[fix #766] Add a variable (and an event) for OS appearance (change)

runtime/doc/autocmd.txt

@@ -290,6 +290,8 @@ Name			triggered by ~
 |EncodingChanged|	after the 'encoding' option has been changed
 |TermChanged|		after the value of 'term' has changed
 |OptionSet|		after setting any option
+|OSAppearanceChanged|	after the variable |v:os_appearance| has changed 
+			{only in MacVim GUI}
 
 	Startup and exit
 |VimEnter|		after doing all the startup stuff
@@ -918,6 +920,11 @@ OptionSet			After setting an option.  The pattern is
 
 				When using |:set| in the autocommand the event
 				is not triggered again.
+                                                        *OSAppearanceChanged*
+OSAppearanceChanged             After changing the variable |v:os_appearance|. 
+                                This change happens only if the OS changes
+                                its appearance and Vim is running with a GUI.
+
 							*QuickFixCmdPre*
 QuickFixCmdPre			Before a quickfix command is run (|:make|,
 				|:lmake|, |:grep|, |:lgrep|, |:grepadd|,

runtime/doc/eval.txt

@@ -2033,6 +2033,18 @@ v:operator	The last operator given in Normal mode.  This is a single
 		commands.
 		Read-only.
 
+                                        *v:os_appearance* *os-appearance-variable*
+v:os_appearance The current OS appearance mode. Useful if you want to change
+		options |background| or |colorscheme| according to the 
+ 		appearance of the GUI frontend. See also |OSAppearanceChanged|.
+		 	value   description ~
+ 			0       Light Mode (always 0 on unsupported platforms)
+ 			1       Dark Mode
+ 			2       High-Contrast Light Mode
+ 			3       High-Contrast Dark Mode
+
+ 		{only in MacVim GUI}
+
 					*v:prevcount* *prevcount-variable*
 v:prevcount	The count given for the last but one Normal mode command.
 		This is the v:count value of the previous command.  Useful if

runtime/doc/gui_mac.txt

@@ -121,6 +121,10 @@ These are the non-standard options that MacVim supports:
 These are the non-standard commands that MacVim supports:
 	|:macaction|	|:macmenu|
 
+                                                       *macvim-autocommands*
+These are the non-standard events that MacVim supports:
+       |OSAppearanceChanged|
+
 							*macvim-find*
 Whenever you search for something in Vim (e.g. using "/"), or hit <D-e> when
 you have text selected, the search query is copied to the macOS "Find

runtime/doc/tags

@@ -4996,6 +4996,7 @@ OS390-bugs	os_390.txt	/*OS390-bugs*
 OS390-has-ebcdic	os_390.txt	/*OS390-has-ebcdic*
 OS390-limitations	os_390.txt	/*OS390-limitations*
 OS390-open-source	os_390.txt	/*OS390-open-source*
+OSAppearanceChanged	autocmd.txt	/*OSAppearanceChanged*
 OffTheSpot	mbyte.txt	/*OffTheSpot*
 OnTheSpot	mbyte.txt	/*OnTheSpot*
 Operator-pending	intro.txt	/*Operator-pending*
@@ -8274,6 +8275,7 @@ options.txt	options.txt	/*options.txt*
 optwin	options.txt	/*optwin*
 or()	eval.txt	/*or()*
 oracle	ft_sql.txt	/*oracle*
+os-appearance-variable	eval.txt	/*os-appearance-variable*
 os2	os_os2.txt	/*os2*
 os390	os_390.txt	/*os390*
 os_390.txt	os_390.txt	/*os_390.txt*
@@ -9753,6 +9755,7 @@ v:option_old	eval.txt	/*v:option_old*
 v:option_oldglobal	eval.txt	/*v:option_oldglobal*
 v:option_oldlocal	eval.txt	/*v:option_oldlocal*
 v:option_type	eval.txt	/*v:option_type*
+v:os_appearance	eval.txt	/*v:os_appearance*
 v:prevcount	eval.txt	/*v:prevcount*
 v:profiling	eval.txt	/*v:profiling*
 v:progname	eval.txt	/*v:progname*

