InputWidget: Cursor behavior around invisible codepoints

Emoji variation selectors would confuse cursor positioning and insertion behavior, breaking the assumption that each line ends with a single newline.

2 files changed, 59 insertions, 35 deletions

diff --git a/src/ui/inputwidget.c b/src/ui/inputwidget.c
index 9f233345..2f0cabbb 100644
--- a/src/ui/inputwidget.c
+++ b/src/ui/inputwidget.c
@@ -360,35 +360,64 @@ static int endX_InputWidget_(const iInputWidget *d, int y) {
     return line->range.end - (isLastLine_InputWidget_(d, line) ? 0 : 1) - line->range.start;
 }
 
+static iBool isCursorFocusable_Char_(iChar c) {
+    return !isDefaultIgnorable_Char(c) &&
+           !isVariationSelector_Char(c) &&
+           !isFitzpatrickType_Char(c);
+}
+
+static iChar at_InputWidget_(const iInputWidget *d, iInt2 pos) {
+    if (pos.y >= 0 && pos.y < size_Array(&d->lines) &&
+        pos.x >= 0 && pos.x <= endX_InputWidget_(d, pos.y)) {
+        iChar ch = 0;
+        decodeBytes_MultibyteChar(charPos_InputWidget_(d, pos),
+                                  constEnd_String(lineString_InputWidget_(d, pos.y)),
+                                  &ch);
+        return ch;
+    }
+    return ' ';
+}
+
 static iInt2 movedCursor_InputWidget_(const iInputWidget *d, iInt2 pos, int xDir, int yDir) {
-    iChar ch;
-    if (xDir < 0) {
-        if (pos.x == 0) {
-            if (pos.y > 0) {
-                pos.x = endX_InputWidget_(d, --pos.y);
+    iChar ch = 0;
+    int   n  = 0;
+    /* TODO: The cursor should never land on any combining codepoints either. */
+    for (;;) {
+        if (xDir < 0) {
+            if (pos.x == 0) {
+                if (pos.y > 0) {
+                    pos.x = endX_InputWidget_(d, --pos.y);
+                }
             }
-        }
-        else {
-            iAssert(pos.x > 0);
-            int n = decodePrecedingBytes_MultibyteChar(charPos_InputWidget_(d, pos),
+            else {
+                iAssert(pos.x > 0);
+                n = decodePrecedingBytes_MultibyteChar(charPos_InputWidget_(d, pos),
                                                        cstr_String(lineString_InputWidget_(d, pos.y)),
                                                        &ch);
-            pos.x -= n;
-        }
-    }
-    else if (xDir > 0) {
-        if (pos.x == endX_InputWidget_(d, pos.y)) {
-            if (pos.y < size_Array(&d->lines) - 1) {
-                pos.y++;
-                pos.x = 0;
+                pos.x -= n;
+                if (!isCursorFocusable_Char_(at_InputWidget_(d, pos))) {
+                    continue;
+                }
             }
         }
-        else {
-            int n = decodeBytes_MultibyteChar(charPos_InputWidget_(d, pos),
+        else if (xDir > 0) {
+            if (pos.x == endX_InputWidget_(d, pos.y)) {
+                if (pos.y < size_Array(&d->lines) - 1) {
+                    pos.y++;
+                    pos.x = 0;
+                }
+            }
+            else {
+                n = decodeBytes_MultibyteChar(charPos_InputWidget_(d, pos),
                                               constEnd_String(lineString_InputWidget_(d, pos.y)),
                                               &ch);
-            pos.x += n;
+                pos.x += n;
+                if (!isCursorFocusable_Char_(at_InputWidget_(d, pos))) {
+                    continue;
+                }
+            }
         }
+        break;
     }
     return pos;
 }
@@ -1026,7 +1055,9 @@ static void insertRange_InputWidget_(iInputWidget *d, iRangecc range) {
             cstr_String(&line->text) + d->cursor.x, constEnd_String(&line->text)
         });
         truncate_String(&line->text, d->cursor.x);
-        appendCStr_String(&line->text, "\n");
+        if (!endsWith_String(&line->text, "\n")) {
+            appendCStr_String(&line->text, "\n");
+        }
         insert_Array(&d->lines, ++d->cursor.y, &split);
         d->cursor.x = 0;
     }
@@ -1059,6 +1090,8 @@ void setCursor_InputWidget(iInputWidget *d, iInt2 pos) {
     iAssert(!isEmpty_Array(&d->lines));
     pos.x = iClamp(pos.x, 0, endX_InputWidget_(d, pos.y));
     d->cursor = pos;
+    iChar ch = at_InputWidget_(d, pos);
+    printf("cursor x:%d ch:%08x (%lc)\n", pos.x, ch, (int)ch);
     /* Update selection. */
     if (isMarking_()) {
         if (isEmpty_Range(&d->mark)) {
@@ -1221,18 +1254,6 @@ static iBool deleteMarked_InputWidget_(iInputWidget *d) {
     return iFalse;
 }
 
