Import tinywl into the project, starting the compositor phase.

Right now nothing interesting is happening, but the new tinywl
implementation is successfully loading a plugin and calling a handler
for 'handle keybinding', which is pretty slick.

8 files changed, 1062 insertions, 9 deletions

diff --git a/harness/CMakeLists.txt b/harness/CMakeLists.txt
index a254afd..a9bad8b 100644
--- a/harness/CMakeLists.txt
+++ b/harness/CMakeLists.txt
@@ -4,7 +4,34 @@ project (
   VERSION 0.1
   LANGUAGES C)
 
-include_directories(include/)
+set(CMAKE_VERBOSE_MAKEFILE ON)
+set(CMAKE_BUILD_TYPE Debug)
+
+include_directories(include/ ../wlroots/include /usr/include/pixman-1 ${CMAKE_CURRENT_BINARY_DIR}/)
+
+add_definitions(-DWLR_USE_UNSTABLE)
+
+execute_process(
+  COMMAND pkg-config --variable=pkgdatadir wayland-protocols
+  OUTPUT_VARIABLE WAYLAND_PROTOCOLS
+  RESULT_VARIABLE ec
+  OUTPUT_STRIP_TRAILING_WHITESPACE
+)
+if(${ec} EQUAL 0)
+else()
+  message(FATAL_ERROR "Failed to execute pkg-config")
+endif()
+
+execute_process(
+  COMMAND pkg-config --variable=wayland_scanner wayland-scanner
+  OUTPUT_VARIABLE WAYLAND_SCANNER
+  RESULT_VARIABLE ec
+  OUTPUT_STRIP_TRAILING_WHITESPACE
+)
+if(${ec} EQUAL 0)
+else()
+  message(FATAL_ERROR "Failed to execute pkg-config")
+endif()
 
 set(PLUGIN_INTF ${CMAKE_BINARY_DIR}/plugin_interface.h)
 add_custom_command(
@@ -24,10 +51,28 @@ add_custom_command(
   DEPENDS ${PROJECT_SOURCE_DIR}/tools/genbuild.pl
 )
 
+add_custom_command(
+  OUTPUT xdg-shell-protocol.h
+  COMMAND ${WAYLAND_SCANNER} server-header
+    ${WAYLAND_PROTOCOLS}/stable/xdg-shell/xdg-shell.xml
+    xdg-shell-protocol.h
+)
+
+add_custom_command(
+  OUTPUT xdg-shell-protocol.c
+  COMMAND ${WAYLAND_SCANNER} private-code
+    ${WAYLAND_PROTOCOLS}/stable/xdg-shell/xdg-shell.xml
+    xdg-shell-protocol.c
+  DEPENDS xdg-shell-protocol.h
+)
+
 file (GLOB_RECURSE SOURCES src/*.c)
 
 set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
 
-add_executable (wtr_harness ${SOURCES} ${PLUGIN_LOAD} ${PLUGIN_INTF})
+add_executable (wtr_harness ${SOURCES} ${PLUGIN_LOAD} ${PLUGIN_INTF}
+  xdg-shell-protocol.c)
 
 target_link_libraries(wtr_harness dl)
+target_link_directories(wtr_harness PUBLIC "../wlroots/build/")
+target_link_libraries(wtr_harness wlroots wayland-server xkbcommon)
diff --git a/harness/include/plugin.h b/harness/include/plugin.h
index db15401..651e2f1 100644
--- a/harness/include/plugin.h
+++ b/harness/include/plugin.h
@@ -92,6 +92,11 @@ typedef struct PLUGIN {
    */
   EXPORT(void (*plugin_teardown)(opqst_t));
 
+  /*
+   * Handles a keybinding.
+   */
+  EXPORT(opqst_t (*plugin_handle_keybinding)(uint32_t keysym, opqst_t state));
+
 } plugin_t;
 
 /** Loads a plugin from the dynamic library handle. Returns a non-zero error
diff --git a/harness/src/main.c b/harness/src/main.c
index 2e22b36..336cafe 100644
--- a/harness/src/main.c
+++ b/harness/src/main.c
@@ -58,7 +58,7 @@ void run_plugin(int argc, char **argv, plugin_t *plugin) {
   return;
 }
 
-int main(int argc, char **argv) {
+int main_(int argc, char **argv) {
   if (!argv[0] && !argv[1]) {
     fprintf(stderr, "Missing argument.\n");
     return 1;
diff --git a/harness/src/plugin.c b/harness/src/plugin.c
index 941cc01..d71608a 100644
--- a/harness/src/plugin.c
+++ b/harness/src/plugin.c
@@ -45,6 +45,7 @@ int read_plugin_from_file(const char *filename, plugin_t *plugin) {
     return 1;
   }
 
