Relative coordinates in a GUI system [Resolved]

[SLH]

I'm making a GUI for directx.

A window has either a parent (window it's displayed in) or NULL (it's the desktop).

A window's coordinates range from 0 to GUI_SCALEX and 0 to GUI_SCALEY.

RESX and RESY dictate the resolution for the screen.

I've attached the code i'm using below.
It works for the desktop window (parent of NULL), but not it's child window.

Can anyone see what i've done wrong?

int VirtXtoPixels(int virtX)
{
	int tmpWidth = (m_pParent) ? m_pParent->m_rPosition.right-m_pParent->m_rPosition.left : RESX;
	int tmpAdd = (m_pParent) ? m_pParent->VirtXtoPixels(m_pParent->m_rPosition.left) : 0;
	return((int)((double)virtX*(double)tmpWidth/GUI_SCALEX) + tmpAdd);
}
int VirtYtoPixels(int virtY)
{
	int tmpHeight = (m_pParent) ? m_pParent->m_rPosition.bottom-m_pParent->m_rPosition.top : RESY;
	int tmpAdd = (m_pParent) ? m_pParent->VirtYtoPixels(m_pParent->m_rPosition.top) : 0;
	return((int)((double)virtY*(double)tmpHeight/GUI_SCALEY) + tmpAdd);
}

FYI ?: is a ternary operator with the following syntax:

Test ? True statement : false statement

[Electroman]

When your running that for the Children you shouldn't be using ResX & ResY? You should be using the Parrents Size?

[SLH]

Thanks for your reply.


I've shown the relative coordinates (the window positions aren't quite right, but you get the idea).

GUI_SCALEX = 1000
GUI_SCALEY = 1000

i.e. if i put a child at 450,450,550,550 it should show up in the middle of it's parent (no matter where the parent is).

If i made the parent window's coordinates 450,450,550,550 it would be in the middle of the screen, so i know that a window with no parent works ok.

[Electroman]

Am I right though in say to position Child you don't bother with ResX & ResY at all all you need is the Parent Width & Hight and also the parents position?

[SLH]

Originally posted by Electroman
When your running that for the Children you shouldn't be using ResX & ResY? You should be using the Parrents Size?

ehh...

I simply call the parents VirtX(orY)toPixels method, to get how much to add to the coordinate i get.

I have to do m_pParents->VirtXtoPixels as opposed to just VirtXtoPixels, otherwise i get infinate recursion.


Formula i'm using:

childrealxpos = parent's real xpos + my real xpos relative to my parent.

parent's real pos i get by recursion
my real xpos relative to parent is this line:return((int)((double)virtX*(double)tmpWidth/GUI_SCALEX) + tmpAdd)

tmpWidth is only calculated in an if operator because the base window (with no parent) is relative to RESX/RESY as opposed to a parent.

[SLH]

Originally posted by Electroman
Am I right though in say to position Child you don't bother with ResX & ResY at all all you need is the Parent Width & Hight and also the parents position?

Correct.

Here's the virtxtopixels re-written using if's as opposed to ?:

int VirtXtoPixels(int virtX)
{
    int tmpWidth;
    if(m_pParent)
        tmpWidth = m_pParent->m_rPosition.right-m_pParent->m_rPosition.left;
    else
        tmpWidth =RESX;

    int tmpAdd;
    if(m_pParent)
        tmpAdd = m_pParent->VirtXtoPixels(m_pParent->m_rPosition.left);
    else
        tmpAdd = 0;
    return((int)((double)virtX*(double)tmpWidth/GUI_SCALEX) + tmpAdd);
}

[Electroman]

yea the ?'s had thown me off a bit, I read the code properly and spotted it though, it was just I'd seen ResX and ResY on both and didn't look further, opps.


Anyway what is the bug? Am I write guessing the whole thing works when the scale is 1000 but goes funny at lower values? Or does it not work at all?

