problem with mdi children

[KlausW]

Hi community,

i want to create simple MDI application but ths child forms should be in a special order of visibility or layer.
For example: if a child form has layer 0 it is always top most of all other child forms. A child form with layer 1 is behind a child form with layer 0 but in front of a childform with layer 2 and so on...

Does anybody know a simply solution?

Thanks

[cloud255]

Hi

Well if you have several forms of each layer I would suggest using a 2 dimensional array.

You can then order the array to ensure that the display order of the layer is preserved and place forms of each layer in the corresponding 'row' of the array.

You could then create a function to loop the array drawing the last entry of the bottom most layer first and working your way up. By attaching a 'layer' property to each of your child forms and calling the display/sort functions you will ensure that children are always displayed in the correct order.

Hope this helps

[KlausW]

First thanks for your post cloud255.

When i create a child form i want to put the form in a layer till i close the form.
How could i tell the child form to be in layer 2 or layer 5?
There could be several child forms in the same layer, then they behave like normal child forms - the focused (or activated) form is in front of the other form.

[cloud255]

@KlausW
My apologies, but I will change my suggestion to using a List<LinkedList<>> instead of a 2 dimensional array. The concept is still pretty much the same, it will just be easier to implement.

You will have to create a struct or class which has a 'layer' property, you will use this property to assign a form to the appropriate part of the List:

//MyChildObject is a custom class/struct which has an integer property 'layer'
 
List<LinkedList<MyChildObject>> Layers;  //List of layers
 
LinkedList<MyChildObject> Children; //list of children in each layer
 
private void CreateNewChild(MyChildObject newChild)
{
       Layers[newChild.layer].AddFirst(newChild); //This adds the new child object to the correct layer and in the first position
}
 

Moving the selected child to the front can be done using the AddFirst method and then deleting the 'old' entry from the linked list using the FindLast method of the linked list.

The structure of List<LinkedList<>> will look something like this:

XXX
XXXXXXXX
XX
XXXXXXXXX
XXXXX
X
XXXXXXXXXXXX

If you are unfamiliar with the list and linkedlist data structures, see the below links:
List
LinkedList Class
Linked list concept

Please feel free to post if you are uncertain of anything.

[KlausW]

I'm familiar with List and LinkedList, that's not the problem.

Imagine the scenario:

If i have three child forms:
one with layer 2 (called form2)
one with layer 4 (called form4)
one with layer 6 (called form6)

all three have the same size and do not overlap each other at he begin.
example 1:
then i move form2 over form4 -> form2 will be in front of the form4. if i move form4 it should be behind form2.
example 2:
if i move form4 "over" form2 it will be behind form2, but if i move form4 over form6 it should be in front of form6. form6 is always behind form4 and form2

It does not depend on moving the form, getting the focus should make the same effect.

[cloud255]

Ok so you want the lowest number level to have focus i.e. layer 2 will have focus if no layer 0 or 1 children exist?

If that is the case you could simply set focus to the first element in the linked list of the at list[2] (a better way would be to loop through the list until you find an element that is not null instead of using an index value).
But this will result in the other children from layer 2 possibly being stacked behind some of the the higher layer children. This too can be avoided by looping through the linked list, starting at the back, and setting focus to child in the linked list. Thus the first node in the linked list at the lowest index of the list will always have focus have focus...

[KlausW]

Thanks for your participation to discuss this problem.

But i only want to "lay" the child forms with different layers in the correct visibility inside of the mdi parent.

[KlausW]

example for the visibility of child forms (but this is not mdi :-( ):

public partial class MDIParent1 : Form
{
 
        private void ShowNewForm(object sender, EventArgs e)
        {
            Form f2 = new Form();
            f2.ShowInTaskbar = false;
            f2.Text = "Layer2";
 
            Form f1 = new Form();
            f1.ShowInTaskbar = false;
            f1.Text = "Layer1";
 
            Form f0 = new Form();
            f0.ShowInTaskbar = false;
            f0.Text = "Layer0";
 
            f0.Owner = f1;
            f1.Owner = f2;
            f2.Owner = this; 
 
            f0.Show();
            f1.Show();
            f2.Show();
        }
 
....
}