Fix QR-code/symbol not rendering on top of QR-code correctly

src/zbar_pipeline.c

@@ -77,6 +77,19 @@ is_3d_code(zbar_symbol_type_t type)
         }
 }
 
+/*
+ * This function gets given the x/y coordinates of the corners of a QR-code/symbol,
+ * but zbar is given an image buffer that may be rotated/mirrored.
+ * So here we adjust the coordinates based on that, so it can be used in src/main.c
+ * to display the symbol on top of the correctly rotated/mirrored camera preview.
+ *
+ * Rotation 0 is the phone in landscape mode (counter-clockwise)
+ * Rotation 90 is the phone in portrait mode upside down
+ * Rotation 180 is the phone in landscape mode (clockwise)
+ * Rotation 270 is the phone in portrait mode
+ *
+ * Mirrored is mainly/only(?) used for front cameras
+ */
 static inline void
 map_coords(int *x, int *y, int width, int height, int rotation, bool mirrored)
 {
@@ -109,6 +122,7 @@ process_symbol(const MPZBarImage *image,
                int height,
                const zbar_symbol_t *symbol)
 {
+        // When device is in portrait mode, swap width/height
         if (image->rotation == 90 || image->rotation == 270) {
                 int tmp = width;
                 width = height;