{
* 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) 2010-2012, Peter Johnson (www.delphidabbler.com).
*
* $Rev$
* $Date$
*
* Displays the caret position of one or more memo controls in associated label
* controls. Labels are automatically updated whenever the caret position
* changes.
}
unit UMemoCaretPosDisplayMgr;
interface
uses
// Delphi
Generics.Collections, Classes, Controls, StdCtrls, Messages;
type
{
TMemoCaretPosDisplayMgr:
Class that displays the caret position of one or more memo controls in
associated label controls. Labels are automatically updated whenever the
caret position changes.
}
TMemoCaretPosDisplayMgr = class(TObject)
strict private
type
{
TMemoHook:
Class used to hook into a memo control's message loop and detect
selection changes, triggering an event when detected.
}
TMemoHook = class(TObject)
strict private
var
fMemo: TMemo; // Memo control to be hooked
fMemoWndProc: Pointer; // Memo's original
fWndProcHook: Pointer; // New hook window procedure
fOnSelChange: TNotifyEvent; // OnSelChange event handler
procedure WndProcHook(var Msg: TMessage);
{Window procedure that replaces and calls into memo control's own
window procedure. Detects selection changes and triggers OnSelChange
event.
@param Msg [in/out] Contains information about message. Result field
updated with message return value.
}
function SetWndProc(WndProc: Pointer): Pointer;
{Assigns a new window procedure to memo control.
@param WndProc [in] Pointer to new window procedure.
@return Pointer to old window procedure.
}
public
constructor Create(const AMemo: TMemo);
{Object constructor. Creates hook object for a specified memo.
@param AMemo [in] Memo control to be hooked.
}
destructor Destroy; override;
{Object destructor. Restores memo's original window procedure.
}
property OnSelChange: TNotifyEvent read fOnSelChange write fOnSelChange;
{Event triggered when a selection change in memo control is detected}
end;
type
// Record of values associated with memo control
TAssociations = record
OnKeyUp: TKeyEvent; // Original OnKeyUp event handler
OnMouseUp: TMouseEvent; // Original OnMouseUp event handler
OnEnter: TNotifyEvent; // Original OnEnter event handler
Hook: TMemoHook; // Object that hooks memo's window proc
DisplayCtrl: TLabel; // Label in which to display caret info
end;
var fMap: TDictionary<TMemo,TAssociations>;
{Maps memo to associated display label and saved event handlers}
procedure OnKeyUpHandler(Sender: TObject; var Key: Word;
Shift: TShiftState);
{OnKeyUp event handler for managed memo controls. Calls any original event
handler then updates caret position display.
@param Sender [in] Memo control that triggered event.
@param Key [in/out] Not used. Passed to any original event handler.
@param Shift [in] Not used. Passed to any original event handler.
}
procedure OnMouseUpHandler(Sender: TObject; Button: TMouseButton;
Shift: TShiftState; X, Y: Integer);
{OnMouseUp event handler for managed memo controls. Calls any original
event handler then updates caret position display.
@param Sender [in] Memo control that triggered event.
@param Button [in] Not used. Passed to any original event handler.
@param Shift [in] Not used. Passed to any original event handler.
@param X [in] Not used. Passed to any original event handler.
@param Y [in] Not used. Passed to any original event handler.
}
procedure OnEnterHandler(Sender: TObject);
{OnEnter event handler for managed memo controls. Calls any original event
handler then updates caret position display.
@param Sender [in] Memo control that triggered event.
}
procedure OnSelChangeHandler(Sender: TObject);
{Handles events triggered when selection changes are reported be memo
hook. Updates caret position display.
@param Sender [in] Memo control that triggered event.
}
procedure UpdateCaretPos(const SourceCtrl: TMemo);
{Updates display of a memo control's caret position.
@param SourceCtrl [in] Memo whose caret position to be displayed.
}
function FindFirstMemoControl(const ParentCtrl: TWinControl): TMemo;
{Finds first memo child control of given parent control.
@param ParentCtrl [in] Parent containing required memo control.
@return Reference to memo control or nil if ParentCtrl has no memo
child control.
}
public
constructor Create;
{Object constructor. Sets up object.
}
destructor Destroy; override;
{Object destructor. Restores original event handlers to managed memo
controls then clears up object.
}
procedure Manage(const SourceCtrl: TMemo; const DisplayCtrl: TLabel);
overload;
{Registers a memo control to have caret position displayed in an
associated label. NOTE: This method must only be called once the memo
control has initialised otherwise selection change events will not be
detected. Calling during a form's OnShow event is recommended.
@param SourceCtrl [in] Memo control whose caret position is to be
displayed.
@param DisplayCtrl [in] Label used to display caret position.
