Truncate Console scrollback history

Hammerspoon/MJConsoleWindowController.h

@@ -7,6 +7,7 @@
 @property NSColor *MJColorForCommand ;
 @property NSColor *MJColorForResult ;
 @property NSFont  *consoleFont ;
+@property NSNumber *maxConsoleOutputHistory ;
 
 + (instancetype) singleton;
 - (void) setup;

Hammerspoon/MJConsoleWindowController.m

@@ -51,6 +51,7 @@ - (void)initializeConsoleColorsAndFont {
     self.MJColorForCommand = [NSColor blackColor] ;
     self.MJColorForResult  = [NSColor colorWithCalibratedHue:0.54 saturation:1.0 brightness:0.7 alpha:1.0] ;
     self.consoleFont       = [NSFont fontWithName:@"Menlo" size:12.0] ;
+    self.maxConsoleOutputHistory = [NSNumber numberWithInt:100000];
 }
 
 - (NSString*) windowNibName {
@@ -139,9 +140,19 @@ - (void) appendString:(NSString*)str type:(MJReplLineType)type {
 
     NSDictionary* attrs = @{NSFontAttributeName: self.consoleFont, NSForegroundColorAttributeName: color};
     NSAttributedString* attrstr = [[NSAttributedString alloc] initWithString:str attributes:attrs];
-    [[self.outputView textStorage] performSelectorOnMainThread:@selector(appendAttributedString:)
-                                       withObject:attrstr
-                                    waitUntilDone:YES];
+
+    dispatch_async(dispatch_get_main_queue(), ^{
+        NSTextStorage *storage = self.outputView.textStorage;
+        int curLength = (int)storage.length;
+        int maxLength = self.maxConsoleOutputHistory.intValue;
+        int addLength = (int)attrstr.length;
+
+        [storage appendAttributedString:attrstr];
+        if (curLength > maxLength && maxLength > 0) {
+            [storage deleteCharactersInRange:NSMakeRange(0, curLength - maxLength + addLength)];
+        }
+        [self.outputView scrollToEndOfDocument:self];
+    });
 }
 
 - (NSString*) run:(NSString*)command {

extensions/console/libconsole.m

@@ -88,6 +88,31 @@ static int console_consolePrintColor(lua_State *L) {
     return 1;
 }
 
+/// hs.console.maxOutputHistory([length]) -> number
+/// Function
+/// Get or set the max length of the Hammerspoon console's scrollback history.
+///
+/// Parameters:
+///  * length - an optional number containing the maximum size in bytes of the Hammerspoon console history.
+///
+/// Returns:
+///  * the current maximum size of the console history
+///
+/// Notes:
+///  * A length value of zero will allow the history to grow infinitely
+///  * The default console history is 100,000 characters
+static int console_maxOutputHistory(lua_State *L) {
+    LuaSkin *skin = [LuaSkin sharedWithState:L];
+
+    if (lua_type(L, 1) != LUA_TNONE) {
+        NSNumber *size = [NSNumber numberWithInt:(int)lua_tointeger(L, 1)];
+        MJConsoleWindowController.singleton.maxConsoleOutputHistory = size;
+    }
+
+    lua_pushinteger(L, MJConsoleWindowController.singleton.maxConsoleOutputHistory.intValue);
+    return 1;
+}
+
 /// hs.console.consoleFont([font]) -> fontTable
 /// Function
 /// Get or set the font used in the Hammerspoon console.
@@ -287,7 +312,7 @@ static int console_smartInsertDeleteEnabled(lua_State *L) {
 
 /// hs.console.getHistory() -> array
 /// Function
-/// Get the Hammerspoon console history as an array.
+/// Get the Hammerspoon console command history as an array.
 ///
 /// Parameters:
 ///  * None
@@ -373,7 +398,7 @@ static int console_getConsole(lua_State *L) {
 
 /// hs.console.setHistory(array) -> nil
 /// Function
-/// Set the Hammerspoon console history to the items specified in the given array.
+/// Set the Hammerspoon console command history to the items specified in the given array.
 ///
 /// Parameters:
 ///  * array - the list of commands to set the Hammerspoon console history to.
@@ -595,6 +620,7 @@ static int console_titleVisibility(lua_State *L) {
     {"smartInsertDeleteEnabled", console_smartInsertDeleteEnabled},
     {"getHistory", console_getHistory},
     {"setHistory", console_setHistory},
+    {"maxOutputHistory", console_maxOutputHistory},
 
     {"getConsole", console_getConsole},
     {"setConsole", console_setConsole},