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Chapter 7 Character Display Routines 128 Fastgraph User's Guide Overview An important part of any program is the capability to display text or other characters on the screen. Fastgraph supports two character sets: the hardware or BIOS character set available with each video mode, and Fastgraph's own software character set for graphics video modes. Fastgraph/Light does not support the software character set. We'll begin this chapter with a review of character space, and then discuss the specifics about hardware and software characters. At the end of the chapter, we'll briefly explain how to implement bit-mapped characters into a program. To simplify things, the example programs presented in this chapter are mode-specific examples, and no testing is done to check if the video mode is available on the user's system. Character Space The coordinate system used for displaying hardware characters is called character space. It is the only coordinate system available in text video modes, but it is a supplementary coordinate system you can use with either screen space or world space in graphics video modes. Character space can be thought of as a grid of rows and columns, with each cell in the grid holding one character. Each cell is identified by its unique (row,column) integer coordinates. The rows and columns are numbered starting at zero; the origin is always the upper left corner of the screen. For example, in the 80-column by 25-row video modes, the (row,column) coordinates of the screen corners are shown in the following diagram. (0,0) (0,79) (24,0) (24,79) The default number of rows and columns depends on the video mode, as shown in the following table. For graphics modes, the table also includes the default width and height in pixels of a character cell. Mode Char. Char. Number Columns Rows Width Height 0 40 25 1 40 25 2 80 25 3 80 25 4 40 25 8 8 5 40 25 8 8 6 80 25 8 8 7 80 25 9 40 25 8 8 11 80 25 9 14 12 40 25 8 8 13 40 25 8 8 Chapter 7: Character Display Routines 129 14 80 25 8 8 15 80 25 8 14 16 80 25 8 14 17 80 30 8 16 18 80 30 8 16 19 40 25 8 8 20 40 25 8 8 21 40 50 8 8 22 40 30 8 8 23 40 60 8 8 24 80 25 8 16 25 80 30 8 16 26 100 37 8 16 27 128 48 8 16 28 100 37 8 16 29 128 48 8 16 Hardware Characters Hardware characters are available in all of Fastgraph's supported video modes. As explained in Chapter 5, text mode characters have a display attribute that defines their foreground color, their background color, and whether or not they blink. Graphics mode characters appear in a single color, as determined by the current color index. Chapter 5 also explained how Fastgraph's fg_setattr and fg_setcolor routines define the attribute or color index in which subsequent hardware characters appear. It is obviously important to define the color or attribute for hardware characters, but it is equally important to define their location on the screen. Fastgraph draws hardware characters at the position defined by the text cursor. Like the graphics cursor, the text cursor is not a cursor in the true sense, but is simply a pair of character space (row,column) coordinates with a special meaning. The fg_setmode routine sets the text cursor position to the character space coordinates (0,0), which of course is the upper left corner of the screen.2 The Fastgraph routine fg_locate changes the text cursor position. It has two integer arguments that specify the (row,column) character space coordinates of the new position. The row values must be between 0 and one less than the number of character rows available. The column values must be between 0 and one less than the number of character columns available. The fg_text routine is Fastgraph's basic character display routine. It displays a string of hardware characters, starting at the text cursor position, using the current color attribute (for text modes) or color index (for graphics modes). If the string reaches the last column in a row, fg_text will wrap the string to the first column of the next row. Additionally, fg_text leaves the cursor one column to the right of the last character displayed (or the first column of the next row if the last character appears at the end of a row). This feature makes it possible for successive calls to fg_text to display adjacent strings. The first argument ____________________ (2) In reality there are eight text cursors, one for each video page. The fg_setmode routine initializes each text cursor position to (0,0). The next chapter describes this in more detail. 