How can I force my window to keep itself updated? - c++builder

Question

Final Update
The solution was to create a TTimer, set its Interval to any value greater than 0, and assign its OnTimer property to an empty function.
I have a TThread that adds new controls to the main form at regular intervals, via Queue(). But the queued functions are never executed until the form receives user input, or the cursor moves over it, and then it executes all the queued functions at once.
With careful logging I have determined conclusively that the functions are being queued as intended by the thread. They simply aren't being executed by the main VCL loop until the form gets user interaction.
It's as if the main application loop doesn't run when there is no user interaction.
How can I force the form to execute queued functions immediately?
If it matters, the form and TThread are created by a .dll, which is called by another .dll, which itself is called by a console application.
Like this:
console application -> dll -> dll created by C++ Builder
Edit
void __fastcall GirkovArpa::Execute() {
while (!Terminated) {
if (GlobalMessageQueue.size() > 0) {
EnterCriticalSection(&myCritSect);
std::cout << ""; // this line is required, else thread won't execute
std::string GlobalMessage = GlobalMessageQueue.at(0);
std::string copy;
copy.assign(GlobalMessage);
GlobalMessageQueue.erase(GlobalMessageQueue.begin());
LeaveCriticalSection(&myCritSect);
Queue([&, copy]() {
// do stuff
});
}
}
}
Edit 2
Node.JS console app => Node DLL addon => C++Builder GUI DLL
My console application is specifically NodeJS. It loads a "NodeJS addon" (a type of DLL), which loads the DLL created with C++ Builder, which exports this function:
void myExportedFunction(const char *str) {
EnterCriticalSection(&myCritSect);
GlobalMessageQueue.push_back(std::string(str));
// CheckSynchronize();
LeaveCriticalSection(&myCritSect);
}
If CheckSynchronize() is not commented out, I get a Segmentation Fault error.
My TThread runs on an infinite loop, checking GlobalMessageQueue, and if it finds it's not empty, it queues a lambda which creates a TControl on the main form.
But the queued lambdas are not executed until the user interacts with the window (simply moving the cursor over the window will suffice).
Edit 3
Here is my full lambda:
Queue([&, copy]() {
std::vector<std::string> words;
boost::split(words, copy, boost::is_any_of(" "));
// CREATE $TControl $Name $Text $Parent
if (words.at(0) == "CREATE") {
if (words.at(1) == "TEXTBOX") {
String formName = stringToString(words.at(4));
TForm *form = getFormByName(formName);
TEdit *textbox = new TEdit(form);
textbox->Parent = form;
textbox->Name = words.at(2).c_str();
textbox->Text = words.at(3).c_str();
textbox->Show();
textbox->OnClick = MyForm->OnClick;
}
if (words.at(1) == "RADIO") {
String formName = stringToString(words.at(4));
TForm *form = getFormByName(formName);
TRadioButton *radio = new TRadioButton(form);
radio->Parent = form;
radio->Name = words.at(2).c_str();
radio->Caption = words.at(3).c_str();
radio->Show();
radio->OnClick = MyForm->OnClick;
}
if (words.at(1) == "BUTTON") {
String formName = stringToString(words.at(4));
TForm *form = getFormByName(formName);
TButton *button = new TButton(form);
button->Parent = form;
button->Name = words.at(2).c_str();
button->Caption = words.at(3).c_str();
button->Show();
button->OnClick = MyForm->OnClick;
}
if (words.at(1) == "FORM") {
createDialog(words.at(2).c_str(), words.at(3).c_str());
}
}
if (words.at(0) == "CHANGE") {
for (int j = 0; j < Screen->FormCount; j++) {
TForm *form = Screen->Forms[j];
if (form->Name == words.at(1).c_str()) {
TRttiContext ctx;
TRttiType *type = ctx.GetType(form->ClassInfo());
TRttiProperty *prop = type->GetProperty(words.at(2).c_str());
TValue value;
if (prop->PropertyType->TypeKind == tkUString) {
value = TValue::From<UnicodeString>(words.at(3).c_str());
} else if (prop->PropertyType->TypeKind == tkInteger) {
value = TValue::From<Integer>(StrToInt(words.at(3).c_str()));
} else {
std::cout << "ERROR" << std::endl;
}
prop->SetValue(form, value);
}
for (int i = 0; i < form->ControlCount; i++) {
TControl *control = form->Controls[i];
if (control->Name == words.at(1).c_str()) {
TRttiContext ctx;
TRttiType *type = ctx.GetType(control->ClassInfo());
TRttiProperty *prop = type->GetProperty(words.at(2).c_str());
TValue value;
if (prop->PropertyType->TypeKind == tkUString) {
value = TValue::From<UnicodeString>(words.at(3).c_str());
} else if (prop->PropertyType->TypeKind == tkInteger) {
