RemObjects Hydra Plugin Can't Handle WM_DEVICECHANGE Windows Messages Directly - delphi

Question

I Creating a Hydra Host Application and a Hydra Plugin. I put a Procedure for Handling a Windows Message in Plugin; but in this case we can't handle this windows message. for solving this problem we can handle It in Host App and then we must talk with pluging via passing an Interface.
In this case I want to find a direct way for handle windows messages in Hydra Plugin. Please help me for solving this problem.
Update 1 for this Question:
this is a simple code for testing:
Plugin Side:
unit VisualPlugin;
interface
uses
{ vcl: } Windows, Messages, SysUtils, Variants, Classes, Graphics,
Controls, Forms, Dialogs, StdCtrls,
{ Hydra: } uHYVisualPlugin, uHYIntf;
type
TVisualPlugin1 = class(THYVisualPlugin)
private
procedure WMDEVICECHANGE(var Msg: TMessage); message WM_DEVICECHANGE;
end;
implementation
uses
{ Hydra: } uHYPluginFactories;
{$R *.dfm}
procedure Create_VisualPlugin1(out anInstance: IInterface);
begin
anInstance := TVisualPlugin1.Create(NIL);
end;
resourcestring
sDescription = '';
const
sRequiredPrivilege = '';
sUserData = '';
{ TVisualPlugin1 }
procedure TVisualPlugin1.WMDEVICECHANGE(var Msg: TMessage);
begin
// ===================================
// This Line Of Code Can't Be Run!!!!!!
ShowMessage('USB Changed');
// ===================================
end;
initialization
THYPluginFactory.Create(HInstance, 'VisualPlugin1', Create_VisualPlugin1,
TVisualPlugin1, 1, 0, sRequiredPrivilege, sDescription, sUserData);
end.
PluginController in Plugin Side:
unit hcPluginController;
interface
uses
{vcl:} SysUtils, Classes,
{Hydra:} uHYModuleController, uHYIntf, uHYCrossPlatformInterfaces;
type
TPluginController = class(THYModuleController)
private
public
end;
var
PluginController : TPluginController;
implementation
uses
{Hydra:} uHYRes;
{$R *.dfm}
procedure HYGetCrossPlatformModule(out result: IHYCrossPlatformModule); stdcall;
begin
result := PluginController as IHYCrossPlatformModule;
end;
function HYGetModuleController : THYModuleController;
begin
result := PluginController;
end;
exports
HYGetCrossPlatformModule,
HYGetModuleController name name_HYGetModuleController;
resourcestring
sDescription = '';
const
sRequiredPrivilege = '';
initialization
PluginController := TPluginController.Create('Plugin.Library', 1, 0, sRequiredPrivilege, sDescription);
finalization
FreeAndNil(PluginController);
end.
Host Application Side:
unit fMain;
interface
uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, uHYModuleManager, uHYIntf, ExtCtrls, StdCtrls;
type
TMainForm = class(TForm)
HYModuleManager1: THYModuleManager;
Panel1: TPanel;
btnLoadPlugin: TButton;
procedure btnLoadPluginClick(Sender: TObject);
procedure FormCreate(Sender: TObject);
procedure FormClose(Sender: TObject; var Action: TCloseAction);
private
{ Private declarations }
public
{ Public declarations }
end;
var
MainForm: TMainForm;
implementation
{$R *.dfm}
var
AppDir: string;
fPlugin: IHYVisualPlugin;
const
PluginDll = 'Plugin.dll';
PluginName = 'VisualPlugin1';
procedure TMainForm.btnLoadPluginClick(Sender: TObject);
begin
if HYModuleManager1.FindModule(AppDir + PluginDll) = nil then
HYModuleManager1.LoadModule(AppDir + PluginDll);
HYModuleManager1.CreateVisualPlugin(PluginName, fPlugin, Panel1);
end;
procedure TMainForm.FormClose(Sender: TObject; var Action: TCloseAction);
begin
HYModuleManager1.ReleaseInstance(fPlugin);
HYModuleManager1.UnloadModules;
end;
procedure TMainForm.FormCreate(Sender: TObject);
begin
AppDir := ExtractFilePath(Application.ExeName);
end;
end.

Answer 1

Not sure about the real cause of the problem, but you can use RegisterDeviceNotification function to achieve same result:
type
DEV_BROADCAST_DEVINTERFACE = record
dbcc_size: DWORD;
dbcc_devicetype: DWORD;
dbcc_reserved: DWORD;
dbcc_classguid: TGUID;
dbcc_name: short;
end;
const
DEVICE_NOTIFY_ALL_INTERFACE_CLASSES = $4;
DBT_DEVTYP_DEVICEINTERFACE = $5;
function RegisterNotification(Handle: THandle): HDEVNOTIFY;
var
Filter: DEV_BROADCAST_DEVINTERFACE;
begin
ZeroMemory(#Filter, SizeOf(DEV_BROADCAST_DEVINTERFACE));
Filter.dbcc_size := SizeOf(DEV_BROADCAST_DEVINTERFACE);
Filter.dbcc_devicetype := DBT_DEVTYP_DEVICEINTERFACE;
Filter.dbcc_reserved := 0;
Filter.dbcc_name := 0;
Result := RegisterDeviceNotification(Handle, #Filter, DEVICE_NOTIFY_WINDOW_HANDLE or DEVICE_NOTIFY_ALL_INTERFACE_CLASSES);
end;
Now inside plugin you need something like this:
TVisualPlugin = class(THYVisualPlugin)
protected
NofitifyHandle: HDEVNOTIFY;
procedure WMDEVICECHANGE(var Msg: TMessage); message WM_DEVICECHANGE;
procedure CreateWnd; override;
procedure DestroyWindowHandle; override;
end;
procedure TVisualPlugin.CreateWnd;
begin
inherited;
if HandleAllocated then
NofitifyHandle := RegisterNotification(Self.Handle);
end;
procedure TVisualPlugin.DestroyWindowHandle;
begin
if Assigned(NofitifyHandle) then begin
UnregisterDeviceNotification(NofitifyHandle);
NofitifyHandle := nil;
end;
inherited;
end;
procedure TVisualPlugin.WMDEVICECHANGE(var Msg: TMessage);
begin
ShowMessage('USB Changed');
end;