How to convert panel coordinates to rectangle coordinates?

positrom2 · Aug 11, 2012

Using Designer I have a panel with coordinates defined by (left,top,width,height). I want to create a rectangle covering the panel. Unfortunately, the rectangle properties are defined differently as (left,top,right,bottom), and I am struggling to get the right values from the panel properties. How to get the rectangle properties from the panel properties?
Thanks, positrom2

Mahares · Aug 11, 2012

I think this is what you are looking for. If not, forgive me:

B4X:

Rectangle.left=Panel.Left
Rectangle.Top=Panel.Top
Rectangle.Right=Panel.Left + Panel.Width
Rectangle.Bottom=Panel.Top + Panel.Height

positrom2 · Aug 11, 2012

Thanks, Mahares,
I had already done as you suggested, but it does not work (the panel color does not change to black).

The panel properties in designer are:
left=0, top=480,width=220,height=300.
The code looks like

B4X:

Dim pnlpeaks As Panel
Dim rect1 As Rect
cvspeaks.Initialize(pnlpeaks)
rect1.Initialize(0, 480, 220, 780)
cvspeaks.DrawRect(rect1, Colors.Black, True, 1)
Activity.invalidate

The color of the panel does not change.

With another rectangle, on a different canvas, painting the panel in black works. But there I had initialized the rectangle for a panel with coordinates
left=220,top=310,width=380,height=470 by

B4X:

rect2.Initialize(0, 0, 100%x, 100%y)

Is there a misunderstanding in the coordinate designations?

Thanks, positrom2

Erel · Aug 11, 2012

You should always use dip units when specifying pixel measurements.

You should invalidate the panel not the activity.

positrom2 · Aug 12, 2012

Erel, thanks, but:

You should always use dip units when specifying pixel measurements.

but: The beginner's guide tells that

The values for the Left, Top, Width and Height properties in the Designer are considered as
dip values.

I also tried

B4X:

rect1.Initialize(0, 480dip, 220dip, 780dip)

with the rect coordinates read out from designer, but it does not give the expected result, whereas (0,0,100%x,100%y) is allright!

So it is unclear to me how the coordinate system for rectangle definition is defined and what dip means in the rectangle definition.

Thanks, positrom2

Mahares · Aug 12, 2012

@positrom: I created on the designer a layout called Rectangle 480x800, with scale:1. I put a panel on it called: pnlPeaks. The panel has the same dimensions as yours: L=0, T=480, W=220 and H=300. See below code where I was able to overlap the rectangle to the panel background. I hope this is what you are looking to achieve.

B4X:

Dim Rect1 As Rect
Dim pnlPeaks As Panel
Dim cvspeaks As Canvas

Activity.LoadLayout("Rectangle")
cvspeaks.Initialize(pnlPeaks)      'Canvas is drawn on panel background
Rect1.Initialize(0,0,220dip,300dip)
cvspeaks.DrawRect(Rect1,Colors.Red,True,0dip)

positrom2 · Aug 12, 2012

Mahares,
Yes, that works. So what I learn is that rectangles drawn on a panel will have their origin in the left, top corner of the panel. Then R=W and B=H which is easy. Maybe I missed that rule when I searched on this issue.
Thanks, positrom2

How to convert panel coordinates to rectangle coordinates?

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