Text Structure and Styling

In the Slides API, text can be contained in shapes or in table cells. Before you can manipulate and style text, you need to understand its structure and how styling works.

This page describes how text is represented in the Slides API.

Sequences of text elements

The text contained in a shape or a table cell is made up of a sequence of TextElement structures. This sequence represents the structure of text, in the order it appears from start to end.

For example, consider the contents of this slide—all contained in one text box:

The slide above has one text box, whose text field contains a sequence of text elements as shown in the following diagram:

More concretely, this sequence of text is represented in the Slides API as follows:

"textElements": [ {
    "endIndex": 224,
    "paragraphMarker": { "style": {} }
  }, {
    "endIndex": 130,
    "textRun": { "content": "Li lingues differe in li grammatica e li vocabules. Omnicos directe al desirabilite de un nov ", "style": {} }
  }, {
    "endIndex": 143,
    "startIndex": 130,
    "textRun": { "content": "lingua franca", "style": { "italic": True } }
  }, {
    "endIndex": 224,
    "startIndex": 143,
    "textRun": { "content": ": solmen va esser necessi far:\n", "style": {} }
  }, {
    "endIndex": 243,
    "startIndex": 224,
    "paragraphMarker": {
      "style": { "indentStart": { "magnitude": 36, "unit": "PT" }, "direction": "LEFT_TO_RIGHT", "indentFirstLine": { "magnitude": 18, "unit": "PT" }, "spacingMode": "COLLAPSE_LISTS" },
      "bullet": { "listId": "foo123", "glyph": "\u25cf" }
    }
  }, {
    "endIndex": 243,
    "startIndex": 224,
    "textRun": { "content": "uniform grammatica\n", "style": {} }
  }, {
    "endIndex": 257,
    "startIndex": 243,
    "paragraphMarker": {
        "style": { "indentStart": { "magnitude": 36, "unit": "PT" }, "direction": "LEFT_TO_RIGHT", "indentFirstLine": { "magnitude": 18, "unit": "PT" }, "spacingMode": "COLLAPSE_LISTS" },
        "bullet": { "listId": "foo123", "glyph": "\u25cf" }
    }
}, {
    "endIndex": 257,
    "startIndex": 243,
    "textRun": { "content": "Pronunciation\n", "style": {} }
}, {
    "endIndex": 277,
    "startIndex": 257,
    "paragraphMarker": {
        "style": { "indentStart": { "magnitude": 36, "unit": "PT" }, "indentFirstLine": { "magnitude": 18, "unit": "PT" }, "spacingMode": "COLLAPSE_LISTS" },
        "bullet": { "listId": "foo123", "glyph": "\u25cf" }
    }
}, {
    "endIndex": 277,
    "startIndex": 257,
    "textRun": { "content": "plu sommun paroles.\n", "style": {} }
}, {
    "endIndex": 500,
    "startIndex": 277,
    "paragraphMarker": { "style": {} }
}, {
    "endIndex": 500,
    "startIndex": 277,
    "textRun": { "content": "Ka swu thefognay, tay waddeant varpa u inzo.\n", "style": {} }
}]

TextElement contents

Each text element contains a zero-based start index and end index, which describe the element's location within the full text of the page element, together with one of the following types of text object:

Modifying text contents

When you need to modify text using the Slides API, you don't have to explicitly create all the appropriate text elements. Instead, you can operate on text like you would in the Slides editor: by inserting text, deleting ranges, and updating styles on ranges. These operations implicitly create ParagraphMarker and TextRun elements as needed to reflect your changes.

Inserting text

You can insert text at an index using the InsertTextRequest request in a call to batchUpdate. This method's insertionIndex field specifies where to insert the text; you can compute this index using the start and end index fields inside text elements.

Text insertion has some side effects that mirror the behavior of the Slides editor:

• Inserting a newline character implicitly creates a new paragraph, creating a ParagraphMarker text element that starts at the newline's index and ends at the following newline. The paragraph style—including bullet and list details — is copied from the current paragraph to the new paragraph.
• The style of inserted characters is determined automatically, generally keeping the same text style that existed at the insertion index. As a result, the text is generally inserted into the existing TextRun at that index. You can update this style later using an UpdateTextStyle request.

Deleting text

You can delete a range of text using the DeleteTextRequest message in a call to batchUpdate. Deleting text involves some subtleties:

• A deletion that crosses a paragraph boundary merges the two paragraphs, deleting the separating ParagraphMarker text element.
• The new merged paragraph will use a combined paragraph style, matching behavior in the Slides editor.
• A deletion whose range encompasses a text run removes all the content from a text run, and it also deletes the text run itself.
• A deletion whose range encompasses an AutoText element deletes the AutoText element.