value = TValue::From<Integer>(StrToInt(words.at(3).c_str()));
} else {
std::cout << "ERROR" << std::endl;
}
prop->SetValue(control, value);
}
}
}
}
// GET NAME PROP
if (words.at(0) == "GET") {
for (int j = 0; j < Screen->FormCount; j++) {
TForm *form = Screen->Forms[j];
if (form->Name == words.at(1).c_str()) {
TRttiContext ctx;
TRttiType *type = ctx.GetType(form->ClassInfo());
TRttiProperty *prop = type->GetProperty(words.at(2).c_str());
TValue result = prop->GetValue(form);
if (result.Kind == tkUString) {
String leString = result.AsString();
std::wstring w(std::wstring(leString.t_str()));
std::string STR(w.begin(), w.end());
std::string output = words.at(1) + " " + words.at(2);
String o = output.c_str();
tellJavaScript(AnsiString(o + ": " + leString).c_str());
} else if (result.Kind == tkInteger) {
int result_int = result.AsInteger();
String result_String = IntToStr(result_int);
String name = words.at(1).c_str();
String prop = words.at(2).c_str();
tellJavaScript(AnsiString(name + " " + prop + ": " + result_String).c_str());
} else {
// assume boolean
String result_String = BoolToStr(result.AsBoolean());
String name = words.at(1).c_str();
String prop = words.at(2).c_str();
tellJavaScript(AnsiString(name + " " + prop + ": " + result_String).c_str());
}
}
for (int i = 0; i < form->ControlCount; i++) {
TControl *control = form->Controls[i];
if (control->Name == words.at(1).c_str()) {
TRttiContext ctx;
TRttiType *type = ctx.GetType(control->ClassInfo());
TRttiProperty *prop = type->GetProperty(words.at(2).c_str());
TValue result = prop->GetValue(control);
if (result.Kind == tkUString) {
String leString = result.AsString();
std::wstring w(std::wstring(leString.t_str()));
std::string STR(w.begin(), w.end());
std::string output = words.at(1) + " " + words.at(2);
String o = output.c_str();
tellJavaScript(AnsiString(o + ": " + leString).c_str());
} else if (result.Kind == tkInteger) {
int result_int = result.AsInteger();
String result_String = IntToStr(result_int);
String name = words.at(1).c_str();
String prop = words.at(2).c_str();
tellJavaScript(AnsiString(name + " " + prop + ": " + result_String).c_str());
} else {
// assume boolean
String result_String = BoolToStr(result.AsBoolean());
String name = words.at(1).c_str();
String prop = words.at(2).c_str();
tellJavaScript(AnsiString(name + " " + prop + ": " + result_String).c_str());
}
}
}
}
}
if (words.at(0) == "DELETE") {
for (int j = 0; j < Screen->FormCount; j++) {
TForm *form = Screen->Forms[j];
if (form->Name == words.at(1).c_str()) {
form->Close();
}
for (int i = 0; i < form->ControlCount; i++) {
TControl *control = form->Controls[i];
if (control->Name == words.at(1).c_str()) {
control->Free();
}
}
}
}
if (words.at(0) == "EXECUTE") {
for (int j = 0; j < Screen->FormCount; j++) {
TForm *form = Screen->Forms[j];
if (form->Name == words.at(1).c_str()) {
std::cout << "EXECUTE <<" << words.at(2) << ">>" << std::endl;
TRttiContext context;
TRttiType *rttiType = context.GetType(form->ClassType());
TRttiMethod *method = rttiType->GetMethod(words.at(2).c_str());
DynamicArray<TRttiParameter *> parameters = method->GetParameters();
TValue args[10];
if (parameters.Length) {
for (int y = parameters.Low; y <= parameters.High; y++) {
String paramType = parameters[y]->ParamType->ToString();
if (paramType == "UnicodeString") {
args[y] = TValue::From<UnicodeString>(stringToString(words.at(y + 3)));
} else if (paramType == "Integer") {
args[y] = TValue::From<Integer>(StrToInt(stringToString(words.at(y + 3))));
}
}
TValue value = method->Invoke(form, args, parameters.High);
} else {
TValue value = method->Invoke(form, NULL, -1);
}
}
for (int i = 0; i < form->ControlCount; i++) {
TControl *control = form->Controls[i];
if (control->Name == words.at(1).c_str()) {
std::cout << "EXECUTE <<" << words.at(2) << ">>" << std::endl;
TRttiContext context;
TRttiType *rttiType = context.GetType(control->ClassType());
TRttiMethod *method = rttiType->GetMethod(words.at(2).c_str());
DynamicArray<TRttiParameter *> parameters = method->GetParameters();
TValue args[10];
if (parameters.Length) {
for (int y = parameters.Low; y <= parameters.High; y++) {
String paramType = parameters[y]->ParamType->ToString();
if (paramType == "UnicodeString") {
args[y] = TValue::From<UnicodeString>(stringToString(words.at(y + 3)));
} else if (paramType == "Integer") {
args[y] = TValue::From<Integer>(StrToInt(stringToString(words.at(y + 3))));
}
}
TValue value = method->Invoke(control, args, parameters.High);
} else {
TValue value = method->Invoke(control, NULL, -1);
}
}
}
}
}
});

