fix(tray): Improve pseudo-transparency handling

- Make sure previously drawn content is cleared
- Redraw tray clients on XCB_EXPOSE
- Prevent void parts of the root pixmap being copied

Ref #187

include/components/renderer.hpp

@@ -57,6 +57,12 @@ class renderer {
   void debug_hints();
 #endif
 
+ protected:
+  struct reserve_area {
+    edge side{edge::NONE};
+    uint16_t size{0U};
+  };
+
  private:
   connection& m_connection;
   const logger& m_log;
@@ -66,6 +72,9 @@ class renderer {
 
   xcb_rectangle_t m_rect{0, 0, 0U, 0U};
 
+  xcb_rectangle_t m_cleared{0, 0, 0U, 0U};
+  reserve_area m_cleararea{};
+
   xcb_window_t m_window;
   xcb_colormap_t m_colormap;
   xcb_visualtype_t* m_visual;

include/x11/generic.hpp

@@ -0,0 +1,24 @@
+#pragma once
+
+#include <xcb/xcb.h>
+
+#include "common.hpp"
+
+POLYBAR_NS
+
+namespace {
+  inline bool operator==(const xcb_rectangle_t& a, const xcb_rectangle_t& b) {
+    return a.width == b.width && a.height == b.height && a.x == b.x && a.y == b.y;
+  }
+  inline bool operator!=(const xcb_rectangle_t& a, const xcb_rectangle_t& b) {
+    return !(a == b);
+  }
+  inline bool operator==(const xcb_rectangle_t& a, int b) {
+    return a.width == b && a.height == b && a.x == b && a.y == b;
+  }
+  inline bool operator!=(const xcb_rectangle_t& a, int b) {
+    return !(a == b);
+  }
+}
+
+POLYBAR_NS_END

include/x11/tray.hpp

@@ -68,6 +68,10 @@ class tray_client {
 
   ~tray_client();
 
+  uint16_t width() const;
+  uint16_t height() const;
+  void clear_window() const;
+
   bool match(const xcb_window_t& win) const;
   bool mapped() const;
   void mapped(bool state);
@@ -114,7 +118,7 @@ class tray_manager : public xpp::event::sink<evt::expose, evt::visibility_notify
   void reconfigure_clients();
   void reconfigure_bg(bool realloc = false);
   void refresh_window();
-  void redraw_window();
+  void redraw_window(bool realloc_bg = false);
 
   void query_atom();
   void create_window();

src/components/renderer.cpp

@@ -1,9 +1,11 @@
 #include "components/renderer.hpp"
 #include "components/logger.hpp"
+#include "components/types.hpp"
 #include "errors.hpp"
 #include "x11/connection.hpp"
 #include "x11/draw.hpp"
 #include "x11/fonts.hpp"
+#include "x11/generic.hpp"
 #include "x11/winspec.hpp"
 #include "x11/xlib.hpp"
 #include "x11/xutils.hpp"
@@ -206,7 +208,39 @@ void renderer::flush(bool clear) {
   right.width += m_bar.borders.at(edge::RIGHT).size;
   right.height += m_bar.size.h;
 
-  m_log.trace("renderer: copy pixmap (clear=%i)", clear);
+  // Calculate the area that was reserved so that we
+  // can clear any previous content drawn at the same location
+  xcb_rectangle_t clear_area{0, 0, 0U, 0U};
+
+  if (m_cleararea.size && m_cleararea.side == edge::RIGHT) {
+    clear_area.x = m_bar.size.w - m_cleararea.size;
+    clear_area.y = 0;
+    clear_area.width = m_cleararea.size;
+    clear_area.height = m_bar.size.h;
+  } else if (m_cleararea.size && m_cleararea.side == edge::LEFT) {
+    clear_area.x = m_rect.x;
+    clear_area.y = m_rect.y;
+    clear_area.width = m_cleararea.size;
+    clear_area.height = m_rect.height;
+  } else if (m_cleararea.size && m_cleararea.side == edge::TOP) {
+    clear_area.x = m_rect.x;
+    clear_area.y = m_rect.y;
+    clear_area.width = m_rect.width;
+    clear_area.height = m_cleararea.size;
+  } else if (m_cleararea.size && m_cleararea.side == edge::TOP) {
+    clear_area.x = m_rect.x;
+    clear_area.y = m_rect.y + m_rect.height - m_cleararea.size;
+    clear_area.width = m_rect.width;
+    clear_area.height = m_cleararea.size;
+  }
+
+  if (clear_area != m_cleared && clear_area != 0) {
+    m_log.trace("renderer: clearing area %dx%d+%d+%d", clear_area.width, clear_area.height, clear_area.x, clear_area.y);
+    m_connection.clear_area(0, m_window, clear_area.x, clear_area.y, clear_area.width, clear_area.height);
+    m_cleared = clear_area;
+  }
+
+  m_log.trace("renderer: copy pixmap (clear=%i, geom=%dx%d+%d+%d)", clear, r.width, r.height, r.x, r.y);
   m_connection.copy_area(m_pixmap, m_window, m_gcontexts.at(gc::FG), 0, 0, r.x, r.y, r.width, r.height);
 
   m_log.trace_x("renderer: draw top border (%lupx, %08x)", top.height, m_bar.borders.at(edge::TOP).color);
@@ -234,6 +268,9 @@ void renderer::flush(bool clear) {
 void renderer::reserve_space(edge side, uint16_t w) {
   m_log.trace_x("renderer: reserve_space(%i, %i)", static_cast<uint8_t>(side), w);
 
