feat(core): add event polling to button driver

[no changelog]

core/embed/io/button/button_fsm.c

@@ -0,0 +1,86 @@
+/*
+ * This file is part of the Trezor project, https://trezor.io/
+ *
+ * Copyright (c) SatoshiLabs
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifdef KERNEL_MODE
+
+#include <trezor_rtl.h>
+
+#include <sys/systick.h>
+
+#include "button_fsm.h"
+
+void button_fsm_init(button_fsm_t* fsm) {
+  memset(fsm, 0, sizeof(button_fsm_t));
+}
+
+bool button_fsm_event_ready(button_fsm_t* fsm, uint32_t new_state) {
+  // Remember state changes
+  fsm->pressed |= new_state & ~fsm->state;
+  fsm->released |= ~new_state & fsm->state;
+  fsm->time = systick_us();
+  // Return true if there are any state changes
+  return (fsm->pressed | fsm->released) != 0;
+}
+
+bool button_fsm_get_event(button_fsm_t* fsm, uint32_t new_state,
+                          button_event_t* event) {
+  uint64_t now = systick_us();
+
+  if ((now - fsm->time) > 100000) {
+    // Reset the history if the button was not read for 100ms
+    fsm->pressed = 0;
+    fsm->released = 0;
+  }
+
+  // Remember state changes and the time of the last read
+  fsm->pressed |= new_state & ~fsm->state;
+  fsm->released |= ~new_state & fsm->state;
+
+  // Bring the automaton out of invalid states,
+  // in case it somehow ends up in one.
+  fsm->released &= fsm->pressed | fsm->state;
+  fsm->pressed &= fsm->released | ~fsm->state;
+
+  uint8_t button_idx = 0;
+  while (fsm->pressed | fsm->released) {
+    uint32_t mask = 1 << button_idx;
+
+    if ((fsm->pressed & mask) != 0 && (fsm->state & mask) == 0) {
+      // Button press was not signalled yet
+      fsm->pressed &= ~mask;
+      fsm->state |= mask;
+      event->button = (button_t)button_idx;
+      event->event_type = BTN_EVENT_DOWN;
+      return true;
+    } else if ((fsm->released & mask) != 0 && (fsm->state & mask) != 0) {
+      // Button release was not signalled yet
+      fsm->released &= ~mask;
+      fsm->state &= ~mask;
+      event->button = (button_t)button_idx;
+      event->event_type = BTN_EVENT_UP;
+      return true;
+    }
+
+    ++button_idx;
+  }
+
+  return false;
+}
+
+#endif  // KERNEL_MODE

core/embed/io/button/button_fsm.h

@@ -0,0 +1,59 @@
+/*
+ * This file is part of the Trezor project, https://trezor.io/
+ *
+ * Copyright (c) SatoshiLabs
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include <io/button.h>
+
+// This module is a simple finite state machine for buttons.
+//
+// It is designed to be used in a polling loop, where the state of the buttons
+// is read periodically. The module keeps track of the state changes and
+// provides a simple interface to get the events that happened since the last
+// call to button_fsm_get_event().
+//
+// The structure is designed to be used in a multi-threaded environment, where
+// each thread has its own state machine. The state machines are stored in an
+// array indexed by the task ID.
+
+typedef struct {
+  // Time of last update of pressed/released data
+  uint64_t time;
+  // Button presses that were detected since last get_event call
+  uint32_t pressed;
+  // Button releases that were detected since last get_event call
+  uint32_t released;
+  // State of buttons signalled to the poller
+  uint32_t state;
+} button_fsm_t;
+
+// Initializes button finite state machine
+void button_fsm_init(button_fsm_t* fsm);
+
+// Checks if button_fsm_get_event() would return `true` on the next call
+bool button_fsm_event_ready(button_fsm_t* fsm, uint32_t new_state);
+
+// Processes the new_state of the button and fills the event structure.
+//
+// `new_state` is the current state of the buttons - each bit represents
+// the state of one button (up to 32 buttons can be handled simultaneously).
+//
+// Returns `true` if the event structure was filled.
+bool button_fsm_get_event(button_fsm_t* fsm, uint32_t new_state,
+                          button_event_t* event);

core/embed/io/button/inc/io/button.h

@@ -68,8 +68,4 @@ void button_deinit(void);
 bool button_get_event(button_event_t* event);
 