Answer 1

It's as if the main application loop doesn't run when there is no user interaction.
It doesn't, actually. Well, more accurately, when there is no pending window messages at all. Once the main thread's message queue is emptied, the VCL calls the Win32 WaitMessage() function, which blocks the calling thread until a new message appears in the message queue. Even traditional non-VCL message loops tend to block the calling thread when there are no messages to process.
How can I force the form to execute queued functions immediately?
You can't force it.
If it matters, the form and TThread are created by a .dll, which is called by another .dll, which itself is called by a console application.
It DOES matter, because TThread::Queue() and TThread:::Synchronize() DO NOT work well inside of a DLL.
TThread::Queue() and TThread::Synchronize() put their requests into an internal queue inside the RTL, set a signal to indicate the queue has pending requests, and then post a message to the TApplication window to "wake up" the main thread (in case the message loop is "sleeping" waiting for a new message to arrive). That request queue is processed at the main thread's earliest convenience.
By default, a VCL message loop processes the TThread queue only when:
the message loop enters an idle state, after all pending messages have been processed and the message queue becomes empty.
the TApplication window receives the "wake up" message.
When the TThread queue is inside a DLL, and the DLL is not sharing the same RTL instance with the main EXE, then the main message loop in the EXE does not know about the TThread queue in the DLL, so it can't process the pending requests during idle times. That just leaves the "wake up" message, which the DLL will post to its own TApplication instance, not to the main EXE's TApplication. The main thread message loop will still dispatch window messages to a DLL's TApplication window.
To solve this, you will have to either:
enable Runtime Packages in the DLL and main EXE, or even change the DLL to be a Package, so that they can share common instances of the RTL and VCL. That does mean you will have to deploy the RTL and VCL .bpl files with your app, though.
export a function from your DLL that calls the RTL's CheckSynchronize() function, and then call that DLL function in your EXE code periodically, such as in a UI timer, or in the TApplication.OnIdle event, etc.

Answer 2

You're correct that the main loop of a typical Windows program does not run until there's some sort of input (usually user input, but there are other kinds as well).
I'm not familiar with the C++ Builder framework.
If you have control of code that makes the main loop, you can modify it to process additional sources of information, such as watching for another thread to signal a synchronization object.
Other options:
Have the thread that's adding items to the queue post a custom message to the main thread's window (or just a thread message) whenever it does one of its regular updates.
Set up a timer on the main thread. It will periodically "wake up" the main loop, just as the user input would.