Development/Tutorials/Qt4 Ruby Tutorial/Chapter 14 - Revision history

AnneW at 14:26, 18 July 2012

2012-07-18T14:26:40Z

AnneW: Marked this version for translation

2011-07-02T14:57:26Z

Marked this version for translation

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Aspotashev: add translate tags

2011-07-01T23:52:13Z

add translate tags

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Neverendingo: Text replace - "" to ""

2011-06-29T20:56:04Z

Text replace - "</code>" to "</syntaxhighlight>"

Neverendingo: Text replace - "`" to ""`


2011-06-29T20:43:20Z
Text replace - "<code ruby>" to "<syntaxhighlight lang="ruby">"

				
				
				
				
			
			← Older revision
			Revision as of 20:43, 29 June 2011
			
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  The '''<tt>CannonField</tt>''' can now receive mouse events to make the user aim the barrel by clicking on it and dragging. '''<tt>CannonField</tt>''' also has a barrier wall.   The '''<tt>CannonField</tt>''' can now receive mouse events to make the user aim the barrel by clicking on it and dragging. '''<tt>CannonField</tt>''' also has a barrier wall.
    
− <code ruby> + <syntaxhighlight lang="ruby">
  @barrelPressed = false   @barrelPressed = false
  </code>   </code>
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  This line has been added to the constructor. Initially, the mouse is not pressed on the barrel.   This line has been added to the constructor. Initially, the mouse is not pressed on the barrel.
    
− <code ruby> + <syntaxhighlight lang="ruby">
  elsif shotR.x() > width() || shotR.y() > height() ||   elsif shotR.x() > width() || shotR.y() > height() ||
       shotR.intersects(barrierRect())        shotR.intersects(barrierRect())
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  Now that we have a barrier, there are three ways to miss. We test for the third, too. (In '''<tt>moveShot()</tt>'''.)   Now that we have a barrier, there are three ways to miss. We test for the third, too. (In '''<tt>moveShot()</tt>'''.)
    
− <code ruby> + <syntaxhighlight lang="ruby">
  def mousePressEvent(event)   def mousePressEvent(event)
     unless event.button() == Qt::LeftButton      unless event.button() == Qt::LeftButton
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  Notice that the [http://doc.qt.nokia.com/latest/qmouseevent.html#pos Qt::MouseEvent::pos()] function returns a point in the widget's coordinate system.   Notice that the [http://doc.qt.nokia.com/latest/qmouseevent.html#pos Qt::MouseEvent::pos()] function returns a point in the widget's coordinate system.
    
− <code ruby> + <syntaxhighlight lang="ruby">
  def mouseMoveEvent(event)   def mouseMoveEvent(event)
     unless @barrelPressed      unless @barrelPressed
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  Remember that '''<tt>setAngle()</tt>''' redraws the cannon.   Remember that '''<tt>setAngle()</tt>''' redraws the cannon.
    
− <code ruby> + <syntaxhighlight lang="ruby">
  def mouseReleaseEvent(event)   def mouseReleaseEvent(event)
     if event.button() == Qt::LeftButton      if event.button() == Qt::LeftButton
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  The paint event has one extra line:   The paint event has one extra line:
    
− <code ruby> + <syntaxhighlight lang="ruby">
  paintBarrier(painter)   paintBarrier(painter)
  </code>   </code>
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  '''<tt>paintBarrier()</tt>''' does the same sort of thing as '''<tt>paintShot()</tt>''', '''<tt>paintTarget()</tt>''', and '''<tt>paintCannon()</tt>'''.   '''<tt>paintBarrier()</tt>''' does the same sort of thing as '''<tt>paintShot()</tt>''', '''<tt>paintTarget()</tt>''', and '''<tt>paintCannon()</tt>'''.
    
− <code ruby> + <syntaxhighlight lang="ruby">
  def paintBarrier( painter )   def paintBarrier( painter )
     painter.setBrush(Qt::Brush.new(Qt::yellow))      painter.setBrush(Qt::Brush.new(Qt::yellow))
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  This function paints the barrier as a rectangle filled with yellow and with a black outline.   This function paints the barrier as a rectangle filled with yellow and with a black outline.
    
