config: add <core><primarySelection>

...to enable/disable primary selection clipboard support. This only works
on launch.

The reason it is useful to be able to disable this is that some clients
(like browsers) support middle-button-click to start scrolling up/down.

With some clients can be disabled via

   gsettings set org.gnome.desktop.interface gtk-enable-primary-paste false

...but for others (like chromium and electron based programs) a compositor
setting is required.

Fixes: #2815

docs/labwc-config.5.scd

@@ -177,6 +177,7 @@ this is for compatibility with Openbox.
   <autoEnableOutputs>yes</autoEnableOutputs>
   <reuseOutputMode>no</reuseOutputMode>
   <xwaylandPersistence>no</xwaylandPersistence>
+  <primarySelection>yes</primarySelection>
 </core>
 ```
 
@@ -235,6 +236,12 @@ this is for compatibility with Openbox.
 
 	Note: changing this setting requires a restart of labwc.
 
+*<core><primarySelection>* [yes|no]
+	Enable or disable the primary selection clipboard. May only be
+	configured at launch. This enables autoscroll (middle-click to scroll
+	up/down) in Chromium and electron based clients without inadvertantly
+	pasting the primary clipboard. Default is yes.
+
 ## PLACEMENT
 
 ```

docs/rc.xml.all

@@ -15,6 +15,7 @@
     <autoEnableOutputs>yes</autoEnableOutputs>
     <reuseOutputMode>no</reuseOutputMode>
     <xwaylandPersistence>no</xwaylandPersistence>
+    <primarySelection>yes</primarySelection>
   </core>
 
   <placement>

include/config/rcxml.h

@@ -73,6 +73,7 @@ struct rcxml {
 	bool reuse_output_mode;
 	enum view_placement_policy placement_policy;
 	bool xwayland_persistence;
+	bool primary_selection;
 	int placement_cascade_offset_x;
 	int placement_cascade_offset_y;
 

src/config/rcxml.c

@@ -1161,6 +1161,8 @@ entry(xmlNode *node, char *nodename, char *content, struct parser_state *state)
 		set_bool(content, &rc.reuse_output_mode);
 	} else if (!strcasecmp(nodename, "xwaylandPersistence.core")) {
 		set_bool(content, &rc.xwayland_persistence);
+	} else if (!strcasecmp(nodename, "primarySelection.core")) {
+		set_bool(content, &rc.primary_selection);
 	} else if (!strcmp(nodename, "policy.placement")) {
 		enum view_placement_policy policy = view_placement_parse(content);
 		if (policy != LAB_PLACE_INVALID) {
@@ -1549,6 +1551,7 @@ rcxml_init(void)
 	rc.auto_enable_outputs = true;
 	rc.reuse_output_mode = false;
 	rc.xwayland_persistence = false;
+	rc.primary_selection = true;
 
 	init_font_defaults(&rc.font_activewindow);
 	init_font_defaults(&rc.font_inactivewindow);

src/server.c

@@ -632,7 +632,9 @@ server_init(struct server *server)
 	 *
 	 * https://wayfire.org/2020/08/04/Wayfire-0-5.html
 	 */
-	wlr_primary_selection_v1_device_manager_create(server->wl_display);
+	if (rc.primary_selection) {
+		wlr_primary_selection_v1_device_manager_create(server->wl_display);
+	}
 
 	server->input_method_manager = wlr_input_method_manager_v2_create(
 		server->wl_display);