text: 
  #include <string.h>
  #include "shared-module/displayio/__init__.h"
  
  #include "lib/utils/interrupt_char.h"
  #include "py/reload.h"
  #include "py/runtime.h"
  #include "shared-bindings/board/__init__.h"
  #include "shared-bindings/displayio/Bitmap.h"
  #include "shared-bindings/displayio/Display.h"
  #include "shared-bindings/displayio/Group.h"
  #include "shared-bindings/displayio/Palette.h"
  #include "shared-module/displayio/area.h"
  #include "supervisor/shared/autoreload.h"
  #include "supervisor/shared/display.h"
  #include "supervisor/memory.h"
  #include "supervisor/usb.h"
  
  primary_display_t displays[CIRCUITPY_DISPLAY_LIMIT];
  
  static inline void swap(int16_t* a, int16_t* b) {
      int16_t temp = *a;
      *a = *b;
      *b = temp;
  }
  
  // Check for recursive calls to displayio_refresh_displays.
  bool refresh_displays_in_progress = false;
  
  void displayio_refresh_displays(void) {
      if (mp_hal_is_interrupted()) {
          return;
      }
      if (reload_requested) {
          // Reload is about to happen, so don't redisplay.
          return;
      }
  
      if (refresh_displays_in_progress) {
          // Don't allow recursive calls to this routine.
          return;
      }
  
      refresh_displays_in_progress = true;
  
      for (uint8_t i = 0; i < CIRCUITPY_DISPLAY_LIMIT; i++) {
          if (displays[i].display.base.type == NULL || displays[i].display.base.type == &mp_type_NoneType) {
              // Skip null display.
              continue;
          }
          displayio_display_obj_t* display = &displays[i].display;
          displayio_display_update_backlight(display);
  
          // Time to refresh at specified frame rate?
          if (!displayio_display_frame_queued(display)) {
              // Too soon. Try next display.
              continue;
          }
          if (displayio_display_refresh_queued(display)) {
              if (!displayio_display_begin_transaction(display)) {
                  // Can't acquire display bus; skip updating this display. Try next display.
                  continue;
              }
              displayio_display_end_transaction(display);
  
              displayio_area_t whole_screen = {
                  .x1 = 0,
                  .y1 = 0,
                  .x2 = display->width,
                  .y2 = display->height
              };
              if (display->transpose_xy) {
                  swap(&whole_screen.x2, &whole_screen.y2);
              }
  
              uint16_t buffer_size = 512;
  
              uint16_t subrectangles = 1;
              uint16_t rows_per_buffer = displayio_area_height(&whole_screen);
              if (displayio_area_size(&whole_screen) > buffer_size) {
                  rows_per_buffer = buffer_size / displayio_area_width(&whole_screen);
                  subrectangles = displayio_area_height(&whole_screen) / rows_per_buffer;
                  buffer_size = rows_per_buffer * displayio_area_width(&whole_screen);
              }
              uint32_t buffer[buffer_size / 2];
  
              for (uint16_t j = 0; j < subrectangles; j++) {
                  displayio_area_t subrectangle = {
                      .x1 = 0,
                      .y1 = rows_per_buffer * j,
                      .x2 = displayio_area_width(&whole_screen),
                      .y2 = rows_per_buffer * (j + 1)
                  };
  
                  displayio_display_begin_transaction(display);
                  displayio_display_set_region_to_update(display, subrectangle.x1, subrectangle.y1,
                                                                  subrectangle.x2, subrectangle.y2);
                  displayio_display_end_transaction(display);
  
                  // Handle display mirroring and transpose.
                  displayio_area_t transformed_subrectangle;
                  displayio_buffer_transform_t transform;
                  if (display->mirror_x) {
                      uint16_t width = displayio_area_width(&whole_screen);
                      transformed_subrectangle.x1 = width - subrectangle.x2;
                      transformed_subrectangle.x2 = width - subrectangle.x1;
                  } else {
                      transformed_subrectangle.x1 = subrectangle.x1;
                      transformed_subrectangle.x2 = subrectangle.x2;
                  }
                  if (display->mirror_y != display->transpose_xy) {
                      uint16_t height = displayio_area_height(&whole_screen);
                      transformed_subrectangle.y1 = height - subrectangle.y2;
                      transformed_subrectangle.y2 = height - subrectangle.y1;
                  } else {
                      transformed_subrectangle.y1 = subrectangle.y1;
                      transformed_subrectangle.y2 = subrectangle.y2;
                  }
                  transform.width = transformed_subrectangle.x2 - transformed_subrectangle.x1;
                  transform.height = transformed_subrectangle.y2 - transformed_subrectangle.y1;
                  if (display->transpose_xy) {
                      int16_t y1 = transformed_subrectangle.y1;
                      int16_t y2 = transformed_subrectangle.y2;
                      transformed_subrectangle.y1 = transformed_subrectangle.x1;
                      transformed_subrectangle.y2 = transformed_subrectangle.x2;
                      transformed_subrectangle.x1 = y1;
                      transformed_subrectangle.x2 = y2;
                  }
                  transform.transpose_xy = display->transpose_xy;
                  transform.mirror_x = display->mirror_x;
                  transform.mirror_y = display->mirror_y;
                  transform.scale = 1;
  
                  uint32_t mask[(buffer_size / 32) + 1];
                  for (uint16_t k = 0; k < (buffer_size / 32) + 1; k++) {
                      mask[k] = 0x00000000;
                  }
                  bool full_coverage = displayio_group_get_area(display->current_group, &transform, &transformed_subrectangle, mask, buffer);
                  if (!full_coverage) {
                      uint32_t index = 0;
                      uint32_t current_mask = 0;
                      for (int16_t y = subrectangle.y1; y < subrectangle.y2; y++) {
                          for (int16_t x = subrectangle.x1; x < subrectangle.x2; x++) {
                              if (index % 32 == 0) {
                                  current_mask = mask[index / 32];
                              }
                              if ((current_mask & (1 << (index % 32))) == 0) {
                                  ((uint16_t*) buffer)[index] = 0x0000;
                              }
                              index++;
                          }
                      }
                  }
  
                  if (!displayio_display_begin_transaction(display)) {
                      // Can't acquire display bus; skip the rest of the data. Try next display.
                      break;
                  }
                  displayio_display_send_pixels(display, buffer, buffer_size / 2);
                  displayio_display_end_transaction(display);
  
