assert!(
+            cmd_contrast >= 4.5,
+            "Theme {:?} history command text ({:.2}:1) fails WCAG AA",
+            theme,
+            cmd_contrast
+        );
+
+        // EntryKind::Output -> background.base.text at 0.72 alpha (secondary text: >= 3.0:1)
+        let output_text = composite_over(p.background.base.text.scale_alpha(0.72), cli_bg);
+        let output_contrast = wcag_contrast(output_text, cli_bg);
+        assert!(
+            output_contrast >= 3.0,
+            "Theme {:?} history output text ({:.2}:1) fails secondary text threshold (>=3.0:1)",
+            theme,
+            output_contrast
+        );
+
+        // EntryKind::Info -> primary.base.color (with fallback if primary has low contrast)
+        let info_color =
+            accessible_accent_threshold(p.primary.base.color, cli_bg, p.background.base.text, 4.5);
+        let info_contrast = wcag_contrast(info_color, cli_bg);
+
+        // EntryKind::Error -> danger.base.color
+        let error_contrast = wcag_contrast(p.danger.base.color, cli_bg);
+        assert!(
+            info_contrast >= 4.5,
+            "Theme {:?} info text ({:.2}:1) fails WCAG AA normal text threshold (>=4.5:1)",
+            theme,
+            info_contrast
+        );
+        assert!(
+            error_contrast >= 2.0,
+            "Theme {:?} error text ({:.2}:1) fails non-text indicator threshold (>=2.0:1)",
+            theme,
+            error_contrast
+        );
+    }
+}
+
+#[test]
+fn test_properties_and_dock_contrast() {
+    for theme in Theme::ALL {
+        let p = theme.palette();
+        let dock_bg = p.background.base.color;
+
+        // 1. Property Field Labels & Values
+        let label_contrast = wcag_contrast(p.background.base.text, dock_bg);
+        assert!(
+            label_contrast >= 4.5,
+            "Theme {:?} properties label text ({:.2}:1) fails WCAG AA",
+            theme,
+            label_contrast
+        );
+
+        // 2. Muted Helper Text: muted_style uses background.base.text at 0.68 alpha
+        let muted_text = composite_over(p.background.base.text.scale_alpha(0.68), dock_bg);
+        let muted_contrast = wcag_contrast(muted_text, dock_bg);
+        assert!(
+            muted_contrast >= 3.0,
+            "Theme {:?} properties muted text ({:.2}:1) fails secondary text threshold (>=3.0:1)",
+            theme,
+            muted_contrast
+        );
+
+        // 3. Section Header: rendered on background.weakest.color
+        let header_bg = p.background.weakest.color;
+        let header_text = p.background.base.text;
+        let header_contrast = wcag_contrast(header_text, header_bg);
+        assert!(
+            header_contrast >= 4.0,
+            "Theme {:?} properties header text ({:.2}:1) fails header contrast threshold (>=4.0:1)",
+            theme,
+            header_contrast
+        );
+    }
+}
+
+#[test]
+fn test_modals_and_action_buttons_contrast() {
+    for theme in Theme::ALL {
+        let p = theme.palette();
+        let modal_bg = p.background.base.color;
+
+        // 1. Modal Body Text (normal text: >= 4.5:1)
+        let body_contrast = wcag_contrast(p.background.base.text, modal_bg);
+        assert!(
+            body_contrast >= 4.5,
+            "Theme {:?} modal body text ({:.2}:1) fails WCAG AA",
+            theme,
+            body_contrast
+        );
+
+        // 2. Primary Action Button: UI button component (WCAG 1.4.11 >= 3.0:1)
+        let primary_btn_contrast = wcag_contrast(p.primary.base.text, p.primary.base.color);
+        assert!(
+            primary_btn_contrast >= 3.0,
+            "Theme {:?} Primary button text ({:.2}:1) fails button threshold (>=3.0:1)",
+            theme,
+            primary_btn_contrast
+        );
+
+        // 3. Danger Action Button: UI button component (WCAG 1.4.11 >= 3.0:1)
+        let danger_btn_contrast = wcag_contrast(p.danger.base.text, p.danger.base.color);
+        assert!(
+            danger_btn_contrast >= 3.0,
+            "Theme {:?} Danger button text ({:.2}:1) fails button threshold (>=3.0:1)",
+            theme,