 // Checks if the specified button is currently pressed
-//
-// The current implementation returns the state of the button at the time
-// `button_get_event()` was called. In the future, we may fix this limitation.
-// For now, `button_get_event()` must be called before `button_is_down()`.
 bool button_is_down(button_t button);

core/embed/io/button/stm32/button.c

@@ -23,6 +23,9 @@
 #include <io/button.h>
 #include <sys/irq.h>
 #include <sys/mpu.h>
+#include <sys/sysevent_source.h>
+
+#include "../button_fsm.h"
 
 #ifdef USE_POWERCTL
 #include <sys/wakeup_flags.h>
@@ -34,15 +37,8 @@
 typedef struct {
   bool initialized;
 
-#ifdef BTN_LEFT_PIN
-  bool left_down;
-#endif
-#ifdef BTN_RIGHT_PIN
-  bool right_down;
-#endif
-#ifdef BTN_POWER_PIN
-  bool power_down;
-#endif
+  // Each task has its own state machine
+  button_fsm_t tls[SYSTASK_MAX_TASKS];
 
 } button_driver_t;
 
@@ -51,7 +47,10 @@ static button_driver_t g_button_driver = {
     .initialized = false,
 };
 
-static void button_setup_pin(GPIO_TypeDef *port, uint16_t pin) {
+// Forward declarations
+static const syshandle_vmt_t g_button_handle_vmt;
+
+static void button_setup_pin(GPIO_TypeDef* port, uint16_t pin) {
   GPIO_InitTypeDef GPIO_InitStructure = {0};
 
   GPIO_InitStructure.Mode = GPIO_MODE_INPUT;
@@ -62,7 +61,7 @@ static void button_setup_pin(GPIO_TypeDef *port, uint16_t pin) {
 }
 
 bool button_init(void) {
-  button_driver_t *drv = &g_button_driver;
+  button_driver_t* drv = &g_button_driver;
 
   if (drv->initialized) {
     return true;
@@ -99,106 +98,76 @@ bool button_init(void) {
   NVIC_EnableIRQ(BTN_EXTI_INTERRUPT_NUM);
 #endif  // BTN_EXTI_INTERRUPT_HANDLER
 
-  drv->initialized = true;
+  if (!syshandle_register(SYSHANDLE_BUTTON, &g_button_handle_vmt, drv)) {
+    goto cleanup;
+  }
 
+  drv->initialized = true;
   return true;
+
+cleanup:
+  button_deinit();
+  return false;
 }
 
 void button_deinit(void) {
+  button_driver_t* drv = &g_button_driver;
+
+  syshandle_unregister(SYSHANDLE_BUTTON);
+
 #ifdef BTN_EXIT_INTERRUPT_HANDLER
   NVIC_DisableIRQ(BTN_EXTI_INTERRUPT_NUM);
 #endif
+
+  memset(drv, 0, sizeof(button_driver_t));
 }
 
-bool button_get_event(button_event_t *event) {
-  button_driver_t *drv = &g_button_driver;
+static uint32_t button_read_state(button_driver_t* drv) {
+  UNUSED(drv);
+  uint32_t state = 0;
 
+#ifdef BTN_LEFT_PIN
+  if (GPIO_PIN_RESET == HAL_GPIO_ReadPin(BTN_LEFT_PORT, BTN_LEFT_PIN)) {
+    state |= (1U << BTN_LEFT);
+  }
+#endif
+
+#ifdef BTN_RIGHT_PIN
+  if (GPIO_PIN_RESET == HAL_GPIO_ReadPin(BTN_RIGHT_PORT, BTN_RIGHT_PIN)) {
+    state |= (1U << BTN_RIGHT);
+  }
+#endif
+
+#ifdef BTN_POWER_PIN
+  if (GPIO_PIN_RESET == HAL_GPIO_ReadPin(BTN_POWER_PORT, BTN_POWER_PIN)) {
+    state |= (1U << BTN_POWER);
+  }
+#endif
+  return state;
+}
+
+bool button_get_event(button_event_t* event) {
+  button_driver_t* drv = &g_button_driver;
   memset(event, 0, sizeof(*event));
 
