WindowServer: Support windows with alpha channels. And per-WSWindow opacity.

This patch also adds a Format concept to GraphicsBitmap. For now there are
only two formats: RGB32 and RGBA32. Windows with alpha channel have their
backing stores created in the RGBA32 format.

Use this to make Terminal windows semi-transparent for that comfy rice look.
There is one problem here, in that window compositing overdraw incurs
multiple passes of blending of the same pixels. This leads to a mismatch in
opacity which is obviously not good. I will work on this in a later patch.

The alpha blending is currently straight C++. It should be relatively easy
to optimize this using SSE instructions.

For now I'm just happy with the cute effect. :^)

Applications/About/main.cpp

@@ -17,7 +17,7 @@ int main(int argc, char** argv)
     window->set_main_widget(widget);
 
     auto* icon_label = new GLabel(widget);
-    icon_label->set_icon(GraphicsBitmap::load_from_file("/res/icons/Serenity.rgb", { 32, 32 }));
+    icon_label->set_icon(GraphicsBitmap::load_from_file(GraphicsBitmap::Format::RGBA32, "/res/icons/Serenity.rgb", { 32, 32 }));
     icon_label->set_relative_rect(
         widget->rect().center().x() - 16,
         10,

Applications/FileManager/DirectoryView.cpp

@@ -12,9 +12,9 @@
 DirectoryView::DirectoryView(GWidget* parent)
     : GWidget(parent)
 {
-    m_directory_icon = GraphicsBitmap::load_from_file("/res/icons/folder16.rgb", { 16, 16 });
-    m_file_icon = GraphicsBitmap::load_from_file("/res/icons/file16.rgb", { 16, 16 });
-    m_symlink_icon = GraphicsBitmap::load_from_file("/res/icons/link16.rgb", { 16, 16 });
+    m_directory_icon = GraphicsBitmap::load_from_file(GraphicsBitmap::Format::RGBA32, "/res/icons/folder16.rgb", { 16, 16 });
+    m_file_icon = GraphicsBitmap::load_from_file(GraphicsBitmap::Format::RGBA32, "/res/icons/file16.rgb", { 16, 16 });
+    m_symlink_icon = GraphicsBitmap::load_from_file(GraphicsBitmap::Format::RGBA32, "/res/icons/link16.rgb", { 16, 16 });
 
     m_scrollbar = new GScrollBar(Orientation::Vertical, this);
     m_scrollbar->set_step(4);
@@ -142,7 +142,7 @@ void DirectoryView::paint_event(GPaintEvent&)
             Rect name_rect(icon_rect.right() + horizontal_padding, y, 100, item_height());
             Rect size_rect(name_rect.right() + horizontal_padding, y, 64, item_height());
             painter.fill_rect(row_rect(painted_item_index), i % 2 ? Color(210, 210, 210) : Color::White);
-            painter.blit_with_alpha(icon_rect.location(), icon_for(entry), { 0, 0, icon_size, icon_size });
+            painter.blit(icon_rect.location(), icon_for(entry), { 0, 0, icon_size, icon_size });
             painter.draw_text(name_rect, entry.name, TextAlignment::CenterLeft, Color::Black);
             if (should_show_size_for(entry))
                 painter.draw_text(size_rect, pretty_byte_size(entry.size), TextAlignment::CenterRight, Color::Black);

Applications/Launcher/main.cpp

@@ -38,7 +38,7 @@ public:
         : GButton(parent)
         , m_executable_path(exec_path)
     {
-        set_icon(GraphicsBitmap::load_from_file(icon_path, { 32, 32 }));
+        set_icon(GraphicsBitmap::load_from_file(GraphicsBitmap::Format::RGBA32, icon_path, { 32, 32 }));
         resize(50, 50);
         on_click = [this] (GButton&) {
             pid_t child_pid = fork();

Applications/Terminal/Terminal.cpp

@@ -143,7 +143,7 @@ unsigned parse_uint(const String& str, bool& ok)
 
 static inline Color lookup_color(unsigned color)
 {
-    return xterm_colors[color];
+    return Color::from_rgb(xterm_colors[color]);
 }
 
 void Terminal::escape$m(const Vector<unsigned>& params)
@@ -668,10 +668,14 @@ void Terminal::keydown_event(GKeyEvent& event)
 }
 
 void Terminal::paint_event(GPaintEvent&)
-{
-    Rect rect { 0, 0, m_pixel_width, m_pixel_height };
+{   
     Painter painter(*this);
 
+    if (m_needs_background_fill) {
+        m_needs_background_fill = false;
+        painter.fill_rect(rect(), Color(Color::Black).with_alpha(255 * m_opacity));
+    }
+
     if (m_rows_to_scroll_backing_store && m_rows_to_scroll_backing_store < m_rows) {
         int first_scanline = m_inset;
         int second_scanline = m_inset + (m_rows_to_scroll_backing_store * m_line_height);
@@ -695,7 +699,7 @@ void Terminal::paint_event(GPaintEvent&)
         line.dirty = false;
         bool has_only_one_background_color = line.has_only_one_background_color();
         if (has_only_one_background_color) {
-            painter.fill_rect(row_rect(row), lookup_color(line.attributes[0].background_color));
+            painter.fill_rect(row_rect(row), lookup_color(line.attributes[0].background_color).with_alpha(255 * m_opacity));
         }
         for (word column = 0; column < m_columns; ++column) {
             bool should_reverse_fill_for_cursor = m_in_active_window && row == m_cursor_row && column == m_cursor_column;
@@ -704,7 +708,7 @@ void Terminal::paint_event(GPaintEvent&)
             auto character_rect = glyph_rect(row, column);
             if (!has_only_one_background_color || should_reverse_fill_for_cursor) {
                 auto cell_rect = character_rect.inflated(0, m_line_spacing);
-                painter.fill_rect(cell_rect, lookup_color(should_reverse_fill_for_cursor ? attribute.foreground_color : attribute.background_color));
+                painter.fill_rect(cell_rect, lookup_color(should_reverse_fill_for_cursor ? attribute.foreground_color : attribute.background_color).with_alpha(255 * m_opacity));
             }
             if (ch == ' ')
                 continue;
@@ -718,7 +722,7 @@ void Terminal::paint_event(GPaintEvent&)
     }
 
     if (m_belling)
-        painter.draw_rect(rect, Color::Red);
+        painter.draw_rect(rect(), Color::Red);
 }
 
 void Terminal::set_window_title(String&& title)

Applications/Terminal/Terminal.h

@@ -144,4 +144,7 @@ private:
     RetainPtr<Font> m_font;
 
     GNotifier m_notifier;
+
+    float m_opacity { 0.8f };
+    bool m_needs_background_fill { true };
 };

Applications/Terminal/main.cpp

@@ -89,6 +89,7 @@ int main(int argc, char** argv)
     window->set_should_exit_app_on_close(true);
 
     Terminal terminal(ptm_fd);
+    window->set_has_alpha_channel(true);
     window->set_main_widget(&terminal);
     window->move_to(300, 300);
     window->show();