gdamore · gdamore · Dec 14, 2025 · Dec 14, 2025
diff --git a/demos/styles/dub.json b/demos/styles/dub.json
@@ -0,0 +1,12 @@
+{
+  "copyright": "Copyright 2025 Garrett D'Amore",
+  "description": "Styles Demo for Dcell",
+  "name": "styles",
+  "targetType": "executable",
+  "targetName": "styles",
+  "targetPath": "bin",
+  "mainSourceFile": "source/styles.d",
+  "dependencies": {
+    "dcell": { "path": "../.." }
+  }
+}
diff --git a/demos/styles/source/styles.d b/demos/styles/source/styles.d
@@ -0,0 +1,179 @@
+/**
+ * Styles world demo for Dcell.
+ *
+ * Copyright: Copyright 2025 Garrett D'Amore
+ * Authors: Garrett D'Amore
+ * License:
+ *   Distributed under the Boost Software License, Version 1.0.
+ *   (See accompanying file LICENSE or https://www.boost.org/LICENSE_1_0.txt)
+ *   SPDX-License-Identifier: BSL-1.0
+ */
+module styles;
+
+import std.stdio;
+import std.string;
+
+import dcell;
+
+void centerStr(Screen s, int y, Style style, string str)
+{
+    s.style = style;
+    s.position = Coord((s.size.x - cast(int)(str.length)) / 2, y);
+    s.write(str);
+}
+
+void displayStyles(Screen s)
+{
+
+    s.style.attr = Attr.bold;
+    s.style.fg = Color.black;
+    s.style.bg = Color.white;
+
+    s.clear();
+
+    s.style.fg = Color.blue;
+    s.style.bg = Color.silver;
+
+    int row = 2;
+    s.position = Coord(2, row);
+    s.write("Press ESC to Exit");
+    row += 2;
+
+    s.style.fg = Color.black;
+    s.style.bg = Color.white;
+
+    s.position = Coord(2, row);
+    s.style.attr = Attr.none;
+    s.write("Note: Style support is dependent on your terminal.");
+    row += 2;
+
+    s.style.attr = Attr.none;
+    s.position = Coord(2, row++);
+    s.write("Plain");
+
+    s.style.attr = Attr.blink;
+    s.position = Coord(2, row++);
+    s.write("Blink");
+
+    s.style.attr = Attr.reverse;
+    s.position = Coord(2, row++);
+    s.write("Reverse");
+
+    s.style.attr = Attr.dim;
+    s.position = Coord(2, row++);
+    s.write("Dim");
+
+    s.style.attr = Attr.underline;
+    s.position = Coord(2, row++);
+    s.write("Underline");
+
+    s.style.attr = Attr.italic;
+    s.position = Coord(2, row++);
+    s.write("Italic");
+
+    s.style.attr = Attr.bold;
+    s.position = Coord(2, row++);
+    s.write("Bold");
+
+    s.style.attr = Attr.bold | Attr.italic;
+    s.position = Coord(2, row++);
+    s.write("Bold Italic");
+
+    s.style.attr = Attr.bold | Attr.italic | Attr.underline;
+    s.position = Coord(2, row++);
+    s.write("Bold Italic Underline");
+
+    s.style.attr = Attr.strikethrough;
+    s.position = Coord(2, row++);
+    s.write("Strikethrough");
+
+    s.style.attr = Attr.doubleUnderline;
+    s.position = Coord(2, row++);
+    s.write("Double Underline");
+
+    s.style.attr = Attr.curlyUnderline;
+    s.position = Coord(2, row++);
+    s.write("Curly Underline");
+
+    s.style.attr = Attr.dottedUnderline;
+    s.position = Coord(2, row++);
+    s.write("Dotted Underline");
+
+    s.style.attr = Attr.dashedUnderline;
