Allow CSI_CUB (CSI n D) [move cursor left] to wrap around the left margin. Fixes bug 2969.

Author: gnachman

VT100Grid.m

@@ -412,11 +412,45 @@ - (int)moveCursorDownOneLineScrollingIntoLineBuffer:(LineBuffer *)lineBuffer
 }
 
 - (void)moveCursorLeft:(int)n {
-    int x = cursor_.x - n;
-    const int leftMargin = [self leftMargin];
+    if ([self haveColumnScrollRegion]) {
+        // Don't allow cursor to wrap around the left margin when there is a
+        // column scroll region.
+        int x = cursor_.x - n;
+        const int leftMargin = [self leftMargin];
+
+        x = MAX(leftMargin, x);
+        self.cursorX = x;
+        return;
+    }
 
-    x = MAX(leftMargin, x);
-    self.cursorX = x;
+    while (n > 0) {
+        if (self.cursorX == 0 && self.cursorY == 0) {
+            // Can't move any farther left.
+            return;
+        } else if (self.cursorX == 0) {
+            // Wrap around?
+            switch ([self continuationMarkForLineNumber:self.cursorY - 1]) {
+                case EOL_SOFT:
+                case EOL_DWC:
+                    // Wrap around to the end of the previous line, even if this leaves the cursor
+                    // on a DWC_RIGHT.
+                    n--;
+                    self.cursorX = [self rightMargin];
+                    self.cursorY = self.cursorY - 1;
+                    break;
+
+                case EOL_HARD:
+                    // Can't wrap across EOL_HARD.
+                    return;
+            }
+        } else {
+            // Move as far as the left margin
+            int x = MAX(0, cursor_.x - n);
+            int moved = self.cursorX - x;
+            n -= moved;
+            self.cursorX = x;
+        }
+    }
 }
 
 - (void)moveCursorRight:(int)n {
@@ -733,6 +767,15 @@ - (int)appendCharsAtCursor:(screen_char_t *)buffer
         int lineNumber = cursor_.y;
         aLine = [self screenCharsAtLineNumber:cursor_.y];
 
+        BOOL mayStompSplitDwc = NO;
+        if (newx == size_.width) {
+            // The cursor is ending at the right margin. See if there's a DWC_SKIP/EOL_DWC pair
+            // there which may be affected.
+            mayStompSplitDwc = (!useScrollRegionCols_ &&
+                                aLine[size_.width].code == EOL_DWC &&
+                                aLine[size_.width - 1].code == DWC_SKIP);
+        }
+
         if (insert) {
             if (cursor_.x + charsToInsert < rightMargin) {
 #ifdef VERBOSE_STRING
@@ -816,6 +859,15 @@ - (int)appendCharsAtCursor:(screen_char_t *)buffer
             aLine[cursor_.x].complexChar = NO;
         }
 
+        if (mayStompSplitDwc &&
+            aLine[size_.width - 1].code != DWC_SKIP &&
+            aLine[size_.width].code == EOL_DWC) {
+            // The line no longer ends in a DWC_SKIP, but the continuation mark is still EOL_DWC.
+            // Change the continuation mark to EOL_SOFT since there's presumably still a DWC at the
+            // start of the next line.
+            aLine[size_.width].code = EOL_SOFT;
+        }
+
         // The next char in the buffer shouldn't be DWC_RIGHT because we
         // wouldn't have inserted its first half due to a check at the top.
         assert(!(idx < len && buffer[idx].code == DWC_RIGHT));

iTermTests/VT100GridTest.m

@@ -600,6 +600,106 @@ - (void)testMoveCursorLeft {
     assert(grid.cursorX == 2);
 }
 
