Honor system dark mode in ComparePlus diff colors

docs/compare-plus-host-inventory.md

@@ -47,8 +47,8 @@ ComparePlus can continue, but there is no equivalent visible macOS UI surface ye
 | `NPPM_GETCURRENTCMDLINE` | Compare.cpp (checkCmdLine) | **IMPLEMENTED** (nppm_handler.mm, returns empty command line) |
 | `NPPM_GETCURRENTNATIVELANGENCODING` | NppHelpers.h | **IMPLEMENTED** (nppm_handler.mm, returns UTF-8) |
 | `NPPN_GLOBALMODIFIED` | Compare.cpp | **NOT EMITTED** |
-| `NPPN_DARKMODECHANGED` | Compare.cpp | **NOT EMITTED** |
-| `NPPN_WORDSTYLESUPDATED` | Compare.cpp | **NOT EMITTED** |
+| `NPPN_DARKMODECHANGED` | Compare.cpp | **EMITTED** (app_delegate.mm `appearanceChanged:`) |
+| `NPPN_WORDSTYLESUPDATED` | Compare.cpp | **NOT EMITTED** (no host style-configurator UI yet to drive it; ComparePlus handles it identically to `NPPN_DARKMODECHANGED`, so dark-mode toggles already refresh its colors) |
 
 ## Command Alias / Navigation Surface
 
@@ -90,4 +90,5 @@ SETLINENUMBERWIDTHMODE, GETBOOKMARKID, GETNATIVELANGFILENAME, GETCURRENTCMDLINE,
 GETCURRENTNATIVELANGENCODING
 
 NPPN: NPPN_READY, NPPN_SHUTDOWN, NPPN_LANGCHANGED, NPPN_FILEBEFORECLOSE, NPPN_FILESAVED,
-NPPN_FILEOPENED, NPPN_FILECLOSED, NPPN_BUFFERACTIVATED, NPPN_BEFORESHUTDOWN, NPPN_TBMODIFICATION
+NPPN_FILEOPENED, NPPN_FILECLOSED, NPPN_BUFFERACTIVATED, NPPN_BEFORESHUTDOWN, NPPN_TBMODIFICATION,
+NPPN_DARKMODECHANGED

macos/platform/app_delegate.mm

@@ -626,6 +626,11 @@ - (void)appearanceChanged:(NSNotification*)notification
 			ScintillaBridge_sendMessage(ctx().scintillaView, SCI_COLOURISE, 0, -1);
 		if (ctx().isSplit && ctx().scintillaView2)
 			ScintillaBridge_sendMessage(ctx().scintillaView2, SCI_COLOURISE, 0, -1);
+
+		SCNotification darkNotif{};
+		darkNotif.nmhdr.hwndFrom = ctx().mainHwnd;
+		darkNotif.nmhdr.code = NPPN_DARKMODECHANGED;
+		pluginManager().notify(&darkNotif);
 	});
 }
 

macos/platform/appearance.h

@@ -3,6 +3,7 @@
 
 #pragma once
 
+bool isAppDarkMode();
 void applyFoldMarkerColorsToView(void* sci, bool isDark);
 void applyAppearanceToView(void* sci, int langIdx, bool isDark);
 void applyAppearance();

macos/platform/appearance.mm

@@ -5,14 +5,21 @@
 #include "appearance.h"
 #include "npp_constants.h"
 #include "app_state.h"
-#include "language_defs.h"
-#include "lexer_styles.h"
-#include "scintilla_config.h"
-#include "scintilla_bridge.h"
-#include "brace_match.h"
-#include "smart_highlight.h"
+#include "language_defs.h"
+#include "lexer_styles.h"
+#include "scintilla_config.h"
+#include "scintilla_bridge.h"
+#include "brace_match.h"
+#include "smart_highlight.h"
 #include "change_history.h"
 
+bool isAppDarkMode()
+{
+	NSAppearanceName appearanceName = [NSApp.effectiveAppearance
+		bestMatchFromAppearancesWithNames:@[NSAppearanceNameAqua, NSAppearanceNameDarkAqua]];
+	return [appearanceName isEqualToString:NSAppearanceNameDarkAqua];
+}
+
 void applyFoldMarkerColorsToView(void* sci, bool isDark)
 {
 	if (!sci) return;
@@ -68,19 +75,17 @@ void applyAppearanceToView(void* sci, int langIdx, bool isDark)
 	configureSmartHighlightIndicator(sci, isDark);
 
 	// Incremental search indicator colors
-	ScintillaBridge_sendMessage(sci, SCI_INDICSETFORE, INDIC_INCREMENTAL_SEARCH,
-		isDark ? 0x50C8FF : 0xFF8000);
-
-	refreshLineNumberMargin(sci);
-}
+	ScintillaBridge_sendMessage(sci, SCI_INDICSETFORE, INDIC_INCREMENTAL_SEARCH,
+		isDark ? 0x50C8FF : 0xFF8000);
+
+	refreshLineNumberMargin(sci);
+}
 
 void applyAppearance()
 {
 	if (!ctx().scintillaView) return;
 
-	NSAppearanceName appearanceName = [NSApp.effectiveAppearance
-		bestMatchFromAppearancesWithNames:@[NSAppearanceNameAqua, NSAppearanceNameDarkAqua]];
-	bool isDark = [appearanceName isEqualToString:NSAppearanceNameDarkAqua];
+	bool isDark = isAppDarkMode();
 
 	int langIdx = 0;
 	if (ctx().activeTab >= 0 && ctx().activeTab < static_cast<int>(ctx().documents.size()))

macos/platform/nppm_handler.mm

@@ -12,6 +12,7 @@
 #include "menu_builder.h"
 #include "string_utils.h"
 #include "compare_plus_visibility.h"
+#include "appearance.h"
 #include "Notepad_plus_msgs.h"
 #include "Scintilla.h"
 
@@ -234,21 +235,21 @@ LRESULT handleNppmMessage(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam)
 		}
 
 		case NPPM_GETEDITORDEFAULTBACKGROUNDCOLOR:
-			// Returned as 0x00BBGGRR (Win32 COLORREF). White matches our
-			// default light-mode Scintilla background. Plugins derive
-			// dependent colors (ComparePlus's "blank" marker shade) from
-			// this; returning 0 / black made the whole diff wash read as
-			// near-black, hiding the actual marker colors.
-			// TODO Phase 5: dark-mode branch.
-			return 0x00FFFFFF;
+			// Returned as 0x00BBGGRR (Win32 COLORREF). Must match the
+			// background Scintilla paints for style 32 in
+			// applyAppearanceToView (SCI_STYLESETBACK), or plugins derive
+			// marker shades against the wrong base — ComparePlus's "blank"
+			// marker in particular.
+			return isAppDarkMode() ? 0x001E1E1E : 0x00FFFFFF;
 
 		case NPPM_GETEDITORDEFAULTFOREGROUNDCOLOR:
-			return 0x00000000;
+			return isAppDarkMode() ? 0x00D4D4D4 : 0x00000000;
 
 		case NPPM_ISDARKMODEENABLED:
-			// Until we wire up real dark-mode detection, report light mode.
-			// ComparePlus picks its color palette based on this.
-			return FALSE;
+			// ComparePlus picks its color palette based on this; on TRUE
+			// it switches to Settings.useDarkColors() so diff backgrounds
+			// stay legible against a dark editor background.
+			return isAppDarkMode() ? TRUE : FALSE;
 
 		case NPPM_ALLOCATEMARKER:
 		{