Tex如何渲染公式.md

[ManimGL 源码解读] Tex 如何渲染公式 - SunJul31 2022

Tex 能根据传入的 tex_strings 渲染公式，根据 tex_to_color_map 设置颜色，根据 tex_strings、isolate 和 tex_to_color_map 拆出 submobjects（比如用于 TransformMatchingTex TransformMatchingShapes 不香吗）。

# manimlib.mobject.svg.tex_mobject.Tex
class Tex(SingleStringTex):
    CONFIG = {...}

    def __init__(self, *tex_strings: str, **kwargs):
        digest_config(self, kwargs)
        self.tex_strings = self.break_up_tex_strings(tex_strings)
        full_string = self.arg_separator.join(self.tex_strings)
        super().__init__(full_string, **kwargs)
        self.break_up_by_substrings()
        self.set_color_by_tex_to_color_map(self.tex_to_color_map)

        if self.organize_left_to_right:
            self.organize_submobjects_left_to_right()
    
    ...

digest_config 处理参数，接着调用 break_up_tex_strings 将 tex_strings 进一步按照 self.isolate 和 self.tex_to_color_map 拆分。

# manimlib.mobject.svg.tex_mobject.Tex.break_up_tex_strings
def break_up_tex_strings(self, tex_strings: Iterable[str]) -> Iterable[str]:
    # Separate out any strings specified in the isolate
    # or tex_to_color_map lists.
    substrings_to_isolate = [*self.isolate, *self.tex_to_color_map.keys()]
    if len(substrings_to_isolate) == 0:
        return tex_strings
    patterns = (
        "({})".format(re.escape(ss))
        for ss in substrings_to_isolate
    )
    pattern = "|".join(patterns)
    pieces = []
    for s in tex_strings:
        if pattern:
            pieces.extend(re.split(pattern, s))
        else:
            pieces.append(s)
    return list(filter(lambda s: s, pieces))

self.tex_strings 被拼在一起（中间用 self.arg_separator 连接，通常是 ""），存在 full_string 里。调用 SingleStringTex 生成 SVG。调用 self.break_up_by_substrings。这个函数大概是，根据 self.tex_strings 再分别调用 SingleStringTex 渲染 SVG 得到 sub_tex_mob，把它设置为自己的 submobjects。

# manimlib.mobject.svg.tex_mobject.Tex.break_up_by_substrings
def break_up_by_substrings(self):
    """
    Reorganize existing submojects one layer
    deeper based on the structure of tex_strings (as a list
    of tex_strings)
    """
    if len(self.tex_strings) == 1:
        submob = self.copy()
        self.set_submobjects([submob])
        return self
    new_submobjects = []
    curr_index = 0
    config = dict(self.CONFIG)
    config["alignment"] = ""
    for tex_string in self.tex_strings:
        tex_string = tex_string.strip()
        if len(tex_string) == 0:
            continue
        sub_tex_mob = SingleStringTex(tex_string, **config)
        num_submobs = len(sub_tex_mob)
        if num_submobs == 0:
            continue
        new_index = curr_index + num_submobs
        sub_tex_mob.set_submobjects(self[curr_index:new_index])
        new_submobjects.append(sub_tex_mob)
        curr_index = new_index
    self.set_submobjects(new_submobjects)
    return self

调用 self.set_color_by_tex_to_color_map 上色。

# manimlib.mobject.svg.tex_mobject.Tex.set_color_by_tex_to_color_map
def set_color_by_tex_to_color_map(
    self,
    tex_to_color_map: dict[str, ManimColor],
    **kwargs
):
    for tex, color in list(tex_to_color_map.items()):
        self.set_color_by_tex(tex, color, **kwargs)
    return self

set_color_by_tex 能对单个 tex 字符串上色。

# manimlib.mobject.svg.tex_mobject.Tex.set_color_by_tex
def set_color_by_tex(self, tex: str, color: ManimColor, **kwargs):
    self.get_parts_by_tex(tex, **kwargs).set_color(color)
    return self

get_parts_by_tex 查找 tex 对应的部分，包装成 VGroup 返回。

# manimlib.mobject.svg.tex_mobject.Tex.get_parts_by_tex
def get_parts_by_tex(
    self, tex: str, substring: bool = True,
    case_sensitive: bool = True
) -> VGroup:
    def test(tex1, tex2):
        if not case_sensitive:
            tex1 = tex1.lower()
            tex2 = tex2.lower()
        if substring: return tex1 in tex2
        else: return tex1 == tex2

    return VGroup(*filter(
        lambda m: isinstance(m, SingleStringTex) and test(tex, m.get_tex()),
        self.submobjects
    ))

若 self.organize_left_to_right，调用 self.organize_submobjects_left_to_right 把 self.submobjects 按横坐标排序（只是下标改变，位置不变）。