+  printf("Loading file.\n");
   return load_plugin_from_dl(lib, plugin);
 }
 
diff --git a/harness/src/wl.c b/harness/src/wl.c
new file mode 100644
index 0000000..aac2bf8
--- /dev/null
+++ b/harness/src/wl.c
@@ -0,0 +1,988 @@
+#define _POSIX_C_SOURCE 200112L
+#include "plugin.h"
+#include <getopt.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <time.h>
+#include <unistd.h>
+#include <wayland-server-core.h>
+#include <wlr/backend.h>
+#include <wlr/render/wlr_renderer.h>
+#include <wlr/types/wlr_compositor.h>
+#include <wlr/types/wlr_cursor.h>
+#include <wlr/types/wlr_data_device.h>
+#include <wlr/types/wlr_input_device.h>
+#include <wlr/types/wlr_keyboard.h>
+#include <wlr/types/wlr_matrix.h>
+#include <wlr/types/wlr_output.h>
+#include <wlr/types/wlr_output_layout.h>
+#include <wlr/types/wlr_pointer.h>
+#include <wlr/types/wlr_seat.h>
+#include <wlr/types/wlr_xcursor_manager.h>
+#include <wlr/types/wlr_xdg_shell.h>
+#include <wlr/util/log.h>
+#include <xkbcommon/xkbcommon.h>
+
+/* For brevity's sake, struct members are annotated where they are used. */
+enum tinywl_cursor_mode {
+  TINYWL_CURSOR_PASSTHROUGH,
+  TINYWL_CURSOR_MOVE,
+  TINYWL_CURSOR_RESIZE,
+};
+
+struct tinywl_server {
+  struct wl_display *wl_display;
+  struct wlr_backend *backend;
+  struct wlr_renderer *renderer;
+
+  struct wlr_xdg_shell *xdg_shell;
+  struct wl_listener new_xdg_surface;
+  struct wl_list views;
+
+  struct wlr_cursor *cursor;
+  struct wlr_xcursor_manager *cursor_mgr;
+  struct wl_listener cursor_motion;
+  struct wl_listener cursor_motion_absolute;
+  struct wl_listener cursor_button;
+  struct wl_listener cursor_axis;
+  struct wl_listener cursor_frame;
+
+  struct wlr_seat *seat;
+  struct wl_listener new_input;
+  struct wl_listener request_cursor;
+  struct wl_listener request_set_selection;
+  struct wl_list keyboards;
+  enum tinywl_cursor_mode cursor_mode;
+  struct tinywl_view *grabbed_view;
+  double grab_x, grab_y;
+  struct wlr_box grab_geobox;
+  uint32_t resize_edges;
+
+  struct wlr_output_layout *output_layout;
+  struct wl_list outputs;
+  struct wl_listener new_output;
+
+  plugin_t plugin;
+};
+
+struct tinywl_output {
+  struct wl_list link;
+  struct tinywl_server *server;
+  struct wlr_output *wlr_output;
+  struct wl_listener frame;
+};
+
+struct tinywl_view {
+  struct wl_list link;
+  struct tinywl_server *server;
+  struct wlr_xdg_surface *xdg_surface;
+  struct wl_listener map;
+  struct wl_listener unmap;
+  struct wl_listener destroy;
+  struct wl_listener request_move;
+  struct wl_listener request_resize;
+  bool mapped;
+  int x, y;
+};
+
+struct tinywl_keyboard {
+  struct wl_list link;
+  struct tinywl_server *server;
+  struct wlr_input_device *device;
+
+  struct wl_listener modifiers;
+  struct wl_listener key;
+};
+
+static void focus_view(struct tinywl_view *view, struct wlr_surface *surface) {
+  /* Note: this function only deals with keyboard focus. */
+  if (view == NULL) {
+    return;
+  }
+  struct tinywl_server *server = view->server;
+  struct wlr_seat *seat = server->seat;
+  struct wlr_surface *prev_surface = seat->keyboard_state.focused_surface;
+  if (prev_surface == surface) {
+    /* Don't re-focus an already focused surface. */
+    return;
+  }
+  if (prev_surface) {
+    /*
+     * Deactivate the previously focused surface. This lets the client know
+     * it no longer has focus and the client will repaint accordingly, e.g.
+     * stop displaying a caret.
+     */
+    struct wlr_xdg_surface *previous =
+        wlr_xdg_surface_from_wlr_surface(seat->keyboard_state.focused_surface);
+    wlr_xdg_toplevel_set_activated(previous, false);
+  }
+  struct wlr_keyboard *keyboard = wlr_seat_get_keyboard(seat);
+  /* Move the view to the front */
+  wl_list_remove(&view->link);
+  wl_list_insert(&server->views, &view->link);
+  /* Activate the new surface */
+  wlr_xdg_toplevel_set_activated(view->xdg_surface, true);
+  /*
+   * Tell the seat to have the keyboard enter this surface. wlroots will keep
+   * track of this and automatically send key events to the appropriate
+   * clients without additional work on your part.
+   */
+  wlr_seat_keyboard_notify_enter(seat, view->xdg_surface->surface,
+                                 keyboard->keycodes, keyboard->num_keycodes,
+                                 &keyboard->modifiers);
+}
+
+static void keyboard_handle_modifiers(struct wl_listener *listener,
+                                      void *data) {
+  /* This event is raised when a modifier key, such as shift or alt, is
+   * pressed. We simply communicate this to the client. */
+  struct tinywl_keyboard *keyboard =
+      wl_container_of(listener, keyboard, modifiers);
+  /*
+   * A seat can only have one keyboard, but this is a limitation of the
+   * Wayland protocol - not wlroots. We assign all connected keyboards to the
+   * same seat. You can swap out the underlying wlr_keyboard like this and
+   * wlr_seat handles this transparently.
+   */
+  wlr_seat_set_keyboard(keyboard->server->seat, keyboard->device);
+  /* Send modifiers to the client. */
+  wlr_seat_keyboard_notify_modifiers(keyboard->server->seat,
+                                     &keyboard->device->keyboard->modifiers);
+}
+
+static bool handle_keybinding(struct tinywl_server *server, xkb_keysym_t sym) {
+  server->plugin.state =
+      server->plugin.plugin_handle_keybinding(sym, server->plugin.state);
+  /*
+   * Here we handle compositor keybindings. This is when the compositor is
+   * processing keys, rather than passing them on to the client for its own
+   * processing.
+   *
+   * This function assumes Alt is held down.
+   */
+  switch (sym) {
+  case XKB_KEY_Escape:
+    wl_display_terminate(server->wl_display);
+    break;
+  case XKB_KEY_F1:
+    /* Cycle to the next view */
+    if (wl_list_length(&server->views) < 2) {
+      break;
+    }
+    struct tinywl_view *current_view =
+        wl_container_of(server->views.next, current_view, link);
+    struct tinywl_view *next_view =
+        wl_container_of(current_view->link.next, next_view, link);
+    focus_view(next_view, next_view->xdg_surface->surface);
+    /* Move the previous view to the end of the list */
+    wl_list_remove(&current_view->link);
+    wl_list_insert(server->views.prev, &current_view->link);
+    break;
+  default:
+    return false;
+  }
+  return true;
+}
+
+static void keyboard_handle_key(struct wl_listener *listener, void *data) {
+  /* This event is raised when a key is pressed or released. */
+  struct tinywl_keyboard *keyboard = wl_container_of(listener, keyboard, key);
+  struct tinywl_server *server = keyboard->server;
+  struct wlr_event_keyboard_key *event = data;
+  struct wlr_seat *seat = server->seat;
+
+  /* Translate libinput keycode -> xkbcommon */
+  uint32_t keycode = event->keycode + 8;
+  /* Get a list of keysyms based on the keymap for this keyboard */
