Implement the output power management protocol.

I thought wlr-randr used this, but it doesn't so I don't even know what
this is for.

Makefile

@@ -16,7 +16,7 @@ LDLIBS    = `$(PKG_CONFIG) --libs $(PKGS)` $(LIBS)
 all: dwl
 dwl: dwl.o util.o
 	$(CC) dwl.o util.o $(LDLIBS) $(LDFLAGS) $(DWLCFLAGS) -o $@
-dwl.o: dwl.c config.mk config.h client.h xdg-shell-protocol.h wlr-layer-shell-unstable-v1-protocol.h
+dwl.o: dwl.c config.mk config.h client.h xdg-shell-protocol.h wlr-layer-shell-unstable-v1-protocol.h wlr-output-power-management-unstable-v1-protocol.h
 util.o: util.c util.h
 
 # wayland-scanner is a tool which generates C headers and rigging for Wayland
@@ -31,6 +31,9 @@ xdg-shell-protocol.h:
 wlr-layer-shell-unstable-v1-protocol.h:
 	$(WAYLAND_SCANNER) server-header \
 		protocols/wlr-layer-shell-unstable-v1.xml $@
+wlr-output-power-management-unstable-v1-protocol.h:
+	$(WAYLAND_SCANNER) server-header \
+		protocols/wlr-output-power-management-unstable-v1.xml $@
 
 config.h:
 	cp config.def.h $@

dwl.c

@@ -32,6 +32,7 @@
 #include <wlr/types/wlr_output.h>
 #include <wlr/types/wlr_output_layout.h>
 #include <wlr/types/wlr_output_management_v1.h>
+#include <wlr/types/wlr_output_power_management_v1.h>
 #include <wlr/types/wlr_pointer.h>
 #include <wlr/types/wlr_presentation_time.h>
 #include <wlr/types/wlr_primary_selection.h>
@@ -283,6 +284,7 @@ static void outputmgrtest(struct wl_listener *listener, void *data);
 static void pointerfocus(Client *c, struct wlr_surface *surface,
 		double sx, double sy, uint32_t time);
 static void printstatus(void);
+static void powermgrsetmodenotify(struct wl_listener *listener, void *data);
 static void quit(const Arg *arg);
 static void rendermon(struct wl_listener *listener, void *data);
 static void requeststartdrag(struct wl_listener *listener, void *data);
@@ -356,6 +358,9 @@ static struct wlr_session_lock_manager_v1 *session_lock_mgr;
 static struct wlr_scene_rect *locked_bg;
 static struct wlr_session_lock_v1 *cur_lock;
 
+static struct wlr_output_power_manager_v1 *power_mgr;
+static struct wl_listener power_mgr_set_mode = {.notify = powermgrsetmodenotify};
+
 static struct wlr_seat *seat;
 static struct wl_list keyboards;
 static unsigned int cursor_mode;
@@ -1885,6 +1890,14 @@ printstatus(void)
 	fflush(stdout);
 }
 
+void
+powermgrsetmodenotify(struct wl_listener *listener, void *data)
+{
+	struct wlr_output_power_v1_set_mode_event *event = data;
+	wlr_output_enable(event->output, event->mode);
+	wlr_output_commit(event->output);
+}
+
 void
 quit(const Arg *arg)
 {
@@ -2192,6 +2205,9 @@ setup(void)
 	activation = wlr_xdg_activation_v1_create(dpy);
 	wl_signal_add(&activation->events.request_activate, &request_activate);
 
