Query keyboard state in Qt 3

[Pieter from Belgium]

At a certain point in the program I would like to find out whether or not the Control key is pressed.
(How) can I do this in Qt3?

So I am looking for a Qt 3 approach for Qt 4's QApplication::keyboardModifiers().

One solution I can think of is to filter all keyboard events and to do explicit bookkeeping of whether the CTRL key is pressed, but I wonder if there is a simpler approach.

Pieter

[zlatko]

just example from QAsistant

bool MyMainWindow::eventFilter( QObject *obj, QEvent *ev )
    {
        if ( obj == textEdit ) {
            if ( e->type() == QEvent::KeyPress ) {
                QKeyEvent *k = (QKeyEvent*)ev;
                qDebug( "Ate key press %d", k->key() );
                return TRUE;
            } else {
                return FALSE;
            }
        } else {
            // pass the event on to the parent class
            return QMainWindow::eventFilter( obj, ev );
        }
    }

bool MyMainWindow::eventFilter( QObject *obj, QEvent *ev )
    {
        if ( obj == textEdit ) {
            if ( e->type() == QEvent::KeyPress ) {
                QKeyEvent *k = (QKeyEvent*)ev;
                qDebug( "Ate key press %d", k->key() );
                return TRUE;
            } else {
                return FALSE;
            }
        } else {
            // pass the event on to the parent class
            return QMainWindow::eventFilter( obj, ev );
        }
    }

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read about eventFilter()

[Chicken Blood Machine]

At a certain point in the program I would like to find out whether or not the Control key is pressed.
(How) can I do this in Qt3?

So I am looking for a Qt 3 approach for Qt 4's QApplication::keyboardModifiers().

I needed the same thing. Here's my implementation (I subclassed QApplication to do this).

#ifdef Q_WS_WIN
#    include <windows.h>
#    include <shellapi.h>
#else /* Q_WS_X11 */
#    include <X11/Xlib.h>
#endif
#include <qpaintdevice.h>
 
// Implement a way to easily deduce which mousebuttons and modifier
// keys are held down
static Qt::ButtonState get_modifiers()
{
    int result = Qt::NoButton;
 
#ifdef Q_WS_WIN
 
    result |= GetAsyncKeyState(VK_SHIFT) < 0 ? Qt::ShiftButton : 0;
    result |= GetAsyncKeyState(VK_MENU) < 0 ? Qt::AltButton : 0;
    result |= GetAsyncKeyState(VK_CONTROL) < 0 ? Qt::ControlButton : 0;
 
    // Check if left and right mousebuttons have been swapped
    bool swap_buttons = GetSystemMetrics(SM_SWAPBUTTON) != 0;
 
    if (swap_buttons)
    {
        result |= GetAsyncKeyState(VK_LBUTTON) < 0 ? Qt::RightButton : 0;
        result |= GetAsyncKeyState(VK_RBUTTON) < 0 ? Qt::LeftButton : 0;
    }
    else
    { 
        result |= GetAsyncKeyState(VK_LBUTTON) < 0 ? Qt::LeftButton : 0;
        result |= GetAsyncKeyState(VK_RBUTTON) < 0 ? Qt::RightButton : 0;   
    }
    result |= GetAsyncKeyState(VK_MBUTTON) < 0 ? Qt::MidButton : 0;
 
#else /* Q_WS_X11 */
 
    Window root, child;
    int root_x, root_y;
    int win_x, win_y;
    uint keys_buttons;
    bool status = XQueryPointer(QPaintDevice::x11AppDisplay(),
            QPaintDevice::x11AppRootWindow(),
            &root, &child,
            &root_x, &root_y,
            &win_x, &win_y,
            &keys_buttons);
 
    if (status)
    {        
        result |=  keys_buttons & ShiftMask ? Qt::ShiftButton : 0;
        result |=  keys_buttons & Mod1Mask ? Qt::AltButton : 0;
        result |=  keys_buttons & Mod4Mask ? Qt::MetaButton : 0;
        result |=  keys_buttons & ControlMask ? Qt::ControlButton : 0; 
 
        result |=  keys_buttons & Button1Mask ? Qt::LeftButton : 0;
        result |=  keys_buttons & Button2Mask ? Qt::MidButton : 0; 
        result |=  keys_buttons & Button3Mask ? Qt::RightButton : 0; 
    }
#endif
    return Qt::ButtonState(result);
}
 
