14.1.7 Setting and Reading the WM_NORMAL_HINTS Property

Xlib provides functions that you can use to set or read the WM_NORMAL_HINTS property for a given window. The functions use the flags and the XSizeHints structure, as defined in the X11/Xutil.h header file.

The size of the XSizeHints structure may grow in future releases, as new components are added to support new ICCCM features. Passing statically allocated instances of this structure into Xlib may result in memory corruption when running against a future release of the library. As such, it is recommended that only dynamically allocated instances of the structure be used.

To allocate an XSizeHints structure, use XAllocSizeHints().

The XSizeHints structure contains:

/* Size hints mask bits */

#define USPosition	(1L << 0)	/* user specified x, y */
#define USSize		(1L << 1)	/* user specified width, height */
#define PPosition	(1L << 2)	/* program specified position */
#define PSize		(1L << 3)	/* program specified size */
#define PMinSize	(1L << 4)	/* program specified minimum size */
#define PMaxSize	(1L << 5)	/* program specified maximum size */
#define PResizeInc	(1L << 6)	/* program specified resize increments */
#define PAspect		(1L << 7)	/* program specified min and max aspect ratios */
#define PBaseSize	(1L << 8)
#define PWinGravity	(1L << 9)
#define PAllHints	(PPosition|PSize|PMinSize|PMaxSize|PResizeInc|PAspect)

/* Values */

typedef struct {
	long flags;		/* marks which fields in this structure are defined */
	int x, y;		/* Obsolete */
	int width, height;	/* Obsolete */
	int min_width, min_height;
	int max_width, max_height;
	int width_inc, height_inc;
	struct {
	       int x;		/* numerator */
	       int y;		/* denominator */
	} min_aspect, max_aspect;
	int base_width, base_height;
	int win_gravity;
	/* this structure may be extended in the future */
} XSizeHints;

The x, y, width, and height members are now obsolete and are left solely for compatibility reasons. The min_width and min_height members specify the minimum window size that still allows the application to be useful. The max_width and max_height members specify the maximum window size. The width_inc and height_inc members define an arithmetic progression of sizes (minimum to maximum) into which the window prefers to be resized. The min_aspect and max_aspect members are expressed as ratios of x and y, and they allow an application to specify the range of aspect ratios it prefers. The base_width and base_height members define the desired size of the window. The window manager will interpret the position of the window and its border width to position the point of the outer rectangle of the overall window specified by the win_gravity member. The outer rectangle of the window includes any borders or decorations supplied by the window manager. In other words, if the window manager decides to place the window where the client asked, the position on the parent window's border named by the win_gravity will be placed where the client window would have been placed in the absence of a window manager.

Note that use of the PAllHints macro is highly discouraged.

To set a window's WM_NORMAL_HINTS property, use XSetWMNormalHints().

To read a window's WM_NORMAL_HINTS property, use XGetWMNormalHints().

To set a window's WM_SIZE_HINTS property, use XSetWMSizeHints().

To read a window's WM_SIZE_HINTS property, use XGetWMSizeHints().

Next: Setting and Reading the WM_CLASS Property

Christophe Tronche, ch@tronche.com