   if (!drv->initialized) {
     return false;
   }
 
-#ifdef BTN_LEFT_PIN
-  bool left_down =
-      (GPIO_PIN_RESET == HAL_GPIO_ReadPin(BTN_LEFT_PORT, BTN_LEFT_PIN));
+  uint32_t new_state = button_read_state(drv);
 
-  if (drv->left_down != left_down) {
-    drv->left_down = left_down;
-    if (left_down) {
-      event->button = BTN_LEFT;
-      event->event_type = BTN_EVENT_DOWN;
-      return true;
-    } else {
-      event->button = BTN_LEFT;
-      event->event_type = BTN_EVENT_UP;
-      return true;
-    }
-  }
-#endif
-
-#ifdef BTN_RIGHT_PIN
-  bool right_down =
-      (GPIO_PIN_RESET == HAL_GPIO_ReadPin(BTN_RIGHT_PORT, BTN_RIGHT_PIN));
-
-  if (drv->right_down != right_down) {
-    drv->right_down = right_down;
-    if (right_down) {
-      event->button = BTN_RIGHT;
-      event->event_type = BTN_EVENT_DOWN;
-      return true;
-    } else {
-      event->button = BTN_RIGHT;
-      event->event_type = BTN_EVENT_UP;
-      return true;
-    }
-  }
-#endif
-
-#ifdef BTN_POWER_PIN
-  bool power_down =
-      (GPIO_PIN_RESET == HAL_GPIO_ReadPin(BTN_POWER_PORT, BTN_POWER_PIN));
-
-  if (drv->power_down != power_down) {
-    drv->power_down = power_down;
-    if (power_down) {
-      event->button = BTN_POWER;
-      event->event_type = BTN_EVENT_DOWN;
-      return true;
-    } else {
-      event->button = BTN_POWER;
-      event->event_type = BTN_EVENT_UP;
-      return true;
-    }
-  }
-#endif
-
-  return 0;
+  button_fsm_t* fsm = &drv->tls[systask_id(systask_active())];
+  return button_fsm_get_event(fsm, new_state, event);
 }
 
 bool button_is_down(button_t button) {
-  button_driver_t *drv = &g_button_driver;
+  button_driver_t* drv = &g_button_driver;
 
   if (!drv->initialized) {
     return false;
   }
 
-  switch (button) {
-#ifdef BTN_LEFT_PIN
-    case BTN_LEFT:
-      return drv->left_down;
-#endif
-#ifdef BTN_RIGHT_PIN
-    case BTN_RIGHT:
-      return drv->right_down;
-#endif
-#ifdef BTN_POWER_PIN
-    case BTN_POWER:
-      return drv->power_down;
-#endif
-    default:
-      return false;
-  }
+  return (button_read_state(drv) & (1 << button)) != 0;
 }
 
 #ifdef BTN_EXTI_INTERRUPT_HANDLER
@@ -221,4 +190,40 @@ void BTN_EXTI_INTERRUPT_HANDLER(void) {
 }
 #endif
 
+static void on_task_created(void* context, systask_id_t task_id) {
+  button_driver_t* drv = (button_driver_t*)context;
+  button_fsm_t* fsm = &drv->tls[task_id];
+  button_fsm_init(fsm);
+}
+
+static void on_event_poll(void* context, bool read_awaited,
+                          bool write_awaited) {
+  button_driver_t* drv = (button_driver_t*)context;
+
+  UNUSED(write_awaited);
+
+  if (read_awaited) {
+    uint32_t state = button_read_state(drv);
+    syshandle_signal_read_ready(SYSHANDLE_BUTTON, &state);
+  }
+}
+
+static bool on_check_read_ready(void* context, systask_id_t task_id,
+                                void* param) {
+  button_driver_t* drv = (button_driver_t*)context;
+  button_fsm_t* fsm = &drv->tls[task_id];
+
+  uint32_t new_state = *(uint32_t*)param;
+
+  return button_fsm_event_ready(fsm, new_state);
+}
+
+static const syshandle_vmt_t g_button_handle_vmt = {
+    .task_created = on_task_created,
+    .task_killed = NULL,
+    .check_read_ready = on_check_read_ready,
+    .check_write_ready = NULL,
+    .poll = on_event_poll,
+};
+
 #endif  // KERNEL_MODE

