commands: Learn mouse_warping.

Place mouse at center of focused view when changing to a workspace on a
different output, if option is enabled. (This replicates existing i3
option.)

This can be triggered in multiple ways:
A) via `workspace <name>` which changes output
B) via `focus <direction>` which changes output
C) via `focus output <name>` which (obviously) changes output

6 files changed, 64 insertions, 9 deletions

diff --git a/include/commands.h b/include/commands.h
index 8e53c74d..f6777930 100644
--- a/include/commands.h
+++ b/include/commands.h
@@ -2,6 +2,7 @@
 #define _SWAY_COMMANDS_H
 #include <stdbool.h>
 #include <json-c/json.h>
+#include <wlc/wlc.h>
 #include "config.h"
 
 
diff --git a/include/input_state.h b/include/input_state.h
index dd5d71a8..52759052 100644
--- a/include/input_state.h
+++ b/include/input_state.h
@@ -66,6 +66,7 @@ extern struct pointer_state {
 } pointer_state;
 
 void pointer_position_set(struct wlc_origin *new_origin, bool force_focus);
+void center_pointer_on(swayc_t *view);
 
 // on button release unset mode depending on the button.
 // on button press set mode conditionally depending on the button
diff --git a/sway.5.txt b/sway.5.txt
index dad55c5f..27735db6 100644
--- a/sway.5.txt
+++ b/sway.5.txt
@@ -102,6 +102,10 @@ Commands
         Moves the focused container to the workspace identified by _name_.
         _name_ may be a special workspace name. See **workspace**.
 
+**mouse_warping** <output|none>::
+        When _output_: place mouse at center of newly focused window when changing
+        output. When _none_: don't move mouse.
+
 **output** <name> <resolution|res WIDTHxHEIGHT> <position|pos X,Y>::
         Configures the specified output. It will use the given resolution and be
         arranged at the given position in the layout tree. You may omit either of
diff --git a/sway/commands.c b/sway/commands.c
index 441b6fd7..00a4d1b0 100644
--- a/sway/commands.c
+++ b/sway/commands.c
@@ -21,6 +21,7 @@
 #include "handlers.h"
 #include "sway.h"
 #include "resize.h"
+#include "input_state.h"
 
 typedef struct cmd_results *sway_cmd(int argc, char **argv);
 
@@ -45,6 +46,7 @@ static sway_cmd cmd_kill;
 static sway_cmd cmd_layout;
 static sway_cmd cmd_log_colors;
 static sway_cmd cmd_mode;
+static sway_cmd cmd_mouse_warping;
 static sway_cmd cmd_move;
 static sway_cmd cmd_output;
 static sway_cmd cmd_reload;
@@ -383,9 +385,13 @@ static struct cmd_results *cmd_focus(int argc, char **argv) {
                 } else if (!workspace_switch(swayc_active_workspace_for(output))) {
                         return cmd_results_new(CMD_FAILURE, "focus output",
                                 "Switching to workspace on output '%s' was blocked", argv[1]);
-                } else {
-                        return cmd_results_new(CMD_SUCCESS, NULL, NULL);
+                } else if (config->mouse_warping) {
+                        swayc_t *focused = get_focused_view(output);
+                        if (focused && focused->type == C_VIEW) {
+                                center_pointer_on(focused);
+                        }
                 }
+                return cmd_results_new(CMD_SUCCESS, NULL, NULL);
         } else if ((error = checkarg(argc, "focus", EXPECTED_EQUAL_TO, 1))) {
                 return error;
         }
@@ -528,6 +534,20 @@ static struct cmd_results *cmd_mode(int argc, char **argv) {
         return cmd_results_new(mode_make ? CMD_BLOCK_MODE : CMD_SUCCESS, NULL, NULL);
 }
 