+  const xkb_keysym_t *syms;
+  int nsyms = xkb_state_key_get_syms(keyboard->device->keyboard->xkb_state,
+                                     keycode, &syms);
+
+  bool handled = false;
+  uint32_t modifiers = wlr_keyboard_get_modifiers(keyboard->device->keyboard);
+  if ((modifiers & WLR_MODIFIER_ALT) &&
+      event->state == WL_KEYBOARD_KEY_STATE_PRESSED) {
+    /* If alt is held down and this button was _pressed_, we attempt to
+     * process it as a compositor keybinding. */
+    for (int i = 0; i < nsyms; i++) {
+      handled = handle_keybinding(server, syms[i]);
+    }
+  }
+
+  if (!handled) {
+    /* Otherwise, we pass it along to the client. */
+    wlr_seat_set_keyboard(seat, keyboard->device);
+    wlr_seat_keyboard_notify_key(seat, event->time_msec, event->keycode,
+                                 event->state);
+  }
+}
+
+static void server_new_keyboard(struct tinywl_server *server,
+                                struct wlr_input_device *device) {
+  struct tinywl_keyboard *keyboard = calloc(1, sizeof(struct tinywl_keyboard));
+  keyboard->server = server;
+  keyboard->device = device;
+
+  /* We need to prepare an XKB keymap and assign it to the keyboard. This
+   * assumes the defaults (e.g. layout = "us"). */
+  struct xkb_context *context = xkb_context_new(XKB_CONTEXT_NO_FLAGS);
+  struct xkb_keymap *keymap =
+      xkb_keymap_new_from_names(context, NULL, XKB_KEYMAP_COMPILE_NO_FLAGS);
+
+  wlr_keyboard_set_keymap(device->keyboard, keymap);
+  xkb_keymap_unref(keymap);
+  xkb_context_unref(context);
+  wlr_keyboard_set_repeat_info(device->keyboard, 25, 600);
+
+  /* Here we set up listeners for keyboard events. */
+  keyboard->modifiers.notify = keyboard_handle_modifiers;
+  wl_signal_add(&device->keyboard->events.modifiers, &keyboard->modifiers);
+  keyboard->key.notify = keyboard_handle_key;
+  wl_signal_add(&device->keyboard->events.key, &keyboard->key);
+
+  wlr_seat_set_keyboard(server->seat, device);
+
+  /* And add the keyboard to our list of keyboards */
+  wl_list_insert(&server->keyboards, &keyboard->link);
+}
+
+static void server_new_pointer(struct tinywl_server *server,
+                               struct wlr_input_device *device) {
+  /* We don't do anything special with pointers. All of our pointer handling
+   * is proxied through wlr_cursor. On another compositor, you might take this
+   * opportunity to do libinput configuration on the device to set
+   * acceleration, etc. */
+  wlr_cursor_attach_input_device(server->cursor, device);
+}
+
+static void server_new_input(struct wl_listener *listener, void *data) {
+  /* This event is raised by the backend when a new input device becomes
+   * available. */
+  struct tinywl_server *server = wl_container_of(listener, server, new_input);
+  struct wlr_input_device *device = data;
+  switch (device->type) {
+  case WLR_INPUT_DEVICE_KEYBOARD:
+    server_new_keyboard(server, device);
+    break;
+  case WLR_INPUT_DEVICE_POINTER:
+    server_new_pointer(server, device);
+    break;
+  default:
+    break;
+  }
+  /* We need to let the wlr_seat know what our capabilities are, which is
+   * communiciated to the client. In TinyWL we always have a cursor, even if
+   * there are no pointer devices, so we always include that capability. */
+  uint32_t caps = WL_SEAT_CAPABILITY_POINTER;
+  if (!wl_list_empty(&server->keyboards)) {
+    caps |= WL_SEAT_CAPABILITY_KEYBOARD;
+  }
+  wlr_seat_set_capabilities(server->seat, caps);
+}
+
+static void seat_request_cursor(struct wl_listener *listener, void *data) {
+  struct tinywl_server *server =
+      wl_container_of(listener, server, request_cursor);
+  /* This event is raised by the seat when a client provides a cursor image */
+  struct wlr_seat_pointer_request_set_cursor_event *event = data;
+  struct wlr_seat_client *focused_client =
+      server->seat->pointer_state.focused_client;
+  /* This can be sent by any client, so we check to make sure this one is
+   * actually has pointer focus first. */
+  if (focused_client == event->seat_client) {
+    /* Once we've vetted the client, we can tell the cursor to use the
+     * provided surface as the cursor image. It will set the hardware cursor
+     * on the output that it's currently on and continue to do so as the
+     * cursor moves between outputs. */
+    wlr_cursor_set_surface(server->cursor, event->surface, event->hotspot_x,
+                           event->hotspot_y);
+  }
+}
+
+static void seat_request_set_selection(struct wl_listener *listener,
+                                       void *data) {
+  /* This event is raised by the seat when a client wants to set the selection,
+   * usually when the user copies something. wlroots allows compositors to
+   * ignore such requests if they so choose, but in tinywl we always honor
+   */
+  struct tinywl_server *server =
+      wl_container_of(listener, server, request_set_selection);
+  struct wlr_seat_request_set_selection_event *event = data;
+  wlr_seat_set_selection(server->seat, event->source, event->serial);
+}
+
+static bool view_at(struct tinywl_view *view, double lx, double ly,
+                    struct wlr_surface **surface, double *sx, double *sy) {
+  /*
+   * XDG toplevels may have nested surfaces, such as popup windows for context
+   * menus or tooltips. This function tests if any of those are underneath the
+   * coordinates lx and ly (in output Layout Coordinates). If so, it sets the
+   * surface pointer to that wlr_surface and the sx and sy coordinates to the
+   * coordinates relative to that surface's top-left corner.
+   */
+  double view_sx = lx - view->x;
+  double view_sy = ly - view->y;
+
+  double _sx, _sy;
+  struct wlr_surface *_surface = NULL;
+  _surface = wlr_xdg_surface_surface_at(view->xdg_surface, view_sx, view_sy,
+                                        &_sx, &_sy);
+
+  if (_surface != NULL) {
+    *sx = _sx;
+    *sy = _sy;
+    *surface = _surface;
+    return true;
+  }
+
+  return false;
+}
+
+static struct tinywl_view *desktop_view_at(struct tinywl_server *server,
+                                           double lx, double ly,
+                                           struct wlr_surface **surface,
+                                           double *sx, double *sy) {
+  /* This iterates over all of our surfaces and attempts to find one under the
+   * cursor. This relies on server->views being ordered from top-to-bottom. */
+  struct tinywl_view *view;
+  wl_list_for_each(view, &server->views, link) {
+    if (view_at(view, lx, ly, surface, sx, sy)) {
+      return view;
+    }
+  }
+  return NULL;
+}
+
+static void process_cursor_move(struct tinywl_server *server, uint32_t time) {
+  /* Move the grabbed view to the new position. */
+  server->grabbed_view->x = server->cursor->x - server->grab_x;
+  server->grabbed_view->y = server->cursor->y - server->grab_y;