130 Fastgraph User's Guide for the fg_text routine is a character string of arbitrary length, and the second argument is an integer value that specifies the number of characters to display from that string. Example 7-1 illustrates the use of the fg_locate and fg_text routines in the 80 by 25 color text mode (mode 3). After establishing the video mode and making the BIOS cursor invisible, the program displays four strings with different attributes. The attributes are selected using the fg_setattr routine, and the strings are displayed by the fg_text routine. The first string appears in yellow (attributes 14,0,0) in the upper left corner of the screen; the fg_locate routine is not necessary because (0,0) is the default text cursor position established by fg_setmode. The second string appears in light green (10,0,0) one space to the right of the first string. Its position relies on the fact fg_text leaves the text cursor positioned one space to the right of the last character displayed (following the "w" of "yellow" in this case). The leading space in " green" leaves a space between the first and second strings. Similarly, the third string appears in blinking light red (12,0,1) one space to the right of the second string. The program then uses the fg_locate routine to move the text cursor to the lower left corner of the screen and displays the "Press any key" string. This string is displayed with a light red foreground against a gray background (12,7,0). The extra spaces surrounding the string extend the background color one character position to the left and right and make the string more visually appealing. Finally, once you press any key, the program restores the original video mode and screen attributes before returning to DOS. Example 7-1. #include <fastgraf.h> void main(void); void main() { int old_mode; old_mode = fg_getmode(); fg_setmode(3); fg_cursor(0); fg_setattr(14,0,0); fg_text("yellow",6); fg_setattr(10,0,0); fg_text(" green",6); fg_setattr(12,0,1); fg_text(" blinking",9); fg_setattr(12,7,0); fg_locate(24,0); fg_text(" Press any key. ",16); fg_waitkey(); fg_setmode(old_mode); fg_reset(); Chapter 7: Character Display Routines 131 } The fg_where routine retrieves the text cursor position in its two integer arguments. This routine is not used as frequently as the fg_locate and fg_text routines because more often than not your program will know the text cursor position implicitly, or you'll know in advance the locations at which text will be displayed. The fg_where routine takes two integer arguments passed as pointers (that is, by reference), and these two arguments respectively receive the text cursor's current row and column position. Example 7-2 produces the same results as example 7-1, but it does so a bit differently. It uses its own routine, put_string, to display a string at a specified row and column. The put_string routine simply calls fg_locate to establish the text cursor position and then calls fg_text to display the string. Note the use of the C library function strlen to determine the string length passed to the fg_text routine. Example 7-2 also uses the fg_where routine to retrieve the new text cursor positions, which are then passed to the put_string routine. Example 7-2. #include <fastgraf.h> #include <string.h> void main(void); void put_string(char*,int,int); void main() { int old_mode; int row, column; old_mode = fg_getmode(); fg_setmode(3); fg_cursor(0); fg_setattr(14,0,0); put_string("yellow",0,0); fg_setattr(10,0,0); fg_where(&row,&column); put_string("green",row,column+1); fg_setattr(12,0,1); fg_where(&row,&column); put_string("blinking",row,column+1); fg_setattr(12,7,0); put_string(" Press any key. ",24,0); fg_waitkey(); fg_setmode(old_mode); fg_reset(); } void put_string(string,row,column) char *string; 132 Fastgraph User's Guide int row, column; { fg_locate(row,column); fg_text(string,strlen(string)); } Sometimes you may wish to change the display attribute of existing text, such as when creating a shadow around the edges of a pop-up window. The Fastgraph routine fg_chgattr performs this function. It applies the current text display attribute (as defined in the most recent call to fg_setattr or fg_setcolor) to a given number of characters, starting at the text cursor position. It leaves the text cursor one column to the right of the last character changed (or the first column of the next row if the last character is at the end of a row). The fg_chgattr routine's argument specifies the number of characters to change. This routine has no effect in graphics video modes. The Fastgraph routine fg_chgtext performs somewhat the opposite function of fg_chgattr. It displays new text but uses the display attributes already assigned to the character cells where the text will appear. The fg_chgtext routine takes the same two arguments as the fg_text routine, displays the characters starting at the text cursor position, and leaves the cursor one column to the right of the last character displayed. Like fg_chgattr, fg_chgtext has no effect in graphics video modes. Example 7-3 illustrates the fg_chgattr and fg_chgtext routines. It runs in the 80-column color text mode (mode 3), but if we change the fg_setmode argument it also would run in the monochrome text mode (mode 7). The program first displays the word "hello" in the upper left corner of the screen, using a gray foreground and black background attribute. After waiting for a