+  m_cleararea.side = side;
+  m_cleararea.size = w;
+
   switch (side) {
     case edge::NONE:
       break;

src/x11/tray.cpp

@@ -52,6 +52,22 @@ tray_client::~tray_client() {
   xembed::unembed(m_connection, window(), m_connection.root());
 }
 
+uint16_t tray_client::width() const {
+  return m_width;
+}
+
+uint16_t tray_client::height() const {
+  return m_height;
+}
+
+void tray_client::clear_window() const {
+  try {
+    m_connection.clear_area_checked(1, window(), 0, 0, width(), height());
+  } catch (const xpp::x::error::window& err) {
+    // ignore
+  }
+}
+
 /**
  * Match given window against client window
  */
@@ -399,8 +415,19 @@ void tray_manager::reconfigure_bg(bool realloc) {
     return m_log.err("Failed to get root pixmap for tray background (realloc=%i)", realloc);
   }
 
-  m_log.trace("tray: rootpixmap=%x (%dx%d+%d+%d), tray=%x, pixmap=%x, gc=%x", m_rootpixmap.pixmap, m_rootpixmap.width,
-      m_rootpixmap.height, m_rootpixmap.x, m_rootpixmap.y, m_tray, m_pixmap, m_gc);
+  if (realloc) {
+    // clang-format off
+    m_log.info("Tray root pixmap (rootpmap=%s, geom=%dx%d+%d+%d, tray=%s, pmap=%s, gc=%s)",
+        m_connection.id(m_rootpixmap.pixmap),
+        m_rootpixmap.width,
+        m_rootpixmap.height,
+        m_rootpixmap.x,
+        m_rootpixmap.y,
+        m_connection.id(m_tray),
+        m_connection.id(m_pixmap),
+        m_connection.id(m_gc));
+    // clang-format on
+  }
 
   m_prevwidth = w;
   m_prevheight = h;
@@ -411,6 +438,14 @@ void tray_manager::reconfigure_bg(bool realloc) {
   auto px = m_rootpixmap.x + x;
   auto py = m_rootpixmap.y + y;
 
+  // Make sure we don't try to copy void content
+  if (px + w > m_rootpixmap.width) {
+    w -= px + w - m_rootpixmap.width;
+  }
+  if (py + h > m_rootpixmap.height) {
+    h -= py + h - m_rootpixmap.height;
+  }
+
   if (realloc) {
     vector<uint8_t> image_data;
     uint8_t image_depth;
@@ -461,10 +496,10 @@ void tray_manager::refresh_window() {
     draw_util::fill(m_connection, m_pixmap, m_gc, 0, 0, width, height);
   }
 
-  m_connection.clear_area(1, m_tray, 0, 0, width, height);
+  m_connection.clear_area(0, m_tray, 0, 0, width, height);
 
   for (auto&& client : m_clients) {
-    m_connection.clear_area(1, client->window(), 0, 0, m_opts.width, height);
+    client->clear_window();
   }
 
   m_connection.flush();
@@ -473,9 +508,9 @@ void tray_manager::refresh_window() {
 /**
  * Redraw window
  */
-void tray_manager::redraw_window() {
+void tray_manager::redraw_window(bool realloc_bg) {
   m_log.info("Redraw tray container (id=%s)", m_connection.id(m_tray));
-  reconfigure_bg(true);
+  reconfigure_bg(realloc_bg);
   refresh_window();
 }
 
@@ -501,7 +536,9 @@ void tray_manager::create_window() {
     << cw_pos(calculate_x(calculate_w()), calculate_y())
     << cw_class(XCB_WINDOW_CLASS_INPUT_OUTPUT)
     << cw_params_backing_store(XCB_BACKING_STORE_WHEN_MAPPED)
-    << cw_params_event_mask(XCB_EVENT_MASK_SUBSTRUCTURE_REDIRECT | XCB_EVENT_MASK_STRUCTURE_NOTIFY)
+    << cw_params_event_mask(XCB_EVENT_MASK_SUBSTRUCTURE_REDIRECT
+                           |XCB_EVENT_MASK_STRUCTURE_NOTIFY
+                           |XCB_EVENT_MASK_EXPOSURE)
     << cw_params_override_redirect(true);
   // clang-format on
 
@@ -880,7 +917,6 @@ int tray_manager::mapped_clients() const {
  */
 void tray_manager::handle(const evt::expose& evt) {
   if (m_activated && !m_clients.empty() && evt->count == 0) {
-    reconfigure_window();
     redraw_window();
   }
 }
@@ -1001,11 +1037,11 @@ void tray_manager::handle(const evt::property_notify& evt) {
   if (!m_activated) {
     return;
   } else if (evt->atom == _XROOTMAP_ID) {
-    redraw_window();
+    redraw_window(true);
   } else if (evt->atom == _XSETROOT_ID) {
-    redraw_window();
+    redraw_window(true);
   } else if (evt->atom == ESETROOT_PMAP_ID) {
-    redraw_window();
+    redraw_window(true);
   } else if (evt->atom == _XEMBED_INFO) {
     auto client = find_client(evt->window);