Difference between revisions of "Development/Tutorials/Qt4 Ruby Tutorial/Chapter 10"

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{{Template:I18n/Language Navigation Bar|Development/Tutorials/Qt4 Ruby Tutorial/Chapter 10}}
 
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series=[[Special:myLanguage/Development/Tutorials/Qt4_Ruby_Tutorial|<translate>Qt4 Ruby Tutorial</translate>]]|
series=[[Development/Tutorials/Qt4_Ruby_Tutorial|Qt4 Ruby Tutorial]]|
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name=<translate>Smooth as Silk</translate>|
 
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== Smooth as Silk ==
 
== Smooth as Silk ==
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[[Image:Qt4_Ruby_Tutorial_Screenshot_10.png|center]]
 
[[Image:Qt4_Ruby_Tutorial_Screenshot_10.png|center]]
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Files:
 
Files:
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* [http://www.darshancomputing.com/qt4-qtruby-tutorial/tutorial/t10/lcdrange.rb lcdrange.rb]
 
* [http://www.darshancomputing.com/qt4-qtruby-tutorial/tutorial/t10/lcdrange.rb lcdrange.rb]
 
* [http://www.darshancomputing.com/qt4-qtruby-tutorial/tutorial/t10/t10.rb t10.rb]
 
* [http://www.darshancomputing.com/qt4-qtruby-tutorial/tutorial/t10/t10.rb t10.rb]
 
* [http://www.darshancomputing.com/qt4-qtruby-tutorial/tutorial/t10/cannon.rb cannon.rb]
 
* [http://www.darshancomputing.com/qt4-qtruby-tutorial/tutorial/t10/cannon.rb cannon.rb]
  
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=== Overview ===
 
=== Overview ===
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In this example, we add a force control.  
 
In this example, we add a force control.  
  
 
=== Line by Line Walkthrough ===
 
=== Line by Line Walkthrough ===
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'''[http://www.darshancomputing.com/qt4-qtruby-tutorial/tutorial/t10/cannon.rb cannon.rb]'''
 
'''[http://www.darshancomputing.com/qt4-qtruby-tutorial/tutorial/t10/cannon.rb cannon.rb]'''
  
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The '''<tt>CannonField</tt>''' now has a force value in addition to the angle.
 
The '''<tt>CannonField</tt>''' now has a force value in addition to the angle.
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The interface to the force follows the same practice as for the angle.
 
The interface to the force follows the same practice as for the angle.
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The force '''<tt>@currentForce</tt>''' is initialized to zero.
 
The force '''<tt>@currentForce</tt>''' is initialized to zero.
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We have made a slight change in the '''<tt>setAngle()</tt>''' function. It repaints only the portion of the widget that contains the cannon.
 
We have made a slight change in the '''<tt>setAngle()</tt>''' function. It repaints only the portion of the widget that contains the cannon.
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The implementation of '''<tt>setForce()</tt>''' is quite similar to that of '''<tt>setAngle()</tt>'''. The only difference is that because we don't show the force value, we don't need to repaint the widget.
 
The implementation of '''<tt>setForce()</tt>''' is quite similar to that of '''<tt>setAngle()</tt>'''. The only difference is that because we don't show the force value, we don't need to repaint the widget.
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We paint as in Chapter 9.
 
We paint as in Chapter 9.
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The '''<tt>cannonRect()</tt>''' function returns the rectangle enclosing the cannon in widget coordinates. First we create a rectangle with the size 50 x 50 and then move it so its bottom-left corner is equal to the widget's own bottom-left corner.
 
The '''<tt>cannonRect()</tt>''' function returns the rectangle enclosing the cannon in widget coordinates. First we create a rectangle with the size 50 x 50 and then move it so its bottom-left corner is equal to the widget's own bottom-left corner.
  
 
The [http://doc.qt.nokia.com/latest/qwidget.html#rect-prop Qt::Widget::rect()] function returns the widget's enclosing rectangle in the widget's own coordinates. The top-left corner of the rectangle is always (0, 0).
 
The [http://doc.qt.nokia.com/latest/qwidget.html#rect-prop Qt::Widget::rect()] function returns the widget's enclosing rectangle in the widget's own coordinates. The top-left corner of the rectangle is always (0, 0).
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'''[http://www.darshancomputing.com/qt4-qtruby-tutorial/tutorial/t10/t10.rb t10.rb]'''
 
'''[http://www.darshancomputing.com/qt4-qtruby-tutorial/tutorial/t10/t10.rb t10.rb]'''
  
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The constructor is mostly the same, but some new bits have been added.
 
The constructor is mostly the same, but some new bits have been added.
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We add a second '''<tt>LCDRange</tt>''', which will be used to set the force.
 
We add a second '''<tt>LCDRange</tt>''', which will be used to set the force.
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We connect the '''<tt>force</tt>''' widget and the '''<tt>cannonField</tt>''' widget, just like we did for the '''<tt>angle</tt>''' widget.
 