keystroke, the program calls fg_chgattr to make the word "hello" appear in reverse video (that is, a black foreground and gray background attribute). After a second keystroke, the program uses fg_chgtext to change the "h" of "hello" to upper case. Following this, the program returns to DOS. Example 7-3. #include <fastgraf.h> void main(void); void main() { int old_mode; old_mode = fg_getmode(); fg_setmode(3); fg_cursor(0); fg_setattr(7,0,0); fg_text("hello",5); fg_waitkey(); fg_locate(0,0); fg_setattr(0,7,0); fg_chgattr(5); fg_waitkey(); Chapter 7: Character Display Routines 133 fg_locate(0,0); fg_chgtext("H",1); fg_waitkey(); fg_setmode(old_mode); fg_reset(); } You also can retrieve the character or attribute stored in a specific character cell. The Fastgraph routine fg_getchar retrieves character values, while fg_getattr retrieves character attributes. Both routines have two integer arguments that specify the (row,column) coordinates for the character cell of interest. Example 7-4 uses fg_getchar and fg_getattr to obtain the character and attribute stored at row 24, column 0. Just before the program exits, it displays these values. Example 7-4. #include <fastgraf.h> #include <stdio.h> void main(void); void main() { int attr, value; int old_mode; old_mode = fg_getmode(); fg_setmode(3); fg_cursor(0); fg_setattr(9,7,0); fg_locate(24,0); fg_text("Test",4); value = fg_getchar(24,0); attr = fg_getattr(24,0); fg_waitkey(); fg_setmode(old_mode); fg_reset(); printf("%c %2.2X\n",value,attr); } If you need to retrieve characters and attributes from a rectangular area, it's more efficient to use the fg_getimage routine (described in Chapter 10) than to call fg_getchar and fg_getattr repeatedly. Displaying hardware characters in graphics video modes is quite different from doing so in text modes. Like text modes, we can still use fg_text to display strings in character space, which of course restricts the places where strings can appear. Graphics modes offer the ability to display strings relative to any pixel, not just character cells. The fg_print and fg_justify routines are provided for this purpose. To compare the two 134 Fastgraph User's Guide methods of displaying strings in graphics modes, let's begin with an example of doing so with fg_text. Example 7-5 is similar to example 7-1, but it runs in the EGA enhanced graphics mode (mode 16) instead of a text mode. In graphics modes, the fg_cursor routine has no effect, so we have omitted it from the program. Furthermore, characters cannot be displayed with a blinking attribute, so we have omitted the blinking characters (we could simulate blinking by repetitively displaying and erasing them, but that is beyond the scope of this example). Because graphics mode characters only have a foreground color, we had to simulate the gray background of the "Press any key" string by first drawing a rectangle where that string appears. The differences between examples 7-5 and 7-1 hold for any graphics video mode, not just mode 16. Example 7-5. #include <fastgraf.h> void main(void); void main() { int old_mode; old_mode = fg_getmode(); fg_setmode(16); fg_setcolor(14); fg_text("yellow",6); fg_setcolor(10); fg_text(" green",6); fg_setcolor(7); fg_rect(0,127,336,349); fg_setcolor(12); fg_locate(24,0); fg_text(" Press any key. ",16); fg_waitkey(); fg_setmode(old_mode); fg_reset(); } Now let's show how to display graphics mode strings using the more flexible screen space coordinate system. The fg_print routine is identical to fg_text, but it displays a string relative to the graphics cursor position (that is, in screen space) rather than the character space position established with fg_locate. By default, fg_print displays strings so their lower left corner is at the graphics cursor position. The fg_justify routine lets you change this default justification. Its two parameters, xjust and yjust, control the string positioning about the current graphics position, as summarized in the following table: value of value of horizontal vertical xjust yjust justification justification Chapter 7: Character Display Routines 135 -1 -1 left lower -1 0 left center -1 1 left upper 0 -1 center lower 0 0 center center 0 1 center upper 1 -1 right lower 1 0 right center 1 1 right upper Any other justification values produce undefined results. In the context of vertical justification, lower justification means the bottom of each character will be at the current graphics y position. Upper justification means the top of each character will be at the graphics y position, while center justification means characters will be centered about the graphics y position. Note that the default justification settings are xjust = -1 and yjust = -1. The fg_print routine leaves the graphics cursor positioned just beyond the bottom right corner of the last character displayed. Example 7-6 illustrates the use of fg_print and fg_justify to display justified text in the VGA 640 by 480 16-color graphics mode (mode 18). The first series of