robustness improvements

* handling of stop = 0 when calculating sizes (avoid unsigned underflow)
* make sure groupLength() is never zero (to avoid div/0)
* gapmaps: check for "(gapSize > 0)" added.

not sure if all the checks are 100% needed, but they will improve robustness in corner cases.

wled00/FX.h

@@ -540,7 +540,7 @@ typedef struct Segment {
     inline uint16_t width(void)          const { return (stop > start)   ? (stop - start)   : 0; } // segment width in physical pixels (length if 1D)
     inline uint16_t height(void)         const { return (stopY > startY) ? (stopY - startY) : 0; } // segment height (if 2D) in physical pixels // WLEDMM make sure its always > 0
     inline uint16_t length(void)         const { return width() * height(); }     // segment length (count) in physical pixels
-    inline uint16_t groupLength(void)    const { return grouping + spacing; }
+    inline uint16_t groupLength(void)    const { return max(1, grouping + spacing); } // WLEDMM length = 0 could lead to div/0 in virtualWidth() and virtualHeight()
     inline uint8_t  getLightCapabilities(void) const { return _capabilities; }
 
     static size_t   getUsedSegmentData(void)    { return _usedSegmentData; } // WLEDMM size_t
@@ -628,6 +628,7 @@ typedef struct Segment {
     inline uint16_t XY(uint_fast16_t x, uint_fast16_t y) { // support function to get relative index within segment (for leds[]) // WLEDMM inline for speed
       uint_fast16_t width  = virtualWidth();   // segment width in logical pixels
       uint_fast16_t height = virtualHeight();  // segment height in logical pixels
+      if ((width == 0) || (height == 0)) return 0; // softhack007 avoid div/0
       return (x%width) + (y%height) * width;
     }
     void setPixelColorXY(int x, int y, uint32_t c); // set relative pixel within segment with color

wled00/FX_2Dfcn.cpp

@@ -115,7 +115,7 @@ void WS2812FX::setUpMatrix() {
           //  1 ... active pixel (it will count and will be mapped)
           JsonArray map = doc.as<JsonArray>();
           gapSize = map.size();
-          if (!map.isNull() && gapSize >= customMappingSize) { // not an empty map
+          if (!map.isNull() && (gapSize > 0) && gapSize >= customMappingSize) { // not an empty map //softhack also check gapSize>0 
             gapTable = new int8_t[gapSize];
             if (gapTable) for (size_t i = 0; i < gapSize; i++) {
               gapTable[i] = constrain(map[i], -1, 1);

wled00/FX_fcn.cpp

@@ -1050,7 +1050,7 @@ uint32_t Segment::getPixelColor(int i)
   i += start;
   /* offset/phase */
   i += offset;
-  if (i >= stop) i -= length();
+  if ((i >= stop) && (stop>0)) i -= length(); // WLEDMM avoid negative index (stop = 0 is a possible value)
   return strip.getPixelColor(i);
 }
 

wled00/json.cpp

@@ -100,7 +100,7 @@ bool deserializeSegment(JsonObject elem, byte it, byte presetId)
 
   uint16_t start = elem["start"] | seg.start;
   if (stop < 0) {
-    uint16_t len = elem["len"];
+    int len = elem["len"]; // WLEDMM bugfix for broken presets with len < 0
     stop = (len > 0) ? start + len : seg.stop;
   }
   // 2D segments
@@ -113,7 +113,7 @@ bool deserializeSegment(JsonObject elem, byte it, byte presetId)
     elem.remove("id");  // remove for recursive call
     elem.remove("rpt"); // remove for recursive call
     elem.remove("n");   // remove for recursive call
-    uint16_t len = stop - start;
+    uint16_t len = (stop >= start) ? (stop - start) : 0;  // WLEDMM stop < 1 is allowed, so we need to avoid underflow
     for (size_t i=id+1; i<strip.getMaxSegments(); i++) {
       start = start + len;
       if (start >= strip.getLengthTotal()) break;
@@ -592,7 +592,7 @@ void serializeSegment(JsonObject& root, Segment& seg, byte id, bool forPreset, b
       root[F("stopY")]  = seg.stopY;
     }
   }
-  if (!forPreset) root["len"] = seg.stop - seg.start;
+  if (!forPreset) root["len"] = (seg.stop >= seg.start) ? (seg.stop - seg.start) : 0; // WLEDMM correct handling for stop=0
   root["grp"]    = seg.grouping;
   root[F("spc")] = seg.spacing;
   root[F("of")]  = seg.offset;

wled00/wled.h

@@ -8,7 +8,7 @@
  */
 
 // version code in format yymmddb (b = daily build)
-#define VERSION 2306210
+#define VERSION 2306211
 
 //uncomment this if you have a "my_config.h" file you'd like to use
 //#define WLED_USE_MY_CONFIG