feat: Add three animations that together simulate a typing animation (#3612)

* feat: Add animations that together simulate typing

AddTextLetterByLetterWithCursor

RemoveTextLetterByLetterWithCursor

Blink

* Revert "feat: Add animations that together simulate typing"

This reverts commit 5fe2568.

* Revert "Revert "feat: Add animations that together simulate typing""

This reverts commit 6a8244a.

* Add new animations to __all__

* Temporarily remove docs example

* Modify "Blink" and add docstring examples back in

To avoid 0-second animations, which fail docstring test

* Address requested changes

Fix imports
Remove redundant constructor arguments
Improve names

* Shorten names

Author: VinhPhmCng

manim/animation/creation.py

@@ -70,6 +70,8 @@ def construct(self):
     "RemoveTextLetterByLetter",
     "ShowSubmobjectsOneByOne",
     "AddTextWordByWord",
+    "TypeWithCursor",
+    "UntypeWithCursor",
 ]
 
 
@@ -80,15 +82,16 @@ def construct(self):
 
 if TYPE_CHECKING:
     from manim.mobject.text.text_mobject import Text
+    from manim.scene.scene import Scene
 
+from manim.constants import RIGHT, TAU
 from manim.mobject.opengl.opengl_surface import OpenGLSurface
 from manim.mobject.opengl.opengl_vectorized_mobject import OpenGLVMobject
 from manim.utils.color import ManimColor
 
 from .. import config
 from ..animation.animation import Animation
 from ..animation.composition import Succession
-from ..constants import TAU
 from ..mobject.mobject import Group, Mobject
 from ..mobject.types.vectorized_mobject import VMobject
 from ..utils.bezier import integer_interpolate
@@ -674,3 +677,176 @@ def __init__(
             )
         )
         super().__init__(*anims, **kwargs)
+
+
+class TypeWithCursor(AddTextLetterByLetter):
+    """Similar to :class:`~.AddTextLetterByLetter` , but with an additional cursor mobject at the end.
+
+    Parameters
+    ----------
+    time_per_char
+        Frequency of appearance of the letters.
+    cursor
+        :class:`~.Mobject` shown after the last added letter.
+    buff
+        Controls how far away the cursor is to the right of the last added letter.
+    keep_cursor_y
+        If ``True``, the cursor's y-coordinate is set to the center of the ``Text`` and remains the same throughout the animation. Otherwise, it is set to the center of the last added letter.
+    leave_cursor_on
+        Whether to show the cursor after the animation.
+
+    .. tip::
+        This is currently only possible for class:`~.Text` and not for class:`~.MathTex`.
+
+
+    Examples
+    --------
+
+    .. manim:: InsertingTextExample
+        :ref_classes: Blink
+
+        class InsertingTextExample(Scene):
+            def construct(self):
+                text = Text("Inserting", color=PURPLE).scale(1.5).to_edge(LEFT)
+                cursor = Rectangle(
+                    color = GREY_A,
+                    fill_color = GREY_A,
+                    fill_opacity = 1.0,
+                    height = 1.1,
+                    width = 0.5,
+                ).move_to(text[0]) # Position the cursor
+
+                self.play(TypeWithCursor(text, cursor))
+                self.play(Blink(cursor, blinks=2))
+
+    """
+
+    def __init__(
+        self,
+        text: Text,
+        cursor: Mobject,
+        buff: float = 0.1,
+        keep_cursor_y: bool = True,
+        leave_cursor_on: bool = True,
+        time_per_char: float = 0.1,
+        reverse_rate_function=False,
+        introducer=True,
+        **kwargs,
+    ) -> None:
+        self.cursor = cursor
+        self.buff = buff
+        self.keep_cursor_y = keep_cursor_y
+        self.leave_cursor_on = leave_cursor_on
+        super().__init__(
+            text,
+            time_per_char=time_per_char,
+            reverse_rate_function=reverse_rate_function,
+            introducer=introducer,
+            **kwargs,
+        )
+
+    def begin(self) -> None:
+        self.y_cursor = self.cursor.get_y()
+        self.cursor.initial_position = self.mobject.get_center()
+        if self.keep_cursor_y:
+            self.cursor.set_y(self.y_cursor)
+
+        self.cursor.set_opacity(0)
+        self.mobject.add(self.cursor)
+        super().begin()
+
+    def finish(self) -> None:
+        if self.leave_cursor_on:
+            self.cursor.set_opacity(1)
+        else:
+            self.cursor.set_opacity(0)
+            self.mobject.remove(self.cursor)
+        super().finish()
+
+    def clean_up_from_scene(self, scene: Scene) -> None:
+        if not self.leave_cursor_on:
+            scene.remove(self.cursor)
+        super().clean_up_from_scene(scene)
+
+    def update_submobject_list(self, index: int) -> None:
+        for mobj in self.all_submobs[:index]:
+            mobj.set_opacity(1)
+
+        for mobj in self.all_submobs[index:]:
+            mobj.set_opacity(0)
+
+        if index != 0:
+            self.cursor.next_to(
+                self.all_submobs[index - 1], RIGHT, buff=self.buff
+            ).set_y(self.cursor.initial_position[1])
+        else:
+            self.cursor.move_to(self.all_submobs[0]).set_y(
+                self.cursor.initial_position[1]
+            )
+
+        if self.keep_cursor_y:
+            self.cursor.set_y(self.y_cursor)
+        self.cursor.set_opacity(1)
+
+
+class UntypeWithCursor(TypeWithCursor):
+    """Similar to :class:`~.RemoveTextLetterByLetter` , but with an additional cursor mobject at the end.
+
+    Parameters
+    ----------
+    time_per_char
+        Frequency of appearance of the letters.
+    cursor
+        :class:`~.Mobject` shown after the last added letter.
+    buff
+        Controls how far away the cursor is to the right of the last added letter.
+    keep_cursor_y
+        If ``True``, the cursor's y-coordinate is set to the center of the ``Text`` and remains the same throughout the animation. Otherwise, it is set to the center of the last added letter.
+    leave_cursor_on
+        Whether to show the cursor after the animation.
+
+    .. tip::
+        This is currently only possible for class:`~.Text` and not for class:`~.MathTex`.
+
+
+    Examples
+    --------
+
+    .. manim:: DeletingTextExample
+        :ref_classes: Blink
+
+        class DeletingTextExample(Scene):
+            def construct(self):
+                text = Text("Deleting", color=PURPLE).scale(1.5).to_edge(LEFT)
+                cursor = Rectangle(
+                    color = GREY_A,
+                    fill_color = GREY_A,
+                    fill_opacity = 1.0,
+                    height = 1.1,
+                    width = 0.5,
+                ).move_to(text[0]) # Position the cursor
+
+                self.play(UntypeWithCursor(text, cursor))
+                self.play(Blink(cursor, blinks=2))
+
+    """
+
+    def __init__(
+        self,
+        text: Text,
+        cursor: VMobject | None = None,
+        time_per_char: float = 0.1,
+        reverse_rate_function=True,
+        introducer=False,
+        remover=True,
+        **kwargs,
+    ) -> None:
+        super().__init__(
+            text,
+            cursor=cursor,
+            time_per_char=time_per_char,
+            reverse_rate_function=reverse_rate_function,
+            introducer=introducer,
+            remover=remover,
+            **kwargs,
+        )

