Painter: Add text elision support (only right-hand side supported.)

Some window titles didn't fit on the taskbar buttons, so I needed a way
to collapse the remaining part of the text into "..."

SharedGraphics/Font.cpp

@@ -160,15 +160,20 @@ bool Font::write_to_file(const String& path)
 
 int Font::width(const String& string) const
 {
-    if (string.is_empty())
+    return width(string.characters(), string.length());
+}
+
+int Font::width(const char* characters, int length) const
+{
+    if (!length)
         return 0;
 
     if (m_fixed_width)
-        return string.length() * m_glyph_width;
+        return length * m_glyph_width;
 
     int width = 0;
-    for (int i = 0; i < string.length(); ++i)
+    for (int i = 0; i < length; ++i)
-        width += glyph_width(string[i]) + 1;
+        width += glyph_width(characters[i]) + 1;
 
     return width - 1;
 }

SharedGraphics/Font.h

@@ -61,6 +61,7 @@ public:
     byte max_glyph_width() const { return m_max_glyph_width; }
     byte glyph_spacing() const { return m_fixed_width ? 0 : 1; }
     int width(const String& string) const;
+    int width(const char*, int) const;
 
     String name() const { return m_name; }
     void set_name(const String& name) { m_name = name; }

SharedGraphics/Painter.cpp

@@ -4,6 +4,7 @@
 #include <SharedGraphics/CharacterBitmap.h>
 #include <AK/Assertions.h>
 #include <AK/StdLibExtras.h>
+#include <AK/StringBuilder.h>
 #include <unistd.h>
 
 Painter::Painter(GraphicsBitmap& bitmap)
@@ -343,8 +344,34 @@ void Painter::draw_scaled_bitmap(const Rect& a_dst_rect, const GraphicsBitmap& s
     draw_bitmap(point, font.glyph_bitmap(ch), color);
 }
 
-void Painter::draw_text(const Rect& rect, const char* text, int length, const Font& font, TextAlignment alignment, Color color)
+void Painter::draw_text(const Rect& rect, const char* text, int length, const Font& font, TextAlignment alignment, Color color, TextElision elision)
 {
+    String elided_text;
+    if (elision == TextElision::Right) {
+        if (font.width(text, length) > rect.width()) {
+            int glyph_spacing = font.glyph_spacing();
+            int new_length = 0;
+            int new_width = font.width("...");
+            for (int i = 0; i < length; ++i) {
+                int glyph_width = font.glyph_width(text[i]);
+                // NOTE: Glyph spacing should not be added after the last glyph on the line,
+                //       but since we are here because the last glyph does not actually fit on the line,
+                //       we don't have to worry about spacing.
+                int width_with_this_glyph_included = new_width + glyph_width + glyph_spacing;
+                if (width_with_this_glyph_included > rect.width())
+                    break;
+                ++new_length;
+                new_width += glyph_width + glyph_spacing;
+            }
+            StringBuilder builder;
+            builder.append(text, new_length);
+            builder.append("...");
+            elided_text = builder.to_string();
+            text = elided_text.characters();
+            length = elided_text.length();
+        }
+    }
+
     Point point;
 
     if (alignment == TextAlignment::TopLeft) {
@@ -374,19 +401,19 @@ void Painter::draw_text(const Rect& rect, const char* text, int length, const Fo
     }
 }
 
-void Painter::draw_text(const Rect& rect, const String& text, TextAlignment alignment, Color color)
+void Painter::draw_text(const Rect& rect, const String& text, TextAlignment alignment, Color color, TextElision elision)
 {
-    draw_text(rect, text.characters(), text.length(), alignment, color);
+    draw_text(rect, text.characters(), text.length(), alignment, color, elision);
 }
 
-void Painter::draw_text(const Rect& rect, const String& text, const Font& font, TextAlignment alignment, Color color)
+void Painter::draw_text(const Rect& rect, const String& text, const Font& font, TextAlignment alignment, Color color, TextElision elision)
 {
-    draw_text(rect, text.characters(), text.length(), font, alignment, color);
+    draw_text(rect, text.characters(), text.length(), font, alignment, color, elision);
 }
 
-void Painter::draw_text(const Rect& rect, const char* text, int length, TextAlignment alignment, Color color)
+void Painter::draw_text(const Rect& rect, const char* text, int length, TextAlignment alignment, Color color, TextElision elision)
 {
-    draw_text(rect, text, length, font(), alignment, color);
+    draw_text(rect, text, length, font(), alignment, color, elision);
 }
 
 void Painter::set_pixel(const Point& p, Color color)

SharedGraphics/Painter.h

@@ -5,6 +5,7 @@
 #include "Rect.h"
 #include "Size.h"
 #include <SharedGraphics/TextAlignment.h>
+#include <SharedGraphics/TextElision.h>
 #include <AK/AKString.h>
 
 class CharacterBitmap;
@@ -28,10 +29,10 @@ public:
     void blit(const Point&, const GraphicsBitmap&, const Rect& src_rect);
     void blit_with_opacity(const Point&, const GraphicsBitmap&, const Rect& src_rect, float opacity);
 
-    void draw_text(const Rect&, const char* text, int length, const Font&, TextAlignment = TextAlignment::TopLeft, Color = Color::Black);
+    void draw_text(const Rect&, const char* text, int length, const Font&, TextAlignment = TextAlignment::TopLeft, Color = Color::Black, TextElision = TextElision::None);
-    void draw_text(const Rect&, const char* text, int length, TextAlignment = TextAlignment::TopLeft, Color = Color::Black);
+    void draw_text(const Rect&, const char* text, int length, TextAlignment = TextAlignment::TopLeft, Color = Color::Black, TextElision = TextElision::None);
-    void draw_text(const Rect&, const String&, const Font&, TextAlignment = TextAlignment::TopLeft, Color = Color::Black);
+    void draw_text(const Rect&, const String&, const Font&, TextAlignment = TextAlignment::TopLeft, Color = Color::Black, TextElision = TextElision::None);
-    void draw_text(const Rect&, const String&, TextAlignment = TextAlignment::TopLeft, Color = Color::Black);
+    void draw_text(const Rect&, const String&, TextAlignment = TextAlignment::TopLeft, Color = Color::Black, TextElision = TextElision::None);
     void draw_glyph(const Point&, char, Color);
     void draw_glyph(const Point&, char, const Font&, Color);
 

SharedGraphics/TextElision.h

@@ -0,0 +1,7 @@
+#pragma once
+
+enum class TextElision {
+    None,
+    Right,
+};
+