+}
+
+static void process_cursor_resize(struct tinywl_server *server, uint32_t time) {
+  /*
+   * Resizing the grabbed view can be a little bit complicated, because we
+   * could be resizing from any corner or edge. This not only resizes the view
+   * on one or two axes, but can also move the view if you resize from the top
+   * or left edges (or top-left corner).
+   *
+   * Note that I took some shortcuts here. In a more fleshed-out compositor,
+   * you'd wait for the client to prepare a buffer at the new size, then
+   * commit any movement that was prepared.
+   */
+  struct tinywl_view *view = server->grabbed_view;
+  double border_x = server->cursor->x - server->grab_x;
+  double border_y = server->cursor->y - server->grab_y;
+  int new_left = server->grab_geobox.x;
+  int new_right = server->grab_geobox.x + server->grab_geobox.width;
+  int new_top = server->grab_geobox.y;
+  int new_bottom = server->grab_geobox.y + server->grab_geobox.height;
+
+  if (server->resize_edges & WLR_EDGE_TOP) {
+    new_top = border_y;
+    if (new_top >= new_bottom) {
+      new_top = new_bottom - 1;
+    }
+  } else if (server->resize_edges & WLR_EDGE_BOTTOM) {
+    new_bottom = border_y;
+    if (new_bottom <= new_top) {
+      new_bottom = new_top + 1;
+    }
+  }
+  if (server->resize_edges & WLR_EDGE_LEFT) {
+    new_left = border_x;
+    if (new_left >= new_right) {
+      new_left = new_right - 1;
+    }
+  } else if (server->resize_edges & WLR_EDGE_RIGHT) {
+    new_right = border_x;
+    if (new_right <= new_left) {
+      new_right = new_left + 1;
+    }
+  }
+
+  struct wlr_box geo_box;
+  wlr_xdg_surface_get_geometry(view->xdg_surface, &geo_box);
+  view->x = new_left - geo_box.x;
+  view->y = new_top - geo_box.y;
+
+  int new_width = new_right - new_left;
+  int new_height = new_bottom - new_top;
+  wlr_xdg_toplevel_set_size(view->xdg_surface, new_width, new_height);
+}
+
+static void process_cursor_motion(struct tinywl_server *server, uint32_t time) {
+  /* If the mode is non-passthrough, delegate to those functions. */
+  if (server->cursor_mode == TINYWL_CURSOR_MOVE) {
+    process_cursor_move(server, time);
+    return;
+  } else if (server->cursor_mode == TINYWL_CURSOR_RESIZE) {
+    process_cursor_resize(server, time);
+    return;
+  }
+
+  /* Otherwise, find the view under the pointer and send the event along. */
+  double sx, sy;
+  struct wlr_seat *seat = server->seat;
+  struct wlr_surface *surface = NULL;
+  struct tinywl_view *view = desktop_view_at(
+      server, server->cursor->x, server->cursor->y, &surface, &sx, &sy);
+  if (!view) {
+    /* If there's no view under the cursor, set the cursor image to a
+     * default. This is what makes the cursor image appear when you move it
+     * around the screen, not over any views. */
+    wlr_xcursor_manager_set_cursor_image(server->cursor_mgr, "left_ptr",
+                                         server->cursor);
+  }
+  if (surface) {
+    /*
+     * Send pointer enter and motion events.
+     *
+     * The enter event gives the surface "pointer focus", which is distinct
+     * from keyboard focus. You get pointer focus by moving the pointer over
+     * a window.
+     *
+     * Note that wlroots will avoid sending duplicate enter/motion events if
+     * the surface has already has pointer focus or if the client is already
+     * aware of the coordinates passed.
+     */
+    wlr_seat_pointer_notify_enter(seat, surface, sx, sy);
+    wlr_seat_pointer_notify_motion(seat, time, sx, sy);
+  } else {
+    /* Clear pointer focus so future button events and such are not sent to
+     * the last client to have the cursor over it. */
+    wlr_seat_pointer_clear_focus(seat);
+  }
+}
+
+static void server_cursor_motion(struct wl_listener *listener, void *data) {
+  /* This event is forwarded by the cursor when a pointer emits a _relative_
+   * pointer motion event (i.e. a delta) */
+  struct tinywl_server *server =
+      wl_container_of(listener, server, cursor_motion);
+  struct wlr_event_pointer_motion *event = data;
+  /* The cursor doesn't move unless we tell it to. The cursor automatically
+   * handles constraining the motion to the output layout, as well as any
+   * special configuration applied for the specific input device which
+   * generated the event. You can pass NULL for the device if you want to move
+   * the cursor around without any input. */
+  wlr_cursor_move(server->cursor, event->device, event->delta_x,
+                  event->delta_y);
+  process_cursor_motion(server, event->time_msec);
+}
+
+static void server_cursor_motion_absolute(struct wl_listener *listener,
+                                          void *data) {
+  /* This event is forwarded by the cursor when a pointer emits an _absolute_
+   * motion event, from 0..1 on each axis. This happens, for example, when
+   * wlroots is running under a Wayland window rather than KMS+DRM, and you
+   * move the mouse over the window. You could enter the window from any edge,
+   * so we have to warp the mouse there. There is also some hardware which
+   * emits these events. */
+  struct tinywl_server *server =
+      wl_container_of(listener, server, cursor_motion_absolute);
+  struct wlr_event_pointer_motion_absolute *event = data;
+  wlr_cursor_warp_absolute(server->cursor, event->device, event->x, event->y);
+  process_cursor_motion(server, event->time_msec);
+}
+
+static void server_cursor_button(struct wl_listener *listener, void *data) {
+  /* This event is forwarded by the cursor when a pointer emits a button
+   * event. */
+  struct tinywl_server *server =
+      wl_container_of(listener, server, cursor_button);
+  struct wlr_event_pointer_button *event = data;
+  /* Notify the client with pointer focus that a button press has occurred */
+  wlr_seat_pointer_notify_button(server->seat, event->time_msec, event->button,
+                                 event->state);
+  double sx, sy;
+  struct wlr_surface *surface;
+  struct tinywl_view *view = desktop_view_at(
+      server, server->cursor->x, server->cursor->y, &surface, &sx, &sy);
+  if (event->state == WLR_BUTTON_RELEASED) {
+    /* If you released any buttons, we exit interactive move/resize mode. */
+    server->cursor_mode = TINYWL_CURSOR_PASSTHROUGH;
+  } else {
+    /* Focus that client if the button was _pressed_ */
+    focus_view(view, surface);
+  }
+}
+
+static void server_cursor_axis(struct wl_listener *listener, void *data) {
+  /* This event is forwarded by the cursor when a pointer emits an axis event,
+   * for example when you move the scroll wheel. */
+  struct tinywl_server *server = wl_container_of(listener, server, cursor_axis);
+  struct wlr_event_pointer_axis *event = data;
+  /* Notify the client with pointer focus of the axis event. */
+  wlr_seat_pointer_notify_axis(server->seat, event->time_msec,