core/embed/io/button/unix/button.c

@@ -20,23 +20,19 @@
 #include <trezor_bsp.h>
 #include <trezor_rtl.h>
 
-#include <SDL.h>
-
 #include <io/button.h>
+#include <sys/sysevent_source.h>
+#include <sys/unix/sdl_event.h>
+
+#include "../button_fsm.h"
 
 // Button driver state
 typedef struct {
   bool initialized;
-
-#ifdef BTN_LEFT_KEY
-  bool left_down;
-#endif
-#ifdef BTN_RIGHT_KEY
-  bool right_down;
-#endif
-#ifdef BTN_POWER_KEY
-  bool power_down;
-#endif
+  // Global state of buttons
+  uint32_t state;
+  // Each task has its own state machine
+  button_fsm_t tls[SYSTASK_MAX_TASKS];
 } button_driver_t;
 
 // Button driver instance
@@ -44,8 +40,12 @@ static button_driver_t g_button_driver = {
     .initialized = false,
 };
 
+// Forward declarations
+static const syshandle_vmt_t g_button_handle_vmt;
+static void button_sdl_event_filter(void* context, SDL_Event* sdl_event);
+
 bool button_init(void) {
-  button_driver_t *drv = &g_button_driver;
+  button_driver_t* drv = &g_button_driver;
 
   if (drv->initialized) {
     return true;
@@ -53,79 +53,128 @@ bool button_init(void) {
 
   memset(drv, 0, sizeof(button_driver_t));
 
+  if (!syshandle_register(SYSHANDLE_BUTTON, &g_button_handle_vmt, drv)) {
+    goto cleanup;
+  }
+
+  if (!sdl_events_register(button_sdl_event_filter, drv)) {
+    goto cleanup;
+  }
+
   drv->initialized = true;
-
   return true;
-}
-
-bool button_get_event(button_event_t *event) {
-  button_driver_t *drv = &g_button_driver;
-
-  memset(event, 0, sizeof(button_event_t));
-
-  if (!drv->initialized) {
-    return 0;
-  }
-
-  SDL_Event sdl_event;
-
-  if (SDL_PollEvent(&sdl_event) > 0 &&
-      (sdl_event.type == SDL_KEYDOWN || sdl_event.type == SDL_KEYUP) &&
-      !sdl_event.key.repeat) {
-    bool down = (sdl_event.type == SDL_KEYDOWN);
-    uint32_t evt_type = down ? BTN_EVENT_DOWN : BTN_EVENT_UP;
-
-    switch (sdl_event.key.keysym.sym) {
-#ifdef BTN_LEFT_KEY
-      case BTN_LEFT_KEY:
-        drv->left_down = down;
-        event->event_type = evt_type;
-        event->button = BTN_LEFT;
-        return true;
-#endif
-#ifdef BTN_RIGHT_KEY
-      case BTN_RIGHT_KEY:
-        drv->right_down = down;
-        event->event_type = evt_type;
-        event->button = BTN_RIGHT;
-        return true;
-#endif
-#ifdef BTN_POWER_KEY
-      case BTN_POWER_KEY:
-        drv->power_down = down;
-        event->event_type = evt_type;
-        event->button = BTN_POWER;
-        return true;
-#endif
-      default:
-        break;
-    }
-  }
 
