C

Qt Quick Ultralite painteditem Example

Demonstrates the use of PaintedItem in a Qt Quick Ultralite Application.

Overview

The painteditem example uses the PaintedItem Qml type to draw directly on the framebuffer. It displays an animation emulating oscillatory motion of a circular blob on a curved ramp.

The example uses the OscillatorPaintedItem class, which overrides the paint() method to draw a curved ramp and a circular blob. The paint() method is called on every update event on the angle property, which is updated every 100ms.

Target platforms

Project structure

The painteditem example consists of following files:

  • CMakeLists.txt
  • oscillator.qml
  • main_baremetal.cpp
  • oscPaintedItem.cpp
  • oscPaintedItem.h

The CMake project file contains a basic build script and the oscillator.qml, which defines the application's UI.

main_baremetal.cpp contains the main function to set up the application on baremetal platforms.

The oscPaintedItem.h and oscPaintedItem.cpp files contain definition for the OscillatorPaintedItem class, which is derived from the PaintedItemDelegate class.

CMake project file
cmake_minimum_required(VERSION 3.17.3)

project(painteditem VERSION 0.0.1 LANGUAGES C CXX ASM)
if (NOT TARGET Qul::QuickUltralite)
    find_package(Qul)
endif()

string(TOLOWER ${QUL_PLATFORM} PLATFORM_LOWERCASE)

qul_add_target(painteditem oscPaintedItem.cpp)

if (PLATFORM_LOWERCASE MATCHES "^rh850" OR PLATFORM_LOWERCASE MATCHES "^tvii")
  target_compile_definitions(painteditem PRIVATE NO_TOUCH)
endif()

qul_target_qml_sources(painteditem oscillator.qml)
qul_target_generate_interfaces(painteditem oscPaintedItem.h)

target_link_libraries(painteditem Qul::QuickUltraliteControlsStyleDefault)

app_target_setup_os(painteditem)

if (OS STREQUAL "FreeRTOS")
    app_target_default_entrypoint(painteditem oscillator)
else()
    target_sources(painteditem PRIVATE
                   main_baremetal.cpp
    )
endif()
PaintedItem

The delegate_ property of the PaintedItem Qml type points to the OscillatorPaintedItem instance.

                    //PaintedItem Object
                    PaintedItem {
                        id: oscillator
                        anchors.right: parent.right
                        anchors.top: parent.top
                        anchors.fill: parent

                        delegate_: OscillatorPaintedItem {
                            id: delegate
                            angle: 0.0
                            initialAngle: 50
                            pivotLength: 50

                            onAngleChanged: {
                                delegate.update()
                            }
                        }
                    }
Text item

Initial angle and the fixed damping factor for the oscillations are displayed at the top-left corner.

                    Text {
                        anchors.top: parent.top
                        anchors.topMargin: 8
                        anchors.left: parent.left
                        anchors.leftMargin: 8
                        text: "Angle: " + delegate.initialAngle + "\ndamping: " + app.dampingFactor
                        font.pixelSize: 13
                    }
Replay button

When the oscillation angle reaches 0, the circular blob is at rest. On pressing the Replay button the animation starts again by setting the initialAngle back to maximum.

                    Button {
                        id: replay

                        //For platforms not supporting touch input, hide Replay button.
                        visible: !root.automaticAnimation

                        anchors.horizontalCenter: parent.horizontalCenter
                        anchors.bottom: parent.verticalCenter
                        height: 40
                        width: 70
                        font.pixelSize: 13
                        text: "Replay"

                        background: Rectangle {
                            color: replay.down ? "#A39D9C" : "#B8B3B2"
                            radius: 8
                        }

                        onClicked: {
                          /*Setting the initialAngle property to maximum value disturbs the equilibrium and
                          triggers the animation again.*/
                          delegate.initialAngle = 50
                        }
Animation timer

The animation is on the angle property, which is updated every 100ms. Each update to the angle property triggers the delegate update, which calls the paint() method of OscillatorPaintedItem.

                    Timer {
                        running: root.automaticAnimation
                        repeat: true
                        interval: 8000
                        onTriggered: delegate.initialAngle = 50
                    }

Files:

Available under certain Qt licenses.
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