tui: Use half-block characters for memory graph

This is easier to read than our previous braille version, and looks
nicer when rendered in a browser or VS Code. It's less granular,
unfortunately. The braille version added a new dot for each ~6%, and
this implementation adds a new half block for each ~11%.

This also fixes a longstanding bug: the graph was only showing half of
the data points it should have been showing. Each data point would
become the right braille column of one cell as well as the left braille
column of the next cell, so we only had half the horizontal granularity
we intended to have.

Signed-off-by: Matt Wozniski <[email protected]>

Author: godlygeek

src/memray/reporters/tui.py

@@ -12,7 +12,6 @@
 from math import ceil
 from typing import Any
 from typing import DefaultDict
-from typing import Deque
 from typing import Dict
 from typing import Iterable
 from typing import List
@@ -96,26 +95,22 @@ def __init__(
         maxval: float = 1.0
         minval: float = 0.0
         self._width = max_data_points
-        self._graph: List[Deque[str]] = [
-            deque(maxlen=self._width) for _ in range(height)
-        ]
         self._height = height
         self._minval = minval
         self._maxval = maxval
-        self._previous_blocks = [0] * height
         values = [minval] * (2 * self._width + 1)
-        self._values = deque(values, maxlen=2 * self._width + 1)
+        self._values = deque(values, maxlen=2 * self._width)
+
         self._lookup = [
-            [" ", "⢀", "⢠", "⢰", "⢸"],
-            ["⡀", "⣀", "⣠", "⣰", "⣸"],
-            ["⡄", "⣄", "⣤", "⣴", "⣼"],
-            ["⡆", "⣆", "⣦", "⣶", "⣾"],
-            ["⡇", "⣇", "⣧", "⣷", "⣿"],
+            [" ", "▗", "▐"],
+            ["▖", "▄", "▟"],
+            ["▌", "▙", "█"],
         ]
+
         self.border_title = "Heap Usage"
 
     def _value_to_blocks(self, value: float) -> List[int]:
-        dots_per_block = 4
+        dots_per_block = 2
         if value < self._minval:
             n_dots = 0
         elif value > self._maxval:
@@ -135,8 +130,8 @@ def _value_to_blocks(self, value: float) -> List[int]:
 
     def add_value(self, value: float) -> None:
         if value > self._maxval:
-            self._reset_max(value)
-        self._add_value_without_redraw(value)
+            self._maxval = value
+        self._values.append(value)
         if self._maxval > 1:
             self.border_subtitle = (
                 f"{size_fmt(int(value))}"
@@ -145,30 +140,20 @@ def add_value(self, value: float) -> None:
             )
         self.refresh()
 
-    def _reset_max(self, value: float) -> None:
-        self._graph = [deque(maxlen=self._width) for _ in range(self._height)]
-        self._maxval = value
-        for old_val in list(self._values):
-            self._add_value_without_redraw(old_val)
-
-    def _add_value_without_redraw(self, value: float) -> None:
-        blocks = self._value_to_blocks(value)
-
-        chars = reversed(
-            tuple(self._lookup[i0][i1] for i0, i1 in zip(self._previous_blocks, blocks))
-        )
+    def render_line(self, y: int) -> Strip:
+        graph: list[list[str]] = [[] for _ in range(self._height)]
+        blocks_by_index = [self._value_to_blocks(value) for value in self._values]
 
-        for row, char in enumerate(chars):
-            self._graph[row].append(char)
+        for left, right in zip(blocks_by_index[::2], blocks_by_index[1::2]):
+            for row, char in enumerate(
+                reversed(tuple(self._lookup[li][ri] for li, ri in zip(left, right)))
+            ):
+                graph[row].append(char)
 
-        self._values.append(value)
-        self._previous_blocks = blocks
-
-    def render_line(self, y: int) -> Strip:
-        if y > len(self._graph):
+        if y > len(graph):
             return Strip.blank(self.size.width)
         data = " " * self.size.width
-        data += "".join(self._graph[y])
+        data += "".join(graph[y])
         data = data[-self.size.width :]
         return Strip([Segment(data, self.rich_style)])