C++ why setWindowText doesn't display any text? - c++

Question

I have code as below, and my question is why in the cell A[0][0] setWindowText put nothing?
if(LOWORD( wParam ) == 104){
int td;
int td_width=80;
int tr = 0;
int tr_height=20;
for (tr=0;tr<2;tr++) {
for (td=0;td<10;td++) {
HWND A[tr][td];
A[tr][td] = CreateWindowEx( 0, "EDIT", NULL, WS_CHILD | WS_VISIBLE | WS_BORDER | ES_MULTILINE | ES_AUTOVSCROLL,
td*td_width, tr*tr_height+50, td_width+1, tr_height+1, hwnd, NULL, hInstance, NULL );
}
SetWindowText(A[0][0], "MK" );
}
}

Answer 1

You're defining A[tr][td] inside the inner most loop. This restricts its scope to just that loop. In other words, on each iteration, you're creating a brand new array and assigning just one of its elements.
It's a little surprising that this even compiles. I guess you have another A array defined somewhere else, and that's the one you're referencing in the SetWindowText call.

Answer 2

As Peter said, you are declaring your array in the wrong spot. But more than that, you are also declaring the array as fixed-length but using run-time values to specify its bounds. That will not work, and should not even compile. A fixed-length array's bounds must be known at compile-time, not at run-time.
Try this instead:
if (LOWORD(wParam) == 104)
{
const int td_width = 80;
const int tr_height = 20;
HWND A[2][10];
for (int tr = 0; tr < 2; ++tr)
{
for (int td = 0; td < 10; ++td)
{
A[tr][td] = CreateWindowEx( 0, TEXT("EDIT"), NULL, WS_CHILD | WS_VISIBLE | WS_BORDER | ES_MULTILINE | ES_AUTOVSCROLL, td*td_width, tr*tr_height+50, td_width+1, tr_height+1, hwnd, NULL, hInstance, NULL );
}
}
SetWindowText(A[0][0], TEXT("MK") );
}