tray: Disable pseudo-transparency for opaque bgs

include/utils/color.hpp

@@ -37,6 +37,7 @@ class rgba {
   uint8_t blue_i() const;
 
   bool has_color() const;
+  bool is_transparent() const;
   rgba apply_alpha_to(rgba other) const;
   rgba try_apply_alpha_to(rgba other) const;
 

include/x11/tray_client.hpp

@@ -25,7 +25,7 @@ namespace tray {
 class client : public non_copyable_mixin, public non_movable_mixin {
  public:
   explicit client(
-      const logger& log, connection& conn, xcb_window_t parent, xcb_window_t win, size s, uint32_t desired_background);
+      const logger& log, connection& conn, xcb_window_t parent, xcb_window_t win, size s, rgba desired_background);
   ~client();
 
   string name() const;
@@ -124,9 +124,10 @@ class client : public non_copyable_mixin, public non_movable_mixin {
   size m_size;
   position m_pos{0, 0};
 
-  rgba m_desired_background;
+  const rgba m_desired_background;
+  const bool m_transparent{m_desired_background.is_transparent()};
   background_manager& m_background_manager;
-  shared_ptr<bg_slice> m_bg_slice;
+  shared_ptr<bg_slice> m_bg_slice{nullptr};
   unique_ptr<cairo::context> m_context;
   unique_ptr<cairo::xcb_surface> m_surface;
 };

src/utils/color.cpp

@@ -154,6 +154,10 @@ bool rgba::has_color() const {
   return m_type != type::NONE;
 }
 
+bool rgba::is_transparent() const {
+  return alpha_i() != 0xFF;
+}
+
 /**
  * Applies the alpha channel of this color to the given color.
  */

src/x11/tray_client.cpp

@@ -33,7 +33,7 @@ namespace tray {
  * 3. Use background color
  */
 client::client(
-    const logger& log, connection& conn, xcb_window_t parent, xcb_window_t win, size s, uint32_t desired_background)
+    const logger& log, connection& conn, xcb_window_t parent, xcb_window_t win, size s, rgba desired_background)
     : m_log(log)
     , m_connection(conn)
     , m_name(ewmh_util::get_wm_name(win))
@@ -350,17 +350,16 @@ void client::configure_notify() const {
 void client::update_bg() const {
   m_log.trace("%s: Update background", name());
 
-  // Composite background slice with background color.
-
   m_context->clear();
 
-  auto root_bg = m_bg_slice->get_surface();
-  if (root_bg != nullptr) {
-    // TODO the compositing doesn't have to be done if the background color is not transparent.
-    // In that case, the bg slice can be completely skipped, we shouldn't event observe the background
-    *m_context << CAIRO_OPERATOR_SOURCE << *root_bg;
-    m_context->paint();
-    *m_context << CAIRO_OPERATOR_OVER;
+  // Composite background slice with background color.
+  if (m_bg_slice) {
+    auto root_bg = m_bg_slice->get_surface();
+    if (root_bg != nullptr) {
+      *m_context << CAIRO_OPERATOR_SOURCE << *root_bg;
+      m_context->paint();
+      *m_context << CAIRO_OPERATOR_OVER;
+    }
   }
   *m_context << m_desired_background;
   m_context->paint();
@@ -372,6 +371,11 @@ void client::update_bg() const {
 }
 
 void client::observe_background() {
+  // Opaque backgrounds don't require pseudo-transparency
+  if (!m_transparent) {
+    return;
+  }
+
   xcb_rectangle_t rect{0, 0, static_cast<uint16_t>(m_size.w), static_cast<uint16_t>(m_size.h)};
   m_bg_slice = m_background_manager.observe(rect, embedder());
 

src/x11/tray_manager.cpp

@@ -122,6 +122,7 @@ void manager::activate() {
   try {
     set_tray_colors();
     set_tray_orientation();
+    // TODO
     // set_tray_visual();
   } catch (const exception& err) {
     m_log.err(err.what());
@@ -353,7 +354,7 @@ void manager::set_tray_orientation() {
       XCB_ATOM_CARDINAL, 32, 1, &orientation);
 }
 
-// TODO remove
+// TODO remove, we should probably not set a visual at all (or only a 24-bit one)
 void manager::set_tray_visual() {
   // TODO use bar visual
   const uint32_t visualid = m_connection.visual_type(XCB_VISUAL_CLASS_TRUE_COLOR, 32)->visual_id;
@@ -436,7 +437,7 @@ void manager::process_docking_request(xcb_window_t win) {
 
   try {
     auto cl = make_unique<client>(
-        m_log, m_connection, m_opts.selection_owner, win, m_opts.client_size, m_bar_opts.background.value());
+        m_log, m_connection, m_opts.selection_owner, win, m_opts.client_size, m_opts.background);
 
     try {
       cl->query_xembed();

tests/unit_tests/utils/color.cpp

@@ -88,6 +88,19 @@ TEST(Rgba, hasColor) {
   EXPECT_FALSE(v.has_color());
 }
 
+TEST(Rgba, isTransparent) {
+  rgba v(0x1243);
+  EXPECT_FALSE(v.is_transparent());
+
+  v = rgba(0xff1243);
+
+  EXPECT_FALSE(v.is_transparent());
+
+  v = rgba(0xfe1243);
+
+  EXPECT_TRUE(v.is_transparent());
+}
+
 TEST(Rgba, channel) {
   rgba v{0xCC123456};
   EXPECT_EQ(0xCC, v.alpha_i());