+    s.position = Coord(2, row++);
+    s.write("Dashed Underline");
+
+    s.style.attr = Attr.underline;
+    s.style.ul = Color.blue;
+    s.position = Coord(2, row++);
+    s.write("Blue Underline");
+
+    s.style.attr = Attr.curlyUnderline;
+    s.style.ul = fromHex(0xc58af9);
+    s.position = Coord(2, row++);
+    s.write("Lavender Curly Underline");
+
+    s.style.attr = Attr.none;
+    s.style.ul = Color.invalid;
+    s.position = Coord(2, row++);
+    s.style.url = "https://github.com/gdamore/dcell";
+    s.write("Hyperlink");
+    s.style.url = "";
+
+    s.style.attr = Attr.none;
+    s.style.fg = Color.red;
+    s.position = Coord(2, row++);
+    s.write("Red Foreground");
+
+    s.style.attr = Attr.none;
+    s.style.bg = Color.red;
+    s.style.fg = Color.black;
+    s.position = Coord(2, row++);
+    s.write("Red Background");
+
+    s.show();
+}
+
+void handleEvent(Screen ts, Event ev)
+{
+    import core.stdc.stdlib : exit;
+
+    switch (ev.type)
+    {
+    case EventType.key:
+        if (ev.key.key == Key.esc || ev.key.key == Key.f1)
+        {
+            ts.stop();
+            exit(0);
+        }
+        break;
+    case EventType.resize:
+        ts.resize();
+        displayStyles(ts);
+        ts.sync();
+        break;
+    default:
+        break;
+    }
+}
+
+void main()
+{
+    import std.stdio;
+
+    auto ts = newScreen();
+    assert(ts !is null);
+    scope (exit)
+    {
+        ts.stop();
+    }
+
+    ts.start();
+
+    displayStyles(ts);
+    for (;;)
+    {
+        Event ev = ts.waitEvent();
+        handleEvent(ts, ev);
+    }
+}
diff --git a/source/dcell/attr.d b/source/dcell/attr.d
@@ -19,10 +19,20 @@ enum Attr
     bold = 1 << 0,
     blink = 1 << 1,
     reverse = 1 << 2, /// foreground and background colors reversed
-    underline = 1 << 3,
-    dim = 1 << 4,
-    italic = 1 << 5,
-    strikethrough = 1 << 6,
-    invalid = 1 << 7, // invalid attribute
+    dim = 1 << 3,
+    italic = 1 << 4,
+    strikethrough = 1 << 5,
+
+    /// Underlines are a bit field, because they can be styled.  Use a ^= underlineMask; a |= plainUnderline.
+    /// If you only use simple underlines you can just set underline as a bool.
+    underline = 1 << 6,
+    plainUnderline = underline | 0 << 7,
+    doubleUnderline = underline | 1 << 7,
+    curlyUnderline = underline | 2 << 7, // underline styles take bits 7-9
+    dottedUnderline = underline | 3 << 7,
+    dashedUnderline = underline | 4 << 7,
+    underlineMask = underline | 7 << 7, // all bits set for underline
+
+    invalid = 1 << 15, // invalid attribute
     init = invalid,
 }
diff --git a/source/dcell/screen.d b/source/dcell/screen.d
@@ -222,7 +222,7 @@ interface Screen
      * The style property is used when writing content to the screen
      * using the simpler write() API.
      */
-    @property Style style() const @safe;
+    @property ref Style style() @safe;
     @property Style style(const(Style)) @safe;
 
