Weird space when using wide characters in c - c

Question

I am trying to draw a square with a given width and height.
I am trying to do so while using the box characters from Unicode.
I am using this code:
#include <stdlib.h>
#include <stdio.h>
#include <wchar.h>
#include <locale.h>
#include "string_prints.h"
#define VERTICAL_PIPE L"║"
#define HORIZONTAL_PIPE L"═"
#define UP_RIGHT_CORNER L"╗"
#define UP_LEFT_CORNER L"╔"
#define DOWN_RIGHT_CORNER L"╝"
#define DOWN_LEFT_CORNER L"╚"
// Function to print the top line
void DrawUpLine(int w){
setlocale(LC_ALL, "");
wprintf(UP_LEFT_CORNER);
for (int i = 0; i < w; i++)
{
wprintf(HORIZONTAL_PIPE);
}
wprintf(UP_RIGHT_CORNER);
}
// Function to print the sides
void DrawSides(int w, int h){
setlocale(LC_ALL, "");
for (int i = 0; i < h; i++)
{
wprintf(VERTICAL_PIPE);
for (int j = 0; j < w; j++)
{
putchar(' ');
}
wprintf(VERTICAL_PIPE);
putchar('\n');
}
}
// Function to print the bottom line
void DrawDownLine(int w){
setlocale(LC_ALL, "");
wprintf(DOWN_LEFT_CORNER);
for (int i = 0; i < w; i++)
{
wprintf(HORIZONTAL_PIPE);
}
wprintf(DOWN_RIGHT_CORNER);
}
void DrawFrame(int w, int h){
DrawUpLine(w);
putchar('\n');
DrawSides(w, h);
putchar('\n');
DrawDownLine(w);
}
But when I am running this code with some int values I get an output with seemingly random spaces and newlines (although the pipes seem at the correct order).
It is being called from main.c from the header like so:
#include <stdlib.h>
#include <stdio.h>
#include <wchar.h>
#include <locale.h>
#include "string_prints.h"
int main(){
DrawFrame(10, 20); // Calling the function
return 0;
}
Also as you can see I don't understand the correct use of setlocale, do you need to do it only once? or more?
Any help appreciated thanks in advance!

Answer 1

Also as you can see I don't understand the correct use of setlocale, do you need to do it only once? or more?
Locale changes applied via setlocale() are persistent within the calling process. You do not need to call that function multiple times unless you want to make multiple changes. But you do need to name a locale to it that serves your intended purpose, or if you call it with an empty string then you or the program user does need to ensure that the environment variables that define the various locale categories are set to values that suit the purpose.
But when I am running this code with some int values I get an output
with seemingly random spaces and newlines.
That sounds like the result of a character-encoding mismatch, or even two (but see also below):
there can be a runtime mismatch because the locale you tell the program to use for output does not match the one expected by the output device (e.g. a terminal) with which the program's output is displayed, and
there can also be a compile time mismatch between the actual character encoding of your source file and the encoding the compiler interprets it as having.
Additionally, use of wide string literal syntax notwithstanding, it is implementation-dependent which characters other than C's basic set may appear in your source code. The wide syntax specifies mostly the form of the storage for the literal (elements of type wchar_t), not so much what character values are valid or how they are interpreted.
Note also that the width of wchar_t is implementation-dependent, and it can be as small as eight bits. It is not necessarily the case that a wchar_t can represent arbitrary Unicode characters -- in fact, it is pretty common for wchar_t to be 16 bits wide, which in fact isn't wide enough for the majority of characters from Unicode's 21-bit code space. You might get an internal representation of wider characters in a two-unit form, such as a UTF-16 surrogate pair, but you also might not -- a great deal of this is left to individual implementations.
Among those things, what encoding the compiler expects, under what circumstances, and how you can influence that are all implementation-dependent. For GCC, for instance, the default source ("input") character set is UTF-8, and you can define a different one via its -finput-charset option. You can also specify both a standard and a wide execution character set via the -fexec-charset and -fwide-exec-charset options, if you wish to do so. GCC relies on iconv for conversions, both at compile time (source charset to execution charset) and at runtime (from execution charset to locale charset). Other implementations have other options (or none), with their own semantics.
So what should you do? In the first place, I suggest taking the source character set out of the equation by using UTF-8 string literals expressed using only basic character set (requires C2011):
#define VERTICAL_PIPE u8"\xe2\x95\x91"
#define HORIZONTAL_PIPE u8"\xe2\x95\x90"
#define UP_RIGHT_CORNER u8"\xe2\x95\x97"
#define UP_LEFT_CORNER u8"\xe2\x95\x94"
#define DOWN_RIGHT_CORNER u8"\xe2\x95\x9d"
#define DOWN_LEFT_CORNER u8"\xe2\x95\x9a"
Note well that the resulting strings are normal, not wide, so you should not use the wide-oriented output functions with them. Instead, use the normal printf, putchar, etc..
And that brings us to another issue with your code: you must not mix wide-oriented and byte-oriented functions writing to the same stream without taking explicit measures to switch (freopen or fwide; see paragraph 7.21.2/4 of the standard). In practice, mixing the two can quite plausibly produce mangled results.
Then also ensure that your local environment variables are set correctly for your actual environment. Chances are good that they already are, but it's worth a check.