Libvgl is a library that enables the programmer access to the graphics modes supported by the console driver (syscons). The library takes care of programming the actual video hardware, and provides a number of simple functions to do various graphic operations. There is also support for a mouse via the standard mouse system in
.Fx , see mouse(4), including the ability to transparently have a mouse pointer superimposed on the graphic image currently being worked on. The library takes care of screen switching by storing the current image in memory before switching to another virtual console, and restoring when the user switches back. This allows several graphic applications at once, but on different virtual consoles.
Below is a short description of the various functions:
VGLInit initialize the library and set up the graphic mode mode.
VGLEnd terminate graphic mode, and restore the screenmode that was active before VGLInit was called.
VGLCheckSwitch if the program goes into longer periods of processing without doing any graphics output, calling this function occasionally will allow the system to switch screens.
VGLTextSetFontFile instruct the char/string functions to use the font in file filename instead of the builtin font.
VGLKeyboardInit set up the keyboard in the "raw" I/O mode and specify the key code to be used. code must be VGL_XLATEKEYS, VGL_CODEKEYS, or VGL_RAWKEYS. When VGL_XLATEKEYS is specified, the keyboard translates the raw keyboard scan code into a character code. If VGL_RAWKEYS is used, the raw keyboard scan code is read as is. VGL_CODEKEYS is the intermediate key code; each key is assigned a unique code whereas more than one raw scan code may be generated when a key is pressed.
VGLKeyboardEnd when you have finished using the keyboard, call this function.
VGLKeyboardGetCh read one byte from the keyboard. As the keyboard I/O is in the "raw" input mode, the function will not block even if there is no input data, and returns 0.
VGLMouseInit initialize the mouse. The optional on-screen mouse pointer is shown if the argument is VGL_MOUSESHOW.
VGLMouseMode either shows the mouse pointer if the argument is VGL_MOUSESHOW, or hides the mouse pointer if the argument is VGL_MOUSEHIDE.
VGLMouseStatus returns the current mouse pointer coordinates and button state in x, y, buttons. The return value reflects if the mouse pointer is currently shown on screen or not.
VGLMouseSetImage with this function it is possible to change the image of the mouse pointer on screen.
VGLMouseSetStdImage this function restores the mouse pointer to the standard arrow.
VGLGetXY retrieves the color of the pixel located at x, y, coordinates of the object argument, and returns it as a byte value.
VGLSetXY sets the color of the pixel located at x, y, coordinates of the object argument to color byte value.
VGLLine draw a line from x1, y1 to x2, y2 in color color.
VGLBox draw a box with upper left hand corner at x1, y1 and lower right hand corner at x2, y2 in color color.
VGLFilledBox draw a filled (solid) box with upper left hand corner at x1, y1 and lower right hand corner at x2, y2 in color color.
VGLEllipse draw an ellipse centered at xc, yc make it a pixels wide, and b pixels high in color color.
VGLFilledEllipse draw a filled (solid) ellipse centered at xc, yc make it a pixels wide, and b pixels high in color color.
VGLBitmapCreate create a bitmap object and initialize it with the specified values and bit data. type must be MEMBUF for the in-memory bitmap. bits may be NULL so that bitmap data may be associated later.
There also is a macro, VGLBITMAP_INITIALIZER "type" "xsize" "ysize" "bits" to initialize a statically declared bitmap object.
VGLBitmapDestroy free the bitmap data and the bitmap object.
VGLBitmapAllocateBits allocate a bit data buffer for the specified object.
VGLBitmapCopy copy a rectangle of pixels from bitmap src upper left hand corner at srcx, srcy to bitmap dst at dstx, dsty of the size width, height.
VGLBitmapPutChar write the character ch at position x, y in foreground color fgcol. If fill is != 0, use the color bgcol as background otherwise the background is transparent. The character is drawn in the direction specified by the argument dir.
VGLBitmapString write the string str at position x, y in foreground color fgcol. If fill is != 0, use the color bgcol as background otherwise the background is transparent. The string is drawn in the direction specified by the argument dir.
VGLClear clears the entire bitmap to color color.
VGLSetPalette this function sets the palette used, the arguments red, green, blue should point to byte arrays of 256 positions each.
VGLSetPaletteIndex set the palette index color to the specified RGB value.
VGLSetBorder set the border color to color color.
VGLSetVScreenSize change the virtual screen size of the display. Note that this function must be called when our vty is in the foreground. And object must be VGLDisplay. Passing an in-memory bitmap to this function results in error.
The desired virtual screen width may not be achievable because of the video card hardware. In such case the video driver (and underlaying video BIOS) may choose the next largest values. Always examine object->VXsize and VYsize after calling this function, in order to see how the virtual screen is actually set up.
In order to set up the largest possible virtual screen, you may call this function with arbitrary large values.
VGLPanSreen change the origin of the displayed screen in the virtual screen. Note that this function must be called when our vty is in the foreground. object must be VGLDisplay. Passing an in-memory bitmap to this function results in error.
VGLBlankDisplay blank the display if the argument blank != 0. This can be done to shut off the screen during display updates that the user should first see when it is done.
Program termination and signal processing
It is important to call VGLEnd before terminating the program. Care must be taken if you install signal handlers and try to call VGLEnd and exit(3) to end the program. If a signal is caught while the program is inside libvgl functions, VGLEnd may not be able to properly restore the graphics hardware.
The recommended way to handle signals and program termination is to have a flag to indicate signals delivery. Your signal handlers set this flag but do not terminate the program immediately. The main part of the program checks the flag to see if it is supposed to terminate, and calls VGLEnd and exit(3) if the flag is set.
Note that VGLInit installs its internal signal handlers for SIGINT, SIGTERM, SIGSEGV, and SIGBUS, and terminates the program at appropriate time, after one of these signals is caught. If you want to have your own signal handlers for these signals, install handlers after VGLInit.
SIGUSR1 and SIGUSR2 are internally used by libvgl to control screen switching and the mouse pointer, and are not available to libvgl client programs.
The vgl library appeared in
.Fx 3.0 .
.An Sren Schmidt Aq sos@FreeBSD.org