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from __future__ import annotations
from textual import events
from textual.app import App, ComposeResult
from textual.geometry import Offset, Region, Size
from textual.reactive import var
from textual.strip import Strip
from textual.scroll_view import ScrollView
from rich.segment import Segment
from rich.style import Style
class CheckerBoard(ScrollView):
COMPONENT_CLASSES = {
"checkerboard--white-square",
"checkerboard--black-square",
"checkerboard--cursor-square",
}
DEFAULT_CSS = """
CheckerBoard > .checkerboard--white-square {
background: #A5BAC9;
}
CheckerBoard > .checkerboard--black-square {
background: #004578;
}
CheckerBoard > .checkerboard--cursor-square {
background: darkred;
}
"""
cursor_square = var(Offset(0, 0))
def __init__(self, board_size: int) -> None:
super().__init__()
self.board_size = board_size
# Each square is 4 rows and 8 columns
self.virtual_size = Size(board_size * 8, board_size * 4)
def on_mouse_move(self, event: events.MouseMove) -> None:
"""Called when the user moves the mouse over the widget."""
mouse_position = event.offset + self.scroll_offset
self.cursor_square = Offset(mouse_position.x // 8, mouse_position.y // 4)
def watch_cursor_square(
self, previous_square: Offset, cursor_square: Offset
) -> None:
"""Called when the cursor square changes."""
def get_square_region(square_offset: Offset) -> Region:
"""Get region relative to widget from square coordinate."""
x, y = square_offset
region = Region(x * 8, y * 4, 8, 4)
# Move the region into the widgets frame of reference
region = region.translate(-self.scroll_offset)
return region
# Refresh the previous cursor square
self.refresh(get_square_region(previous_square))
# Refresh the new cursor square
self.refresh(get_square_region(cursor_square))
def render_line(self, y: int) -> Strip:
"""Render a line of the widget. y is relative to the top of the widget."""
scroll_x, scroll_y = self.scroll_offset # The current scroll position
y += scroll_y # The line at the top of the widget is now `scroll_y`, not zero!
row_index = y // 4 # four lines per row
white = self.get_component_rich_style("checkerboard--white-square")
black = self.get_component_rich_style("checkerboard--black-square")
cursor = self.get_component_rich_style("checkerboard--cursor-square")
if row_index >= self.board_size:
return Strip.blank(self.size.width)
is_odd = row_index % 2
def get_square_style(column: int, row: int) -> Style:
"""Get the cursor style at the given position on the checkerboard."""
if self.cursor_square == Offset(column, row):
square_style = cursor
else:
square_style = black if (column + is_odd) % 2 else white
return square_style
segments = [
Segment(" " * 8, get_square_style(column, row_index))
for column in range(self.board_size)
]
strip = Strip(segments, self.board_size * 8)
# Crop the strip so that is covers the visible area
strip = strip.crop(scroll_x, scroll_x + self.size.width)
return strip
class BoardApp(App):
def compose(self) -> ComposeResult:
yield CheckerBoard(100)
if __name__ == "__main__":
app = BoardApp()
app.run()
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