− <code ruby> + <syntaxhighlight lang="ruby">
  def barrierRect()   def barrierRect()
     return Qt::Rect.new(145, height() - 100, 15, 99)      return Qt::Rect.new(145, height() - 100, 15, 99)
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  This function returns the rectangle of the barrier. We fix the bottom edge of the barrier to the bottom edge of the widget.   This function returns the rectangle of the barrier. We fix the bottom edge of the barrier to the bottom edge of the widget.
    
− <code ruby> + <syntaxhighlight lang="ruby">
  def barrelHit(pos)   def barrelHit(pos)
     matrix = Qt::Matrix.new()      matrix = Qt::Matrix.new()
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  '''[http://www.darshancomputing.com/qt4-qtruby-tutorial/tutorial/t14/gamebrd.rb gamebrd.rb]'''   '''[http://www.darshancomputing.com/qt4-qtruby-tutorial/tutorial/t14/gamebrd.rb gamebrd.rb]'''
    
− <code ruby> + <syntaxhighlight lang="ruby">
  cannonBox = Qt::Frame.new()   cannonBox = Qt::Frame.new()
  cannonBox.setFrameStyle(Qt::Frame::WinPanel | Qt::Frame::Sunken)   cannonBox.setFrameStyle(Qt::Frame::WinPanel | Qt::Frame::Sunken)
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  We create and set up a [http://doc.qt.nokia.com/latest/qframe.html Qt::Frame], and set its frame style. This results in a 3D frame around the '''<tt>CannonField</tt>'''.   We create and set up a [http://doc.qt.nokia.com/latest/qframe.html Qt::Frame], and set its frame style. This results in a 3D frame around the '''<tt>CannonField</tt>'''.
    
− <code ruby> + <syntaxhighlight lang="ruby">
  Qt::Shortcut.new(Qt::KeySequence.new(Qt::Key_Enter.to_i),   Qt::Shortcut.new(Qt::KeySequence.new(Qt::Key_Enter.to_i),
                    self, SLOT('fire()'))                     self, SLOT('fire()'))
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  Qt::CTRL, Qt::Key_Enter, Qt::Key_Return, and Qt::Key_Q are all constants declared in the Qt namespace. Unfortunately, in the current version of qtruby, they need to be converted to integers before we can use them in our shortcuts.   Qt::CTRL, Qt::Key_Enter, Qt::Key_Return, and Qt::Key_Q are all constants declared in the Qt namespace. Unfortunately, in the current version of qtruby, they need to be converted to integers before we can use them in our shortcuts.
    
− <code ruby> + <syntaxhighlight lang="ruby">
  leftLayout = Qt::VBoxLayout.new()   leftLayout = Qt::VBoxLayout.new()
  leftLayout.addWidget(angle)   leftLayout.addWidget(angle)



Alisha at 14:23, 16 January 2010
2010-01-16T14:23:51Z


				
				
				
				
			
			← Older revision
			Revision as of 14:23, 16 January 2010
			
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  === Exercises ===   === Exercises ===
  Write a space invaders game.   Write a space invaders game.
−  
− (This exercise was first done by [mailto:igorr@ifi.uio.no Igor Rafienko]. You can [http://heim.ifi.uio.no/~igorr/download.html download his game].)  
    
  The new exercise is: Write a Breakout game.   The new exercise is: Write a Breakout game.



Alisha at 03:04, 13 January 2010
2010-01-13T03:04:54Z


				
				
				
				
			
			← Older revision
			Revision as of 03:04, 13 January 2010
			
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  Final exhortation: Go forth now and create masterpieces of the programming art!   Final exhortation: Go forth now and create masterpieces of the programming art!
  + 
  + [[Category:Ruby]]



Alisha at 16:36, 31 December 2009
2009-12-31T16:36:45Z

Show changes


Alisha: Created page with '{{Template:I18n/Language Navigation Bar|Development/Tutorials/Qt4 Ruby Tutorial/Chapter 14}} {{TutorialBrowser|  series=[[Development/Tutorials/Qt4_Ruby_Tutorial|Qt4 Ruby Tutoria...'
2009-12-31T10:46:17Z
Created page with '{{Template:I18n/Language Navigation Bar|Development/Tutorials/Qt4 Ruby Tutorial/Chapter 14}} {{TutorialBrowser|  series=[[Development/Tutorials/Qt4_Ruby_Tutorial|Qt4 Ruby Tutoria...'
New page
{{Template:I18n/Language Navigation Bar|Development/Tutorials/Qt4 Ruby Tutorial/Chapter 14}}