+                               event->orientation, event->delta,
+                               event->delta_discrete, event->source);
+}
+
+static void server_cursor_frame(struct wl_listener *listener, void *data) {
+  /* This event is forwarded by the cursor when a pointer emits an frame
+   * event. Frame events are sent after regular pointer events to group
+   * multiple events together. For instance, two axis events may happen at the
+   * same time, in which case a frame event won't be sent in between. */
+  struct tinywl_server *server =
+      wl_container_of(listener, server, cursor_frame);
+  /* Notify the client with pointer focus of the frame event. */
+  wlr_seat_pointer_notify_frame(server->seat);
+}
+
+/* Used to move all of the data necessary to render a surface from the top-level
+ * frame handler to the per-surface render function. */
+struct render_data {
+  struct wlr_output *output;
+  struct wlr_renderer *renderer;
+  struct tinywl_view *view;
+  struct timespec *when;
+};
+
+static void render_surface(struct wlr_surface *surface, int sx, int sy,
+                           void *data) {
+  /* This function is called for every surface that needs to be rendered. */
+  struct render_data *rdata = data;
+  struct tinywl_view *view = rdata->view;
+  struct wlr_output *output = rdata->output;
+
+  /* We first obtain a wlr_texture, which is a GPU resource. wlroots
+   * automatically handles negotiating these with the client. The underlying
+   * resource could be an opaque handle passed from the client, or the client
+   * could have sent a pixel buffer which we copied to the GPU, or a few other
+   * means. You don't have to worry about this, wlroots takes care of it. */
+  struct wlr_texture *texture = wlr_surface_get_texture(surface);
+  if (texture == NULL) {
+    return;
+  }
+
+  /* The view has a position in layout coordinates. If you have two displays,
+   * one next to the other, both 1080p, a view on the rightmost display might
+   * have layout coordinates of 2000,100. We need to translate that to
+   * output-local coordinates, or (2000 - 1920). */
+  double ox = 0, oy = 0;
+  wlr_output_layout_output_coords(view->server->output_layout, output, &ox,
+                                  &oy);
+  ox += view->x + sx, oy += view->y + sy;
+
+  /* We also have to apply the scale factor for HiDPI outputs. This is only
+   * part of the puzzle, TinyWL does not fully support HiDPI. */
+  struct wlr_box box = {
+      .x = ox * output->scale,
+      .y = oy * output->scale,
+      .width = surface->current.width * output->scale,
+      .height = surface->current.height * output->scale,
+  };
+
+  /*
+   * Those familiar with OpenGL are also familiar with the role of matricies
+   * in graphics programming. We need to prepare a matrix to render the view
+   * with. wlr_matrix_project_box is a helper which takes a box with a desired
+   * x, y coordinates, width and height, and an output geometry, then
+   * prepares an orthographic projection and multiplies the necessary
+   * transforms to produce a model-view-projection matrix.
+   *
+   * Naturally you can do this any way you like, for example to make a 3D
+   * compositor.
+   */
+  float matrix[9];
+  enum wl_output_transform transform =
+      wlr_output_transform_invert(surface->current.transform);
+  wlr_matrix_project_box(matrix, &box, transform, 0, output->transform_matrix);
+
+  /* This takes our matrix, the texture, and an alpha, and performs the actual
+   * rendering on the GPU. */
+  wlr_render_texture_with_matrix(rdata->renderer, texture, matrix, 1);
+
+  /* This lets the client know that we've displayed that frame and it can
+   * prepare another one now if it likes. */
+  wlr_surface_send_frame_done(surface, rdata->when);
+}
+
+static void output_frame(struct wl_listener *listener, void *data) {
+  /* This function is called every time an output is ready to display a frame,
+   * generally at the output's refresh rate (e.g. 60Hz). */
+  struct tinywl_output *output = wl_container_of(listener, output, frame);
+  struct wlr_renderer *renderer = output->server->renderer;
+
+  struct timespec now;
+  clock_gettime(CLOCK_MONOTONIC, &now);
+
+  /* wlr_output_attach_render makes the OpenGL context current. */
+  if (!wlr_output_attach_render(output->wlr_output, NULL)) {
+    return;
+  }
+  /* The "effective" resolution can change if you rotate your outputs. */
+  int width, height;
+  wlr_output_effective_resolution(output->wlr_output, &width, &height);
+  /* Begin the renderer (calls glViewport and some other GL sanity checks) */
+  wlr_renderer_begin(renderer, width, height);
+
+  float color[4] = {0.3, 0.3, 0.3, 1.0};
+  wlr_renderer_clear(renderer, color);
+
+  /* Each subsequent window we render is rendered on top of the last. Because
+   * our view list is ordered front-to-back, we iterate over it backwards. */
+  struct tinywl_view *view;
+  wl_list_for_each_reverse(view, &output->server->views, link) {
+    if (!view->mapped) {
+      /* An unmapped view should not be rendered. */
+      continue;
+    }
+    struct render_data rdata = {
+        .output = output->wlr_output,
+        .view = view,
+        .renderer = renderer,
+        .when = &now,
+    };
+    /* This calls our render_surface function for each surface among the
+     * xdg_surface's toplevel and popups. */
+    wlr_xdg_surface_for_each_surface(view->xdg_surface, render_surface, &rdata);
+  }
+
+  /* Hardware cursors are rendered by the GPU on a separate plane, and can be
+   * moved around without re-rendering what's beneath them - which is more
+   * efficient. However, not all hardware supports hardware cursors. For this
+   * reason, wlroots provides a software fallback, which we ask it to render
+   * here. wlr_cursor handles configuring hardware vs software cursors for you,
+   * and this function is a no-op when hardware cursors are in use. */
+  wlr_output_render_software_cursors(output->wlr_output, NULL);
+
+  /* Conclude rendering and swap the buffers, showing the final frame
+   * on-screen. */
+  wlr_renderer_end(renderer);
+  wlr_output_commit(output->wlr_output);
+}
+
+static void server_new_output(struct wl_listener *listener, void *data) {
+  /* This event is raised by the backend when a new output (aka a display or
+   * monitor) becomes available. */
+  struct tinywl_server *server = wl_container_of(listener, server, new_output);
+  struct wlr_output *wlr_output = data;
+
+  /* Some backends don't have modes. DRM+KMS does, and we need to set a mode
+   * before we can use the output. The mode is a tuple of (width, height,
+   * refresh rate), and each monitor supports only a specific set of modes. We
+   * just pick the monitor's preferred mode, a more sophisticated compositor
+   * would let the user configure it. */
+  if (!wl_list_empty(&wlr_output->modes)) {
+    struct wlr_output_mode *mode = wlr_output_preferred_mode(wlr_output);
