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Drop the FT2Font intermediate buffer. #30059

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Merged
QuLogic merged 1 commit into from
Jan 29, 2026
Merged

Drop the FT2Font intermediate buffer. #30059

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110 changes: 68 additions & 42 deletions lib/matplotlib/backends/backend_agg.py
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Original file line number Diff line number Diff line change
Expand Up @@ -22,7 +22,7 @@
"""

from contextlib import nullcontext
from math import radians, cos, sin
import math

import numpy as np
from PIL import features
Expand All @@ -32,7 +32,7 @@
from matplotlib.backend_bases import (
_Backend, FigureCanvasBase, FigureManagerBase, RendererBase)
from matplotlib.font_manager import fontManager as _fontManager, get_font
from matplotlib.ft2font import LoadFlags
from matplotlib.ft2font import LoadFlags, RenderMode
from matplotlib.mathtext import MathTextParser
from matplotlib.path import Path
from matplotlib.transforms import Bbox, BboxBase
Expand Down Expand Up @@ -71,7 +71,7 @@ def __init__(self, width, height, dpi):
self._filter_renderers = []

self._update_methods()
self.mathtext_parser = MathTextParser('agg')
self.mathtext_parser = MathTextParser('path')

self.bbox = Bbox.from_bounds(0, 0, self.width, self.height)

Expand Down Expand Up @@ -173,48 +173,75 @@ def draw_path(self, gc, path, transform, rgbFace=None):

def draw_mathtext(self, gc, x, y, s, prop, angle):
"""Draw mathtext using :mod:`matplotlib.mathtext`."""
ox, oy, width, height, descent, font_image = \
self.mathtext_parser.parse(s, self.dpi, prop,
antialiased=gc.get_antialiased())

xd = descent * sin(radians(angle))
yd = descent * cos(radians(angle))
x = round(x + ox + xd)
y = round(y - oy + yd)
self._renderer.draw_text_image(font_image, x, y + 1, angle, gc)
# y is downwards.
parse = self.mathtext_parser.parse(
s, self.dpi, prop, antialiased=gc.get_antialiased())
cos = math.cos(math.radians(angle))
sin = math.sin(math.radians(angle))
for font, size, _char, glyph_index, dx, dy in parse.glyphs: # dy is upwards.
font.set_size(size, self.dpi)
hf = font._hinting_factor
font._set_transform(
[[round(0x10000 * cos / hf), round(0x10000 * -sin)],
[round(0x10000 * sin / hf), round(0x10000 * cos)]],
[round(0x40 * (x + dx * cos - dy * sin)),
# FreeType's y is upwards.
round(0x40 * (self.height - y + dx * sin + dy * cos))]
)
bitmap = font._render_glyph(
glyph_index, get_hinting_flag(),
RenderMode.NORMAL if gc.get_antialiased() else RenderMode.MONO)
buffer = np.asarray(bitmap.buffer)
if not gc.get_antialiased():
buffer *= 0xff
# draw_text_image's y is downwards & the bitmap bottom side.
self._renderer.draw_text_image(
buffer,
bitmap.left, int(self.height) - bitmap.top + buffer.shape[0],
0, gc)
rgba = gc.get_rgb()
if len(rgba) == 3 or gc.get_forced_alpha():
rgba = rgba[:3] + (gc.get_alpha(),)
gc1 = self.new_gc()
gc1.set_linewidth(0)
gc1.set_snap(gc.get_snap())
for dx, dy, w, h in parse.rects: # dy is upwards & the rect top side.
if gc1.get_snap() in [None, True]:
# Prevent thin bars from disappearing by growing symmetrically.
if w < 1:
dx -= (1 - w) / 2
w = 1
if h < 1:
dy -= (1 - h) / 2
h = 1
path = Path._create_closed(
[(dx, dy), (dx + w, dy), (dx + w, dy + h), (dx, dy + h)])
self._renderer.draw_path(
gc1, path,
mpl.transforms.Affine2D()
.rotate_deg(angle).translate(x, self.height - y),
rgba)
gc1.restore()