calls to fg_move, fg_justify, and fg_print display the string "Fastgraph" left justified, centered, and right justified against the top row of the screen. The second series of such calls also displays the string in these positions, but each is centered vertically in the middle of the screen. The final series displays the strings against the bottom row of the screen. The nine calls to fg_justify in example 7-6 represent all possible justification settings for strings displayed with fg_print. Example 7-6. #include <fastgraf.h> void main(void); void main() { int old_mode; old_mode = fg_getmode(); fg_setmode(18); fg_setcolor(9); fg_fillpage(); fg_setcolor(14); fg_move(0,0); fg_justify(-1,1); fg_print("Fastgraph",9); fg_move(320,0); fg_justify(0,1); fg_print("Fastgraph",9); fg_move(639,0); fg_justify(1,1); fg_print("Fastgraph",9); fg_move(0,240); fg_justify(-1,0); 136 Fastgraph User's Guide fg_print("Fastgraph",9); fg_move(320,240); fg_justify(0,0); fg_print("Fastgraph",9); fg_move(639,240); fg_justify(1,0); fg_print("Fastgraph",9); fg_move(0,479); fg_justify(-1,-1); fg_print("Fastgraph",9); fg_move(320,479); fg_justify(0,-1); fg_print("Fastgraph",9); fg_move(639,479); fg_justify(1,-1); fg_print("Fastgraph",9); fg_waitkey(); fg_setmode(old_mode); fg_reset(); } Example 7-7 demonstrates a side effect that occurs when displaying characters in graphics modes. This example uses the MCGA graphics mode (mode 19) and displays two character strings at the same location. If we were to do this in a text mode, the first string would disappear once we displayed the second string. In graphics modes, however, the portions of the first string not covered by characters from the second string are still visible. The reason for this may not be clear at first, but remember when we display characters in graphics modes, we aren't really displaying characters but merely a pixel representation of the characters. Fastgraph has no way to distinguish such pixels from any other pixels, no matter if we use fg_text or fg_print for string display. Example 7-7. #include <fastgraf.h> void main(void); void main() { int old_mode; old_mode = fg_getmode(); fg_setmode(19); fg_setcolor(14); fg_text("yellow",6); fg_locate(0,0); fg_setcolor(10); fg_text(" green",6); fg_waitkey(); fg_setmode(old_mode); fg_reset(); } Chapter 7: Character Display Routines 137 To avoid this problem, the recommended procedure for displaying characters in graphics modes is to first erase the area where the text will appear. The easiest way to do this is to use the fg_rect routine to draw a rectangle in the background color. In example 7-7, we could do this by inserting the statements fg_setcolor(0); fg_rect(0,47,0,7); immediately before the call to fg_locate. The parameters passed to the fg_rect routine represent the 48 by 8 pixel region that corresponds to the first six character cells of row 0 in the 320 by 200 graphics modes. Character Height In VGA and SVGA graphics modes (modes 17 to 29), it's possible to change the height of characters displayed with fg_print or fg_text. By default, characters are 16 pixels high in the VGA and SVGA graphics modes (17, 18, 24 to 29) and 8 pixels high in the MCGA and XVGA graphics modes (19 to 23). The fg_fontsize routine lets you display characters from the BIOS 8x8, 8x14, or 8x16 fonts in any of these modes. Its only parameter specifies the character height in pixels; it must be 8, 14, or 16. If the character height is some other value, or if fg_fontsize is used in a video mode numbered 16 or less (that is, in a non-VGA mode), nothing happens. When we change the character height with fg_fontsize, the number of text rows on the screen changes accordingly. The following table shows the number of text rows available in each supported video mode when using the different character sizes. The values in boldface type represent the default character size and number of rows for that video mode. Mode No. of rows with Number 8x8 8x14 8x16 17 60 34 30 18 60 34 30 19 25 14 12 20 25 14 12 21 50 28 25 22 30 17 15 23 60 34 30 24 50 28 25 25 60 34 30 26 75 42 37 27 96 54 48 28 75 42 37 29 96 54 48 Example 7-8 shows how to use fg_fontsize to activate the 8x8 character font in the 16-color 640 by 480 VGA graphics mode (mode 18). In this mode, characters displayed with fg_print or fg_text are normally 16 pixels high, 138 Fastgraph User's Guide giving 30 character rows per screen. When we use the 8x8 font, this increases to 60 rows because the characters are now half as tall as before. The example program uses fg_text to display the string "8x8 ROM font" 60 times, once in each row. Example 7-8. #include <fastgraf.h> void main(void); void main() { int old_mode; int row; old_mode = fg_getmode(); fg_setmode(18); fg_setcolor(9); fg_fillpage(); fg_setcolor(15); fg_fontsize(8); for (row = 0; row < 60; row++) { fg_locate(row,34); fg_text("8x8 ROM font",12); } fg_waitkey(); fg_setmode(old_mode); fg_reset(); } Conversion Routines In Chapter 4 we introduced Fastgraph's