+cleanup:
+  button_deinit();
   return false;
 }
 
-bool button_is_down(button_t button) {
-  button_driver_t *drv = &g_button_driver;
+void button_deinit(void) {
+  button_driver_t* drv = &g_button_driver;
+
+  syshandle_unregister(SYSHANDLE_BUTTON);
+
+  sdl_events_unregister(button_sdl_event_filter, drv);
+
+  memset(drv, 0, sizeof(button_driver_t));
+}
+
+// Called from global event loop to filter and process SDL events
+static void button_sdl_event_filter(void* context, SDL_Event* sdl_event) {
+  button_driver_t* drv = &g_button_driver;
+
+  if (sdl_event->type != SDL_KEYDOWN && sdl_event->type != SDL_KEYUP) {
+    return;
+  }
+
+  if (sdl_event->key.repeat) {
+    return;
+  }
+
+  button_t button;
+
+  switch (sdl_event->key.keysym.sym) {
+#ifdef BTN_LEFT_KEY
+    case BTN_LEFT_KEY:
+      button = BTN_LEFT;
+      break;
+#endif
+#ifdef BTN_RIGHT_KEY
+    case BTN_RIGHT_KEY:
+      button = BTN_RIGHT;
+      break;
+#endif
+#ifdef BTN_POWER_KEY
+    case BTN_POWER_KEY:
+      button = BTN_POWER;
+      break;
+#endif
+    default:
+      return;
+  }
+
+  if (sdl_event->type == SDL_KEYDOWN) {
+    drv->state |= (1 << button);
+  } else {
+    drv->state &= ~(1 << button);
+  }
+}
+
+static uint32_t button_read_state(button_driver_t* drv) {
+  sdl_events_poll();
+  return drv->state;
+}
+
+bool button_get_event(button_event_t* event) {
+  button_driver_t* drv = &g_button_driver;
+  memset(event, 0, sizeof(*event));
 
   if (!drv->initialized) {
     return false;
   }
 
-  switch (button) {
-#ifdef BTN_LEFT_KEY
-    case BTN_LEFT:
-      return drv->left_down;
-#endif
-#ifdef BTN_RIGHT_KEY
-    case BTN_RIGHT:
-      return drv->right_down;
-#endif
-#ifdef BTN_POWER_KEY
-    case BTN_POWER:
-      return drv->power_down;
-#endif
-    default:
-      return false;
+  uint32_t new_state = button_read_state(drv);
+
+  button_fsm_t* fsm = &drv->tls[systask_id(systask_active())];
+  return button_fsm_get_event(fsm, new_state, event);
+}
+
+bool button_is_down(button_t button) {
+  button_driver_t* drv = &g_button_driver;
+
+  if (!drv->initialized) {
+    return false;
+  }
+
+  return (button_read_state(drv) & (1 << button)) != 0;
+}
+
+static void on_event_poll(void* context, bool read_awaited,
+                          bool write_awaited) {
+  button_driver_t* drv = (button_driver_t*)context;
+
+  UNUSED(write_awaited);
+
+  if (read_awaited) {
+    uint32_t state = button_read_state(drv);
+    syshandle_signal_read_ready(SYSHANDLE_BUTTON, &state);
   }
 }
+
+static bool on_check_read_ready(void* context, systask_id_t task_id,
+                                void* param) {
+  button_driver_t* drv = (button_driver_t*)context;
+  button_fsm_t* fsm = &drv->tls[task_id];
+
+  uint32_t new_state = *(uint32_t*)param;
+
+  return button_fsm_event_ready(fsm, new_state);
+}
+
+static const syshandle_vmt_t g_button_handle_vmt = {
+    .task_created = NULL,
+    .task_killed = NULL,
+    .check_read_ready = on_check_read_ready,
+    .check_write_ready = NULL,
+    .poll = on_event_poll,
+};

core/embed/projects/bootloader/bootui.c

@@ -70,15 +70,11 @@ void ui_click(void) {
 
 void ui_click(void) {
   for (;;) {
-    button_event_t event = {0};
-    button_get_event(&event);
     if (button_is_down(BTN_LEFT) && button_is_down(BTN_RIGHT)) {
       break;
     }
   }
   for (;;) {
-    button_event_t event = {0};
-    button_get_event(&event);
     if (!button_is_down(BTN_LEFT) && !button_is_down(BTN_RIGHT)) {
       break;
     }

