The document describes how to use events filters in Qt to handle key press and mouse events in a GUI application. It shows code to detect key presses and mouse clicks, movements and button presses, and update the window title or show messages based on the detected events. It then shows how to make a label movable by tracking mouse movements and presses.

1. Ring Documentation, Release 1.3
49.42 KeyPress and Mouse Move Events
In this example we will learn how to use the Events Filter to know about KeyPress and Mouse Move Events
Load "guilib.ring"
new qApp {
win1 = new qWidget()
{
setWindowTitle("Test using Event Filter!")
setGeometry(100,100,400,400)
setmousetracking(true)
myfilter = new qallevents(win1)
myfilter.setKeyPressEvent("pWork()")
myfilter.setMouseButtonPressevent("pClick()")
myfilter.setmousemoveevent("pMove()")
installeventfilter(myfilter)
show()
}
exec()
}
49.42. KeyPress and Mouse Move Events 458

2. Ring Documentation, Release 1.3
func pWork
win1.setwindowtitle('KeyPress! : ' + myfilter.getkeycode())
func pClick
new qmessagebox(win1) {
setgeometry(100,100,400,100)
setwindowtitle("click event!")
settext("x : " + myfilter.getx() +
" y : " + myfilter.gety() + " button : " +
myfilter.getbutton() )
show()
}
func pMove
win1.setwindowtitle("Mouse Move , X : " + myfilter.getx() +
" Y : " + myfilter.gety() )
The application during the runtime
49.43 Moving Objects using the Mouse
In the next example we will learn how to program movable objects where the user can move a label
Load "guilib.ring"
lPress = false
49.43. Moving Objects using the Mouse 459

3. Ring Documentation, Release 1.3
nX = 0
nY = 0
new qApp {
win1 = new qWidget()
{
setWindowTitle("Move this label!")
setGeometry(100,100,400,400)
setstylesheet("background-color:white;")
Label1 = new qLabel(Win1){
setGeometry(100,100,200,50)
setText("Welcome")
setstylesheet("font-size: 30pt")
myfilter = new qallevents(label1)
myfilter.setEnterevent("pEnter()")
myfilter.setLeaveevent("pLeave()")
myfilter.setMouseButtonPressEvent("pPress()")
myfilter.setMouseButtonReleaseEvent("pRelease()")
myfilter.setMouseMoveEvent("pMove()")
installeventfilter(myfilter)
}
show()
}
exec()
}
Func pEnter
Label1.setStyleSheet("background-color: purple; color:white;font-size: 30pt;")
Func pLeave
Label1.setStyleSheet("background-color: white; color:black;font-size: 30pt;")
Func pPress
lPress = True
nX = myfilter.getglobalx()
ny = myfilter.getglobaly()
Func pRelease
lPress = False
pEnter()
Func pMove
nX2 = myfilter.getglobalx()
ny2 = myfilter.getglobaly()
ndiffx = nX2 - nX
ndiffy = nY2 - nY
if lPress
Label1 {
move(x()+ndiffx,y()+ndiffy)
setStyleSheet("background-color: Green;
color:white;font-size: 30pt;")
nX = nX2
ny = nY2
49.43. Moving Objects using the Mouse 460

4. Ring Documentation, Release 1.3
}
ok
The application during the runtime
49.43. Moving Objects using the Mouse 461

5. Ring Documentation, Release 1.3
49.43. Moving Objects using the Mouse 462

6. Ring Documentation, Release 1.3
49.44 Inheritance from GUI Classes
Example :
Load "guilib.ring"
New MyWindow()
new qApp { exec() }
class mywindow from qwidget
Func init
super.init()
setwindowtitle("First Window")
setgeometry(100,100,400,400)
setstylesheet("background-color: purple;")
settooltip("my first window!")
show()
The application during the runtime
49.44. Inheritance from GUI Classes 463

7. Ring Documentation, Release 1.3
49.45 Using QDesktopWidget Class
In the next example we will learn about using the QDesktopWidget class
Load "guilib.ring"
New qApp {
win1 = New qWidget()
{
resize(400,400)
btn1 = new qPushbutton(win1)
{
setText("Center")
move(100,100)
resize(100,30)
setClickEvent("pCenter()")
}
Show()
}
exec()
}
Func pCenter
oDesktop = new qDesktopWidget()
49.45. Using QDesktopWidget Class 464

8. Ring Documentation, Release 1.3
oRect = oDesktop.screenGeometry( oDesktop.primaryScreen() )
win1.move((oRect.width()-win1.width()) /2 , (oRect.Height()-win1.Height())/2 )
win1.show()
The application during the runtime
49.46 Rotate Text
The next example rotate text using a Timer.
Load "guilib.ring"
nAngle = 0
New qapp {
win1 = new qwidget() {
setwindowtitle("Rotate Text")
resize(800,600)
label1 = new qlabel(win1) {
settext("")
myfilter = new qallevents(win1)
myfilter.setMouseButtonPressevent("pClick()")
installeventfilter(myfilter)
}
new qtimer(win1) {
setinterval(50)
49.46. Rotate Text 465

9. Ring Documentation, Release 1.3
settimeoutevent("pTime()")
start()
}
pDraw()
L1 = new qVBoxLayout() { AddWidget(Label1) } SetLayout(L1)
showMaximized()
}
exec()
}
Func pDraw
p1 = new qpicture()
color = new qcolor() {
setrgb(0,0,255,255)
}
pen = new qpen() {
setcolor(color)
setwidth(50)
}
painter = new qpainter() {
begin(p1)
setpen(pen)
myfont = font()
myfont.setpointsize(50)
setfont(myfont)
rotate(nAngle)
drawtext(350,0*nAngle,"welcome")
drawtext(0,0*nAngle,"welcome")
endpaint()
}
label1 {
setpicture(p1)
show()
}
Func pClick
win1 { setwindowtitle("Click Event") }
Func pTime
nAngle++
if nAngle = 90
nAngle = 10
ok
pDraw()
The application during the runtime
49.46. Rotate Text 466

10. Ring Documentation, Release 1.3
49.47 Change Focus
The next example change the focus using the ENTER key.
load "guilib.ring"
new qApp {
win = new qWidget() {
resize(600,600)
SetWindowTitle("Change Focus")
text1 = new qLineEdit(win)
text2 = new qLineEdit(win)
text3 = new qLineEdit(win)
text4 = new qLineEdit(win)
layout1 = new qVBoxLayout() {
AddWidget(text1)
AddWidget(text2)
AddWidget(text3)
AddWidget(text4)
}
setLayout(Layout1)
49.47. Change Focus 467