Add off-by-default support for the REP code. Issue 6249

sources/VT100CSIParser.m

@@ -394,6 +394,11 @@ static void SetCSITypeAndDefaultParameters(CSIParam *param, VT100Token *result)
             iTermParserSetCSIParameterIfDefault(param, 0, 1);
             break;
+        case 'b':       // Repeat
+            result->type = VT100CSI_REP;
+            iTermParserSetCSIParameterIfDefault(param, 0, 1);
+            break;
+
         case 'B':       // Cursor Down
             result->type = VT100CSI_CUD;
             iTermParserSetCSIParameterIfDefault(param, 0, 1);

sources/VT100Screen.m

@@ -17,6 +17,7 @@
 #import "iTermPreferences.h"
 #import "iTermSelection.h"
 #import "iTermShellHistoryController.h"
+#import "iTermTextExtractor.h"
 #import "iTermTemporaryDoubleBufferedGridController.h"
 #import "NSArray+iTerm.h"
 #import "NSColor+iTerm.h"
@@ -4113,6 +4114,26 @@ static NSString *const kInilineFileInset = @"inset";  // NSValue of NSEdgeInsets
                                                           payload:payload];
 }
+- (void)terminalRepeatPreviousCharacter:(int)times {
+    if (![iTermAdvancedSettingsModel supportREPCode]) {
+        return;
+    }
+    if (self.cursorX == 1 && self.cursorY == 1) {
+        return;
+    }
+    VT100GridCoord coord = currentGrid_.cursor;
+    coord.y += [self numberOfScrollbackLines];
+    iTermTextExtractor *extractor = [[[iTermTextExtractor alloc] initWithDataSource:self] autorelease];
+    VT100GridCoord pred = [extractor predecessorOfCoord:coord];
+    if (pred.x < 0 || pred.y < 0) {
+        return;
+    }
+    screen_char_t c = [extractor characterAt:pred];
+    for (int i = 0; i < times; i++) {
+        [self appendScreenCharArrayAtCursor:&c length:1 shouldFree:NO];
+    }
+}
+
 #pragma mark - Private
 - (VT100GridCoordRange)commandRange {

sources/VT100Terminal.m

@@ -1633,6 +1633,10 @@ static const int kMaxScreenRows = 4096;
             [self executeDecSetReset:token];
             break;
+        case VT100CSI_REP:
+            [delegate_ terminalRepeatPreviousCharacter:token.csi->p[0]];
+            break;
+
             // ANSI CSI
         case ANSICSI_CBT:
             [delegate_ terminalBackTab:token.csi->p[0]];

sources/VT100TerminalDelegate.h

@@ -404,4 +404,6 @@ typedef NS_ENUM(NSUInteger, VT100AttentionRequestType) {
 - (void)terminalCustomEscapeSequenceWithParameters:(NSDictionary<NSString *, NSString *> *)parameters
                                            payload:(NSString *)payload;
+- (void)terminalRepeatPreviousCharacter:(int)times;
+
 @end

sources/VT100Token.h

@@ -95,7 +95,8 @@ typedef enum {
     VT100CSI_RESET_MODIFIERS,       // CSI > Ps n (Set all modifiers values to -1, disabled)
     VT100CSI_DECSLRM,               // Set left-right margin
     VT100CSI_DECRQCRA,              // Request Checksum of Rectangular Area
-
+    VT100CSI_REP,                   // Repeat
+    
     // some xterm extensions
     XTERMCC_WIN_TITLE,            // Set window title
     XTERMCC_ICON_TITLE,

sources/VT100Token.m

@@ -160,6 +160,7 @@ static iTermObjectPool *gPool;
                           @(VT100CSI_DECDSR):                 @"VT100CSI_DECDSR",
                           @(VT100CSI_SET_MODIFIERS):          @"VT100CSI_SET_MODIFIERS",
                           @(VT100CSI_RESET_MODIFIERS):        @"VT100CSI_RESET_MODIFIERS",
+                          @(VT100CSI_REP):                    @"VT100CSI_REP",
                           @(VT100CSI_DECSLRM):                @"VT100CSI_DECSLRM",
                           @(XTERMCC_WIN_TITLE):               @"XTERMCC_WIN_TITLE",
                           @(XTERMCC_ICON_TITLE):              @"XTERMCC_ICON_TITLE",

sources/iTermAdvancedSettingsModel.h

@@ -197,5 +197,6 @@
 + (BOOL)sensitiveScrollWheel;
 + (BOOL)disableCustomBoxDrawing;
 + (BOOL)useExperimentalFontMetrics;
++ (BOOL)supportREPCode;
 @end

sources/iTermAdvancedSettingsModel.m

@@ -287,5 +287,6 @@ DEFINE_BOOL(killSessionsOnLogout, NO, @"Experimental Features: Kill sessions on
 DEFINE_BOOL(experimentalKeyHandling, NO, @"General: Improved support for input method editors like AquaSKK.");
 DEFINE_BOOL(useExperimentalFontMetrics, NO, @"Experimental Features: Use a more theoretically correct technique to measure line height.\nYou must restart iTerm2 or adjust a session's font size for this change to take effect.");
+DEFINE_BOOL(supportREPCode, NO, @"Experimental Features: Enable support for REP (Repeat previous character) escape sequence?");
 @end