+// Make sure that moveCursorLeft wraps around soft EOLs
+- (void)testMoveCursorLeftWrappingAroundSoftEOL {
+    VT100Grid *grid = [self mediumGrid]; // 4x4
+
+    NSString *string = @"abcdef";
+    screen_char_t *line = [self screenCharLineForString:string];
+    LineBuffer *lineBuffer = [[[LineBuffer alloc] initWithBlockSize:1000] autorelease];
+    [grid appendCharsAtCursor:line
+                       length:[string length]
+      scrollingIntoLineBuffer:lineBuffer
+          unlimitedScrollback:YES
+      useScrollbackWithRegion:NO
+                   wraparound:YES
+                         ansi:NO
+                       insert:NO];
+    assert([[grid compactLineDump] isEqualToString:
+            @"abcd\n"
+            @"ef..\n"
+            @"....\n"
+            @"...."]);
+
+    assert(grid.cursorX == 2);
+    assert(grid.cursorY == 1);
+    [grid moveCursorLeft:4];
+    assert(grid.cursorX == 2);
+    assert(grid.cursorY == 0);
+}
+
+// Make sure that moveCursorLeft wraps around soft EOLs
+- (void)testMoveCursorLeftWrappingAroundDoubleWideCharEOL {
+    VT100Grid *grid = [[[VT100Grid alloc] initWithSize:VT100GridSizeMake(3, 3)
+                                              delegate:self] autorelease];
+
+    NSString *string = @"abc-";  // c is double-width
+    screen_char_t *line = [self screenCharLineForString:string];
+    LineBuffer *lineBuffer = [[[LineBuffer alloc] initWithBlockSize:1000] autorelease];
+    [grid appendCharsAtCursor:line
+                       length:[string length]
+      scrollingIntoLineBuffer:lineBuffer
+          unlimitedScrollback:YES
+      useScrollbackWithRegion:NO
+                   wraparound:YES
+                         ansi:NO
+                       insert:NO];
+    assert([[grid compactLineDump] isEqualToString:
+            @"ab>\n"
+            @"c-.\n"
+            @"..."]);
+
+    assert(grid.cursorX == 2);
+    assert(grid.cursorY == 1);
+    [grid moveCursorLeft:4];
+    assert(grid.cursorX == 1);
+    assert(grid.cursorY == 0);
+}
+
+// Make sure that moveCursorLeft wraps around soft EOLs
+- (void)testMoveCursorLeftNotWrappingAroundHardEOL {
+    VT100Grid *grid = [self mediumGrid]; // 4x4
+
+    NSString *string = @"abc";
+    screen_char_t *line = [self screenCharLineForString:string];
+    LineBuffer *lineBuffer = [[[LineBuffer alloc] initWithBlockSize:1000] autorelease];
+    [grid appendCharsAtCursor:line
+                       length:[string length]
+      scrollingIntoLineBuffer:lineBuffer
+          unlimitedScrollback:YES
+      useScrollbackWithRegion:NO
+                   wraparound:YES
+                         ansi:NO
+                       insert:NO];
+    [grid moveCursorDownOneLineScrollingIntoLineBuffer:lineBuffer
+                                   unlimitedScrollback:YES
+                               useScrollbackWithRegion:NO];
+    grid.cursorX = 0;
+
+    string = @"d";
+    line = [self screenCharLineForString:string];
+    [grid appendCharsAtCursor:line
+                       length:[string length]
+      scrollingIntoLineBuffer:lineBuffer
+          unlimitedScrollback:YES
+      useScrollbackWithRegion:NO
+                   wraparound:YES
+                         ansi:NO
+                       insert:NO];
+
+    assert([[grid compactLineDump] isEqualToString:
+            @"abc.\n"
+            @"d...\n"
+            @"....\n"
+            @"...."]);
+
+    assert(grid.cursorX == 1);
+    assert(grid.cursorY == 1);
+    [grid moveCursorLeft:4];
+    assert(grid.cursorX == 0);
+    assert(grid.cursorY == 1);
+}
+
 - (void)testMoveCursorRight {
     VT100Grid *grid = [self mediumGrid];
     grid.cursorX = 2;
@@ -2377,6 +2477,37 @@ - (void)testAppendCharsAtCursor {
                                         expectCursor:VT100GridCoordMake(3, 0)
                                     expectLineBuffer:@""
                                        expectDropped:0];
+
+    // Overwriting a DWC_SKIP converts EOL_DWC to EOL_SOFT
+    isAnsi_ = NO;
+    wraparoundMode_ = YES;
+    [self doAppendCharsAtCursorTestWithInitialBuffer:@"abc>>\n"
+                                                     @"D-..!"
+                                        scrollRegion:VT100GridRectMake(0, 0, -1, -1)
+                             useScrollbackWithRegion:YES
+                                 unlimitedScrollback:NO
+                                           appending:@"d"
+                                                  at:VT100GridCoordMake(3, 0)
+                                              expect:@"abcd+\n"
+                                                     @"D-..!"
+                                        expectCursor:VT100GridCoordMake(4, 0)
+                                    expectLineBuffer:@""
+                                       expectDropped:0];
+
+    isAnsi_ = NO;
+    wraparoundMode_ = YES;
+    [self doAppendCharsAtCursorTestWithInitialBuffer:@"abc>>\n"
+                                                     @"D-..!"
+                                        scrollRegion:VT100GridRectMake(0, 0, -1, -1)
+                             useScrollbackWithRegion:YES
+                                 unlimitedScrollback:NO
+                                           appending:@"def"
+                                                  at:VT100GridCoordMake(3, 0)
+                                              expect:@"abcd+\n"
+                                                     @"ef..!"
+                                        expectCursor:VT100GridCoordMake(2, 1)
+                                    expectLineBuffer:@""
+                                       expectDropped:0];
 }
 
 - (void)testCoordinateBefore {

tests/move_cursor_left_wraps

@@ -0,0 +1,14 @@
+Make sure your terminal is 80 cols wide.
+
+Puts a ! in the empty spot at the end of the first line                        v
+yyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyxｅa!
+
+
+Puts a ! over the x                                                           v
+yyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyxｅa!
+
+
+Puts a ! between the >marks<
+  v
+x>O<xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx!
+