+    wlr_output_set_mode(wlr_output, mode);
+    wlr_output_enable(wlr_output, true);
+    if (!wlr_output_commit(wlr_output)) {
+      return;
+    }
+  }
+
+  /* Allocates and configures our state for this output */
+  struct tinywl_output *output = calloc(1, sizeof(struct tinywl_output));
+  output->wlr_output = wlr_output;
+  output->server = server;
+  /* Sets up a listener for the frame notify event. */
+  output->frame.notify = output_frame;
+  wl_signal_add(&wlr_output->events.frame, &output->frame);
+  wl_list_insert(&server->outputs, &output->link);
+
+  /* Adds this to the output layout. The add_auto function arranges outputs
+   * from left-to-right in the order they appear. A more sophisticated
+   * compositor would let the user configure the arrangement of outputs in the
+   * layout.
+   *
+   * The output layout utility automatically adds a wl_output global to the
+   * display, which Wayland clients can see to find out information about the
+   * output (such as DPI, scale factor, manufacturer, etc).
+   */
+  wlr_output_layout_add_auto(server->output_layout, wlr_output);
+}
+
+static void xdg_surface_map(struct wl_listener *listener, void *data) {
+  /* Called when the surface is mapped, or ready to display on-screen. */
+  struct tinywl_view *view = wl_container_of(listener, view, map);
+  view->mapped = true;
+  focus_view(view, view->xdg_surface->surface);
+}
+
+static void xdg_surface_unmap(struct wl_listener *listener, void *data) {
+  /* Called when the surface is unmapped, and should no longer be shown. */
+  struct tinywl_view *view = wl_container_of(listener, view, unmap);
+  view->mapped = false;
+}
+
+static void xdg_surface_destroy(struct wl_listener *listener, void *data) {
+  /* Called when the surface is destroyed and should never be shown again. */
+  struct tinywl_view *view = wl_container_of(listener, view, destroy);
+  wl_list_remove(&view->link);
+  free(view);
+}
+
+static void begin_interactive(struct tinywl_view *view,
+                              enum tinywl_cursor_mode mode, uint32_t edges) {
+  /* This function sets up an interactive move or resize operation, where the
+   * compositor stops propegating pointer events to clients and instead
+   * consumes them itself, to move or resize windows. */
+  struct tinywl_server *server = view->server;
+  struct wlr_surface *focused_surface =
+      server->seat->pointer_state.focused_surface;
+  if (view->xdg_surface->surface != focused_surface) {
+    /* Deny move/resize requests from unfocused clients. */
+    return;
+  }
+  server->grabbed_view = view;
+  server->cursor_mode = mode;
+
+  if (mode == TINYWL_CURSOR_MOVE) {
+    server->grab_x = server->cursor->x - view->x;
+    server->grab_y = server->cursor->y - view->y;
+  } else {
+    struct wlr_box geo_box;
+    wlr_xdg_surface_get_geometry(view->xdg_surface, &geo_box);
+
+    double border_x =
+        (view->x + geo_box.x) + ((edges & WLR_EDGE_RIGHT) ? geo_box.width : 0);
+    double border_y = (view->y + geo_box.y) +
+                      ((edges & WLR_EDGE_BOTTOM) ? geo_box.height : 0);
+    server->grab_x = server->cursor->x - border_x;
+    server->grab_y = server->cursor->y - border_y;
+
+    server->grab_geobox = geo_box;
+    server->grab_geobox.x += view->x;
+    server->grab_geobox.y += view->y;
+
+    server->resize_edges = edges;
+  }
+}
+
+static void xdg_toplevel_request_move(struct wl_listener *listener,
+                                      void *data) {
+  /* This event is raised when a client would like to begin an interactive
+   * move, typically because the user clicked on their client-side
+   * decorations. Note that a more sophisticated compositor should check the
+   * provided serial against a list of button press serials sent to this
+   * client, to prevent the client from requesting this whenever they want. */
+  struct tinywl_view *view = wl_container_of(listener, view, request_move);
+  begin_interactive(view, TINYWL_CURSOR_MOVE, 0);
+}
+
+static void xdg_toplevel_request_resize(struct wl_listener *listener,
+                                        void *data) {
+  /* This event is raised when a client would like to begin an interactive
+   * resize, typically because the user clicked on their client-side
+   * decorations. Note that a more sophisticated compositor should check the
+   * provided serial against a list of button press serials sent to this
+   * client, to prevent the client from requesting this whenever they want. */
+  struct wlr_xdg_toplevel_resize_event *event = data;
+  struct tinywl_view *view = wl_container_of(listener, view, request_resize);
+  begin_interactive(view, TINYWL_CURSOR_RESIZE, event->edges);
+}
+
+static void server_new_xdg_surface(struct wl_listener *listener, void *data) {
+  /* This event is raised when wlr_xdg_shell receives a new xdg surface from a
+   * client, either a toplevel (application window) or popup. */
+  struct tinywl_server *server =
+      wl_container_of(listener, server, new_xdg_surface);
+  struct wlr_xdg_surface *xdg_surface = data;
+  if (xdg_surface->role != WLR_XDG_SURFACE_ROLE_TOPLEVEL) {
+    return;
+  }
+
+  /* Allocate a tinywl_view for this surface */
+  struct tinywl_view *view = calloc(1, sizeof(struct tinywl_view));
+  view->server = server;
+  view->xdg_surface = xdg_surface;
+
+  /* Listen to the various events it can emit */
+  view->map.notify = xdg_surface_map;
+  wl_signal_add(&xdg_surface->events.map, &view->map);
+  view->unmap.notify = xdg_surface_unmap;
+  wl_signal_add(&xdg_surface->events.unmap, &view->unmap);
+  view->destroy.notify = xdg_surface_destroy;
+  wl_signal_add(&xdg_surface->events.destroy, &view->destroy);
+
+  /* cotd */
+  struct wlr_xdg_toplevel *toplevel = xdg_surface->toplevel;
+  view->request_move.notify = xdg_toplevel_request_move;
+  wl_signal_add(&toplevel->events.request_move, &view->request_move);
+  view->request_resize.notify = xdg_toplevel_request_resize;
+  wl_signal_add(&toplevel->events.request_resize, &view->request_resize);
+
+  /* Add it to the list of views. */
+  wl_list_insert(&server->views, &view->link);
+}
+
+int main(int argc, char *argv[]) {
+  wlr_log_init(WLR_DEBUG, NULL);
+  char *startup_cmd = NULL;
+  char *plugin = NULL;
+
+  int c;
+
+  for (int i = 0; i < argc; ++i) {
+    printf("ARG: %s\n", argv[i]);
+  }
+
+  while ((c = getopt(argc, argv, "s:p:h")) != -1) {
+    switch (c) {
+    case 's':
+      startup_cmd = optarg;
+      break;
+    case 'p':
+      plugin = optarg;
+      break;
+    default:
+      printf("Usage: %s [-s startup command] -p plugin\n", argv[0]);
+      return 0;
+    }
+  }
+
+  if (optind < argc || !plugin) {
+    printf("Usage: %s [-s startup command] -p plugin\n", argv[0]);
+    return 0;
+  }
+
+  struct tinywl_server server;
+
+  if (read_plugin_from_file(plugin, &server.plugin)) {