manim/animation/indication.py

@@ -34,6 +34,7 @@ def construct(self):
     "ApplyWave",
     "Circumscribe",
     "Wiggle",
+    "Blink",
 ]
 
 from typing import Callable, Iterable, Optional, Tuple, Type, Union
@@ -53,6 +54,7 @@ def construct(self):
 from ..animation.fading import FadeIn, FadeOut
 from ..animation.movement import Homotopy
 from ..animation.transform import Transform
+from ..animation.updaters.update import UpdateFromFunc
 from ..constants import *
 from ..mobject.mobject import Mobject
 from ..mobject.types.vectorized_mobject import VGroup, VMobject
@@ -76,8 +78,6 @@ class FocusOn(Transform):
         The color of the spotlight.
     run_time
         The duration of the animation.
-    kwargs
-        Additional arguments to be passed to the :class:`~.Succession` constructor
 
     Examples
     --------
@@ -643,3 +643,68 @@ def __init__(
             super().__init__(
                 ShowPassingFlash(frame, time_width, run_time=run_time), **kwargs
             )
+
+
+class Blink(Succession):
+    """Blink the mobject.
+
+    Parameters
+    ----------
+    mobject
+        The mobject to be blinked.
+    time_on
+        The duration that the mobject is shown for one blink.
+    time_off
+        The duration that the mobject is hidden for one blink.
+    blinks
+        The number of blinks
+    hide_at_end
+        Whether to hide the mobject at the end of the animation.
+    kwargs
+        Additional arguments to be passed to the :class:`~.Succession` constructor.
+
+    Examples
+    --------
+
+    .. manim:: BlinkingExample
+
+        class BlinkingExample(Scene):
+            def construct(self):
+                text = Text("Blinking").scale(1.5)
+                self.add(text)
+                self.play(Blink(text, blinks=3))
+
+    """
+
+    def __init__(
+        self,
+        mobject: Mobject,
+        time_on: float = 0.5,
+        time_off: float = 0.5,
+        blinks: int = 1,
+        hide_at_end: bool = False,
+        **kwargs
+    ):
+        animations = [
+            UpdateFromFunc(
+                mobject,
+                update_function=lambda mob: mob.set_opacity(1.0),
+                run_time=time_on,
+            ),
+            UpdateFromFunc(
+                mobject,
+                update_function=lambda mob: mob.set_opacity(0.0),
+                run_time=time_off,
+            ),
+        ] * blinks
+
+        if not hide_at_end:
+            animations.append(
+                UpdateFromFunc(
+                    mobject,
+                    update_function=lambda mob: mob.set_opacity(1.0),
+                    run_time=time_on,
+                ),
+            )
+
+        super().__init__(*animations, **kwargs)