From 536c2319416a153e4581c1982a4c451a22fbdc10 Mon Sep 17 00:00:00 2001
From: "G.K.MacGregor" <gkthemac@gmail.com>
Date: Sun, 23 Oct 2022 12:30:50 +0100
Subject: [PATCH] Fix detect-on-load of Level 3.5 objects and DRCS mode

---
 levelonepage.cpp | 36 ++++++++++++++++++++++--------------
 1 file changed, 22 insertions(+), 14 deletions(-)

diff --git a/levelonepage.cpp b/levelonepage.cpp
index f9dd32d..f29f489 100644
--- a/levelonepage.cpp
+++ b/levelonepage.cpp
@@ -25,6 +25,8 @@
 
 #include "levelonepage.h"
 
+#include "x26triplets.h"
+
 LevelOnePage::LevelOnePage()
 {
 	m_enhancements.reserve(maxEnhancements());
@@ -403,17 +405,21 @@ bool LevelOnePage::isPaletteDefault(int fromColour, int toColour) const
 
 int LevelOnePage::levelRequired() const
 {
+	// X/28/4 present i.e. CLUTs 0 or 1 redefined - Level 3.5
 	if (!isPaletteDefault(0, 15))
 		return 3;
 
 	// TODO Check for X/28/1 for DCLUT for mode 1-3 DRCS characters - return 3
 
+	// Assume Level 2.5 if any X/28 page enhancements are present, otherwise assume Level 1
 	int levelSeen = (!isPaletteDefault(16,31) || m_leftSidePanelDisplayed || m_rightSidePanelDisplayed || m_defaultScreenColour !=0 || m_defaultRowColour !=0 || m_blackBackgroundSubst || m_colourTableRemap !=0 || m_defaultCharSet != 0 || m_secondCharSet != 0xf) ? 2 : 0;
 
+	// If there's no X/26 triplets, exit here as Level 1 or 2.5
 	if (m_enhancements.isEmpty())
 		return levelSeen;
 
 	for (int i=0; i<m_enhancements.size(); i++) {
+		// Font style - Level 3.5 only triplet
 		if (m_enhancements.at(i).modeExt() == 0x2e) // Font style
 			return 3;
 
@@ -426,9 +432,10 @@ int LevelOnePage::levelRequired() const
 				case 0x22: // G3 character @ Level 1.5
 				case 0x2f: // G2 character
 				case 0x30 ... 0x3f: // G0 character with diacritical
-					levelSeen = qMax(levelSeen, 1);
+					levelSeen = 1;
 					break;
 			}
+
 		if (levelSeen < 2)
 			switch (m_enhancements.at(i).modeExt()) {
 				// Check for Level 2.5 triplets
@@ -436,25 +443,26 @@ int LevelOnePage::levelRequired() const
 				case 0x01: // Full row colour
 				case 0x10 ... 0x13: // Origin Modifer and Object Invocation
 				case 0x15 ... 0x17: // Object Definition
-					// Check if Object Definition is required only at Level 3.5
-					if ((m_enhancements.at(i).address() & 0x18) == 0x10)
-						return 3;
-					else
-						levelSeen = qMax(levelSeen, 2);
-					break;
 				case 0x18: // DRCS Mode
-					// Check if DRCS is required only at Level 3.5
-					if ((m_enhancements.at(i).data() & 0x30) == 0x20)
-						return 3;
-					else
-						levelSeen = qMax(levelSeen, 2);
-					break;
 				case 0x20: // Foreground colour
 				case 0x21: // G1 character
 				case 0x23: // Background colour
 				case 0x27 ... 0x29: // Flash functions, G0 and G2 charset designation, G0 character @ Level 2.5
 				case 0x2b ... 0x2d: // G3 character @ Level 2.5, display attributes, DRCS character
-					levelSeen = qMax(levelSeen, 2);
+					levelSeen = 2;
+					break;
+			}
+
+		if (levelSeen == 2)
+			switch (m_enhancements.at(i).modeExt()) {
+				// Check for triplets with "required at Level 3.5 only" parameters
+				case 0x15 ... 0x17: // Object Definition
+					if ((m_enhancements.at(i).address() & 0x18) == 0x10)
+						return 3;
+					break;
+				case 0x18: // DRCS Mode
+					if ((m_enhancements.at(i).data() & 0x30) == 0x20)
+						return 3;
 					break;
 			}
 	}