{{TutorialBrowser|



series=[[Development/Tutorials/Qt4_Ruby_Tutorial|Qt4 Ruby Tutorial]]|



name=Facing the Wall|



pre=[[Development/Tutorials/Qt4_Ruby_Tutorial/Chapter_13|Tutorial 13 - Game Over]]

}}

== Facing the Wall ==

[[Image:Qt4_Ruby_Tutorial_Screenshot_14.png|center]]

Files:

* [http://www.darshancomputing.com/qt4-qtruby-tutorial/tutorial/t14/lcdrange.rb lcdrange.rb]

* [http://www.darshancomputing.com/qt4-qtruby-tutorial/tutorial/t14/gamebrd.rb gamebrd.rb]

* [http://www.darshancomputing.com/qt4-qtruby-tutorial/tutorial/t14/t14.rb t14.rb]

* [http://www.darshancomputing.com/qt4-qtruby-tutorial/tutorial/t14/cannon.rb cannon.rb]



=== Overview ===

This is the final example: a complete game.



We add keyboard accelerators and introduce mouse events to CannonField. We put a frame around the CannonField and add a barrier (wall) to make the game more challenging. 



=== Line by Line Walkthrough ===

'''[http://www.darshancomputing.com/qt4-qtruby-tutorial/tutorial/t14/cannon.rb cannon.rb]'''



The CannonField can now receive mouse events to make the user aim the barrel by clicking on it and dragging. CannonField also has a barrier wall.



    @barrelPressed = false



This line has been added to the constructor. Initially, the mouse is not pressed on the barrel.



    elsif shotR.x() > width() || shotR.y() > height() ||

        shotR.intersects(barrierRect())



Now that we have a barrier, there are three ways to miss. We test for the third, too. (In moveShot().)



  def mousePressEvent(event)

    unless event.button() == Qt::LeftButton

      return

    end



    if barrelHit(event.pos())

      @barrelPressed = true

    end

  end



This is a Qt event handler. It is called when the user presses a mouse button when the mouse cursor is over the widget.



If the event was not generated by the left mouse button, we return immediately. Otherwise, we check if the position of the mouse cursor is within the cannon's barrel. If it is, we set barrelPressed to true.



Notice that the Qt::MouseEvent::pos() function returns a point in the widget's coordinate system.



  def mouseMoveEvent(event)

    unless @barrelPressed

      return

    end



    pos = event.pos();



    if pos.x() <= 0

      pos.setX(1)

    end



    if pos.y() >= height()

      pos.setY(height() - 1)

    end



    rad = atan2((rect().bottom() - pos.y()), pos.x())

    setAngle((rad * 180 / 3.14159265).round())

  end



This is another Qt event handler. It is called when the user already has pressed the mouse button inside this widget and then moves/drags the mouse. (You can make Qt send mouse move events even when no buttons are pressed. See Qt::Widget::setMouseTracking().)



This handler repositions the cannon's barrel according to the position of the mouse cursor.



First, if the barrel is not pressed, we return. Next, we fetch the mouse cursor's position. If the mouse cursor is to the left or below the widget, we adjust the point to be inside the widget.



Then we calculate the angle between the bottom edge of the widget and the imaginary line between the bottom-left corner of the widget and the cursor position. Finally we set the cannon's angle to the new value converted to degrees.



Remember that setAngle() redraws the cannon.



  def mouseReleaseEvent(event)

    if event.button() == Qt::LeftButton

      @barrelPressed = false

    end

  end



This Qt event handler is called whenever the user releases a mouse button and it was pressed inside this widget.



If the left button is released, we can be sure that the barrel is no longer pressed.



The paint event has one extra line:



    paintBarrier(painter)



paintBarrier() does the same sort of thing as paintShot(), paintTarget(), and paintCannon().



  def paintBarrier( painter )

    painter.setBrush(Qt::Brush.new(Qt::yellow))

    painter.setPen(Qt::Color.new(Qt::black))

    painter.drawRect(barrierRect())

  end



This function paints the barrier as a rectangle filled with yellow and with a black outline.



  def barrierRect()

    return Qt::Rect.new(145, height() - 100, 15, 99)

  end



This function returns the rectangle of the barrier. We fix the bottom edge of the barrier to the bottom edge of the widget.



  def barrelHit(pos)

    matrix = Qt::Matrix.new()

    matrix.translate(0, height())

    matrix.rotate(-@currentAngle)

    matrix = matrix.inverted()

    return @barrelRect.contains(matrix.map(pos))

  end



This function returns true if the point is in the barrel; otherwise it returns false.



