QGraphicsPathItem about qt

[therecipe]

Hey

It seems like accessing scene.Width() or scene.Height() in line.boundingRect() causes a infinite recursion and crashes the program. (The scene probably checks all added objects to determine its own size)
But you could use the QGraphicsView size (which is different from the QGraphicsScene size).

The scene.RemoveItem function should work, just click inside the scene and the line should disappear.

package main

import (
    "os"

    "github.com/therecipe/qt/core"
    "github.com/therecipe/qt/gui"
    "github.com/therecipe/qt/widgets"
)

var (
    canvas *widgets.QWidget
    scene  *widgets.QGraphicsScene
    view   *widgets.QGraphicsView
)

type line struct{ *widgets.QGraphicsPathItem }

func main() {
    widgets.NewQApplication(len(os.Args), os.Args)

    NewCanvas().Show()

    widgets.QApplication_Exec()
}

func NewCanvas() *widgets.QWidget {
    canvas = widgets.NewQWidget(nil, 0)
    scene = widgets.NewQGraphicsScene(nil)
    view = widgets.NewQGraphicsView(nil)

    var l = &line{QGraphicsPathItem: widgets.NewQGraphicsPathItem(nil)}
    l.ConnectBoundingRect(l.boundingRect)
    l.ConnectPaint(l.paint)

    scene.AddItem(l)

    //test scene.RemoveItem
    scene.ConnectMousePressEvent(func(e *widgets.QGraphicsSceneMouseEvent) { scene.RemoveItem(l) })

    view.SetScene(scene)

    var layout = widgets.NewQVBoxLayout()
    layout.AddWidget(view, 0, 0)

    canvas.SetLayout(layout)

    return canvas
}

func (l *line) paint(p *gui.QPainter, o *widgets.QStyleOptionGraphicsItem, w *widgets.QWidget) {
    var color = gui.NewQColor3(0, 0, 0, 255)
    var brush = gui.NewQBrush3(color, 0) // solid = 1, nobrush = 0
    var pen = gui.NewQPen3(color)
    pen.SetWidth(1)

    p.SetRenderHint(1, true) // Antiailiasing
    p.SetPen(pen)
    p.SetBrush(brush)

    path := gui.NewQPainterPath()

    sx, sy, tx, ty := 0.0, 0.0, scene.Width(), scene.Height()/2

    path.MoveTo2(sx, sy)
    path.LineTo2(tx, ty)
    p.DrawPath(path)
}

func (l *line) boundingRect() *core.QRectF {
    /*
        //accessing scene.Width() and scene.Height() here causes infinite recursion
        println("called boundingRect")
        return core.NewQRectF4(0.0, 0.0, scene.Width(), scene.Height()/2)
    */
    return core.NewQRectF4(0.0, 0.0, float64(view.Width()), float64(view.Height())/2)
}

[5k3105]

Thanks. Confirmed my error.

Btw, I am having a difficult time keeping the canvas updated. I use these two methods:

c.View.Viewport().Repaint()

and

c.Scene.Update(c.Scene.SceneRect())

Neither seem to be working like I want. When I draw lines and remove them sometimes they stay on the scene until I draw several more lines and they eventually disappear. Sometimes when I erase a box on the canvas a line underneath the box will not redraw itself unless I zoom in and out.

[5k3105]

QGraphicsItem.PrepareGeometryChange() AND View.Viewport().Repaint() getting me most of the way there :/