+	power_mgr = wlr_output_power_manager_v1_create(dpy);
+	wl_signal_add(&power_mgr->events.set_mode, &power_mgr_set_mode);
+
 	/* Creates an output layout, which a wlroots utility for working with an
 	 * arrangement of screens in a physical layout. */
 	output_layout = wlr_output_layout_create();

protocols/wlr-output-power-management-unstable-v1.xml

@@ -0,0 +1,128 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<protocol name="wlr_output_power_management_unstable_v1">
+  <copyright>
+    Copyright © 2019 Purism SPC
+
+    Permission is hereby granted, free of charge, to any person obtaining a
+    copy of this software and associated documentation files (the "Software"),
+    to deal in the Software without restriction, including without limitation
+    the rights to use, copy, modify, merge, publish, distribute, sublicense,
+    and/or sell copies of the Software, and to permit persons to whom the
+    Software is furnished to do so, subject to the following conditions:
+
+    The above copyright notice and this permission notice (including the next
+    paragraph) shall be included in all copies or substantial portions of the
+    Software.
+
+    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+    IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+    FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+    THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+    LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+    FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+    DEALINGS IN THE SOFTWARE.
+  </copyright>
+
+  <description summary="Control power management modes of outputs">
+    This protocol allows clients to control power management modes
+    of outputs that are currently part of the compositor space. The
+    intent is to allow special clients like desktop shells to power
+    down outputs when the system is idle.
+
+    To modify outputs not currently part of the compositor space see
+    wlr-output-management.
+
+    Warning! The protocol described in this file is experimental and
+    backward incompatible changes may be made. Backward compatible changes
+    may be added together with the corresponding interface version bump.
+    Backward incompatible changes are done by bumping the version number in
+    the protocol and interface names and resetting the interface version.
+    Once the protocol is to be declared stable, the 'z' prefix and the
+    version number in the protocol and interface names are removed and the
+    interface version number is reset.
+  </description>
+
+  <interface name="zwlr_output_power_manager_v1" version="1">
+    <description summary="manager to create per-output power management">
+      This interface is a manager that allows creating per-output power
+      management mode controls.
+    </description>
+
+    <request name="get_output_power">
+      <description summary="get a power management for an output">
+        Create a output power management mode control that can be used to
+        adjust the power management mode for a given output.
+      </description>
+      <arg name="id" type="new_id" interface="zwlr_output_power_v1"/>
+      <arg name="output" type="object" interface="wl_output"/>
+    </request>
+
+    <request name="destroy" type="destructor">
+      <description summary="destroy the manager">
+        All objects created by the manager will still remain valid, until their
+        appropriate destroy request has been called.
+      </description>
+    </request>
+  </interface>
+
+  <interface name="zwlr_output_power_v1" version="1">
+    <description summary="adjust power management mode for an output">
+      This object offers requests to set the power management mode of
+      an output.
+    </description>
+
+    <enum name="mode">
+      <entry name="off" value="0"
+             summary="Output is turned off."/>
+      <entry name="on" value="1"
+             summary="Output is turned on, no power saving"/>
+    </enum>
+
+    <enum name="error">
+      <entry name="invalid_mode" value="1" summary="inexistent power save mode"/>
+    </enum>
+
+    <request name="set_mode">
+      <description summary="Set an outputs power save mode">
+        Set an output's power save mode to the given mode. The mode change
+        is effective immediately. If the output does not support the given
+        mode a failed event is sent.
+      </description>
+      <arg name="mode" type="uint" enum="mode" summary="the power save mode to set"/>
+    </request>
+
+    <event name="mode">
+      <description summary="Report a power management mode change">
+        Report the power management mode change of an output.
+
+        The mode event is sent after an output changed its power
+        management mode. The reason can be a client using set_mode or the
+        compositor deciding to change an output's mode.
+        This event is also sent immediately when the object is created
+        so the client is informed about the current power management mode.
+      </description>
+      <arg name="mode" type="uint" enum="mode"
+           summary="the output's new power management mode"/>
+    </event>
+
+    <event name="failed">
+      <description summary="object no longer valid">
+        This event indicates that the output power management mode control
+        is no longer valid. This can happen for a number of reasons,
+        including:
+        - The output doesn't support power management
+        - Another client already has exclusive power management mode control
+          for this output
+        - The output disappeared
+
+        Upon receiving this event, the client should destroy this object.
+      </description>
+    </event>
+
+    <request name="destroy" type="destructor">
+      <description summary="destroy this power management">
+        Destroys the output power management mode control object.
+      </description>
+    </request>
+  </interface>
+</protocol>