}
procedure Manage(const ParentCtrl: TWinControl; const DisplayCtrl: TLabel);
overload;
{Registers first memo child control of given parent control to have caret
position displayed in an associated label. NOTE 1: This method must only
be called once the memo control has initialised otherwise selection change
events will not be detected. Calling during a form's OnShow event is
recommended. NOTE 2: Parent control MUST have at least one memo control as
a child.
@param ParentCtrl [in] Parent of memo control whose caret position is to
be displayed.
@param DisplayCtrl [in] Label used to display caret position.
}
end;
implementation
uses
// Delphi
SysUtils, Windows;
{ TMemoCaretPosDisplayMgr }
constructor TMemoCaretPosDisplayMgr.Create;
{Object constructor. Sets up object.
}
begin
inherited Create;
fMap := TDictionary<TMemo,TAssociations>.Create;
end;
destructor TMemoCaretPosDisplayMgr.Destroy;
{Object destructor. Restores original event handlers to managed memo controls
then clears up object.
}
var
DataPair: TPair<TMemo,TAssociations>; // each key and value pair from map
SourceCtrl: TMemo; // each memo control in map
Associations: TAssociations; // associated data for each SourceCtrl
begin
for DataPair in fMap do
begin
// restore saved event handlers
SourceCtrl := DataPair.Key;
Associations := DataPair.Value;
SourceCtrl.OnKeyUp := Associations.OnKeyUp;
SourceCtrl.OnMouseUp := Associations.OnMouseUp;
SourceCtrl.OnEnter := Associations.OnEnter;
Associations.Hook.Free;
end;
fMap.Free;
inherited;
end;
function TMemoCaretPosDisplayMgr.FindFirstMemoControl(
const ParentCtrl: TWinControl): TMemo;
{Finds first memo child control of given parent control.
@param ParentCtrl [in] Parent containing required memo control.
@return Reference to memo control or nil if ParentCtrl has no memo child
control.
}
var
Ctrl: TControl;
Idx: Integer;
begin
for Idx := 0 to Pred(ParentCtrl.ControlCount) do
begin
Ctrl := ParentCtrl.Controls[Idx];
if Ctrl is TMemo then
Exit(Ctrl as TMemo);
end;
Result := nil;
end;
procedure TMemoCaretPosDisplayMgr.Manage(const ParentCtrl: TWinControl;
const DisplayCtrl: TLabel);
{Registers first memo child control of given parent control to have caret
position displayed in an associated label. NOTE 1: This method must only be
called once the memo control has initialised otherwise selection change events
will not be detected. Calling during a form's OnShow event is recommended.
NOTE 2: Parent control MUST have at least one memo control as a child.
@param ParentCtrl [in] Parent of memo control whose caret position is to be
displayed.
@param DisplayCtrl [in] Label used to display caret position.
}
begin
Manage(FindFirstMemoControl(ParentCtrl), DisplayCtrl);
end;
procedure TMemoCaretPosDisplayMgr.Manage(const SourceCtrl: TMemo;
const DisplayCtrl: TLabel);
{Registers a memo control to have caret position displayed in an associated
label.
@param SourceCtrl [in] Memo control whose caret position is to be displayed.
@param DisplayCtrl [in] Label used to display caret position.
}
var
Associations: TAssociations; // data to be associated with memo control
begin
Assert(Assigned(SourceCtrl), ClassName + '.Manage: SourceCtrl is nil');
Assert(Assigned(DisplayCtrl), ClassName + '.Manage: DisplayCtrl is nil');
Assert(not fMap.ContainsKey(SourceCtrl),
ClassName + '.Manage: Source memo already managed');
// save old event handlers
Associations.OnKeyUp := SourceCtrl.OnKeyUp;
Associations.OnMouseUp := SourceCtrl.OnMouseUp;
Associations.OnEnter := SourceCtrl.OnEnter;
// record display label
Associations.DisplayCtrl := DisplayCtrl;
// add menu hook object
Associations.Hook := TMemoHook.Create(SourceCtrl);
Associations.Hook.OnSelChange := OnSelChangeHandler;
// hook required event handlers (each of these calls any saved handler)
SourceCtrl.OnKeyUp := OnKeyUpHandler;
SourceCtrl.OnMouseUp := OnMouseUpHandler;
SourceCtrl.OnEnter := OnEnterHandler;
// add control to list of managed controls
fMap.Add(SourceCtrl, Associations);
// initialise caret position display
UpdateCaretPos(SourceCtrl);
end;
procedure TMemoCaretPosDisplayMgr.OnEnterHandler(Sender: TObject);
{OnEnter event handler for managed memo controls. Calls any original event
handler then updates caret position display.
@param Sender [in] Memo control that triggered event.
