GUIs and Color Here's a first crack at an 8-puzzle widget:

How It Was Produced  A BulletinBoard container widget bb of 500 x 500 pixels was created. Resources:  XmNheight (500)  XmNwidth (500)  XmNshadowThickness (5 pixels)  Nine PushButton widgets were created as children of bb inside of a doubly nested loop:  XmNheight (100)  XmNwidth (100)

How It Was Produced (cont'd)  To make the buttons appear to pop out of the screen, use resources:  XmNshadowType (XmSHADOW_OUT)  XmNshadowThickness (5)  To make the tiles white, use resource XmNbackground (see later slide)  To display the tile number:  convert it to a string  convert the string to a Motif compound string (recall XmStringCreateLocalized)  give the compound string as value to the resource XmNlabelString

Changing the XmNbackground Resource Suppose you want your 8-puzzle board to look like this:

About Colors  The XmNbackground resource requires a value of type Pixel  A Pixel is a special kind of integer, one that is a valid index into a Colormap  A Colormap is an array of colors; most displays provide a hardware colormap  To specify a new background color, the programmer must know:  the symbolic name of the desired color, and  how to set the XmNbackground resource to the Pixel value associated with that color

Role of the Colormap R G B.. R = Red G = Green B = Blue Frame Buffer Pixel Value Colormap blue

Color Database (Human Readable) ! $XConsortium: rgb.txt,v /02/20 18:39:36 rws Exp $ snow ghost white GhostWhite white smoke WhiteSmoke gainsboro floral white FloralWhite old lace OldLace linen antique white AntiqueWhite papaya whip PapayaWhip blanched almond... [ about 720 more ]... Directory: /usr/X/lib File: rgb.txt The numbers stand for the intensity of the red, green, and blue components of the color

Setting Color Programmatically  The desired bulletin board and push button background colors are DarkRed and PowderBlue  To find their indexes into the colormap (pixels) a programmer can use: XAllocNamedColor(Display *display, Colormap cmap, char *name, XColor *color, XColor *exact) This requires knowing how to retrieve displays, screens, and colormaps.

Getting A Pixel By Color Name Pixel GetPixelByName (Widget w, char* colorname) { Display *dpy = XtDisplay( w ); int scr = DefaultScreen (dpy); Colormap cmap = DefaultColormap (dpy, scr); XColor color, ignore; If (XAllocNamedColor (dpy,cmap,colorname,&color,&ignore)) return color.pixel; else { XtWarning ("Couldn't allocate color" ); return BlackPixel (dpy, scr); { } Now use GetPixelByName(bb,"DarkRed") paired with resource XmNbackground when creating bb.

Using GetPixelByName Widget bb = XtVaCreateManagedWidget ( "puzzle", xmBulletinBoardWidgetClass, form, Nheight, 3*TILE_SIZE+2*BB_SHADOW, XmNwidth, 3*TILE_SIZE+2*BB_SHADOW, XmNmarginHeight, 0, XmNmarginWidth, 0, XmNshadowThickness, BB_SHADOW, XmNshadowType, XmSHADOW_IN, XmNbackground, GetPixelByName(bb, ``DarkRed''), NULL ); Use the same approach to make the color of the tile pushbuttons “PowderBlue”.

Disadvantages of Setting Color Programmatically  GetPixelByName is not defined in either Xt or Xm; you have to write it  Anytime you want to change the background color you have to recompile the program  A better way is to use the Resource Manager