routines for converting coordinates between character space and screen space. In this section we'll review these routines and then present an example that uses some of them. The fg_xalpha and fg_yalpha routines convert screen space coordinates to character space. The fg_xalpha routine converts a screen space x coordinate to the character space column that contains the coordinate. Similarly, the fg_yalpha routine converts a screen space y coordinate to the character space row that contains the coordinate. The fg_xconvert and fg_yconvert routines convert character space coordinates to screen space. The fg_xconvert routine converts a character space column to the screen space coordinate of its leftmost pixel. Similarly, the fg_yconvert routine converts a character space row to the screen space coordinate of its top (lowest-numbered) pixel. Example 7-5 demonstrated how to display characters in a graphics mode. Because characters do not have a background color in graphics modes, that example used fg_rect to simulate a background color by drawing a gray rectangle before displaying the text. It was necessary to determine the Chapter 7: Character Display Routines 139 screen coordinates of the character cells so we could pass the correct parameters to fg_rect. By using the fg_xconvert and fg_yconvert routines, we can let Fastgraph calculate the required screen coordinates. This method has the additional benefit of working in any graphics mode, whereas the coordinates passed to fg_rect in example 7-5 would only work properly in a 640 by 350 graphics mode. Example 7-9 shows how we could extend example 7-5 to use the fg_xconvert and fg_yconvert routines. Example 7-9. #include <fastgraf.h> void main(void); void main() { int old_mode; int minx, maxx, miny, maxy; fg_old_mode = fg_getmode(); fg_setmode(16); fg_setcolor(14); fg_text("yellow",6); fg_setcolor(10); fg_text(" green",6); fg_setcolor(7); minx = fg_xconvert(0); maxx = fg_xconvert(16) - 1; miny = fg_yconvert(24); maxy = fg_yconvert(25) - 1; fg_rect(minx,maxx,miny,maxy); fg_setcolor(12); fg_locate(24,0); fg_text(" Press any key. ",16); fg_waitkey(); fg_setmode(old_mode); fg_reset(); } Software Characters Software characters, also called stroke characters or vector characters in other literature, are only are available in graphics video modes. Unlike the fixed-size hardware characters, you can display software characters in any size, at any angle, and at any position. In addition, software characters are proportionally spaced. However, software characters take longer to draw than do hardware characters. Fastgraph includes two software character fonts, called the primary font and the alternate font. The primary font contains upper and lower case letters, numbers, punctuation, and most of the other printable ASCII 140 Fastgraph User's Guide characters. The alternate font contains upper and lower case Greek letters and other mathematical and scientific symbols. The Fastgraph routine fg_swchar displays a string of software characters in the current color index (as defined by the most recent call to fg_setcolor). The string may contain any characters from the primary font, the alternate font, or both. You can display the characters left justified, centered, or right justified relative to the graphics cursor position. Just as the fg_text routine updates the text cursor position, fg_swchar sets the graphics cursor position just to the right of the last character drawn. The characters are clipped according to the current clipping region. In addition to the characters, the string passed to fg_swchar also may contain operators for switching fonts, underlining, subscripting, or superscripting characters. Because fg_swchar internally uses world space coordinates, you must call the fg_initw routine at some point in your program before the first call to fg_swchar. You also must establish a world space coordinate system with the fg_setworld routine. The fg_swchar routine has three arguments. The first argument is the character string to display. The second argument is an integer value that specifies the number of characters in the string, including any characters used as special operators. The third argument is an integer value that determines the position of the string relative to the graphics cursor position. If this value is negative, the lower left corner of the first character will be at the graphics cursor position. If it is positive, the lower right corner of the last character will be at the graphics cursor position. If it is zero, the string will be horizontally centered at the graphics cursor position. The size of software characters is determined by the values passed to the fg_setsize, fg_setsizew, and fg_setratio routines. The fg_setsize routine has a single integer argument that defines the height of software characters in screen space units, while the fg_setsizew routine has a single floating point argument that defines the height in world space units. If neither of these routines