qt 4.7-在父窗口中特定位置的位置对话框

Question

Environment:

• XP and later, OS X 10.6.8 and later
• Qt 4.7.1 64 bit, building under OS X 10.6.8
• Qt Creator 2.1.0

Issue:

I have a mainwindow. In it, some container levels down, is a gui element cb_B_8 , a button. I can get that element's position and size this way, and it comes to me precisely relative to the mainwindow area under its titlebar ( theParent is the mainwindow instance):

QPoint buttpos = theParent->ui->cb_B_8->pos(); // = 473,576
QRect  butrect = theParent->ui->cb_B_8->rect(); // = 0,0,32,26

That makes perfect sense to me.

So now I open a dialog this way:

void MainWindow::mybandersnatch(int i)
{
setband *tt;
    tt = new setband(this,i);
    tt->show();
    tt->raise();
}

}

The dialog starts like this:

setband::setband(QWidget *parent, int bindex) :
QDialog(parent),
ui(new Ui::setband)
{
    theParent = parent; // dialog local copy of parent
    ...

It opens in the center of my mainwindow ( theParent )

I want to re-position this dialog so that the top of the dialog window is directly under the lower edge of the button.

I have been unable to retrieve the dialog's position relative to the window that is its parent; and I have also been unable to position the dialog relative to that window. I have tried a few things that seemed likely but have come up empty.

Conceptually, considering I have the button's position relative to the window, if I had the dialog's position relative to the window, and could likewise set it relative to the window, I want to set it exactly this way:

newDialogYpos = button.yPos + button.yHeight; // below button

buttonXcenter = button.xPos + (button.width / 2);
dialogHalfWidth = dialog.width / 2;
newDialogXpos = buttonXcenter - dialogHalfWidth;

One slight twist to this is it has to work on multi-display computers. Seems like some of the positioning is relative to the main display, which is pathological for my needs - the dialog has to end up relative to the app, not the main display. I've tried these things to get positions, and come up dry:

t = this->rect(); // = 0,0 410x320 (dialog)
dp = this->pos(); // = 0,0 (dialog)
ap = QApplication::desktop()->screen()->pos(); // = 0,0 ?
mtp = this->window()->mapFromParent(tmw->pos()); // = 0,0 ?

// main display is 1680x1050, app is not on this display
// this display is 1280x1024 (I have 8 displays on this machine)
// this display is immediately to the right of the main display
// app window is fullscreen, so at top left of 1280x1024 display
// this result seems to incorporate other display positions + widths:
// ------------------------------------------------------------------
w = QApplication::desktop()->screen()->rect(); // = 0,0 3080x1050

Appreciate any insight.

Answer 1

The pos of a widget inside another is in the coordinate system of its parent. You need to use the parent's mapToGlobal() to get screen coordinates.

Answer 2

So, I got everything I was asking figured out, although apparently the Qt get titlebar height method is broken. The following works on all of the eight displays in my system:

void setband::positionDialog()
{
QPoint mw; // mainwindow position
QPoint bp; // button position
QRect r;   // button rect
QRect d;   // dialog rect
QPoint sp; // target position of all this
QPoint addend; // the delta required to move from dialog position
int tbh; // titlebar height (qt returns 0 for this, sigh)

    bp = theParent->ui->cb_B_11->pos();                 // = 473,576
    mw = theParent->pos();                              // = 1600,0
    d = this->rect();                                   // = 0,0 410x320 (dialog)
    r = theParent->ui->cb_B_11->rect();                 // = 0,0 32,26
    addend.setX(-((d.width() / 2) - (r.width() / 2)));  // position dialog centered on X re button
//  tbh = QApplication::style()->pixelMetric(QStyle::PM_TitleBarHeight); // get title bar height returns 0?!?
    tbh = 25;                                           // use bloody guesswork, then
    addend.setY(tbh + r.height());                      // need to move past button pos+height+titlebarHeight
    sp = mw + bp + addend;                              // combine all this
    this->move(sp);                                     // and move
}