Title: Creating custom hints for yoru application/component
Question: This is a simple solution to creating/adding custom hints to your application or component (mostly usefull to component writing, or people drawing images/information to onscreen canvas's).
Answer:
Often when development custom components, or displaying information on a canvas, you want to display a fly over hint -inside- the component instead of beneath it like standard hints, this can be accomplished with a THintWindow and TTimer component.
Simply add the following to your form/component:
type
THintEvent = procedure(Sender: TObject;
var AHint: string) of object;
private
HintWindow: THintWindow;
HintTimer: TTimer;
fShowHint: Boolean;
fOnHint: THintEvent;
published
property ShowHint: Boolean read fShowHint write fShowHint;
property OnHint: THintEvent read fOnHint write fOnHint;
and in the Create code:
begin
...
HintWindow := THintWindow.Create(Self);
HintWindow.Color := clInfoBk;
HintTimer := TTimer.Create(Self);
HintTimer.Enabled := False;
HintTimer.Interval := 3000;
HintTimer.OnTimer := HintTimerEvent;
...
end;
Add the following procedure:
procedure TMapField.TimerHWinEvent(Sender: TObject);
begin
HintWindow.ReleaseHandle; // Hide the Hint Window
HintTimer.Enabled := False;
end;
Now we're ready to actually display your hint, usually this code would be called in response to some move movement event, personally I write a function called HandleHint (called from the mouse event) which goes something this:
procedure TForm1.HandleHint(X,Y: Integer);
var
p: TPoint;
s: string;
sWidth: integer;
sHeight: integer;
i, iWidth: integer;
sList: TStringList;
begin
sList := TStringList.Create;
GetCursorPos(P);
s := 'Set this to whatever your hint will be';
// Provide an event to modify s - usefull for when in components
if Assigned(fOnHint) then fOnHint(Self, s);
// Only show the hint if ShowHint is true and it differs from
// the last hint we showed.
if (ShowHint) and (HintWindow.Caption s) then
begin
HintTimer.Enabled := False;
// Find longest string for a multi-line hint.
sList.Text := s;
sWidth := 0;
for i := 0 to sList.Count - 1 do
begin
iWidth := HintWindow.Canvas.TextWidth(sList.Strings[i]);
if iWidth sWidth then sWidth := iWidth;
end;
sHeight := HintWindow.Canvas.TextHeight(s) * sList.Count;
HintWindow.ActivateHint(
Rect(P.X,P.Y, P.x + sWidth + 6, P.Y + sHeight),s);
HintTimer.Enabled := True;
end; // if (ShowHint)...
end;
And as with all good code, in your Destroy method, don't forget to free what we made:
begin
...
HintWindow.Free;
HintTimer.Free;
...
end;
Mark Derricutt / Talios