Qt 5.7 | Qt Quick | QML Advanced Tutorial 1 - Creating the Game Canvas and Blocks

Qt 5.7.1 Reference Documentation

QML Advanced Tutorial ◦ QML Advanced Tutorial 2 - Populating the Game Canvas

# QML Advanced Tutorial 1 - Creating the Game Canvas and Blocks

### Creating the application screen

The first step is to create the basic QML items in your application.

To begin with, we create our Same Game application with a main screen like this:

This is defined by the main application file, `samegame.qml`, which looks like this:

      import QtQuick 2.0

      Rectangle {
          id: screen

          width: 490; height: 720

          SystemPalette { id: activePalette }

          Item {
              width: parent.width
              anchors { top: parent.top; bottom: toolBar.top }

              Image {
                  id: background
                  anchors.fill: parent
                  source: "../shared/pics/background.jpg"
                  fillMode: Image.PreserveAspectCrop
              }
          }

          Rectangle {
              id: toolBar
              width: parent.width; height: 30
              color: activePalette.window
              anchors.bottom: screen.bottom

              Button {
                  anchors { left: parent.left; verticalCenter: parent.verticalCenter }
                  text: "New Game"
                  onClicked: console.log("This doesn't do anything yet...")
              }

              Text {
                  id: score
                  anchors { right: parent.right; verticalCenter: parent.verticalCenter }
                  text: "Score: Who knows?"
              }
          }
      }

This gives you a basic game window that includes the main canvas for the blocks, a "New Game" button and a score display.

One item you may not recognize here is the SystemPalette item. This provides access to the Qt system palette and is used to give the button a more native look-and-feel.

Notice the anchors for the `Item`, `Button` and `Text` types are set using group (dot) notation for readability.

### Adding `Button` and `Block` components

The `Button` item in the code above is defined in a separate component file named `Button.qml`. To create a functional button, we use the QML types Text and MouseArea inside a Rectangle. Here is the `Button.qml` code:

      import QtQuick 2.0

      Rectangle {
          id: container

          property string text: "Button"

          signal clicked

          width: buttonLabel.width + 20; height: buttonLabel.height + 5
          border { width: 1; color: Qt.darker(activePalette.button) }
          antialiasing: true
          radius: 8

          // color the button with a gradient
          gradient: Gradient {
              GradientStop {
                  position: 0.0
                  color: {
                      if (mouseArea.pressed)
                          return activePalette.dark
                      else
                          return activePalette.light
                  }
              }
              GradientStop { position: 1.0; color: activePalette.button }
          }

          MouseArea {
              id: mouseArea
              anchors.fill: parent
              onClicked: container.clicked();
          }

          Text {
              id: buttonLabel
              anchors.centerIn: container
              color: activePalette.buttonText
              text: container.text
          }
      }

This essentially defines a rectangle that contains text and can be clicked. The MouseArea has an `onClicked()` handler that is implemented to emit the `clicked()` signal of the `container` when the area is clicked.

In Same Game, the screen is filled with small blocks when the game begins. Each block is just an item that contains an image. The block code is defined in a separate `Block.qml` file:

      import QtQuick 2.0

      Item {
          id: block

          Image {
              id: img
              anchors.fill: parent
              source: "../shared/pics/redStone.png"
          }
      }

At the moment, the block doesn't do anything; it is just an image. As the tutorial progresses we will animate and give behaviors to the blocks. We have not added any code yet to create the blocks; we will do this in the next chapter.

We have set the image to be the size of its parent Item using `anchors.fill: parent`. This means that when we dynamically create and resize the block items later on in the tutorial, the image will be scaled automatically to the correct size.

Notice the relative path for the Image type's `source` property. This path is relative to the location of the file that contains the Image type. Alternatively, you could set the Image source to an absolute file path or a URL that contains an image.

You should be familiar with the code so far. We have just created some basic types to get started. Next, we will populate the game canvas with some blocks.

Files:

- tutorials/samegame/samegame1/Block.qml
- tutorials/samegame/samegame1/Button.qml
- tutorials/samegame/samegame1/samegame.qml
- tutorials/samegame/samegame1/samegame1.qmlproject