Resolve #4154: DR doesn't show readable background image changes.

While DR is unlikely to support every possible case (especially stuff driven by a game script), this particular GUI as reported in the issue report can be supported by running the GUI script in ContentsFadeIn and setting the gui::curPage state variable as done by TDM's readable GUI code.

plugins/dm.gui/ReadableEditorDialog.cpp

@@ -758,13 +758,11 @@ void ReadableEditorDialog::initGuiState(const gui::IGuiPtr& gui)
     gui->setStateString("curPage", string::to_string(_currentPageIndex + 1));
     gui->setStateString("numPages", string::to_string(_numPages->GetValue()));
 
-#if 0
     // ContentsFadeIn is reponsible of setting custom backgrounds
     if (gui->findWindowDef("ContentsFadeIn"))
     {
-        gui->findWindowDef("ContentsFadeIn")->notime = false;
+        gui->findWindowDef("ContentsFadeIn")->notime.setValue(false);
     }
-#endif
 
     // Initialise the time of this GUI
 	gui->initTime(0);

plugins/dm.gui/gui/GuiScript.cpp

@@ -340,9 +340,10 @@ GuiExpressionPtr GuiScript::getExpression(parser::DefTokeniser& tokeniser)
 	return GuiExpression::CreateFromTokens(_owner.getGui(), tokeniser);
 }
 
-GuiExpressionPtr GuiScript::getIfExpression(parser::DefTokeniser& tokeniser)
+std::shared_ptr<IGuiExpression<bool>> GuiScript::getIfExpression(parser::DefTokeniser& tokeniser)
 {
-	return getExpression(tokeniser);
+	// Parse the IF condition and pack it into a bool-typed expression
+	return std::make_shared<TypedExpression<bool>>(getExpression(tokeniser));
 }
 
 const Statement& GuiScript::getStatement(std::size_t index)
@@ -442,8 +443,12 @@ void GuiScript::execute()
 		case Statement::ST_TRANSITION:
 			break;
 		case Statement::ST_IF:
-			// TODO: Evaluate expression, for now just perform the jump
-			_ip = st.jmpDest;
+			// Evaluate expression
+			if (!st._condition || st._condition->evaluate() == false)
+			{
+				// Expression evaluated to false, jump over the block
+				_ip = st.jmpDest;
+			}
 			break;
 		case Statement::ST_SET_FOCUS:
 			break;

plugins/dm.gui/gui/GuiScript.h

@@ -45,7 +45,7 @@ struct Statement
 	Arguments args;
 
 	// Condition used by ST_IF
-	GuiExpressionPtr _condition;
+	std::shared_ptr<IGuiExpression<bool>> _condition;
 
 	// The jump destination used by ST_IF and ST_JMP
 	std::size_t jmpDest;
@@ -97,7 +97,7 @@ class GuiScript
 	std::size_t getCurPosition();
 
 	GuiExpressionPtr getExpression(parser::DefTokeniser& tokeniser);
-	GuiExpressionPtr getIfExpression(parser::DefTokeniser& tokeniser);
+	std::shared_ptr<IGuiExpression<bool>> getIfExpression(parser::DefTokeniser& tokeniser);
 
 	// Reads a "statement", which can be single one or a group (surrounded by curly braces)
 	void parseStatement(parser::DefTokeniser& tokeniser);