{
* This Source Code Form is subject to the terms of the Mozilla Public License,
* v. 2.0. If a copy of the MPL was not distributed with this file, You can
* obtain one at http://mozilla.org/MPL/2.0/
*
* Copyright (C) 2009-2012, Peter Johnson (www.delphidabbler.com).
*
* $Rev$
* $Date$
*
* Implements a class that maintains the expansion state of a set of section
* nodes from the overview tree view. The class can record the current state and
* restore it later.
}
unit UOverviewTreeState;
interface
uses
// Delphi
ComCtrls, Generics.Collections,
// Project
UView;
type
/// <summary>
/// Class that records state of a section (level 0) node in the overview
/// pane's treeview.
/// </summary>
TOverviewTreeSectionState = class(TObject)
strict private
var
/// <summary>Value of Expanded property.</summary>
fExpanded: Boolean;
/// <summary>Value of ViewKey property.</summary>
fViewKey: IViewKey;
public
constructor Create(ViewKey: IViewKey; const Expanded: Boolean);
{Constructor. Sets up object.
@param ViewItem [in] View item represented by section node.
@param Expended [in] True if node is expanded, False if not.
}
destructor Destroy; override;
{Destructor. Tears down object.
}
property Expanded: Boolean read fExpanded;
{Whether section node is expanded}
property ViewKey: IViewKey read fViewKey;
end;
type
{
TOverviewTreeState:
Class that maintains the expansion state of a set of section nodes from the
overview tree view. The class can record the current state and restore it
later.
}
TOverviewTreeState = class(TObject)
strict private
type
// Enumeration indicating required state of tree at next restoration
TResorationState = (
rsFullExpand, // tree must be fully expanded when restored
rsFullCollapse, // tree must be fully collapsed when restored
rsAsSaved // tree must be restored according to saved state
);
// Class that maintains a list of section state objects
TSectionStates = TObjectList<TOverviewTreeSectionState>;
var
fTV: TTreeView; // Reference to treeview
fSections: TSectionStates; // List of section state objects
fRestoreState: TResorationState; // Current restoration state of tree
function FindSection(ViewKey: IViewKey;
out FoundSection: TOverviewTreeSectionState): Boolean;
{Finds a section object that references a specified view item.
@param ViewItem [in] View item being searched for.
@param FoundSection [in] Section object or nil if view item not found.
@return True if view item found, False if not.
}
function IsSectionNode(const Node: TTreeNode): Boolean;
{Checks if a node is a section node.
@param Node [in] Node to be checked.
@return True if node is a section node.
}
public
constructor Create(const TV: TTreeView);
{Constructor. Sets up object to work with a treeview.
@param TV [in] Treeview whose state is to be managed.
}
destructor Destroy; override;
{Destructor. Tears down object.
}
procedure SaveState;
{Saves expansion state of all section nodes in treeview.
}
procedure RestoreState;
{Restores state of all section nodes in overview. How tree is restored
depends on required restoration state and if a previous state has been
recorded.
}
end;
implementation
uses
// Project
UPreferences, UViewItemTreeNode;
{ TOverviewTreeSectionState }
constructor TOverviewTreeSectionState.Create(ViewKey: IViewKey;
const Expanded: Boolean);
{Constructor. Sets up object.
@param ViewItem [in] View item represented by section node.
@param Expended [in] True if node is expanded, False if not.
}
begin
inherited Create;
fViewKey := ViewKey;
fExpanded := Expanded;
end;
destructor TOverviewTreeSectionState.Destroy;
{Destructor. Tears down object.
}
begin
fViewKey := nil;
inherited;
end;
{ TOverviewTreeState }
constructor TOverviewTreeState.Create(const TV: TTreeView);
{Constructor. Sets up object to work with a treeview.
@param TV [in] Treeview whose state is to be managed.
}
begin
inherited Create;
fSections := TSectionStates.Create(True);
fTV := TV;
case Preferences.OverviewStartState of
ossExpanded: fRestoreState := rsFullExpand;
ossCollapsed: fRestoreState := rsFullCollapse;
end;
end;
destructor TOverviewTreeState.Destroy;
{Destructor. Tears down object.
}
begin
fSections.Free;
inherited;
end;
function TOverviewTreeState.FindSection(ViewKey: IViewKey;
out FoundSection: TOverviewTreeSectionState): Boolean;
{Finds a section object that references a specified view item.
@param ViewItem [in] View item being searched for.
@param FoundSection [in] Section object or nil if view item not found.
@return True if view item found, False if not.
}
var
Section: TOverviewTreeSectionState; // each section state in list
begin
Result := False;
FoundSection := nil;
for Section in fSections do
begin
if Section.ViewKey.IsEqual(ViewKey) then
begin
FoundSection := Section;
Exit(True);
end;
end;
end;
function TOverviewTreeState.IsSectionNode(const Node: TTreeNode): Boolean;
{Checks if a node is a section node.
@param Node [in] Node to be checked.
@return True if node is a section node.
}
begin
// A section node is a view item tree node at level 0
Result := (Node.Level = 0) and (Node is TViewItemTreeNode);
end;
procedure TOverviewTreeState.RestoreState;
{Restores state of all section nodes in overview. How tree is restored depends
on required restoration state and if a previous state has been recorded.
}
var
Node: TTreeNode; // each node in treeview
Section: TOverviewTreeSectionState; // object describing a section's state
begin
case fRestoreState of
rsFullExpand: fTV.FullExpand;
rsFullCollapse: fTV.FullCollapse;
rsAsSaved:
begin
for Node in fTV.Items do
begin
if IsSectionNode(Node) and
FindSection(
(Node as TViewItemTreeNode).ViewItem.GetKey, Section
) then
Node.Expanded := Section.Expanded;
end;
end;
end;
end;
procedure TOverviewTreeState.SaveState;
{Saves expansion state of all section nodes in treeview.
}
// ---------------------------------------------------------------------------
procedure RecordSection(const Node: TViewItemTreeNode);
{Records reference to a treeview section whose expansion state is to be
maintained by the object.
@param Node [in] Treeview node whose state is to be recorded.
}
begin
fSections.Add(
TOverviewTreeSectionState.Create(Node.ViewItem.GetKey, Node.Expanded)
);
end;
// ---------------------------------------------------------------------------
var
Node: TTreeNode; // each node in treeview
begin
fSections.Clear;
for Node in fTV.Items do
begin
if IsSectionNode(Node) then
RecordSection(Node as TViewItemTreeNode);
end;
// note that tree must be restored from this saved state
fRestoreState := rsAsSaved;
end;
end.
