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Thread: Problem of highlighting text in QPlainTextEdit

  1. #1
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    Default Re: Problem of highlighting text in QPlainTextEdit

    Hello,

    My Qt SDK version 4.7.4

    I use QPlainTextEdit::setExtraSelections() to highlight some words in QPlainTextEdit. Following is my code:

    Qt Code:
    1. int pos = block.position() + p;
    2.  
    3. QTextEdit::ExtraSelection selection;
    4. selection.cursor = QTextCursor(ui->plainTextEdit->document());
    5. selection.cursor.setPosition( pos );
    6. selection.cursor.setPosition( pos+highlighText.length(), QTextCursor::KeepAnchor );
    7. selection.format.setBackground( backBrush );
    8. selection.format.setForeground( textBrush );
    9. selection.format.setProperty( QTextFormat::OutlinePen, outlinePen );
    10.  
    11. extraSelections.append( selection );
    To copy to clipboard, switch view to plain text mode 

    Everything seems Ok. But when I move the caret on the position of highlighted text. The highlighted text is not diaplay ok. Please refer to the screenshot.

    2012-4-17 11-27-39.png


    Added after 4 minutes:


    I attached a demo for the problem.

    Can anybody help me?
    Attached Files Attached Files
    Last edited by topfortune; 17th April 2012 at 05:48.

  2. #2
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    Default Re: Problem of highlighting text in QPlainTextEdit

    maybe you can force periodical the paint event. It looks like Qt <-> WinXP problem. I have got a similar problem with QPlaintextEdits on some Windows machines with Qt 4.5.3.

  3. #3
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    Default Re: Problem of highlighting text in QPlainTextEdit

    Quote Originally Posted by dennis81 View Post
    maybe you can force periodical the paint event. It looks like Qt <-> WinXP problem. I have got a similar problem with QPlaintextEdits on some Windows machines with Qt 4.5.3.
    I built and run the demo on Ubuntu. And the problem also exists on Linux. I think it must be a bug of Qt. I really don't want to modify the source code of Qt for the problem.

  4. #4
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    Default Re: Problem of highlighting text in QPlainTextEdit

    Can anybody help me? Please....

  5. #5
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    Default Re: Problem of highlighting text in QPlainTextEdit

    Hey,

    I appreciate your effort to prepare the example, in return (and because I had some spare time) I've got solution for you

    It seems in fact to be a bug in Qt, from what I've found the paint event for QPlainTextEdit contains wrong rectangle.

    You can fix it yourself without affecting Qt source, here's how:

    Qt Code:
    1. class FixedQPlainTextEdit : public QPlainTextEdit // I guess the name tells you everything :)
    2. {
    3. public:
    4. FixedQPlainTextEdit( QWidget* parent = 0 ) : QPlainTextEdit( parent ) {}
    5.  
    6. protected:
    7. void paintEvent( QPaintEvent* e )
    8. {
    9. QPaintEvent* fixed_event = new QPaintEvent( e->rect().adjusted( -1, -1, 0, 0 ) ); // left and top edge need to be adjusted by -1
    10. QPlainTextEdit::paintEvent( fixed_event );
    11. delete fixed_event;
    12. }
    13. };
    14.  
    15. // below is your example code using the FixedQPlainTextEdit class
    16. MainWindow::MainWindow( QWidget* p )
    17. :
    18. {
    19. QPlainTextEdit* e = new FixedQPlainTextEdit();
    20. e->appendPlainText( "#include <QtGui/QApplication>" );
    21. e->appendPlainText( "#include \"mainwindow.h\"" );
    22. e->appendPlainText( "" );
    23. e->appendPlainText( "int main(int argc, char *argv[])" );
    24. e->appendPlainText( "{" );
    25. e->appendPlainText( " QApplication a(argc, argv);" );
    26. e->appendPlainText( " MainWindow w;" );
    27. e->appendPlainText( " w.show();" );
    28. e->appendPlainText( "" );
    29. e->appendPlainText( " return a.exec();" );
    30. e->appendPlainText( "}" );
    31.  
    32. this->setCentralWidget( e );
    33.  
    34. QList<QTextEdit::ExtraSelection> extraSelections;
    35.  
    36. QBrush backBrush( Qt::yellow );
    37. QBrush textBrush( Qt::black );
    38. QPen outlinePen( Qt::gray, 1 );
    39. QString highlighText = "QApplication";
    40.  
    41. for( int i=0; i<e->document()->blockCount(); i++ )
    42. {
    43. QTextBlock block = e->document()->findBlockByNumber( i );
    44. if( block.isValid() )
    45. {
    46. QString text = block.text();
    47. int p;
    48.  
    49. if( (p=text.indexOf(highlighText)) != -1 )
    50. {
    51. int pos = block.position() + p;
    52.  
    53. QTextEdit::ExtraSelection selection;
    54. selection.cursor = QTextCursor(e->document());
    55. selection.cursor.setPosition( pos );
    56. selection.cursor.setPosition( pos+highlighText.length(), QTextCursor::KeepAnchor );
    57. selection.format.setBackground( backBrush );
    58. selection.format.setForeground( textBrush );
    59. selection.format.setProperty( QTextFormat::OutlinePen, outlinePen );
    60.  
    61. extraSelections.append( selection );
    62. }
    63. }
    64. }
    65.  
    66. e->setExtraSelections( extraSelections );
    67. }
    To copy to clipboard, switch view to plain text mode 

    Edit:
    Btw the issue was also visible if you placed the cursor under the highlighted field.

  6. #6
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    Default Re: Problem of highlighting text in QPlainTextEdit

    Hi Spitfire,

    It's perfect! Thank you so much for your solution. Thank you so much!!!

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