is called, Fastgraph will use its default character height of one world space unit. The fg_setratio routine has a single floating point argument that defines the aspect ratio for software characters. The aspect ratio is the ratio of character width to character height. For example, an aspect ratio of 2.0 means characters are twice as wide as they are high. If the fg_setratio routine is not called, Fastgraph uses its default aspect ratio of 1. Example 7-10 displays both of the software character fonts. The program uses the enhanced EGA graphics mode (mode 16), but it could run in any graphics mode by changing the fg_setmode argument. After establishing the video mode, the program calls the fg_initw routine to initialize Fastgraph's world space parameters; this is required since the software character drawing routines internally use world space coordinates. The next statement is a call to fg_setworld that establishes a world space coordinate system with 0.01 world space units per pixel. Following this is a call to fg_setsizew that defines the character height as 0.21 world space units, or 21 pixels. Note we could have instead used the fg_setsize routine here with an integer argument of 21. The next part of the program draws the characters in the primary font on the upper half of the screen. After doing this, the program draws the alternate font characters on the lower half. In each case it does this with Chapter 7: Character Display Routines 141 the fg_swchar routine. By default, the string passed to fg_swchar will produce characters from the primary font. However, you can insert a back slash character (\) in the string to toggle between the two fonts. Don't forget the C language applies a special meaning to the back slash character within strings, so you must use two consecutive back slashes to insert a single back slash in the string. Example 7-10. #include <fastgraf.h> void main(void); void main() { int old_mode; old_mode = fg_getmode(); fg_setmode(16); fg_initw(); fg_setworld(0.0,6.39,0.0,3.49); fg_setsizew(0.21); fg_setcolor(15); fg_locate(0,26); fg_text("Software characters - font 1",28); fg_setcolor(10); fg_movew(0.0,3.1); fg_swchar("ABCDEFGHIJKLMNOPQRSTUVWXYZ",26,-1); fg_movew(0.0,2.8); fg_swchar("abcdefghijklmnopqrstuvwxyz",26,-1); fg_movew(0.0,2.5); fg_swchar("0123456789",10,-1); fg_movew(0.0,2.2); fg_swchar("!\"#$%&'()*+,-./:;<=>?[]^`{|}~",29,-1); fg_setcolor(15); fg_locate(12,26); fg_text("Software characters - font 2",28); fg_setcolor(10); fg_movew(0.0,1.4); fg_swchar("\\ABCDEFGHIJKLMNOPRSTUWXYZ",25,-1); fg_movew(0.0,1.1); fg_swchar("\\abcdefghijklmnoprstuwxyz",25,-1); fg_movew(0.0,0.4); fg_swchar("\\012345678#$%&()*+/<=>?[]{}",27,-1); fg_waitkey(); fg_setmode(old_mode); fg_reset(); } Example 7-10 displays all characters in each font. If you compare the primary font strings with the alternate font strings, you'll see the alternate font contains fewer characters. For example, the letters Q and V 142 Fastgraph User's Guide (either upper or lower case) have no corresponding character in the alternate font. You might have also noticed the primary font does not support the full printable ASCII character set. Any character in a string passed to the fg_swchar routine that does not have a corresponding character in the current font will display a blank character. In addition to the font change operator (the back slash character), fg_swchar recognizes three other operators. The superscript operator is a back slash followed by a caret (\^). It causes the next character to appear as a superscript. Similarly, the subscript operator is a back slash followed by a lower case v (\v); it causes the next character to appear as a subscript. The size of superscripted and subscripted characters is one half the height of the other characters. The underline operator is the underscore character (_). It causes all subsequent characters in the string to be underlined until another underscore character is found, or until the end of the string. When using these operators, be sure to include them as part of the string length count passed to fg_swchar. Example 7-11 illustrates the use of the font selection, superscript, subscript, and underline operators with the fg_swchar routine. Again, because the back slash character has a special meaning to the C programming language, we must use two consecutive back slashes to represent a single back slash within the string. The program displays four strings: cos˝È + sin˝È = 1 H2O U232 One word is underlined. The theta symbol (È) in the first string is produced by displaying the character "h" in the alternate font. Note another font selection operator (\) appears immediately after the "h" to revert to the primary font. The first string also includes superscript operators (\^) to display the exponents in the equation. The second string includes a single subscripted character, while the third string shows how to display three consecutive subscripted characters. Finally, the fourth string illustrates