src/MacVim/MMBackend.m

@@ -198,6 +198,7 @@ - (void)handleFindReplace:(NSDictionary *)args;
 - (void)useSelectionForFind;
 - (void)handleMarkedText:(NSData *)data;
 - (void)handleGesture:(NSData *)data;
+- (void)handleOSAppearanceChange:(NSData *)data;
 #ifdef FEAT_BEVAL
 - (void)bevalCallback:(id)sender;
 #endif
@@ -2110,6 +2111,8 @@ - (void)handleInputEvent:(int)msgid data:(NSData *)data
         ASLogDebug(@"SetWindowPositionMsgID: x=%d y=%d", winposX, winposY);
     } else if (GestureMsgID == msgid) {
         [self handleGesture:data];
+    } else if (NotifyAppearanceChangeMsgID == msgid) {
+        [self handleOSAppearanceChange:data];
     } else if (ActivatedImMsgID == msgid) {
         [self setImState:YES];
     } else if (DeactivatedImMsgID == msgid) {
@@ -3326,6 +3329,17 @@ - (void)handleGesture:(NSData *)data
     }
 }
 
+- (void)handleOSAppearanceChange:(NSData *)data {
+    const void *bytes = [data bytes];
+    int flag = *((int*)bytes);  bytes += sizeof(int);
+    // 0 : (default) The standard (light) system appearance.
+    // 1 : The standard dark system appearance.
+    // 2 : The high-contrast version of the standard light system appearance.
+    // 3 : The high-contrast version of the standard dark system appearance.
+    set_vim_var_nr(VV_OS_APPEARANCE, flag);
+    apply_autocmds(EVENT_OSAPPCHANGED, NULL, NULL, FALSE, curbuf);
+}
+
 #ifdef FEAT_BEVAL
 - (void)bevalCallback:(id)sender
 {

src/MacVim/MMVimController.h

@@ -67,6 +67,8 @@
 - (void)file:(NSString *)filename draggedToTabAtIndex:(NSUInteger)tabIndex;
 - (void)filesDraggedToTabBar:(NSArray *)filenames;
 - (void)dropString:(NSString *)string;
+- (void)appearanceChanged:(int)flag;
+
 - (void)passArguments:(NSDictionary *)args;
 - (void)sendMessage:(int)msgid data:(NSData *)data;
 - (BOOL)sendMessageNow:(int)msgid data:(NSData *)data

src/MacVim/MMVimController.m

@@ -176,6 +176,10 @@ - (id)initWithBackend:(id)backend pid:(int)processIdentifier
 
     isInitialized = YES;
 
+    // After MMVimController's initialization is completed,
+    // set up the variable `v:os_appearance`.
+    [self appearanceChanged:getCurrentAppearance([windowController vimView].effectiveAppearance)];
+
     return self;
 }
 
@@ -358,6 +362,13 @@ - (void)dropString:(NSString *)string
     }
 }
 
+- (void)appearanceChanged:(int)flag
+{
+    [self sendMessage:NotifyAppearanceChangeMsgID
+                 data:[NSData dataWithBytes: &flag
+               length:sizeof(flag)]];
+}
+
 - (void)passArguments:(NSDictionary *)args
 {
     if (!args) return;

src/MacVim/MMVimView.m

@@ -664,6 +664,10 @@ - (void)setFrame:(NSRect)frame
     [self frameSizeMayHaveChanged:NO];
 }
 
+- (void)viewDidChangeEffectiveAppearance
+{
+    [vimController appearanceChanged:getCurrentAppearance(self.effectiveAppearance)];
+}
 @end // MMVimView
 