I had similar issues with the Vector Game I made cos I included a scaling thing which allowed the camera to zoom in and out, the problem was that I had to make it scale from the centre not 0,0 and also the positioning of the objects was being related to 0,0 not the centre. maybe that will help?

[SLH]

I don't change GUI_SCALEX or GUI_SCALEY, but even if i do the child window are displayed in the wrong positions.

A window with NULL m_pParent works.

The coordinates (0,0) for a child window seems to work, but any other value doesn't.

Meaning if the child's top-left corner is placed as (0,0) it is correctly displayed in it's parent's top left. However, the child's bottom-right corner is displayed wrongly, sometimes outside the parent all together.

[Electroman]

What do you keep Scale set to? If you set it to 1 then I would expect everything to work fine? Just tried putting some numbers thoguh it and they seemed ok with Scale at 1 anyway?

[SLH]

Originally posted by Electroman
What do you keep Scale set to? If you set it to 1 then I would expect everything to work fine? Just tried putting some numbers thoguh it and they seemed ok with Scale at 1 anyway?

?? Where/what is 'Scale'?

[Electroman]

Posted by SLH
?? Where/what is 'Scale'?

I mean GUI_SCALEX & GUI_SCALEY . Sorry couldn't think of the exact names .

[SLH]

The are both = 1000, i never change them.

[Electroman]

Posted by SLH
The are both = 1000, i never change them.

Try them at 1 and see if that looks right .

[SLH]

Thanks for your continued help. Your suggestion didn't work, unfortunatly.


To explain what i'm doing more throughly:

When i setup a window i give it coordinates as a proportion of GUI_SCALEX and GUI_SCALEY (stored in the RECT m_rPosition)

The position where the window is actually drawn depends on where it's parent is, if it has one, and these coordinates.

A window with no parent is drawn relative to the screen's resolution, hence RESX and RESY in the 'else' of the (m_pParent) if statements.

A window with a parent is drawn in a position relative to the parent i.e. moving the parent will also move the child, hence working out the width/height of the parent, so i know how far along the parent to draw the child.

Sorry if i'm not explaining myself very well.

[Electroman]

Yea I understand what you're tryign to do but I hadn't realised the Rect m_rPosition had been scaled first of all.


BTW shouldn't tmpAdd be devided by GUI_SCALEX or GUI_SCALEY when you add it on? Apart from that I would have thought it would work.....unless you need some brackets in the tmpWidth/GUI_SCALEX bit to makesure the order it happens in is right? Can't remember but I'm pretty sure Devision is first so they shouldn't be needed.

[SLH]

Since tmpAdd is calculated using the parent's call to VirttoPixels it should be an absolute value, and so shouldn't need to be divided by GUI_SCALE.

I did try it though, but it didn't work

[SLH]

Sorted it!

Here's my final code:

int VirtXtoPixels(int virtX)
	{
		int tmpAdd;
		int tmpWidth;
		if(!m_pParent)
			return (int)((double)virtX/GUI_SCALE * (double)RESX);

		tmpWidth = m_pParent->VirtXtoPixels(m_pParent->m_rPosition.right-m_pParent->m_rPosition.left);
		tmpAdd = m_pParent->VirtXtoPixels(m_pParent->m_rPosition.left);
		return (int)(virtX/GUI_SCALE * tmpWidth + tmpAdd);
		
	}
	int VirtYtoPixels(int virtY)
	{
		int tmpAdd;
		int tmpHeight;
		if(!m_pParent)
			return (int)((double)virtY/GUI_SCALE * (double)RESY);

		tmpHeight = m_pParent->VirtYtoPixels(m_pParent->m_rPosition.bottom-m_pParent->m_rPosition.top);
		tmpAdd = m_pParent->VirtYtoPixels(m_pParent->m_rPosition.top);
		return (int)(virtY/GUI_SCALE * tmpHeight + tmpAdd);
	}