![]() |
Home · Overviews · Examples |
The QTextCursor class offers an API to access and modify QTextDocuments. More...
The QTextCursor class offers an API to access and modify QTextDocuments.
Text cursors are objects that are used to access and modify the contents and underlying structure of text documents via a programming interface that mimics the behavior of a cursor in a text editor. QTextCursor contains information about both the cursor's position within a QTextDocument and any selection that it has made.
QTextCursor is modeled on the way a text cursor behaves in a text editor, providing a programmatic means of performing standard actions through the user interface. A document can be thought of as a single string of characters with the cursor's position being between any two characters (or at the very beginning or very end of the document). Documents can also contain tables, lists, images, and other objects in addition to text but, from the developer's point of view, the document can be treated as one long string. Some portions of that string can be considered to lie within particular blocks (e.g. paragraphs), or within a table's cell, or a list's item, or other structural elements. When we refer to "current character" we mean the character immediately after the cursor position in the document; similarly the "current block" is the block that contains the cursor position.
A QTextCursor also has an anchor position. The text that is between the anchor and the position is the selection. If anchor == position there is no selection.
The cursor position can be changed programmatically using setPosition and movePosition; the latter can also be used to select text. For selections see selectionStart, selectionEnd, hasSelection, clearSelection, and removeSelectedText.
If the position is at the start of a block atBlockStart returns true; and if it is at the end of a block atBlockEnd returns true. The format of the current character is returned by charFormat, and the format of the current block is returned by blockFormat.
Formatting can be applied to the current text document using the setCharFormat, mergeCharFormat, setBlockFormat and mergeBlockFormat functions. The 'set' functions will replace the cursor's current character or block format, while the 'merge' functions add the given format properties to the cursor's current format. If the cursor has a selection the given format is applied to the current selection. Note that when only parts of a block is selected the block format is applied to the entire block. The text at the current character position can be turned into a list using createList.
Deletions can be achieved using deleteChar, deletePreviousChar, and removeSelectedText.
Text strings can be inserted into the document with the insertText function, blocks (representing new paragraphs) can be inserted with insertBlock.
Existing fragments of text can be inserted with insertFragment but, if you want to insert pieces of text in various formats, it is usually still easier to use insertText and supply a character format.
Various types of higher-level structure can also be inserted into the document with the cursor:
Actions can be grouped (i.e. treated as a single action for undo/redo) using beginEditBlock and endEditBlock.
Cursor movements are limited to valid cursor positions. In Latin writing this is usually after every character in the text. In some other writing systems cursor movements are limited to "clusters" (e.g. a syllable in Devanagari, or a base letter plus diacritics). Functions such as movePosition and deleteChar limit cursor movement to these valid positions.
See also Rich Text Processing.
Copyright © 2007 Trolltech | Trademarks | Qt Jambi 4.3.2_01 |