+    fprintf(stderr, "Failed to read plugin from file.\n");
+    return 1;
+  }
+
+  server.plugin.plugin_metaload(argc, argv);
+  server.plugin.plugin_load(argc, argv);
+  server.plugin.state = server.plugin.plugin_cold_start();
+
+  /* The Wayland display is managed by libwayland. It handles accepting
+   * clients from the Unix socket, manging Wayland globals, and so on. */
+  server.wl_display = wl_display_create();
+  /* The backend is a wlroots feature which abstracts the underlying input and
+   * output hardware. The autocreate option will choose the most suitable
+   * backend based on the current environment, such as opening an X11 window
+   * if an X11 server is running. */
+  server.backend = wlr_backend_autocreate(server.wl_display);
+
+  /* If we don't provide a renderer, autocreate makes a GLES2 renderer for us.
+   * The renderer is responsible for defining the various pixel formats it
+   * supports for shared memory, this configures that for clients. */
+  server.renderer = wlr_backend_get_renderer(server.backend);
+  wlr_renderer_init_wl_display(server.renderer, server.wl_display);
+
+  /* This creates some hands-off wlroots interfaces. The compositor is
+   * necessary for clients to allocate surfaces and the data device manager
+   * handles the clipboard. Each of these wlroots interfaces has room for you
+   * to dig your fingers in and play with their behavior if you want. Note that
+   * the clients cannot set the selection directly without compositor approval,
+   * see the handling of the request_set_selection event below.*/
+  wlr_compositor_create(server.wl_display, server.renderer);
+  wlr_data_device_manager_create(server.wl_display);
+
+  /* Creates an output layout, which a wlroots utility for working with an
+   * arrangement of screens in a physical layout. */
+  server.output_layout = wlr_output_layout_create();
+
+  /* Configure a listener to be notified when new outputs are available on the
+   * backend. */
+  wl_list_init(&server.outputs);
+  server.new_output.notify = server_new_output;
+  wl_signal_add(&server.backend->events.new_output, &server.new_output);
+
+  /* Set up our list of views and the xdg-shell. The xdg-shell is a Wayland
+   * protocol which is used for application windows. For more detail on
+   * shells, refer to my article:
+   *
+   * https://drewdevault.com/2018/07/29/Wayland-shells.html
+   */
+  wl_list_init(&server.views);
+  server.xdg_shell = wlr_xdg_shell_create(server.wl_display);
+  server.new_xdg_surface.notify = server_new_xdg_surface;
+  wl_signal_add(&server.xdg_shell->events.new_surface, &server.new_xdg_surface);
+
+  /*
+   * Creates a cursor, which is a wlroots utility for tracking the cursor
+   * image shown on screen.
+   */
+  server.cursor = wlr_cursor_create();
+  wlr_cursor_attach_output_layout(server.cursor, server.output_layout);
+
+  /* Creates an xcursor manager, another wlroots utility which loads up
+   * Xcursor themes to source cursor images from and makes sure that cursor
+   * images are available at all scale factors on the screen (necessary for
+   * HiDPI support). We add a cursor theme at scale factor 1 to begin with. */
+  server.cursor_mgr = wlr_xcursor_manager_create(NULL, 24);
+  wlr_xcursor_manager_load(server.cursor_mgr, 1);
+
+  /*
+   * wlr_cursor *only* displays an image on screen. It does not move around
+   * when the pointer moves. However, we can attach input devices to it, and
+   * it will generate aggregate events for all of them. In these events, we
+   * can choose how we want to process them, forwarding them to clients and
+   * moving the cursor around. More detail on this process is described in my
+   * input handling blog post:
+   *
+   * https://drewdevault.com/2018/07/17/Input-handling-in-wlroots.html
+   *
+   * And more comments are sprinkled throughout the notify functions above.
+   */
+  server.cursor_motion.notify = server_cursor_motion;
+  wl_signal_add(&server.cursor->events.motion, &server.cursor_motion);
+  server.cursor_motion_absolute.notify = server_cursor_motion_absolute;
+  wl_signal_add(&server.cursor->events.motion_absolute,
+                &server.cursor_motion_absolute);
+  server.cursor_button.notify = server_cursor_button;
+  wl_signal_add(&server.cursor->events.button, &server.cursor_button);
+  server.cursor_axis.notify = server_cursor_axis;
+  wl_signal_add(&server.cursor->events.axis, &server.cursor_axis);
+  server.cursor_frame.notify = server_cursor_frame;
+  wl_signal_add(&server.cursor->events.frame, &server.cursor_frame);
+
+  /*
+   * Configures a seat, which is a single "seat" at which a user sits and
+   * operates the computer. This conceptually includes up to one keyboard,
+   * pointer, touch, and drawing tablet device. We also rig up a listener to
+   * let us know when new input devices are available on the backend.
+   */
+  wl_list_init(&server.keyboards);
+  server.new_input.notify = server_new_input;
+  wl_signal_add(&server.backend->events.new_input, &server.new_input);
+  server.seat = wlr_seat_create(server.wl_display, "seat0");
+  server.request_cursor.notify = seat_request_cursor;
+  wl_signal_add(&server.seat->events.request_set_cursor,
+                &server.request_cursor);
+  server.request_set_selection.notify = seat_request_set_selection;
+  wl_signal_add(&server.seat->events.request_set_selection,
+                &server.request_set_selection);
+
+  /* Add a Unix socket to the Wayland display. */
+  const char *socket = wl_display_add_socket_auto(server.wl_display);
+  if (!socket) {
+    wlr_backend_destroy(server.backend);
+    return 1;
+  }
+
+  /* Start the backend. This will enumerate outputs and inputs, become the DRM
+   * master, etc */
+  if (!wlr_backend_start(server.backend)) {
+    wlr_backend_destroy(server.backend);
+    wl_display_destroy(server.wl_display);
+    return 1;
+  }
+
+  /* Set the WAYLAND_DISPLAY environment variable to our socket and run the
+   * startup command if requested. */
+  setenv("WAYLAND_DISPLAY", socket, true);
+  if (startup_cmd) {
+    if (fork() == 0) {
+      execl("/bin/sh", "/bin/sh", "-c", startup_cmd, (void *)NULL);
+    }
+  }
+  /* Run the Wayland event loop. This does not return until you exit the
+   * compositor. Starting the backend rigged up all of the necessary event
+   * loop configuration to listen to libinput events, DRM events, generate
+   * frame events at the refresh rate, and so on. */
+  wlr_log(WLR_INFO, "Running Wayland compositor on WAYLAND_DISPLAY=%s", socket);
+  wl_display_run(server.wl_display);
+
+  /* Once wl_display_run returns, we shut down the server. */
+  wl_display_destroy_clients(server.wl_display);
+  wl_display_destroy(server.wl_display);
+  return 0;
+}
diff --git a/src/Main.hs b/src/Main.hs
index bdffd6f..75e21bd 100644
--- a/src/Main.hs
+++ b/src/Main.hs
@@ -3,6 +3,7 @@
 module Main (main) where
 