                  // TODO(tannewt): Make refresh displays faster so we don't starve other
                  // background tasks.
                  usb_background();
              }
          }
          displayio_display_finish_refresh(display);
      }
  
      // All done.
      refresh_displays_in_progress = false;
  }
  
  void common_hal_displayio_release_displays(void) {
      for (uint8_t i = 0; i < CIRCUITPY_DISPLAY_LIMIT; i++) {
          mp_const_obj_t bus_type = displays[i].fourwire_bus.base.type;
          if (bus_type == NULL) {
              continue;
          } else if (bus_type == &displayio_fourwire_type) {
              common_hal_displayio_fourwire_deinit(&displays[i].fourwire_bus);
          } else if (bus_type == &displayio_parallelbus_type) {
              common_hal_displayio_parallelbus_deinit(&displays[i].parallel_bus);
          }
          displays[i].fourwire_bus.base.type = &mp_type_NoneType;
      }
      for (uint8_t i = 0; i < CIRCUITPY_DISPLAY_LIMIT; i++) {
          release_display(&displays[i].display);
          displays[i].display.base.type = &mp_type_NoneType;
      }
  
      supervisor_stop_terminal();
  }
  
  void reset_displays(void) {
      #if CIRCUITPY_DISPLAYIO
      // The SPI buses used by FourWires may be allocated on the heap so we need to move them inline.
      for (uint8_t i = 0; i < CIRCUITPY_DISPLAY_LIMIT; i++) {
          if (displays[i].fourwire_bus.base.type != &displayio_fourwire_type) {
              continue;
          }
          displayio_fourwire_obj_t* fourwire = &displays[i].fourwire_bus;
          if (((uint32_t) fourwire->bus) < ((uint32_t) &displays) ||
              ((uint32_t) fourwire->bus) > ((uint32_t) &displays + CIRCUITPY_DISPLAY_LIMIT)) {
              busio_spi_obj_t* original_spi = fourwire->bus;
              #if BOARD_SPI
                  // We don't need to move original_spi if it is the board.SPI object because it is
                  // statically allocated already. (Doing so would also make it impossible to reference in
                  // a subsequent VM run.)
                  if (original_spi == common_hal_board_get_spi()) {
                      continue;
                  }
              #endif
              memcpy(&fourwire->inline_bus, original_spi, sizeof(busio_spi_obj_t));
              fourwire->bus = &fourwire->inline_bus;
              // Check for other displays that use the same spi bus and swap them too.
              for (uint8_t j = i + 1; j < CIRCUITPY_DISPLAY_LIMIT; j++) {
                  if (displays[i].fourwire_bus.bus == original_spi) {
                      displays[i].fourwire_bus.bus = &fourwire->inline_bus;
                  }
              }
          }
      }
  
      for (uint8_t i = 0; i < CIRCUITPY_DISPLAY_LIMIT; i++) {
          if (displays[i].display.base.type == NULL) {
              continue;
          }
          displayio_display_obj_t* display = &displays[i].display;
          display->auto_brightness = true;
          common_hal_displayio_display_show(display, &circuitpython_splash);
      }
      #endif
  }
  
  void displayio_area_shift(displayio_area_t* area, int16_t dx, int16_t dy) {
      area->x1 += dx;
      area->y1 += dy;
      area->x2 += dx;
      area->y2 += dy;
  }
  
  bool displayio_area_compute_overlap(const displayio_area_t* a,
                                      const displayio_area_t* b,
                                      displayio_area_t* overlap) {
      overlap->x1 = a->x1;
      if (b->x1 > overlap->x1) {
          overlap->x1 = b->x1;
      }
      overlap->x2 = a->x2;
      if (b->x2 < overlap->x2) {
          overlap->x2 = b->x2;
      }
      if (overlap->x1 > overlap->x2) {
          return false;
      }
      overlap->y1 = a->y1;
      if (b->y1 > overlap->y1) {
          overlap->y1 = b->y1;
      }
      overlap->y2 = a->y2;
      if (b->y2 < overlap->y2) {
          overlap->y2 = b->y2;
      }
      if (overlap->y1 > overlap->y2) {
          return false;
      }
      return true;
  }
  
  uint16_t displayio_area_width(const displayio_area_t* area) {
      return area->x2 - area->x1;
  }
  
  uint16_t displayio_area_height(const displayio_area_t* area) {
      return area->y2 - area->y1;
  }
  
  uint32_t displayio_area_size(const displayio_area_t* area) {
      return displayio_area_width(area) * displayio_area_height(area);
  }
  
  bool displayio_area_equal(const displayio_area_t* a, const displayio_area_t* b) {
      return a->x1 == b->x1 &&
             a->y1 == b->y1 &&
             a->x2 == b->x2 &&
             a->y2 == b->y2;
  }
  