def draw_text(self, gc, x, y, s, prop, angle, ismath=False, mtext=None):
# docstring inherited
if ismath:
return self.draw_mathtext(gc, x, y, s, prop, angle)
font = self._prepare_font(prop)
# We pass '0' for angle here, since it will be rotated (in raster
# space) in the following call to draw_text_image).
font.set_text(s, 0, flags=get_hinting_flag(),
font.set_text(s, angle, flags=get_hinting_flag(),
features=mtext.get_fontfeatures() if mtext is not None else None,
language=mtext.get_language() if mtext is not None else None)
font.draw_glyphs_to_bitmap(
antialiased=gc.get_antialiased())
d = font.get_descent() / 64.0
# The descent needs to be adjusted for the angle.
xo, yo = font.get_bitmap_offset()
xo /= 64.0
yo /= 64.0

rad = radians(angle)
xd = d * sin(rad)
yd = d * cos(rad)
# Rotating the offset vector ensures text rotates around the anchor point.
# Without this, rotated text offsets incorrectly, causing a horizontal shift.
# Applying the 2D rotation matrix.
rotated_xo = xo * cos(rad) - yo * sin(rad)
rotated_yo = xo * sin(rad) + yo * cos(rad)
# Subtract rotated_yo to account for the inverted y-axis in computer graphics,
# compared to the mathematical convention.
x = round(x + rotated_xo + xd)
y = round(y - rotated_yo + yd)

self._renderer.draw_text_image(font, x, y + 1, angle, gc)
for bitmap in font._render_glyphs(
x, self.height - y,
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@QuLogic QuLogic Oct 28, 2025

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If this were trimmed to integers (int(x), int(self.height - y)) then for boxarrow_test_image, all but the first letter in each string remain the same as the old images. I guess keeping the fractional part (i.e., as its written now) gives us the proper sub-pixel positioning?

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@anntzer anntzer Oct 29, 2025 •
edited
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That's the intent, at least. Looks like something similar to #30059 (comment) was happening as well?

RenderMode.NORMAL if gc.get_antialiased() else RenderMode.MONO,
):
buffer = bitmap.buffer
if not gc.get_antialiased():
buffer *= 0xff
self._renderer.draw_text_image(
buffer,
bitmap.left, int(self.height) - bitmap.top + buffer.shape[0],
0, gc)

def get_text_width_height_descent(self, s, prop, ismath):
# docstring inherited
Expand All @@ -224,9 +251,8 @@ def get_text_width_height_descent(self, s, prop, ismath):
return super().get_text_width_height_descent(s, prop, ismath)

if ismath:
ox, oy, width, height, descent, font_image = \
self.mathtext_parser.parse(s, self.dpi, prop)
return width, height, descent
parse = self.mathtext_parser.parse(s, self.dpi, prop)
return parse.width, parse.height, parse.depth

font = self._prepare_font(prop)
font.set_text(s, 0.0, flags=get_hinting_flag())
Expand All @@ -248,8 +274,8 @@ def draw_tex(self, gc, x, y, s, prop, angle, *, mtext=None):
Z = np.array(Z * 255.0, np.uint8)

w, h, d = self.get_text_width_height_descent(s, prop, ismath="TeX")
xd = d * sin(radians(angle))
yd = d * cos(radians(angle))
xd = d * math.sin(math.radians(angle))
yd = d * math.cos(math.radians(angle))
x = round(x + xd)
y = round(y + yd)
self._renderer.draw_text_image(Z, x, y, angle, gc)
Expand Down
6 changes: 5 additions & 1 deletion lib/matplotlib/font_manager.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1712,7 +1712,7 @@ def get_font(font_filepaths, hinting_factor=None):

hinting_factor = mpl._val_or_rc(hinting_factor, 'text.hinting_factor')

