Tilegrid transpose fix

[dhalbert]

Fixes #4284.

Setting TileGrid.transpose_xy forces the x,y, height, and width to be recalculated using _update_current_x() and _update_current_y(). Those routines did not handle the case of absolute_transform being NULL, and used NULL as a pointer to a transform, so they got random values.

This fix guards against that. It also makes null_transform, an identity transform defined for use in vectorio, be a global. I used it in the fix.

An alternative fix would be to never use a NULL pointer as absolute_transform, and use &null_transform to signify the identity transform. However, absolute_transform == NULL is overloaded as a signal the object has no parent, and so some other indicator (like a new bool) would have to be added to indicate no parent. I chose not to make that change now.

I tested this with a simple quotes example on a PyPortal Titano. @jposada202020 if you would like to test this in the context of your full program, that would be great. Thanks.

[jposada202020]

Yes, I will try this tonight, Both in the "simple" code example and in the New Veritcal label proposal. Thanks @dhalbert . I will report my tests in here.

[jposada202020]

This was tested in using the new proposal Vertical Library PR122 adafruit/Adafruit_CircuitPython_Display_Text#122

in
Adafruit CircuitPython 6.1.0 on 2021-01-21; Seeeduino Wio Terminal with samd51p19

Results

and in the MAGTAG
Adafruit CircuitPython 6.2.0-beta.3-14-gb1268107a-dirty on 2021-03-04; Adafruit MagTag with ESP32S2

Results

Test code

import board
import displayio
from adafruit_bitmap_font import bitmap_font
from adafruit_display_text import vertical_label
from adafruit_display_text import label
import time
import digitalio

display = board.DISPLAY

# wait until we can draw
time.sleep(display.time_to_refresh)

# main group to hold everything
group = displayio.Group()

# white background. Scaled to save RAM
bg_bitmap = displayio.Bitmap(display.width // 8, display.height // 8, 1)
bg_palette = displayio.Palette(1)
bg_palette[0] = 0xFFFFFF
bg_sprite = displayio.TileGrid(bg_bitmap, x=0, y=0, pixel_shader=bg_palette)
bg_group = displayio.Group(scale=8)
bg_group.append(bg_sprite)
group.append(bg_group)


text = "Reporting"
MEDIUM_FONT = bitmap_font.load_font("/fonts/Helvetica-Bold-16.bdf")
BIG_FONT = bitmap_font.load_font("/fonts/LeagueSpartan-Bold-16.bdf")


bitmap = displayio.Bitmap(320, 3, 2)
palette = displayio.Palette(2)
palette[0] = 0x004400
palette[1] = 0x00FFFF
tile_grid = displayio.TileGrid(bitmap, pixel_shader=palette, x=0, y=115)

bitmap2 = displayio.Bitmap(3, 260, 2)
tile_grid2 = displayio.TileGrid(bitmap2, pixel_shader=palette, x=120, y=10)



text_areah = label.Label(
    BIG_FONT,
    text=text,
    color=0xFFFFFF,
    background_color=0x666666,
    x=0,
    y=100,
)

group.append(text_areah)


text_area3 = vertical_label.Label(BIG_FONT,
 text="Pythoñ", 
 color=0x00FF00, 
 background_color=0x990022,  
 background_tight=False, 
 padding_top=5, 
 padding_bottom=0, 
 padding_left=0,
 padding_right=0,
 x=120,
 y=80,
 base_alignment= True,
 scale=1,)
group.append(text_area3)

text_area4 = vertical_label.Label(MEDIUM_FONT,
 text="Circuit", 
 color=0x00FF00, 
 background_color=0x990099,  
 background_tight=False, 
 padding_top=4, 
 padding_bottom=15, 
 padding_left=10,
 padding_right=3,
 base_alignment= True,
 x=100,
 y=80
 ,)
group.append(text_area4)
text_area = vertical_label.Label(MEDIUM_FONT, text="V6.2.0",
 color=0x00FF00, background_color=0x330099, padding_left=0,
  padding_right=0, padding_bottom=0, padding_top=0, anchor_point=(0.0, 0.0),
  anchored_position=(130,120),
  scale=2,)
text_area2 = label.Label(MEDIUM_FONT,
 text=text, color=0xAA5522, 
 background_color=0x22FF44, 
 padding_left=0, 
 padding_right=0, 
 padding_bottom=0, 
 padding_top=0, 
 x=20,
 y=140)

group.append(text_area)
group.append(text_area2)

group.append(tile_grid)
group.append(tile_grid2)

# show the main group and refresh.
display.show(group)
display.refresh()

while True:
  pass

[jepler]

Makes sense to me, but I didn't test.

[tannewt]

This PR regresses TinyUSB from 52855 to 28029