-static iChar at_InputWidget_(const iInputWidget *d, iInt2 pos) {
-    if (pos.y >= 0 && pos.y < size_Array(&d->lines) &&
-        pos.x >= 0 && pos.x <= endX_InputWidget_(d, pos.y)) {
-        iChar ch = 0;
-        decodeBytes_MultibyteChar(charPos_InputWidget_(d, pos),
-                                  constEnd_String(lineString_InputWidget_(d, pos.y)),
-                                  &ch);
-        return ch;
-    }
-    return ' ';
-}
-
 static iBool isWordChar_InputWidget_(const iInputWidget *d, iInt2 pos) {
     return isAlphaNumeric_Char(at_InputWidget_(d, pos));
 }
diff --git a/src/ui/text.c b/src/ui/text.c
index 0a8386e4..639d8f13 100644
--- a/src/ui/text.c
+++ b/src/ui/text.c
@@ -1433,6 +1433,7 @@ static iRect run_Font_(iFont *d, const iRunArgs *args) {
     iBool        isFirst            = iTrue;
     const iBool  checkHitPoint      = wrap && !isEqual_I2(wrap->hitPoint, zero_I2());
     const iBool  checkHitChar       = wrap && wrap->hitChar;
+    iBool        wasCharHit         = iFalse;
     while (!isEmpty_Range(&wrapRuns)) {
         if (isFirst) {
             isFirst = iFalse;
@@ -1452,9 +1453,10 @@ static iRect run_Font_(iFont *d, const iRunArgs *args) {
             for (size_t runIndex = wrapRuns.start; runIndex < wrapRuns.end; runIndex++) {
                 const iAttributedRun *run = at_Array(&attrText.runs, runIndex);
                 if (run->flags.isLineBreak) {
-                    if (checkHitChar) {
+                    if (checkHitChar && !wasCharHit) {
                         if (wrap->hitChar == sourcePtr_AttributedText_(&attrText, run->logical.start)) {
                             wrap->hitAdvance_out = init_I2(wrapAdvance, yCursor);
+                            wasCharHit = iTrue;
                         }
                     }
                     wrapPosRange.end   = run->logical.start;
@@ -1479,9 +1481,10 @@ static iRect run_Font_(iFont *d, const iRunArgs *args) {
                     if (logPos < wrapPosRange.start || logPos >= wrapPosRange.end) {
                         continue;
                     }
-                    if (checkHitChar) {
+                    if (checkHitChar && !wasCharHit) {
                         if (wrap->hitChar == sourcePtr_AttributedText_(&attrText, logPos)) {
                             wrap->hitAdvance_out = init_I2(wrapAdvance, yCursor);
+                            wasCharHit = iTrue;
                         }
                     }
                     /* Check if the hit point is on the left side of this line. */