Add ghost plugin

Allows windows to become click-through.

metadata/ghost.xml

@@ -0,0 +1,17 @@
+<?xml version="1.0"?>
+<wayfire>
+	<plugin name="ghost">
+	<_short>Ghost Windows</_short>
+	<category>Window Management</category>
+	<option name="ghost_match" type="string">
+		<_short>Ghosted Windows</_short>
+		<_long>Automatically sets the matched windows to be click-through.</_long>
+		<default></default>
+	</option>
+	<option name="ghost_window" type="activator">
+		<_short>Ghost Window</_short>
+		<_long>Makes the active window click-through to whatever is below.</_long>
+		<default></default>
+	</option>
+	</plugin>
+</wayfire>

metadata/meson.build

@@ -7,6 +7,7 @@ install_data('focus-change.xml', install_dir: wayfire.get_variable(pkgconfig: 'm
 install_data('focus-steal-prevent.xml', install_dir: wayfire.get_variable(pkgconfig: 'metadatadir'))
 install_data('follow-focus.xml', install_dir: wayfire.get_variable(pkgconfig: 'metadatadir'))
 install_data('force-fullscreen.xml', install_dir: wayfire.get_variable(pkgconfig: 'metadatadir'))
+install_data('ghost.xml', install_dir: wayfire.get_variable(pkgconfig: 'metadatadir'))
 install_data('hide-cursor.xml', install_dir: wayfire.get_variable(pkgconfig: 'metadatadir'))
 install_data('join-views.xml', install_dir: wayfire.get_variable(pkgconfig: 'metadatadir'))
 install_data('keycolor.xml', install_dir: wayfire.get_variable(pkgconfig: 'metadatadir'))

src/ghost.cpp

@@ -0,0 +1,117 @@
+#include <wayfire/output.hpp>
+#include <wayfire/opengl.hpp>
+#include <wayfire/core.hpp>
+#include <wayfire/plugin.hpp>
+#include <wayfire/matcher.hpp>
+#include <wayfire/view-transform.hpp>
+#include <wayfire/signal-definitions.hpp>
+#include <wayfire/toplevel-view.hpp>
+#include <wayfire/window-manager.hpp>
+#include <wayfire/view-transform.hpp>
+#include <wayfire/txn/transaction-manager.hpp>
+#include <wayfire/scene-render.hpp>
+#include <wayfire/plugins/ipc/ipc-activator.hpp>
+
+const std::string shade_transformer_name = "ghost_transformer";
+
+namespace wf
+{
+namespace ghost
+{
+using namespace wf::scene;
+class ghost_view : public wf::scene::view_2d_transformer_t
+{
+    wayfire_view view;
+
+  public:
+
+    ghost_view(wayfire_view view) : wf::scene::view_2d_transformer_t(view)
+    {
+        this->view = view;
+    }
+
+    std::optional<wf::scene::input_node_t> find_node_at(const wf::pointf_t& at) override
+    {
+        return {};
+    }
+
+    virtual ~ghost_view()
+    {}
+};
+
+class ghost_plugin : public wf::plugin_interface_t
+{
+    wf::ipc_activator_t ghost_window{"ghost/ghost_window"};
+    wf::view_matcher_t ghost_match{"ghost/ghost_match"};
+
+    void pop_transformer(wayfire_view view)
+    {
+        if (view->get_transformed_node()->get_transformer(shade_transformer_name))
+        {
+            view->get_transformed_node()->rem_transformer(shade_transformer_name);
+        }
+    }
+
+    void remove_shade_transformers()
+    {
+        for (auto& view : wf::get_core().get_all_views())
+        {
+            pop_transformer(view);
+        }
+    }
+
+    std::shared_ptr<wf::ghost::ghost_view> ensure_transformer(wayfire_view view)
+    {
+        auto tmgr = view->get_transformed_node();
+        if (auto tr = tmgr->get_transformer<wf::ghost::ghost_view>(shade_transformer_name))
+        {
+            return tr;
+        }
+
+        auto node = std::make_shared<wf::ghost::ghost_view>(view);
+        tmgr->add_transformer(node, wf::TRANSFORMER_2D, shade_transformer_name);
+        auto tr = tmgr->get_transformer<wf::ghost::ghost_view>(shade_transformer_name);
+
+        return tr;
+    }
+
+  public:
+
+    void init() override
+    {
+        for (auto& view : wf::get_core().get_all_views())
+        {
+            if (ghost_match.matches(view))
+            {
+                ensure_transformer(view);
+            }
+        }
+
+        ghost_window.set_handler(ghost_view_cb);
+        wf::get_core().connect(&on_view_map);
+    }
+
+    wf::ipc_activator_t::handler_t ghost_view_cb = [=] (wf::output_t *output, wayfire_view view)
+    {
+        ensure_transformer(view);
+        return true;
+    };
+
+    wf::signal::connection_t<wf::view_mapped_signal> on_view_map = [=] (wf::view_mapped_signal *ev)
+    {
+        if (ghost_match.matches(ev->view))
+        {
+            ensure_transformer(ev->view);
+        }
+    };
+
+    void fini() override
+    {
+        remove_shade_transformers();
+        on_view_map.disconnect();
+    }
+};
+}
+}
+
+DECLARE_WAYFIRE_PLUGIN(wf::ghost::ghost_plugin);

src/meson.build

@@ -36,6 +36,10 @@ force_fullscreen = shared_module('force-fullscreen', 'force-fullscreen.cpp',
     dependencies: [wayfire],
     install: true, install_dir: join_paths(get_option('libdir'), 'wayfire'))
 
+ghost = shared_module('ghost', 'ghost.cpp',
+    dependencies: [wayfire],
+    install: true, install_dir: join_paths(get_option('libdir'), 'wayfire'))
+
 if giomm.found()
 glib_main_loop = shared_module('glib-main-loop', 'glib-main-loop.cpp',
     dependencies: [wayfire, giomm],