Component like a breadcrumb
lazarus / 31-LCL

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Renat.Su · 2022-02-12 17:13

Can tell me if there is a LCL component in Lazarus from wich I can
easily make something like breadcrumbs on websites?

I have a tree structure with table/list. I would like to have an
elegant way to navigate back

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wp · 2022-02-12 21:58

I think you must write one yourself... But I think it's not too
difficult.
Inherit the control from a TCustomControl which must be prepared to
accept child controls. But for simplicity, you should simply start
with a descendant of TPanel.Borrow the TreeNodes from the TreeView so
have something to store the hierarchy of breadcrumb items. Establish a
property Items which is nothing else then the TTreeNodes of a
TreeView. Later, at runtime, add the items in the same way as you add
the nodes to a TreeView.Insert a TCombobox into the panel, at the left
side of the panel. Load the top-level nodes into the combobox; store
the nodes in the Objects property of the combobox.When the user
selects an item in the combobox add another combobox after the first
one. Find the tree node from the clicked item and populate the new
combobox with the child nodes of the clicked node.etc... Every click
into the last combobox adds the associated tree items into a new
following comboboxWhen the user drops down an intermediate combobox
destroy all comboboxes following since they are not needed any more.
Now we are back at step 4The only problem is that the combobox arrows
point downward rather than to the right. If that is an issue you could
add a TLabel for the selected item, instead of a TCombobox, and place
a speedbutton next to it, with a right-facing glyph. A click on the
speedbutton should open a popup menu with the items that were in the
combobox in the first solution.

[EDIT]
Hmmm.... Thinking about it in more detail, I see a problem with the
TreeNodes because they only can be created with the owner being a
TCustomTreeView. You probably must create an independent tree
structure for the breadcrumbs (TBreadCrumbItem corresponding to
TTreeNode, TBreadCrumbItems corresponding to TTreeNodes); I think you
can copy most of the code from the treeview controls.

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Sieben · 2022-02-12 22:52

If he only wants to navigate back a row of autosizing TLabel should do
the job as well. No need for a tree structure.

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wp · 2022-02-13 19:37

In the attachment there is a simple breadcrumb-like toolbar which it
mimics the breadcrumb bar of the Windows explorer. (not fully complete
since it does not handle the case when the breadcrumbs are wider than
the width of the toolbar). Tested on Windows only, on Linux you should
adapt the FRoot string in FormCreate().