Qt::ButtonState MyApplication::keyboardModifiers()
{
    return Qt::ButtonState(get_modifiers() & Qt::KeyButtonMask);
}
 
Qt::ButtonState MyApplication::mouseButtons()
{
    return Qt::ButtonState(get_modifiers() & Qt::MouseButtonMask);
}

#ifdef Q_WS_WIN
#    include <windows.h>
#    include <shellapi.h>
#else /* Q_WS_X11 */
#    include <X11/Xlib.h>
#endif
#include <qpaintdevice.h>

// Implement a way to easily deduce which mousebuttons and modifier
// keys are held down
static Qt::ButtonState get_modifiers()
{
    int result = Qt::NoButton;

#ifdef Q_WS_WIN
    
    result |= GetAsyncKeyState(VK_SHIFT) < 0 ? Qt::ShiftButton : 0;
    result |= GetAsyncKeyState(VK_MENU) < 0 ? Qt::AltButton : 0;
    result |= GetAsyncKeyState(VK_CONTROL) < 0 ? Qt::ControlButton : 0;
    
    // Check if left and right mousebuttons have been swapped
    bool swap_buttons = GetSystemMetrics(SM_SWAPBUTTON) != 0;
    
    if (swap_buttons)
    {
        result |= GetAsyncKeyState(VK_LBUTTON) < 0 ? Qt::RightButton : 0;
        result |= GetAsyncKeyState(VK_RBUTTON) < 0 ? Qt::LeftButton : 0;
    }
    else
    { 
        result |= GetAsyncKeyState(VK_LBUTTON) < 0 ? Qt::LeftButton : 0;
        result |= GetAsyncKeyState(VK_RBUTTON) < 0 ? Qt::RightButton : 0;   
    }
    result |= GetAsyncKeyState(VK_MBUTTON) < 0 ? Qt::MidButton : 0;

#else /* Q_WS_X11 */
    
    Window root, child;
    int root_x, root_y;
    int win_x, win_y;
    uint keys_buttons;
    bool status = XQueryPointer(QPaintDevice::x11AppDisplay(),
            QPaintDevice::x11AppRootWindow(),
            &root, &child,
            &root_x, &root_y,
            &win_x, &win_y,
            &keys_buttons);
    
    if (status)
    {        
        result |=  keys_buttons & ShiftMask ? Qt::ShiftButton : 0;
        result |=  keys_buttons & Mod1Mask ? Qt::AltButton : 0;
        result |=  keys_buttons & Mod4Mask ? Qt::MetaButton : 0;
        result |=  keys_buttons & ControlMask ? Qt::ControlButton : 0; 
        
        result |=  keys_buttons & Button1Mask ? Qt::LeftButton : 0;
        result |=  keys_buttons & Button2Mask ? Qt::MidButton : 0; 
        result |=  keys_buttons & Button3Mask ? Qt::RightButton : 0; 
    }
#endif
    return Qt::ButtonState(result);
}

Qt::ButtonState MyApplication::keyboardModifiers()
{
    return Qt::ButtonState(get_modifiers() & Qt::KeyButtonMask);
}

Qt::ButtonState MyApplication::mouseButtons()
{
    return Qt::ButtonState(get_modifiers() & Qt::MouseButtonMask);
}

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One solution I can think of is to filter all keyboard events and to do explicit bookkeeping of whether the CTRL key is pressed, but I wonder if there is a simpler approach.

That's exactly how they implement it in Qt4!