Updating text style

The rendered appearance of text in a slide is determined by text style properties:

• Paragraph styles like indention, alignment, and bullet glyphs, are defined by properties on paragraph markers.
• Character styles like bold, italic, and underline, are defined by properties on individual text runs.

Updating character style

You can update character styles using the UpdateTextStyleRequest message in a call to batchUpdate.

Like other text operations, the character style is applied to a range of text and implicitly creates new TextRun objects as needed.

Setting some character styles implicitly updates other related styles to match the behavior in the Slides editor. For example, adding a link automatically changes the text foreground color and underline properties. See the TextStyle reference documentation for more details.

Updating paragraph style

You can update paragraph styles using the UpdateParagraphStyleRequest message in a call to batchUpdate.

The Slides API supports a CreateParagraphBulletsRequest that mirrors the functionality of the bullet presets in the Slides editor for creation of bulleted and numbered lists. Similarly, DeleteParagraphBulletsRequest removes any existing bullets on paragraphs.

Inherited styles

Some shapes, known as placeholders, can inherit text styles from other, parent shapes: see placeholders to learn more about shape inheritance in general.

This section focuses on how style inheritance works to create the final, rendered text styles displayed in a slide.

Style representation in placeholders

The section on placeholders describes how inheritance works between parent and child shapes. Inheritance of text styles is handled by additional features within the inheritance model:

• Properties of ParagraphMaker text elements define paragraph formatting.
• Properties of TextRun text elements define character formatting.
• The content of parent placeholders contains eight such ParagraphMarker/TextRun pairs (to support eight levels of list nesting).
• A child placeholder inherits its default text properties from these text elements in its parent's text content.

The following diagram shows one way to visualize these relationships:

The first ParagraphMarker/TextRun in the parent shape determines most of the inherited text styling; the styling in the remaining seven pairs only affects paragraphs at progressively more-deeply nested bullet levels:

To access these pairs of text elements, use their explicit index within the textElements field as shown in the snippet below, which shows setting the default (inheritable) styling for level 0 and non-list paragraphs:

"text": {
  "textElements": [  {
     "startIndex": 0,
     "endIndex": 1,
     "paragraphMarker": {
       "style": {  "alignment": "START",  ...  },
       "bullet": {  "nestingLevel": 0,  ...  }
     }
   },{
     "startIndex": 0,
     "endIndex": 1,
     "textRun": {
       "content": "\n",
       "style": {  "foregroundColor": {  "opaqueColor": {  "themeColor": "DARK1"  }  },  }
     }
   },{
     ...
   } ]
 }

Note that the content field of a parent shape's TextRun always consists of a single newline character.

Inherited styles can be overridden

A child shape can specify styling properties on the ParagraphMarker and TextRun elements in its content. These locally specified properties will override any inherited properties within their local scope. Elements that do not specify any style will use the corresponding style inherited from the parent.

Removing an explicit style property from a child shape, so that it is no longer set, will cause it to inherit from the parent.

Example

Given the inheritance shown in the diagram above, suppose the shape ParentPlaceholder has the following text content:

"text": {
  "textElements": [
    { "startIndex": 0,  "endIndex": 1,
      "paragraphMarker": {
        "style": {"alignment": "START", ...},
        "bullet": {"nestingLevel": 0, ...}
      }
    },
    { "startIndex": 0,  "endIndex": 1,
      "textRun": {
        "content": "\n",
        "style": {"foregroundColor": {"opaqueColor": {"themeColor": "DARK1"} }, }
        ...
      }
    },
    { "startIndex": 1,  "endIndex": 2,
      "paragraphMarker": {
        "style": {"alignment": "END", ...},
        "bullet": {"nestingLevel": 1, ...}
      }
    },
    { "startIndex": 1,  "endIndex": 2,
      "textRun": {
        "content": "\n",
        "style": {"foregroundColor": {"opaqueColor": {"themeColor": "LIGHT1"} }, ...}
      }
    },
   ...
  ]
}

And suppose the shape ChildPlaceholder has the following text content:

"text": {
  "textElements": [
    { "startIndex": 0,  "endIndex": 1,
      "paragraphMarker": {
        "style": {},
      }
    },
    { "startIndex": 0,  "endIndex": 1,
      "textRun": {
        "content": "This is my first paragraph\n",
        "style": {},
      }
      ...
    },
    {  "startIndex": 1,  "endIndex": 2,
      "paragraphMarker": {
        "style": {},
        "bullet": {
          "nestingLevel": 1,
          "listId": "someListId",
          "glyph": "●"
        }
      }
    },
    { "startIndex": 1,  "endIndex": 2,
      "textRun": {
        "content": "This paragraph is in a list\n",
        "style": {},
        ...
      }
    }
  ]
}

This results in the outcomes described in the following paragraphs.