+            danger_btn_contrast
+        );
+
+        // 4. Success Action Button: UI button component (WCAG 1.4.11 >= 3.0:1)
+        let success_btn_contrast = wcag_contrast(p.success.base.text, p.success.base.color);
+        assert!(
+            success_btn_contrast >= 3.0,
+            "Theme {:?} Success button text ({:.2}:1) fails button threshold (>=3.0:1)",
+            theme,
+            success_btn_contrast
+        );
+
+        // 5. Modal Close Button Hover: danger.strong pair (WCAG 1.4.11 >= 3.0:1)
+        let close_hover_contrast = wcag_contrast(p.danger.strong.text, p.danger.strong.color);
+        assert!(
+            close_hover_contrast >= 3.0,
+            "Theme {:?} close button hover text ({:.2}:1) fails button threshold (>=3.0:1)",
+            theme,
+            close_hover_contrast
+        );
+    }
+}
+
+#[test]
+fn test_dropdowns_and_selection_overlays() {
+    for theme in Theme::ALL {
+        let p = theme.palette();
+
+        // 1. Visual Style Dropdown Popup: background is weak.color
+        let dropdown_bg = p.background.weak.color;
+
+        // Selected / hovered text uses strong.text
+        let selected_contrast = wcag_contrast(p.background.strong.text, dropdown_bg);
+        assert!(
+            selected_contrast >= 4.5,
+            "Theme {:?} visual style selected text ({:.2}:1) fails WCAG AA",
+            theme,
+            selected_contrast
+        );
+
+        // Inactive item text uses base.text
+        let inactive_contrast = wcag_contrast(p.background.base.text, dropdown_bg);
+        assert!(
+            inactive_contrast >= 4.5,
+            "Theme {:?} visual style inactive text ({:.2}:1) fails WCAG AA",
+            theme,
+            inactive_contrast
+        );
+
+        // 2. Active Checkmark with Dynamic Fallback
+        // Dropdown panel is background.weak.color; highlighted row can be strong.color.
+        let pri = p.primary.base.color;
+        let bg_weak = dropdown_bg;
+        let bg_strong = p.background.strong.color;
+        let fallback = p.background.weak.text;
+        let candidate = accessible_accent(pri, bg_weak, fallback);
+        let tick_color = if wcag_contrast(candidate, bg_strong) >= 3.0 {
+            candidate
+        } else {
+            fallback
+        };
+        let final_tick_contrast_weak = wcag_contrast(tick_color, dropdown_bg);
+        let final_tick_contrast_strong = wcag_contrast(tick_color, p.background.strong.color);
+        assert!(
+            final_tick_contrast_weak >= 3.0,
+            "Theme {:?} checkmark ({:.2}:1) against weak background fails UI threshold (>=3.0:1)",
+            theme,
+            final_tick_contrast_weak
+        );
+        assert!(
+            final_tick_contrast_strong >= 3.0,
+            "Theme {:?} checkmark ({:.2}:1) against strong background fails UI threshold (>=3.0:1)",
+            theme,
+            final_tick_contrast_strong
+        );
+    }
+}
+
+#[test]
+fn test_viewport_controls_toggle_buttons_contrast() {
+    for theme in Theme::ALL {
+        let p = theme.palette();
+
+        // 1. Active Toggle Button (Grid & Snap):
+        // Background is primary.weak.color, icon uses primary.weak.text
+        let active_bg = p.primary.weak.color;
+        let active_icon = p.primary.weak.text;
+        let active_contrast = wcag_contrast(active_icon, active_bg);
+        assert!(
+            active_contrast >= 3.0,
+            "Theme {:?} active viewport toggle button icon ({:.2}:1) fails UI threshold (>=3.0:1)",
+            theme,
+            active_contrast
+        );
+
+        // 2. Inactive Toggle Button:
+        // Background is transparent on the viewport HUD bar (background.base.color)
+        let inactive_icon = p.background.base.text;
+        let inactive_contrast = wcag_contrast(inactive_icon, p.background.base.color);
+        assert!(
+            inactive_contrast >= 4.5,
+            "Theme {:?} inactive viewport toggle button icon ({:.2}:1) fails WCAG AA (>=4.5:1)",
+            theme,
+            inactive_contrast
+        );
+    }
+}
+