how to underline characters. Note example 7-11 also uses the fg_setratio routine. The first three strings are drawn with an aspect ratio of 2, making them twice as wide as they are high. The fourth string is drawn with an aspect ratio of 1 (Fastgraph's default aspect ratio for software characters), so the character height is the same as the character width. Also, the strings are centered instead of left justified as in the previous example. Example 7-11. #include <fastgraf.h> void main(void); void main() { int old_mode; old_mode = fg_getmode(); fg_setmode(16); Chapter 7: Character Display Routines 143 fg_setcolor(10); fg_initw(); fg_setworld(0.0,6.39,0.0,3.49); fg_setratio(2.0); fg_setsizew(0.21); fg_movew(3.2,3.0); fg_swchar("cos\\^2\\h\\ + sin\\^2\\h\\ = 1",25,0); fg_movew(3.2,2.0); fg_swchar("H\\v2O U\\v2\\v3\\v2",18,0); fg_movew(3.2,1.0); fg_setratio(1.0); fg_swchar("One _word_ is underlined.",25,0); fg_waitkey(); fg_setmode(old_mode); fg_reset(); } The fg_setangle routine defines the angle or orientation at which software characters are displayed. Its only argument is a floating point value that specifies the angle, measured in degrees counterclockwise from the positive x axis. If a program draws software characters before calling fg_setangle, Fastgraph will use its default angle of zero degrees (that is, the characters will be oriented horizontally). In most programs, the alternate font is not needed. However, if you use the fg_swchar routine, Fastgraph will include the definitions of these characters in your program's data segment. To prevent wasting this space, Fastgraph includes the fg_swtext routine. The fg_swtext routine is same as the fg_swchar routine, except it does not include the alternate font. Since the font selection operator does not apply when using fg_swtext, the routine simply ignores it. You should only use fg_swtext if do not use fg_swchar. If you use both routines, your program will still work correctly, but its data segment will contain an extra copy of the primary font definitions. Example 7-12 demonstrates the use of the fg_setangle and fg_swtext routines. The program draws a series of strings of the form "nnn degrees", where nnn is a multiple of 15, radiating from the screen center. Each string appears at the specified angle. For example, the string "15 degrees" is drawn at an angle of 15 degrees. Example 7-12. #include <fastgraf.h> void main(void); void main() { char string[24]; int angle; int old_mode; old_mode = fg_getmode(); fg_setmode(16); 144 Fastgraph User's Guide fg_setcolor(10); fg_initw(); fg_setworld(0.0,6.39,0.0,3.49); fg_setsizew(0.21); for (angle = 0; angle < 360; angle += 15) { fg_movew(3.2,1.75); fg_setangle((double)angle); sprintf(string," %3d degrees",angle); fg_swtext(string,16,-1); } fg_waitkey(); fg_setmode(old_mode); fg_reset(); } The final routine pertaining to software characters is fg_swlength, which returns the length of a specified string of software characters in world space units. The length is returned as the routine's floating point function value. The fg_swlength routine has two arguments -- a string of software characters, and an integer value specifying the number of characters in the string. As with fg_swchar and fg_swtext, the count includes any of the special operator characters. Example 7-13 demonstrates a typical use of the fg_swlength routine. The program displays the string "hello there." in light green against a gray background in the middle of the screen. As in our previous software character examples, the program uses mode 16 and first performs the necessary initializations to use software characters. Following this, the program uses the fg_swlength routine to compute the length in world space units of the string. Note we have added blank characters to each end of the string passed to fg_swlength; this increases the length of the actual string and will effectively give the gray rectangle an extended border on its left and right sides. The string length returned by fg_swlength is multiplied by 0.5, giving the distance from the middle of the screen to either side of the rectangle. The program then uses this value to compute the minimum and maximum x coordinates passed to fg_rectw. After drawing the gray rectangle, the program uses fg_swtext to draw the string of software characters in the middle of the screen. It then waits for a keystroke before restoring the original video mode and screen attributes and returning to DOS. Example 7-13. #include <fastgraf.h> void main(void); void main() { int old_mode; double half; double fg_swlength(); old_mode = fg_getmode(); fg_setmode(16); fg_initw(); Chapter 7: Character Display Routines 145 fg_setworld(0.0,6.39,0.0,3.49); fg_setsizew(0.21); fg_setcolor(7); half = fg_swlength(" Hello there. ",14) * 0.5; fg_rectw(3.2-half,3.2+half,1.6,1.9); fg_setcolor(10); fg_movew(3.2,1.65); fg_swtext("Hello there.",12,0); fg_waitkey(); fg_setmode(old_mode); fg_reset(); } Bit-Mapped Characters Bit-mapped characters