About NULL, NIL, 0
Programmers with C Delphi know that NULL in C is nil in Delphi, meaning empty pointer
In C (void *) 0 is Pointer in DLEPHI (0)
However, this is not absolute, because Handle
Handle in C is a pointer
In Delphi, Handle is understood as an integer, so everything starts from here.
Let's take a function! CREATEWINDOW
The declaration of C is:
HWND CREATEWINDOW
LPCTSTR LPCLASSNAME, / / POINTER TO Registered Class Name
LPCTSTR LPWINDOWNAME, / / POINTER TO WINDOW NAME
DWORD DWSTYLE, / / WINDOW STYLE
Int x, // horizontal position of window
Int Y, // Vertical Position of Window
INT NWIDTH, / / WINDOW WIDTH
INT NHEIGHT, // WINDOW HEIGHT
HWND HWNDPARENT, // Handle to Parent or Owner Window
Hmenu Hmenu, // Handle to Menu Or Child-Window Identifier
Handle Hinstance, // Handle to Application Instance
LPVOID LPPARAM / / POINTER TO WINDOW-CREATION DATA
);
Let's take a look at several pointers (7, return value, the first two parameters, the last four parameters)
Let's take a look at the declaration in Delphi:
Function CREATEWINDOW
LpClassName: Pchar; // Pointer to Registered Class Name
Lpwindowname: Pchar; // Pointer to Window Name
DWStyle: Integer; // WINDOW STYLE
x: Integer; // Horizontal Position Of Window
Y: integer; // Vertical Position of window
NWIDTH: Integer; // WINDOW WIDTH
NHEIGHT: Integer; // WINDOW HEIGHT
HWndparent: integer; // handle to parent or owner window
HMENU: Integer; // Handle To Menu Or Child-Window Identifier
Hinstance: Integer; // Handle to Application Instance
LPParam: Pointer // Pointer to Window-Creation Data
: Integer;
How many pointers? (There are three, the first two and the last parameter)
If this function is called, it is exaggerated, all pointers (in C ) are replaced by NULL, in Delphi, the function call should be like this:
HWnd: = CreateWindow ('', '', WS_CHILD, 0, 0, 100, 100, 0, 0, 0, NIL); // This function is only an example. If null refers to Handle, in Delphi, it is equivalent to 0 ; Others? Equivalent to NIL (Pchar is ready to put down) (see the second one) is some of my opinions, I hope everyone will correct