core/embed/projects/bootloader/main.c

@@ -362,8 +362,6 @@ int bootloader_main(void) {
     }
   }
 #elif defined USE_BUTTON
-  button_event_t btn_evt = {0};
-  button_get_event(&btn_evt);
   if (button_is_down(BTN_LEFT)) {
     touched = 1;
   }

core/embed/projects/prodtest/cmd/prodtest_button.c

@@ -67,10 +67,6 @@ static void test_button_combination(cli_t* cli, uint32_t timeout, button_t btn1,
   cli_trace(cli, "Waiting for button combination to be pressed...");
 
   while (true) {
-    // Event must be read before calling `button_is_down()`
-    button_event_t e = {0};
-    button_get_event(&e);
-
     if (button_is_down(btn1) && button_is_down(btn2)) {
       break;
     } else if (ticks_expired(expire_time)) {
@@ -84,10 +80,6 @@ static void test_button_combination(cli_t* cli, uint32_t timeout, button_t btn1,
   cli_trace(cli, "Waiting for buttons to be released...");
 
   while (true) {
-    // Event must be read before calling `button_is_down()`
-    button_event_t e = {0};
-    button_get_event(&e);
-
     if (!button_is_down(btn1) && !button_is_down(btn2)) {
       break;
     } else if (ticks_expired(expire_time)) {

core/site_scons/models/T2B1/emulator.py

@@ -50,6 +50,7 @@ def configure(
 
     if "input" in features_wanted:
         sources += ["embed/io/button/unix/button.c"]
+        sources += ["embed/io/button/button_fsm.c"]
         paths += ["embed/io/button/inc"]
         features_available.append("button")
         defines += [("USE_BUTTON", "1")]

core/site_scons/models/T2B1/trezor_r_v10.py

@@ -50,6 +50,7 @@ def configure(
 
     if "input" in features_wanted:
         sources += ["embed/io/button/stm32/button.c"]
+        sources += ["embed/io/button/button_fsm.c"]
         paths += ["embed/io/button/inc"]
         features_available.append("button")
         defines += [("USE_BUTTON", "1")]

core/site_scons/models/T3B1/emulator.py

@@ -50,6 +50,7 @@ def configure(
 
     if "input" in features_wanted:
         sources += ["embed/io/button/unix/button.c"]
+        sources += ["embed/io/button/button_fsm.c"]
         paths += ["embed/io/button/inc"]
         features_available.append("button")
         defines += [("USE_BUTTON", "1")]

core/site_scons/models/T3B1/trezor_t3b1_revB.py

@@ -49,6 +49,7 @@ def configure(
 
     if "input" in features_wanted:
         sources += ["embed/io/button/stm32/button.c"]
+        sources += ["embed/io/button/button_fsm.c"]
         paths += ["embed/io/button/inc"]
         features_available.append("button")
         defines += [("USE_BUTTON", "1")]

core/site_scons/models/T3W1/trezor_t3w1_revA.py

@@ -63,6 +63,7 @@ def configure(
         paths += ["embed/io/touch/inc"]
         features_available.append("touch")
         sources += ["embed/io/button/stm32/button.c"]
+        sources += ["embed/io/button/button_fsm.c"]
         paths += ["embed/io/button/inc"]
         features_available.append("button")
         defines += [

core/site_scons/models/T3W1/trezor_t3w1_revB.py

@@ -63,6 +63,7 @@ def configure(
         paths += ["embed/io/touch/inc"]
         features_available.append("touch")
         sources += ["embed/io/button/stm32/button.c"]
+        sources += ["embed/io/button/button_fsm.c"]
         paths += ["embed/io/button/inc"]
         features_available.append("button")
         defines += [

core/site_scons/models/T3W1/trezor_t3w1_revC.py

@@ -63,6 +63,7 @@ def configure(
         paths += ["embed/io/touch/inc"]
         features_available.append("touch")
         sources += ["embed/io/button/stm32/button.c"]
+        sources += ["embed/io/button/button_fsm.c"]
         paths += ["embed/io/button/inc"]
         features_available.append("button")
         defines += [