Here we use the class Qt::Matrix. Qt::Matrix defines a coordinate system mapping. It can perform the same transformations as the Qt::Painter.



Here we perform the same transformation steps as we do when drawing the barrel in the paintCannon() function. First we translate the coordinate system and then we rotate it.



Now we need to check whether the point pos (in widget coordinates) lies inside the barrel. To do this, we invert the transformation matrix. The inverted matrix performs the inverse transformation that we used when drawing the barrel. We map the point pos using the inverted matrix and return true if it is inside the original barrel rectangle.



'''[http://www.darshancomputing.com/qt4-qtruby-tutorial/tutorial/t14/gamebrd.rb gamebrd.rb]'''



    cannonBox = Qt::Frame.new()

    cannonBox.setFrameStyle(Qt::Frame::WinPanel | Qt::Frame::Sunken)



We create and set up a Qt::Frame, and set its frame style. This results in a 3D frame around the CannonField.



    Qt::Shortcut.new(Qt::KeySequence.new(Qt::Key_Enter.to_i),

                     self, SLOT('fire()'))

    Qt::Shortcut.new(Qt::KeySequence.new(Qt::Key_Return.to_i),

                     self, SLOT('fire()'))

    Qt::Shortcut.new(Qt::KeySequence.new(Qt::CTRL.to_i + Qt::Key_Q.to_i),

                     self, SLOT('close()'))



Here we create and set up three Qt::Shortcut objects. These objects intercept keyboard events to a widget and call slots if certain keys are pressed. Note that a Qt::Shortcut object is a child of a widget and will be destroyed when that widget is destroyed. Qt::Shortcut itself is not a widget and has no visible effect on its parent.



We define three shortcut keys. We want the fire() slot to be called when the user presses Enter or Return. We also want the application to quit when key Ctrl+Q is pressed. Instead of connecting to Qt::CoreApplication::quit(), we connect to Qt::Widget::close() this time. Since the GameBoard is the application's main widget, this has the same effect as QCoreApplication::quit().



Qt::CTRL, Qt::Key_Enter, Qt::Key_Return, and Qt::Key_Q are all constants declared in the Qt namespace. Unfortunately, in the current version of qtruby, they need to be converted to integers before we can use them in our shortcuts.



    leftLayout = Qt::VBoxLayout.new()

    leftLayout.addWidget(angle)

    leftLayout.addWidget(force)



    gridLayout = Qt::GridLayout.new()

    gridLayout.addWidget(quit, 0, 0)

    gridLayout.addLayout(topLayout, 0, 1)

    gridLayout.addLayout(leftLayout, 1, 0)

    gridLayout.addWidget(@cannonField, 1, 1, 2, 1)

    gridLayout.setColumnStretch(1, 10)

    setLayout(gridLayout)



We give cannonBox its own Qt::VBoxLayout, and we add cannonField to that layout. This implicitly makes cannonField a child of cannonBox. Because nothing else is in the box, the effect is that the Qt::VBoxLayout will put a frame around the CannonField. We put cannonBox, not cannonField, in the grid layout.



=== Running the Application ===

The cannon now shoots when you press Enter. You can also position the cannon's angle using the mouse. The barrier makes it a little more challenging to play the game. We also have a nice looking frame around the CannonField.



=== Exercises ===

Write a space invaders game.



(This exercise was first done by Igor Rafienko. You can download his game.)



The new exercise is: Write a Breakout game.



Final exhortation: Go forth now and create masterpieces of the programming art!

