feat: consolidate test structure and enhance header visibility across themes

src/theme_manager.py

@@ -77,6 +77,56 @@ class ThemeManager:
         """Get the currently active theme."""
         return self.current_theme
 
+    def _get_contrasting_colors(self, colors: dict[str, str]) -> dict[str, str]:
+        """Get contrasting colors for headers with improved visibility."""
+
+        def get_luminance(color_str: str) -> float:
+            """Calculate relative luminance of a color."""
+            if not color_str or not color_str.startswith("#"):
+                return 0.5
+            try:
+                rgb = tuple(int(color_str[i : i + 2], 16) for i in (1, 3, 5))
+                # Calculate relative luminance
+                return (0.299 * rgb[0] + 0.587 * rgb[1] + 0.114 * rgb[2]) / 255
+            except (ValueError, IndexError):
+                return 0.5
+
+        def get_contrast_ratio(bg: str, fg: str) -> float:
+            """Calculate contrast ratio between two colors."""
+            bg_lum = get_luminance(bg)
+            fg_lum = get_luminance(fg)
+            lighter = max(bg_lum, fg_lum)
+            darker = min(bg_lum, fg_lum)
+            return (lighter + 0.05) / (darker + 0.05)
+
+        # Start with the provided select colors
+        header_bg = colors["select_bg"]
+        header_fg = colors["select_fg"]
+
+        # Calculate contrast ratio
+        contrast = get_contrast_ratio(header_bg, header_fg)
+
+        # If contrast is poor (less than 3:1), use high-contrast alternatives
+        if contrast < 3.0:
+            bg_luminance = get_luminance(colors["bg"])
+
+            if bg_luminance > 0.5:  # Light theme
+                header_bg = "#1e1e1e"  # Very dark gray background for maximum contrast
+                header_fg = "#ffffff"  # Pure white for maximum contrast
+            else:  # Dark theme - use dark background with light text
+                header_bg = "#1e1e1e"  # Very dark gray for consistency
+                header_fg = "#ffffff"  # Pure white for maximum contrast
+
+            self.logger.debug(
+                f"Poor header contrast ({contrast:.2f}), using fallback colors: "
+                f"bg={header_bg}, fg={header_fg}"
+            )
+
+        return {
+            "header_bg": header_bg,
+            "header_fg": header_fg,
+        }
+
     def _configure_custom_styles(self) -> None:
         """Configure custom styles for better appearance."""
         if not self.style:
@@ -86,6 +136,9 @@ class ThemeManager:
             # Get current theme colors for consistent styling
             colors = self.get_theme_colors()
 
+            # Get improved header colors with better contrast
+            header_colors = self._get_contrasting_colors(colors)
+
             # Configure frame styles with better padding and borders
             self.style.configure(
                 "Card.TFrame",
@@ -155,11 +208,26 @@ class ThemeManager:
                 padding=(8, 6),
                 relief="flat",
                 borderwidth=1,
-                background=colors["select_bg"],
-                foreground=colors["select_fg"],
+                background=header_colors["header_bg"],
+                foreground=header_colors["header_fg"],
                 font=("TkDefaultFont", 9, "bold"),
             )
 
+            # Ensure header style mapping to override theme defaults
+            self.style.map(
+                "Modern.Treeview.Heading",
+                background=[
+                    ("active", header_colors["header_bg"]),
+                    ("pressed", header_colors["header_bg"]),
+                    ("", header_colors["header_bg"]),
+                ],
+                foreground=[
+                    ("active", header_colors["header_fg"]),
+                    ("pressed", header_colors["header_fg"]),
+                    ("", header_colors["header_fg"]),
+                ],
+            )
+
             # Configure comprehensive row selection colors for better visibility
             self.style.map(
                 "Modern.Treeview",