CODEWITHSUNDEEP
c++qtfonts
pavelkolodin
pavelkolodin

Reputation: 2967

Qt: heightForWidth for word-wrapped text

I have a box with a varying width and a word-wrapped text. I need to set new height every time user changes box's width. The box is displayed by QPainter inside paintEvent(QPaintEvent *) function. There is several solutions, for example current (not very smart, i do this in resizeEvent(QResizeEvent *)):

unsigned new_height = 0; // the height i want to find out.
unsigned given_width = width();
QPainter painter (this); // i need painter, because i want to ask it's default font.
QLabel lab;              // the widget that can do word-wrap.
lab.setText( "A word wrapped text" ); // the text
lab.setFont( painter.font() );        // set QPainter's default font.
lab.setWordWrap( true );              // enable word-wrap
new_height = lab.heightForWidth( given_width ); // tada! :)

But the code is overkill:
1) Creading QPainter is not good outside paintEvent(QPaintEvent *);
2) BUT i need QPainter to request what font is default for it to ask metrics for that font.

Should i change my code and do this operation with help of QPainter::boundingRect() inside the paintEvent(QPaintEvent *) function? But i'd like to reduce CPU consumption inside the paintEvent(QPaintEvent *) and calculate new height only when width changed, but not every time it displayed.

What is other solutions for the purpose of subject? QFontMectircs?

Upvotes: 0

Views: 1966

Answers (1)

Stephen Chu
Stephen Chu

Reputation: 12832

I think you have the right idea of using QFontMetrics. The whole idea of the class is to assist the situations like you have here. Take a look at QFontMetricsF::boundingRect()

Use your target paint rectangle as the input rect, but set the height to the max that your widget height. I'd just put something like INT_MAX in it just to be sure. :)

Upvotes: 1

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