@@ Line 1: / Line 1: @@
 <languages />
-{{Template:I18n/Language Navigation Bar|Development/Tutorials/Qt4 Ruby Tutorial/Chapter 14}}
 {{<translate><!--T:1-->

@@ Line 28: / Line 28: @@
 <syntaxhighlight lang="ruby">
 @barrelPressed = false
-</code>
+</syntaxhighlight>
 This line has been added to the constructor. Initially, the mouse is not pressed on the barrel.
@@ Line 35: / Line 35: @@
 elsif shotR.x() > width() || shotR.y() > height() ||
      shotR.intersects(barrierRect())
-</code>
+</syntaxhighlight>
 Now that we have a barrier, there are three ways to miss. We test for the third, too. (In '''<tt>moveShot()</tt>'''.)
@@ Line 49: / Line 49: @@
    end
 end
-</code>
+</syntaxhighlight>
 This is a Qt event handler. It is called when the user presses a mouse button when the mouse cursor is over the widget.
@@ Line 76: / Line 76: @@
    setAngle((rad * 180 / 3.14159265).round())
 end
-</code>
+</syntaxhighlight>
 This is another Qt event handler. It is called when the user already has pressed the mouse button inside this widget and then moves/drags the mouse. (You can make Qt send mouse move events even when no buttons are pressed. See [http://doc.qt.nokia.com/latest/qwidget.html#mouseTracking-prop Qt::Widget::setMouseTracking()].)
@@ Line 94: / Line 94: @@
    end
 end
-</code>
+</syntaxhighlight>
 This Qt event handler is called whenever the user releases a mouse button and it was pressed inside this widget.
@@ Line 104: / Line 104: @@
 <syntaxhighlight lang="ruby">
 paintBarrier(painter)
-</code>
+</syntaxhighlight>
 '''<tt>paintBarrier()</tt>''' does the same sort of thing as '''<tt>paintShot()</tt>''', '''<tt>paintTarget()</tt>''', and '''<tt>paintCannon()</tt>'''.
@@ Line 114: / Line 114: @@
    painter.drawRect(barrierRect())
 end
-</code>
+</syntaxhighlight>
 This function paints the barrier as a rectangle filled with yellow and with a black outline.
@@ Line 122: / Line 122: @@
    return Qt::Rect.new(145, height() - 100, 15, 99)
 end
-</code>
+</syntaxhighlight>
 This function returns the rectangle of the barrier. We fix the bottom edge of the barrier to the bottom edge of the widget.
@@ Line 134: / Line 134: @@
    return @barrelRect.contains(matrix.map(pos))
 end
-</code>
+</syntaxhighlight>
 This function returns '''<tt>true</tt>''' if the point is in the barrel; otherwise it returns '''<tt>false</tt>'''.
@@ Line 149: / Line 149: @@
 cannonBox = Qt::Frame.new()
 cannonBox.setFrameStyle(Qt::Frame::WinPanel | Qt::Frame::Sunken)
-</code>
+</syntaxhighlight>
 We create and set up a [http://doc.qt.nokia.com/latest/qframe.html Qt::Frame], and set its frame style. This results in a 3D frame around the '''<tt>CannonField</tt>'''.
@@ Line 160: / Line 160: @@
 Qt::Shortcut.new(Qt::KeySequence.new(Qt::CTRL.to_i + Qt::Key_Q.to_i),
                   self, SLOT('close()'))
-</code>
+</syntaxhighlight>
 Here we create and set up three [http://doc.qt.nokia.com/latest/qshortcut.html Qt::Shortcut] objects. These objects intercept keyboard events to a widget and call slots if certain keys are pressed. Note that a [http://doc.qt.nokia.com/latest/qshortcut.html Qt::Shortcut] object is a child of a widget and will be destroyed when that widget is destroyed. [http://doc.qt.nokia.com/latest/qshortcut.html Qt::Shortcut] itself is not a widget and has no visible effect on its parent.
@@ Line 180: / Line 180: @@
 gridLayout.setColumnStretch(1, 10)
 setLayout(gridLayout)
-</code>
+</syntaxhighlight>
 We give '''<tt>cannonBox</tt>''' its own [http://doc.qt.nokia.com/latest/qvboxlayout.html Qt::VBoxLayout], and we add '''<tt>CannonField</tt>''' to that layout. This implicitly makes '''<tt>CannonField</tt>''' a child of '''<tt>cannonBox</tt>'''. Because nothing else is in the box, the effect is that the [http://doc.qt.nokia.com/latest/qvboxlayout.html Qt::VBoxLayout] will put a frame around the '''<tt>CannonField</tt>'''. We put '''<tt>cannonBox</tt>''', not '''<tt>CannonField</tt>''', in the grid layout.

← Older revision		Revision as of 03:04, 13 January 2010
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	Final exhortation: Go forth now and create masterpieces of the programming art!		Final exhortation: Go forth now and create masterpieces of the programming art!
		+
		+	[[Category:Ruby]]