Style inheritance for a plain paragraph

The child shape's first paragraph, which includes the text "This is my first paragraph", is a plain paragraph (not in a list). No elements in its text content specify any style properties, so it inherits all its character and paragraph styles from its parent. This causes the following rendering:

• Text: "This is my first paragraph" is the text rendered. Text itself is never inherited.
• Alignment: The text is rendered with START alignment, inherited from the parent's first ParagraphMarker.
• Foreground color: The text is rendered with DARK1 foreground color, inherited from the parent's first TextRun.

Style inheritance for a list paragraph

The next paragraph, which includes the text "This paragraph is in a list", is in a bulleted list at nesting level 1, since its corresponding ParagraphMarker has its bullet field set to this level. As a result, it inherits text and paragraph style from nesting level 1 in the parent. This results in the following rendering:

• Text: "This paragraph is in a list" is the text rendered. Text itself is never inherited.
• Alignment: The text is rendered with "END" alignment, inherited from the parent's second ParagraphMarker.
• Foreground color: The text is rendered with LIGHT1 text foreground color, inherited from the parent's second TextRun.

Interactions between updating and inheriting text and paragraph styles

Text styles that aren't set in a child shape will inherit values from its parent. Text styles that are set in the child will "override" the parent values in some local scope.

You can use an UpdateTextStyleRequest to unset a child shape's text style, so that it no longer has a local override and thus inherits its syltes from the parent shape. Additionally, updating the child's text style to match the value inherited from a parent implicitly unsets the style so that it uses the inherited value.

This does not affect the visual appearance of text immediately after an update, but it may matter if you later update a paragraph or text style in a parent placeholder. This inheritance behavior matches the behavior of the Slides editor, so you can experiment with the outcomes of style changes before working against the API.

Example

Consider the definitions in the previous example for ChildPlaceholder and ParentPlaceholder.

Now suppose you submit this UpdateTextStyleRequest:

{ "updateTextStyle": {
    "objectId": "ChildPlaceholder",
    "style": {"foregroundColor": {"opaqueColor": {"themeColor": "DARK1"} }, },
    "textRange": { "type": "ALL" },
    "fields": "foregroundColor"
  }
}

This request attempts to set a DARK1 foregroundColor to all of ChildPlaceholder's text, using a field mask to specify that only the foreground color of the element should change. This request has the following outcomes:

• First paragraph: The new foregroundColor matches the inherited foregroundColor, so this style is unchanged and still inherits.
• Second paragraph: The new foregroundColor doesn't match the inherited foregroundColor, so the second paragraph's foreground color is updated to DARK1.

ChildPlaceholder's text content is now:

"text": {
  "textElements": [
    { "startIndex": 0,  "endIndex": 1,
      "paragraphMarker": {
        "style": {},
      }
    },
    { "startIndex": 0,  "endIndex": 1,
      "textRun": {
        "content": "This is my first paragraph\n",
        "style": {},
      }
      ...
    },
    { "startIndex": 1,  "endIndex": 2,
      "paragraphMarker": {
        "style": {},
        "bullet": {"nestingLevel": 1, "listId": "someListId", "glyph": "●" }
      }
    },
    { "startIndex": 1,  "endIndex": 2,
      "textRun": {
        "content": "This paragraph is in a list\n",
        "style": {"foregroundColor": {"opaqueColor": {"themeColor": "DARK1"} }, },
        ...
      }
    }
  ]
}

Bullet glyph text style

Like normal text, bullet glyphs have a text style that controls how the glyph is rendered. These text styles cannot be modified using the Slides API directly. However, if you use an UpdateTextStyleRequest to update a complete paragraph that includes a bullet, the Slides API updates the bullet glyph's text style to match.

Bullet glyph text styles follow a slightly different inheritance hierarchy than normal text styles.

1. A bullet at a certain nesting level first inherits from the TextStyle set in the NestingLevel.bullet_style field inside the bullet's List object.
2. It next inherits from the corresponding NestingLevel.bullet_style in its parent placeholder's List.
3. Finally it seeks to inherit from remaining parent placeholder objects.