     /**

diff --git a/source/dcell/style.d b/source/dcell/style.d
@@ -22,6 +22,7 @@ struct Style
 {
     Color fg; /// foreground color
     Color bg; /// background color
+    Color ul; /// underline color (when underline is in use)
     string url; /// clickable URL, or none if empty
     Attr attr; /// text attributes
 }
diff --git a/source/dcell/ttyscreen.d b/source/dcell/ttyscreen.d
@@ -94,6 +94,13 @@ class TtyScreen : Screen
         enum string enableDrag = "\x1b[?1002h";
         enum string enableMotion = "\x1b[?1003h";
         enum string mouseSgr = "\x1b[?1006h"; // SGR reporting (use with other enables)
+        enum string doubleUnder = "\x1b[4:2m";
+        enum string curlyUnder = "\x1b[4:3m";
+        enum string dottedUnder = "\x1b[4:4m";
+        enum string dashedUnder = "\x1b[4:5m";
+        enum string underColor = "\x1b[58:5:%dm";
+        enum string underRGB = "\x1b[58:2::%d:%d:%dm";
+        enum string underFg = "\x1b[59m";
 
         // these can be overridden (e.g. disabled for legacy)
         string enterURL = "\x1b]8;;%s\x1b\\";
@@ -122,13 +129,6 @@ class TtyScreen : Screen
         // variables.)
         int numColors = 256;
 
-        // doubleUnder       = "\x1b[4:2m"
-        // curlyUnder        = "\x1b[4:3m"
-        // dottedUnder       = "\x1b[4:4m"
-        // dashedUnder       = "\x1b[4:5m"
-        // underColor        = "\x1b[58:5:%dm"
-        // underRGB          = "\x1b[58:2::%d:%d:%dm"
-        // underFg           = "\x1b[59m"
         // requestWindowSize = "\x1b[18t"                          // For modern terminals
     }
 
@@ -314,6 +314,9 @@ class TtyScreen : Screen
 
     void clear()
     {
+        // save the style currently in effect, so when
+        // we later send the clear, we can use it.
+        baseStyle = style;
         fill(" ");
         clear_ = true;
         // because we are going to clear it in the next cycle,
@@ -502,7 +505,7 @@ class TtyScreen : Screen
 
     // This is the default style we use when writing content using
     // put and similar APIs.
-    @property Style style() const @safe
+    @property ref Style style() @safe
     {
         return cells.style;
     }
@@ -552,6 +555,7 @@ private:
     bool clear_; // if a screen clear is requested
     Coord pos_; // location where we will update next
     Style style_; // current style
+    Style baseStyle;
     Coord cursorPos;
     Cursor cursorShape;
     MouseEnable mouseEn; // saved state for suspend/resume
@@ -589,6 +593,24 @@ private:
         {
             return;
         }
+
+        if (style.ul.isValid && (style.attr & Attr.underlineMask))
+        {
+            if (style.ul == Color.reset)
+            {
+                puts(vt.underFg);
+            }
+            else if (style.ul.isRGB && vt.numColors > 256)
+            {
+                auto rgb = decompose(style.ul);
+                puts(format!(vt.underRGB)(rgb[0], rgb[1], rgb[2]));
+            }
+            else
+            {
+                auto ul = toPalette(style.ul, vt.numColors);
+                puts(format!(vt.underColor)(ul));
+            }
+        }
         if (fg == Color.reset || bg == Color.reset)
         {
             puts(vt.resetFgBg);
@@ -641,25 +663,51 @@ private:
     {
         auto attr = style.attr;
         if (attr & Attr.bold)
-            puts(Vt.bold);
-        if (attr & Attr.underline)
-            puts(Vt.underline);
+            puts(vt.bold);
         if (attr & Attr.reverse)
-            puts(Vt.reverse);
+            puts(vt.reverse);
         if (attr & Attr.blink)
-            puts(Vt.blink);
+            puts(vt.blink);
         if (attr & Attr.dim)
-            puts(Vt.dim);
+            puts(vt.dim);
         if (attr & Attr.italic)
-            puts(Vt.italic);
+            puts(vt.italic);
         if (attr & Attr.strikethrough)
-            puts(Vt.strikeThrough);
+            puts(vt.strikeThrough);
+        switch (attr & Attr.underlineMask)
+        {
+        case Attr.plainUnderline:
+            puts(vt.underline);
+            break;
+        case attr.doubleUnderline:
+            puts(vt.underline);
+            puts(vt.doubleUnder);
+            break;
+        case Attr.curlyUnderline:
+            puts(vt.underline);
+            puts(vt.curlyUnder);
+            break;
+        case Attr.dottedUnderline:
+            puts(vt.underline);
+            puts(vt.dottedUnder);
+            break;
+        case Attr.dashedUnderline:
+            puts(vt.underline);
+            puts(vt.dashedUnder);
+            break;
+        default:
+            break;
+        }
     }
 
     void clearScreen()
     {
         if (clear_)
         {
+            // We want to use the style that was in effect
+            // when the clear function was called.
+            Style savedStyle = style;
+            style = baseStyle;
             clear_ = false;
             puts(vt.sgr0);
             puts(vt.exitURL);
@@ -668,6 +716,7 @@ private:
             style_ = style;
             puts(Vt.clear);
             flush();
+            style = savedStyle;
         }
     }