Introduce TEX_LEN macro for texture arrays lengths (#2541)

include/tex_len.h

@@ -0,0 +1,14 @@
+#ifndef TEX_LEN_H
+#define TEX_LEN_H
+
+/**
+ * Compute a length for an array holding a texture.
+ * `type` is the array's element type.
+ * `width`, `height` are the texture dimensions.
+ * `bpp` is the texture's pixel size, in bits per pixels.
+ * The calculation computes the size of the texture in bits `width * height * bpp`,
+ * then divides by 8 to get the size in bytes, then divides by the element type size.
+ */
+#define TEX_LEN(type, width, height, bpp) ((width) * (height) * (bpp) / 8 / sizeof(type))
+
+#endif