I'm using WebView4Delphi VCL for a POS frontend and experimented with various ways to communicate between local devices and the web application. Works fine to use a hostObject for web -> local comm to print receipts and show things on a customer display. Now I need to add the other way: Listening on a COM-Port and send everything we receive from there to the web server.
browser.PostWebMessageAsString() seems like a good mechanism for that. When triggered in on-button-click-pascal-code, the .html page receives the event with
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<script>
function rcvMsg(e) {
console.log('got msg '+JSON.stringify(e.data)+'" from '+e.origin);
}
if (typeof chrome.webview != 'undefined')
chrome.webview.addEventListener("message",rcvMsg,false);
</script>Also checked with the debugger if the com-port-listening-thread has the same TWVBrowser instance ... it does. And it's initialized.
Any ideas, what it might be, that I'm missing here or how to get additional intel?
Kind regards,
Paul
This are (hopefully) the relevant parts of the code in question ...
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type
TLottoComThread = class(TThread)
procedure Execute; override;
end;
TMainForm = class(TForm)
WVWindowParent1: TWVWindowParent;
Timer1: TTimer;
WVBrowser1: TWVBrowser;
...
end;
var
MainForm: TMainForm;
LottoThread: TLottoComThread;
LottoComFile: THandle;
LottoRcvBuf: TBytes;
LottoBufRead: LongWord;
implementation
procedure TLottoComThread.Execute;
var
CommTimeouts: TCommTimeouts;
FEventMask: DWORD;
ComStat: TComStat;
CPDCB: TDCB;
result: Boolean;
begin
SetLength(LottoRcvBuf, 512);
while not(Terminated) do begin
if LottoComFile = INVALID_HANDLE_VALUE then begin // not open?
LottoComFile := CreateFile(ComPortLotto, GENERIC_READ or GENERIC_WRITE, 0, nil, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, 0);
if LottoComFile = INVALID_HANDLE_VALUE then begin
MessageDlgPos(ComPortLotto + ' (Lotto Terminal) ist nicht verfügbar', TMsgDlgType.mtError, [mbOK], 0, -1, -1);
exit;
end;
FillChar(CPDCB, SizeOf(TDCB), 0);
with CPDCB do begin
DCBlength := SizeOf(TDCB);
BaudRate := CBR_9600;
ByteSize := 8;
Parity := EVENPARITY;
StopBits := ONESTOPBIT;
ErrorChar := '?';
EofChar := chr(13);
end;
if SetCommState(LottoComFile, CPDCB) then begin
SetCommMask(LottoComFile, EV_RXCHAR or EV_ERR);
with CommTimeouts do begin // in ms
ReadIntervalTimeout := 10;
ReadTotalTimeoutMultiplier := 2;
ReadTotalTimeoutConstant := 1000;
WriteTotalTimeoutMultiplier := 2;
WriteTotalTimeoutConstant := 1000;
end;
SetCommTimeouts(LottoComFile, CommTimeouts);
end;
end;
if LottoComFile <> INVALID_HANDLE_VALUE then begin
if WaitCommEvent(LottoComFile, FEventMask, nil) then
if (FEventMask and EV_RXCHAR) > 0 then
if ReadFile(LottoComFile, LottoRcvBuf[0], 512, LottoBufRead, nil) then begin
if LottoBufRead > 0 then begin
// TODO send to browser, make it post a message .. works in Button OnClick-method, but not here
result := MainForm.WVBrowser1.PostWebMessageAsString('{"lotto":"Hello world"}');
OutputDebugString(PChar('Received ' + IntToStr(LottoBufRead) + 'b on ' + ComPortLotto + ', posted ' + BoolToStr(result)));
end;
end else begin
OutputDebugString(PChar('Could not read ' + ComPortLotto + ' error ' + IntToStr(GetLastError)));
end;
end;
end;
if (LottoComFile <> INVALID_HANDLE_VALUE) then begin
CloseHandle(LottoComFile);
LottoComFile := INVALID_HANDLE_VALUE;
end;
end;