Debugger: Add asynchronous expression evaluation interface.

- Add UserInterfaceListener hook to request expression evaluation.
- Add corresponding events/handlers in Team and TeamDebugger.

These allow callers to request evaluation of expressions by the
debugger core's worker threads with asynchronous notifications of
results. While not strictly necessary right now, this paves the way
for further changes to come, as handling of variables will
potentially require resolving their values if they haven't been
already, and this shouldn't be done from user interface threads.

src/apps/debugger/controllers/TeamDebugger.cpp

@@ -40,6 +40,7 @@
 #include "MessageCodes.h"
 #include "SettingsManager.h"
 #include "SourceCode.h"
+#include "SourceLanguage.h"
 #include "SpecificImageDebugInfo.h"
 #include "SpecificImageDebugInfoLoadingState.h"
 #include "StackFrame.h"
@@ -701,6 +702,40 @@ TeamDebugger::MessageReceived(BMessage* message)
 			break;
 		}
 
+		case MSG_EVALUATE_EXPRESSION:
+		{
+			SourceLanguage* language;
+			if (message->FindPointer("language",
+				reinterpret_cast<void**>(&language)) != B_OK) {
+				break;
+			}
+
+			// ExpressionEvaluationRequested() acquires a reference
+			// on our behalf.
+			BReference<SourceLanguage> reference(language, true);
+
+			const char* expression;
+			if (message->FindString("expression", &expression) != B_OK)
+				break;
+
+			type_code resultType;
+			if (message->FindInt32("type",
+				reinterpret_cast<int32*>(&resultType)) != B_OK) {
+				break;
+			}
+
+			StackFrame* frame;
+			if (message->FindPointer("frame",
+				reinterpret_cast<void**>(&frame)) != B_OK) {
+				// the stack frame isn't needed, unless variable
+				// evaluation is desired.
+				frame = NULL;
+			}
+
+			_HandleEvaluateExpression(language, expression, resultType, frame);
+			break;
+		}
+
 		case MSG_GENERATE_DEBUG_REPORT:
 		{
 			fReportGenerator->PostMessage(message);
@@ -1050,6 +1085,23 @@ TeamDebugger::InspectRequested(target_addr_t address,
 }
 
 
+void
+TeamDebugger::ExpressionEvaluationRequested(SourceLanguage* language,
+	const char* expression, type_code resultType, StackFrame* frame)
+{
+	BMessage message(MSG_EVALUATE_EXPRESSION);
+	message.AddPointer("language", language);
+	message.AddString("expression", expression);
+	message.AddInt32("type", resultType);
+	if (frame != NULL)
+		message.AddPointer("frame", frame);
+
+	BReference<SourceLanguage> reference(language);
+	if (PostMessage(&message) == B_OK)
+		reference.Detach();
+}
+
+
 void
 TeamDebugger::DebugReportRequested(entry_ref* targetPath)
 {
@@ -1928,6 +1980,20 @@ TeamDebugger::_HandleInspectAddress(target_addr_t address,
 }
 
 
+void
+TeamDebugger::_HandleEvaluateExpression(SourceLanguage* language,
+	const char* expression, type_code resultType, StackFrame* frame)
+{
+	status_t result = fWorker->ScheduleJob(
+		new(std::nothrow) ExpressionEvaluationJob(fTeam, language,
+			expression, resultType, frame));
+	if (result != B_OK) {
+		_NotifyUser("Evaluate Expression", "Failed to evaluate expression: %s",
+			strerror(result));
+	}
+}
+
+
 status_t
 TeamDebugger::_HandleSetArguments(int argc, const char* const* argv)
 {