 

src/MacVim/MacVim.h

@@ -261,6 +261,7 @@ extern const char * const MMVimMsgIDStrings[];
     MSG(AddToMRUMsgID) \
     MSG(BackingPropertiesChangedMsgID) \
     MSG(SetBlurRadiusMsgID) \
+    MSG(NotifyAppearanceChangeMsgID) \
     MSG(EnableLigaturesMsgID) \
     MSG(DisableLigaturesMsgID) \
     MSG(EnableThinStrokesMsgID) \

src/MacVim/Miscellaneous.h

@@ -160,3 +160,5 @@ NSArray *normalizeFilenames(NSArray *filenames);
 BOOL shouldUseYosemiteTabBarStyle();
 BOOL shouldUseMojaveTabBarStyle();
 BOOL shouldUseBufferedDrawing();
+
+int getCurrentAppearance(NSAppearance *appearance);

src/MacVim/Miscellaneous.m

@@ -330,3 +330,26 @@ - (NSInteger)tag
 #endif
     return NO;
 }
+
+
+int
+getCurrentAppearance(NSAppearance *appearance){
+    int flag = 0; // for macOS 10.13 or eariler always return 0;
+#if MAC_OS_X_VERSION_MIN_REQUIRED >= MAC_OS_X_VERSION_10_14
+    if (@available(macOS 10.14, *)) {
+        NSAppearanceName appearanceName = [appearance bestMatchFromAppearancesWithNames:
+                @[NSAppearanceNameAqua
+                , NSAppearanceNameDarkAqua
+                , NSAppearanceNameAccessibilityHighContrastAqua
+                , NSAppearanceNameAccessibilityHighContrastDarkAqua]];
+        if ([appearanceName isEqualToString:NSAppearanceNameDarkAqua]) {
+            flag = 1;
+        } else if ([appearanceName isEqualToString:NSAppearanceNameAccessibilityHighContrastAqua]) {
+            flag = 2;
+        } else if ([appearanceName isEqualToString:NSAppearanceNameAccessibilityHighContrastDarkAqua]) {
+            flag = 3;
+        }
+    }
+#endif
+    return flag;
+}

src/autocmd.c

@@ -151,6 +151,7 @@ static struct event_name
     {"InsertCharPre",	EVENT_INSERTCHARPRE},
     {"MenuPopup",	EVENT_MENUPOPUP},
     {"OptionSet",	EVENT_OPTIONSET},
+    {"OSAppearanceChanged", EVENT_OSAPPCHANGED},
     {"QuickFixCmdPost",	EVENT_QUICKFIXCMDPOST},
     {"QuickFixCmdPre",	EVENT_QUICKFIXCMDPRE},
     {"QuitPre",		EVENT_QUITPRE},

src/evalvars.c

@@ -143,6 +143,7 @@ static struct vimvar
     {VV_NAME("event",		 VAR_DICT), VV_RO},
     {VV_NAME("versionlong",	 VAR_NUMBER), VV_RO},
     {VV_NAME("echospace",	 VAR_NUMBER), VV_RO},
+    {VV_NAME("os_appearance",    VAR_NUMBER), VV_RO},
 };
 
 // shorthand

src/vim.h

@@ -1322,6 +1322,7 @@ enum auto_event
     EVENT_INSERTLEAVE,		// when leaving Insert mode
     EVENT_MENUPOPUP,		// just before popup menu is displayed
     EVENT_OPTIONSET,		// option was set
+    EVENT_OSAPPCHANGED,   // after changing the OS appearance
     EVENT_QUICKFIXCMDPOST,	// after :make, :grep etc.
     EVENT_QUICKFIXCMDPRE,	// before :make, :grep etc.
     EVENT_QUITPRE,		// before :quit
@@ -1992,7 +1993,8 @@ typedef int sock_T;
 #define VV_EVENT	90
 #define VV_VERSIONLONG	91
 #define VV_ECHOSPACE	92
-#define VV_LEN		93	// number of v: vars
+#define VV_OS_APPEARANCE 93
+#define VV_LEN		94	// number of v: vars
 
 // used for v_number in VAR_SPECIAL
 #define VVAL_FALSE	0L