combine the properties of hardware and software characters. Like hardware characters, they are a fixed size, but they are almost always more visually appealing. Because they are not scalable, they do not require floating point arithmetic, and therefore they are much faster than software characters. Fastgraph makes no special provision for bit-mapped characters because it treats them as if they were any other bit-mapped image. For example, to use a five-pixel by five-pixel bit-mapped font, you can construct characters as shown below and then store these representations in an image array. * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * The image display routines fg_drawmap and fg_drwimage, discussed in Chapter 10, could then be used to display specific characters from the image array. Also, the Fastgraph/Fonts add-on product greatly simplifies adding bit- mapped font support to Fastgraph applications. Summary of Character Display Routines This section summarizes the functional descriptions of the Fastgraph routines presented in this chapter. More detailed information about these routines, including their arguments and return values, may be found in the Fastgraph Reference Manual. FG_CHGATTR applies the current text display attribute to a given number of characters, starting at the text cursor position. This routine leaves the text cursor one column to the right of the last character changed (or the first column of the next row if the last character is at the end of a row). It has no effect in graphics video modes. 146 Fastgraph User's Guide FG_CHGTEXT displays a string of hardware characters, starting at the text cursor position, using the existing text display attributes. This routine leaves the text cursor one column to the right of the last character displayed (or the first column of the next row if the last character is at the end of a row). It has no effect in graphics video modes. FG_FONTSIZE enables the 8x8, 8x14, or 8x16 ROM BIOS character font for strings displayed with fg_print and fg_text. This routine is meaningful only in VGA and SVGA graphics video modes. FG_GETATTR returns the character attribute stored at the specified position on the active video page. It has no effect in graphics video modes. FG_GETCHAR returns the character value stored at the specified position on the active video page. It has no effect in graphics video modes. FG_JUSTIFY defines the horizontal and vertical justification settings for strings displayed with the fg_print. FG_LOCATE establishes the text cursor position for the active video page. FG_PRINT displays a string of hardware characters, relative to the graphics cursor position, using the current color index. By default, strings are displayed such that the bottom row of the first character is at the current graphics position. On return, the graphics cursor is positioned just to the right of the last character displayed. FG_SETANGLE defines the angle or orientation at which software characters are displayed. The angle is measured in degrees counterclockwise from the positive x axis. FG_SETATTR establishes the current text display attribute in text video modes. This routine has no effect in graphics video modes. FG_SETCOLOR establishes the current color index (which may be a virtual color index in graphics modes). In text modes, the fg_setcolor routine provides an alternate method of establishing the current text display attribute. FG_SETRATIO defines the aspect ratio for software characters. The aspect ratio is the ratio of character width to character height. FG_SETSIZE defines the height of software characters in screen space units. FG_SETSIZEW defines the height of software characters in world space units. FG_SWCHAR displays a string of software characters using the current color index. The string may be left justified, centered, or right justified relative to the graphics cursor position. The string passed to fg_swchar may contain special operators that allow switching between fonts, underlining, superscripting, or subscripting. This routine has no effect in text video modes. Chapter 7: Character Display Routines 147 FG_SWLENGTH returns the length in world space units of a string of software characters. FG_SWTEXT is a scaled down version of the fg_swchar routine. It does not include the alternate font character definitions and thus requires less memory than fg_swchar. FG_TEXT displays a string of hardware characters, starting at the text cursor position, using the current color attribute (for text modes) or color index (for graphics modes). This routine leaves the text cursor one column to the right of the last character displayed (or the first column of the next row if the last character is at the end of a row). FG_WHERE retrieves the row and column numbers of the text cursor position. FG_XALPHA and FG_YALPHA convert screen space coordinates to character space. FG_XCONVERT and FG_YCONVERT convert character space coordinates to screen space. 148 Fastgraph User's Guide