Add "Center" window placement strategy

Center strategy: try to put window at the center of the usable area. If
window would overlap with existing windows, fall back to "Auto"
placement strategy.

It's very useful for fresh workplaces.

WPrefs.app/WindowHandling.c

@@ -82,7 +82,8 @@ static char *placements[] = {
 	"random",
 	"manual",
 	"cascade",
-	"smart"
+	"smart",
+	"center"
 };
 
 static void sliderCallback(WMWidget * w, void *data)
@@ -151,6 +152,8 @@ static int getPlacement(char *str)
 		return 3;
 	else if (strcasecmp(str, "smart") == 0)
 		return 4;
+	else if (strcasecmp(str, "center") == 0)
+		return 5;
 	else
 		wwarning(_("bad option value %s in WindowPlacement. Using default value"), str);
 	return 0;
@@ -266,6 +269,7 @@ static void createPanel(Panel * p)
 	WMAddPopUpButtonItem(panel->placP, _("Manual"));
 	WMAddPopUpButtonItem(panel->placP, _("Cascade"));
 	WMAddPopUpButtonItem(panel->placP, _("Smart"));
+	WMAddPopUpButtonItem(panel->placP, _("Center"));
 
 	panel->porigL = WMCreateLabel(panel->placF);
 	WMResizeWidget(panel->porigL, 120, 32);

src/WindowMaker.h

@@ -153,6 +153,7 @@ typedef enum {
 #define WPM_SMART	2
 #define WPM_RANDOM	3
 #define WPM_AUTO        4
+#define WPM_CENTER      5
 
 /* text justification */
 #define WTJ_CENTER	0

src/defaults.c

@@ -204,6 +204,7 @@ static WOptionEnumeration sePlacements[] = {
 	{"Cascade", WPM_CASCADE, 0},
 	{"Random", WPM_RANDOM, 0},
 	{"Manual", WPM_MANUAL, 0},
+	{"Center", WPM_CENTER, 0},
 	{NULL, 0, 0}
 };
 

src/placement.c

@@ -360,6 +360,46 @@ smartPlaceWindow(WWindow *wwin, int *x_ret, int *y_ret, unsigned int width,
 	*y_ret = min_isect_y;
 }
 
+static Bool
+center_place_window(WWindow *wwin, int *x_ret, int *y_ret,
+		 unsigned int width, unsigned int height, WArea usableArea)
+{
+	WScreen *scr = wwin->screen_ptr;
+	int try_x, try_y;
+	int swidth, sheight;
+	WWindow *win;
+
+	set_width_height(wwin, &width, &height);
+	swidth = usableArea.x2 - usableArea.x1;
+	sheight = usableArea.y2 - usableArea.y1;
+
+	if (width > swidth || height > sheight)
+		return False;
+
+	try_x = (usableArea.x1 + usableArea.x2 - width) / 2;
+	try_y = (usableArea.y1 + usableArea.y2 - height) / 2;
+
+	for (win = scr->focused_window; win != NULL; win = win->next) {
+		int w = win->frame->core->width;
+		int h = win->frame->core->height;
+		int x = win->frame_x;
+		int y = win->frame_y;
+
+		if ((x < (try_x + width)) && ((x + w) > try_x) &&
+		    (y < (try_y + height)) && ((y + h) > try_y) &&
+		    (win->flags.mapped ||
+		     (win->flags.shaded &&
+		      win->frame->workspace == scr->current_workspace &&
+		      !(win->flags.miniaturized || win->flags.hidden))))
+			return False;
+	}
+
+	*x_ret = try_x;
+	*y_ret = try_y;
+
+	return True;
+}
+
 static Bool
 autoPlaceWindow(WWindow *wwin, int *x_ret, int *y_ret,
 		unsigned int width, unsigned int height, int tryCount, WArea usableArea)
@@ -502,6 +542,11 @@ void PlaceWindow(WWindow *wwin, int *x_ret, int *y_ret, unsigned width, unsigned
 		smartPlaceWindow(wwin, x_ret, y_ret, width, height, usableArea);
 		break;
 
+	case WPM_CENTER:
+		if (center_place_window(wwin, x_ret, y_ret, width, height, usableArea))
+			break;
+		/* fall through to auto placement */
+
 	case WPM_AUTO:
 		if (autoPlaceWindow(wwin, x_ret, y_ret, width, height, 0, usableArea)) {
 			break;
@@ -513,7 +558,7 @@ void PlaceWindow(WWindow *wwin, int *x_ret, int *y_ret, unsigned width, unsigned
 		   automagicness aren't going to want to place their window */
 
 	case WPM_CASCADE:
-		if (wPreferences.window_placement == WPM_AUTO)
+		if (wPreferences.window_placement == WPM_AUTO || wPreferences.window_placement == WPM_CENTER)
 			scr->cascade_index++;
 
 		cascadeWindow(scr, wwin, x_ret, y_ret, width, height, h, usableArea);