return _get_font(
font = _get_font(
# must be a tuple to be cached
paths,
hinting_factor,
Expand All @@ -1721,6 +1721,10 @@ def get_font(font_filepaths, hinting_factor=None):
thread_id=threading.get_ident(),
enable_last_resort=mpl.rcParams['font.enable_last_resort'],
)
# Ensure the transform is always consistent.
font._set_transform([[round(0x10000 / font._hinting_factor), 0], [0, 0x10000]],
[0, 0])
return font


def _load_fontmanager(*, try_read_cache=True):
Expand Down
8 changes: 8 additions & 0 deletions lib/matplotlib/ft2font.pyi
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Original file line number Diff line number Diff line change
Expand Up @@ -70,6 +70,14 @@ class LoadFlags(Flag):
TARGET_LCD = cast(int, ...)
TARGET_LCD_V = cast(int, ...)

class RenderMode(Enum):
NORMAL = cast(int, ...)
LIGHT = cast(int, ...)
MONO = cast(int, ...)
LCD = cast(int, ...)
LCD_V = cast(int, ...)
SDF = cast(int, ...)

class StyleFlags(Flag):
NORMAL = cast(int, ...)
ITALIC = cast(int, ...)
Expand Down
2 changes: 1 addition & 1 deletion lib/matplotlib/tests/test_axes.py
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Original file line number Diff line number Diff line change
Expand Up @@ -6446,7 +6446,7 @@ def test_pie_linewidth_0():
plt.axis('equal')


@image_comparison(['pie_center_radius.png'], style='mpl20', tol=0.01)
@image_comparison(['pie_center_radius.png'], style='mpl20', tol=0.011)
def test_pie_center_radius():
# The slices will be ordered and plotted counter-clockwise.
labels = 'Frogs', 'Hogs', 'Dogs', 'Logs'
Expand Down
1 change: 1 addition & 0 deletions lib/matplotlib/text.py
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Original file line number Diff line number Diff line change
@@ -1,3 +1,3 @@
"""
Classes for including text in a figure.
"""
Expand Down Expand Up @@ -871,6 +871,7 @@
gc.set_alpha(self.get_alpha())
gc.set_url(self._url)
gc.set_antialiased(self._antialiased)
gc.set_snap(self.get_snap())
self._set_gc_clip(gc)

angle = self.get_rotation()
Expand Down
11 changes: 11 additions & 0 deletions src/ft2font.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -283,6 +283,17 @@ void FT2Font::set_size(double ptsize, double dpi)
}
}

void FT2Font::_set_transform(
std::array<std::array<FT_Fixed, 2>, 2> matrix, std::array<FT_Fixed, 2> delta)
{
FT_Matrix m = {matrix[0][0], matrix[0][1], matrix[1][0], matrix[1][1]};
FT_Vector d = {delta[0], delta[1]};
FT_Set_Transform(face, &m, &d);
for (auto & fallback : fallbacks) {
fallback->_set_transform(matrix, delta);
}
}

void FT2Font::set_charmap(int i)
{
if (i >= face->num_charmaps) {
Expand Down
7 changes: 7 additions & 0 deletions src/ft2font.h
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Original file line number Diff line number Diff line change
Expand Up @@ -19,6 +19,7 @@

extern "C" {
#include <ft2build.h>
#include FT_BITMAP_H
#include FT_FREETYPE_H
#include FT_GLYPH_H
#include FT_OUTLINE_H
Expand Down Expand Up @@ -111,6 +112,8 @@ class FT2Font
void close();
void clear();
void set_size(double ptsize, double dpi);
void _set_transform(
std::array<std::array<FT_Fixed, 2>, 2> matrix, std::array<FT_Fixed, 2> delta);
void set_charmap(int i);
void select_charmap(unsigned long i);
std::vector<raqm_glyph_t> layout(std::u32string_view text, FT_Int32 flags,
Expand Down Expand Up @@ -155,6 +158,10 @@ class FT2Font
{
return image;
}
std::vector<FT_Glyph> &get_glyphs()
{
return glyphs;
}
FT_Glyph const &get_last_glyph() const
{
return glyphs.back();
Expand Down
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