}
var
SavedOnEnter: TNotifyEvent; // original event handler
begin
// call any original event hander
SavedOnEnter := fMap[Sender as TMemo].OnEnter;
if Assigned(SavedOnEnter) then
SavedOnEnter(Sender);
UpdateCaretPos(Sender as TMemo);
end;
procedure TMemoCaretPosDisplayMgr.OnKeyUpHandler(Sender: TObject; var Key: Word;
Shift: TShiftState);
{OnKeyUp event handler for managed memo controls. Calls any original event
handler then updates caret position display.
@param Sender [in] Memo control that triggered event.
@param Key [in/out] Not used. Passed to any original event handler.
@param Shift [in] Not used. Passed to any original event handler.
}
var
SavedOnKeyUp: TKeyEvent; // original event handler
begin
// call any original event hander
SavedOnKeyUp := fMap[Sender as TMemo].OnKeyUp;
if Assigned(SavedOnKeyUp) then
SavedOnKeyUp(Sender, Key, Shift);
UpdateCaretPos(Sender as TMemo);
end;
procedure TMemoCaretPosDisplayMgr.OnMouseUpHandler(Sender: TObject;
Button: TMouseButton; Shift: TShiftState; X, Y: Integer);
{OnMouseUp event handler for managed memo controls. Calls any original event
handler then updates caret position display.
@param Sender [in] Memo control that triggered event.
@param Button [in] Not used. Passed to any original event handler.
@param Shift [in] Not used. Passed to any original event handler.
@param X [in] Not used. Passed to any original event handler.
@param Y [in] Not used. Passed to any original event handler.
}
var
SavedOnMouseUp: TMouseEvent; // original event handler
begin
// call any original event hander
SavedOnMouseUp := fMap[Sender as TMemo].OnMouseUp;
if Assigned(SavedOnMouseUp) then
SavedOnMouseUp(Sender, Button, Shift, X, Y);
UpdateCaretPos(Sender as TMemo);
end;
procedure TMemoCaretPosDisplayMgr.OnSelChangeHandler(Sender: TObject);
{Handles events triggered when selection changes are reported be memo hook.
Updates caret position display.
@param Sender [in] Memo control that triggered event.
}
begin
UpdateCaretPos(Sender as TMemo);
end;
procedure TMemoCaretPosDisplayMgr.UpdateCaretPos(const SourceCtrl: TMemo);
{Updates display of a memo control's caret position.
@param SourceCtrl [in] Memo whose caret position to be displayed.
}
var
DisplayCtrl: TLabel; // label in which caret position to be displayed
begin
DisplayCtrl := fMap[SourceCtrl].DisplayCtrl;
DisplayCtrl.Caption := Format(
'%d: %d', [SourceCtrl.CaretPos.Y, SourceCtrl.CaretPos.X]
);
end;
{ TMemoCaretPosDisplayMgr.TMemoHook }
constructor TMemoCaretPosDisplayMgr.TMemoHook.Create(const AMemo: TMemo);
{Object constructor. Creates hook object for a specified memo.
@param AMemo [in] Memo control to be hooked.
}
begin
inherited Create;
fMemo := AMemo;
// hook memo's window procedure
fWndProcHook := Classes.MakeObjectInstance(WndProcHook);
fMemoWndProc := SetWndProc(fWndProcHook);
end;
destructor TMemoCaretPosDisplayMgr.TMemoHook.Destroy;
{Object destructor. Restores memo's original window procedure.
}
begin
fOnSelChange := nil;
if Assigned(fWndProcHook) then
begin
// restore original window procedure
SetWndProc(fMemoWndProc);
Classes.FreeObjectInstance(fWndProcHook);
end;
inherited;
end;
function TMemoCaretPosDisplayMgr.TMemoHook.SetWndProc(
WndProc: Pointer): Pointer;
{Assigns a new window procedure to memo control.
@param WndProc [in] Pointer to new window procedure.
@return Pointer to old window procedure.
}
begin
Result := Pointer(
SetWindowLong(fMemo.Handle, GWL_WNDPROC, Integer(WndProc))
);
end;
procedure TMemoCaretPosDisplayMgr.TMemoHook.WndProcHook(var Msg: TMessage);
{Window procedure that replaces and calls into memo control's own window
procedure. Detects selection changes and triggers OnSelChange event.
@param Msg [in/out] Contains information about message. Result field updated
with message return value.
}
begin
Msg.Result := CallWindowProc(
fMemoWndProc, fMemo.Handle, Msg.Msg, Msg.WParam, Msg.LParam
);
if (Msg.Msg = EM_SETSEL) and Assigned(fOnSelChange) then
fOnSelChange(fMemo);
end;
end.