+static struct cmd_results *cmd_mouse_warping(int argc, char **argv) {
+        struct cmd_results *error = NULL;
+        if ((error = checkarg(argc, "mouse_warping", EXPECTED_EQUAL_TO, 1))) {
+                return error;
+        } else if (strcasecmp(argv[0], "output") == 0) {
+                config->mouse_warping = true;
+        } else if (strcasecmp(argv[0], "none") == 0) {
+                config->mouse_warping = false;
+        } else {
+                return cmd_results_new(CMD_FAILURE, "mouse_warping", "Expected 'mouse_warping output|none'");
+        }
+        return cmd_results_new(CMD_SUCCESS, NULL, NULL);
+}
+
 static struct cmd_results *cmd_move(int argc, char **argv) {
         struct cmd_results *error = NULL;
         if (config->reading) return cmd_results_new(CMD_FAILURE, "move", "Can't be used in config file.");
@@ -1165,7 +1185,16 @@ static struct cmd_results *cmd_workspace(int argc, char **argv) {
                                 ws = workspace_create(argv[0]);
                         }
                 }
+                swayc_t *old_output = swayc_active_output();
                 workspace_switch(ws);
+                swayc_t *new_output = swayc_active_output();
+
+                if (config->mouse_warping && old_output != new_output) {
+                        swayc_t *focused = get_focused_view(ws);
+                        if (focused && focused->type == C_VIEW) {
+                                center_pointer_on(focused);
+                        }
+                }
         } else {
                 if (strcasecmp(argv[1], "output") == 0) {
                         if ((error = checkarg(argc, "workspace", EXPECTED_EQUAL_TO, 3))) {
@@ -1217,6 +1246,7 @@ static struct cmd_handler handlers[] = {
         { "layout", cmd_layout },
         { "log_colors", cmd_log_colors },
         { "mode", cmd_mode },
+        { "mouse_warping", cmd_mouse_warping },
         { "move", cmd_move },
         { "output", cmd_output },
         { "reload", cmd_reload },
diff --git a/sway/focus.c b/sway/focus.c
index 1aa7579b..7f0b1599 100644
--- a/sway/focus.c
+++ b/sway/focus.c
@@ -4,6 +4,8 @@
 #include "log.h"
 #include "workspace.h"
 #include "layout.h"
+#include "config.h"
+#include "input_state.h"
 
 bool locked_container_focus = false;
 bool locked_view_focus = false;
@@ -49,14 +51,24 @@ static void update_focus(swayc_t *c) {
 }
 
 bool move_focus(enum movement_direction direction) {
-        swayc_t *view = get_focused_container(&root_container);
-        view = get_swayc_in_direction(view, direction);
-        if (view) {
-                if (direction == MOVE_PARENT) {
-                        return set_focused_container(view);
-                } else {
-                        return set_focused_container(get_focused_view(view));
+        swayc_t *old_view = get_focused_container(&root_container);
+        swayc_t *new_view = get_swayc_in_direction(old_view, direction);
+        if (!new_view) {
+                return false;
+        } else if (direction == MOVE_PARENT) {
+                return set_focused_container(new_view);
+        } else if (config->mouse_warping) {
+                swayc_t *old_op = old_view->type == C_OUTPUT ?
+                        old_view : swayc_parent_by_type(old_view, C_OUTPUT);
+                swayc_t *focused = get_focused_view(new_view);
+                if (set_focused_container(focused)) {
+                        if (old_op != swayc_active_output() && focused && focused->type == C_VIEW) {
+                                center_pointer_on(focused);
+                        }
+                        return true;
                 }
+        } else {
+                return set_focused_container(get_focused_view(new_view));
         }
         return false;
 }
diff --git a/sway/input_state.c b/sway/input_state.c
index bd46a5ac..ee3dc7cf 100644
--- a/sway/input_state.c
+++ b/sway/input_state.c
@@ -185,6 +185,13 @@ void pointer_position_set(struct wlc_origin *new_origin, bool force_focus) {
         wlc_pointer_set_origin(new_origin);
 }
 
+void center_pointer_on(swayc_t *view) {
+        struct wlc_origin new_origin;
+        new_origin.x = view->x + view->width/2;
+        new_origin.y = view->y + view->height/2;
+        pointer_position_set(&new_origin, true);
+}
+
 // Mode set left/right click
 
 static void pointer_mode_set_left(void) {