Title: Changing TForm BorderIcons
Question: Has you know you can enable or disable a form bordericons (system menu, minimize, maximize and help) just by including or excluding the value you want from the bordericons set.
Answer:
Anyway, this method has (at least) one disadvantage. To the change to this
property have efect, VCL internal structure need's to call a function
(TWinControl.RecreateWnd). As you can see this method causes the activation of
at least one event (OnShow), and the flick of the form.
So, one option to avoid this is by using the following function that can
enable/disable bordericons by bypassing TWinControl.RecreateWnd
procedure SetBorderIcons(Value: TBorderIcons);
var
FStyle, FAppStyle: LongWord;
FExStyle, FAppExStyle: LongWord;
begin
// Get old style's
FStyle := GetWindowLong(Handle, GWL_STYLE);
FExStyle := GetWindowLong(Handle, GWL_EXSTYLE);
FAppStyle := GetWindowLong(Application.Handle, GWL_STYLE);
FAppExStyle := GetWindowLong(Application.Handle, GWL_EXSTYLE);
// Process styles, according to the parameters
if BorderStyle in [bsSingle, bsSizeable, bsNone] then
if (FormStyle fsMDIChild) or (biSystemMenu in Value) then
begin
if biMinimize in Value then
begin
FStyle := FStyle or WS_MINIMIZEBOX;
FAppStyle := FAppStyle or WS_MINIMIZEBOX;
end
else
begin
FStyle := FStyle and not WS_MINIMIZEBOX;
FAppStyle := FAppStyle and not WS_MINIMIZEBOX;
end;
if biMaximize in Value then
begin
FStyle := FStyle or WS_MAXIMIZEBOX;
FAppStyle := FAppStyle or WS_MAXIMIZEBOX;
end
else
begin
FStyle := FStyle and not WS_MAXIMIZEBOX;
FAppStyle := FAppStyle and not WS_MAXIMIZEBOX;
end;
end;
if biSystemMenu in Value then
begin
FStyle := FStyle or WS_SYSMENU;
FAppStyle := FAppStyle or WS_SYSMENU;
end
else
begin
FStyle := FStyle and not WS_SYSMENU;
FAppStyle := FAppStyle and not WS_SYSMENU;
end;
if (biHelp in Value) then
FExStyle := FExStyle or WS_EX_CONTEXTHELP
else
FExStyle := FExStyle and not WS_EX_CONTEXTHELP;
// Update new style's
SetWindowLong(Handle, GWL_STYLE, FStyle);
SetWindowLong(Handle, GWL_EXSTYLE, FExStyle);
SetWindowLong(Application.Handle, GWL_STYLE, FAppStyle);
SetWindowLong(Application.Handle, GWL_EXSTYLE, FAppExStyle);
// Force repaint the Non Client (NC) area, for updating form
SetWindowPos(Handle, 0, 0, 0, 0, 0,
SWP_NOZORDER or SWP_NOSIZE or SWP_NOMOVE or SWP_DRAWFRAME or SWP_SHOWWINDOW);
end;
The only problem with this routine (and I hope someone could help) is that it
doesn't update form's BorderIcons. I tried to access FBorderIcons private
variable in TCustomForm, but because it is private...