 import Control.Monad.Writer (MonadWriter (tell), execWriter)
+import Text.Printf
 import Wetterhorn.Core
 
 foreign export ccall wetterhorn :: IO Wetterhorn
@@ -12,10 +13,9 @@ wetterhorn =
   initWetterhorn $
     WConfig
       "This is a string"
-      ( do
-          (WState str i) <- getWState
-          wio $ putStrLn $ "Handle something!!! :) " ++ str ++ " " ++ show i
-          incrementState
+      ( \sym -> do
+          wio $
+            printf "Got Key: %x\n" sym
       )
 
 main :: IO ()
diff --git a/src/Wetterhorn/Core.hs b/src/Wetterhorn/Core.hs
index e04cb49..7b5690f 100644
--- a/src/Wetterhorn/Core.hs
+++ b/src/Wetterhorn/Core.hs
@@ -19,7 +19,7 @@ import Control.Arrow (first)
 import Control.Exception
 import Data.ByteString (ByteString)
 import qualified Data.ByteString.Char8 as CH
-import Foreign (StablePtr, newStablePtr)
+import Foreign (StablePtr, Word32, newStablePtr)
 
 -- This is this opaque state presented to the harness.
 type Wetterhorn = StablePtr (WConfig, WState)
@@ -36,7 +36,7 @@ data WState = WState
 
 data WConfig = WConfig
   { someConfig :: String,
-    handleSomething :: W ()
+    keybindingHandler :: Word32 -> W ()
   }
 
 readWState :: ByteString -> IO WState
diff --git a/src/Wetterhorn/FFI.hs b/src/Wetterhorn/FFI.hs
index bfb3cbd..d941493 100644
--- a/src/Wetterhorn/FFI.hs
+++ b/src/Wetterhorn/FFI.hs
@@ -18,6 +18,13 @@ import Foreign
 import Foreign.C (CChar)
 import Wetterhorn.Core
 
+runForeign :: (WConfig -> W ()) -> Wetterhorn -> IO Wetterhorn
+runForeign fn stblptr = do
+  (conf, st) <- deRefStablePtr stblptr
+  freeStablePtr stblptr
+  (_, state') <- runW (fn conf) (conf, st)
+  newStablePtr (conf, state')
+
 -- | This function should be defined somewhere in the code. This is kind of like
 -- the "main" function in XMonad.
 foreign import ccall wetterhorn :: IO Wetterhorn
@@ -59,3 +66,10 @@ pluginMarshalState stblptr outlen = do
   forM_ (zip [0 ..] (BS.unpack bs)) $ \(off, w8) -> do
     pokeByteOff ret off w8
   return ret
+
+foreign export ccall "plugin_handle_keybinding"
+  pluginHandleKeybinding ::
+    Word32 -> Wetterhorn -> IO Wetterhorn
+
+pluginHandleKeybinding :: Word32 -> Wetterhorn -> IO Wetterhorn
+pluginHandleKeybinding sym = runForeign (`keybindingHandler` sym)