We connect the '''<tt>force</tt>''' widget and the '''<tt>cannonField</tt>''' widget, just like we did for the '''<tt>angle</tt>''' widget.
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In Chapter 9, we put '''<tt>angle</tt>''' in the lower-left cell of the layout. Now we want to have two widgets in that cell, so we make a vertical box, put the vertical box in the grid cell, and put each of '''<tt>angle</tt>''' and '''<tt>range</tt>''' in the vertical box.
 
In Chapter 9, we put '''<tt>angle</tt>''' in the lower-left cell of the layout. Now we want to have two widgets in that cell, so we make a vertical box, put the vertical box in the grid cell, and put each of '''<tt>angle</tt>''' and '''<tt>range</tt>''' in the vertical box.
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We initialize the force value to 25.
 
We initialize the force value to 25.
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=== Running the Application ===
 
=== Running the Application ===
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We now have a force control.
 
We now have a force control.
  
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[[Category:Ruby]]
 
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Revision as of 00:38, 2 July 2011

Other languages:English 100% • ‎Finnish 100% • ‎Russian 39%


Contents

Development/Tutorials/Qt4 Ruby Tutorial/Chapter 10


Smooth as Silk
Tutorial Series   Qt4 Ruby Tutorial
Previous   Tutorial 9 - With Cannon You Can
What's Next   Tutorial 11 - Giving It a Shot
Further Reading   n/a

Smooth as Silk

Qt4 Ruby Tutorial Screenshot 10.png

Files:

Overview

In this example, we add a force control.

Line by Line Walkthrough

cannon.rb

The CannonField now has a force value in addition to the angle.

signals 'angleChanged(int)', 'forceChanged(int)'
slots 'setAngle(int)', 'setForce(int)'

The interface to the force follows the same practice as for the angle.

def initialize(parent = nil)
  super()
 
  @currentAngle = 45
  @currentForce = 0
 
  setPalette(Qt::Palette.new(Qt::Color.new(250, 250, 200)))
  setAutoFillBackground(true)
end

The force @currentForce is initialized to zero.

def setAngle(angle)
  if angle < 5
    angle = 5
  elsif angle > 70
    angle = 70
  end
 
  if @currentAngle == angle
    return
  end
 
  @currentAngle = angle
  update(cannonRect())
  emit angleChanged(@currentAngle)
end

We have made a slight change in the setAngle() function. It repaints only the portion of the widget that contains the cannon.

def setForce(force)
  if force < 0
    force = 0
  end
  if @currentForce == force
    return
  end
 
  @currentForce = force
  emit forceChanged(@currentForce)
end

The implementation of setForce() is quite similar to that of setAngle(). The only difference is that because we don't show the force value, we don't need to repaint the widget.

def paintEvent(event)
  painter = Qt::Painter.new(self)
 
  painter.setPen(Qt::NoPen)
  painter.setBrush(Qt::Brush.new(Qt::blue))
 
  painter.translate(0, height())
  painter.drawPie(Qt::Rect.new(-35, -35, 70, 70), 0, 90 * 16)
  painter.rotate(-@currentAngle)
  painter.drawRect(Qt::Rect.new(30, -5, 20, 10))
  painter.end()
end

We paint as in Chapter 9.

def cannonRect()
  result = Qt::Rect.new(0, 0, 50, 50)
  result.moveBottomLeft(rect().bottomLeft())
  return result
end

The cannonRect() function returns the rectangle enclosing the cannon in widget coordinates. First we create a rectangle with the size 50 x 50 and then move it so its bottom-left corner is equal to the widget's own bottom-left corner.

The Qt::Widget::rect() function returns the widget's enclosing rectangle in the widget's own coordinates. The top-left corner of the rectangle is always (0, 0).

t10.rb

The constructor is mostly the same, but some new bits have been added.

force = LCDRange.new()
force.setRange(10, 50)

We add a second LCDRange, which will be used to set the force.

connect(force, SIGNAL('valueChanged(int)'),
         cannonField, SLOT('setForce(int)'))
connect(cannonField, SIGNAL('forceChanged(int)'),
         force, SLOT('setValue(int)'))

We connect the force widget and the cannonField widget, just like we did for the angle widget.

leftLayout = Qt::VBoxLayout.new()
leftLayout.addWidget(angle)
leftLayout.addWidget(force)
 
gridLayout = Qt::GridLayout.new()
gridLayout.addWidget(quit, 0, 0)
gridLayout.addLayout(leftLayout, 1, 0)
gridLayout.addWidget(cannonField, 1, 1, 2, 1)
gridLayout.setColumnStretch(1, 10)

In Chapter 9, we put angle in the lower-left cell of the layout. Now we want to have two widgets in that cell, so we make a vertical box, put the vertical box in the grid cell, and put each of angle and range in the vertical box.

force.setValue(25)

We initialize the force value to 25.

Running the Application

We now have a force control.

Exercises

Make the size of the cannon barrel be dependent on the force.

Put the cannon in the bottom-right corner.

Try adding a better keyboard interface. For example, make + and - increase and decrease the force and enter shoot. If you're bothered by the way the Left and Right keys work, change that too. [Hint: Reimplement Qt::Widget::keyPressEvent().]


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