Query availability of features

vga_ext_set(VGA_EXT_AVAILABLE, VGA_AVAIL_SET)

returns an int with the i-th bit set if i is a valid what parameter for vga_ext_set().

vga_ext_set(VGA_EXT_AVAILABLE, VGA_AVAIL_ACCEL)

returns an integer with the i-th bit set if i is a valid what parameter for vga_accel(3). For nicer code, the following integers are predefined to have a bit set in the right position:

ACCELFLAG_FILLBOX, ACCELFLAG_SCREENCOPY, ACCELFLAG_PUTIMAGE, ACCELFLAG_DRAWLINE, ACCELFLAG_SETFGCOLOR, ACCELFLAG_SETBGCOLOR, ACCELFLAG_SETTRANSPARENCY, ACCELFLAG_SETRASTEROP, ACCELFLAG_PUTBITMAP, ACCELFLAG_SCREENCOPYBITMAP, ACCELFLAG_DRAWHLINELIST, ACCELFLAG_SETMODE, and ACCELFLAG_SYNC.

vga_ext_set(VGA_EXT_AVAILABLE, VGA_AVAIL_ROP)

returns an integer as VGA_AVAIL_ACCEL does, but this time listing the vga_accel(3) operations which obey a vga_accel(ACCEL_SETRASTEROP, ...) setting.

vga_ext_set(VGA_EXT_AVAILABLE, VGA_AVAIL_TRANSPARENCY)

returns an integer as VGA_AVAIL_ACCEL does, but this time listing the vga_accel(3) operations which obey a vga_accel(ACCEL_SETTRANSPARENCY, ...) setting.

vga_ext_set(VGA_EXT_AVAILABLE, VGA_AVAIL_ROPMODES)

returns an integer with the i-th bit set if i is a valid mode parameter for a vga_accel(ACCEL_SETRASTEROP, mode) call. For example:

vga_ext_set(VGA_EXT_AVAILABLE, VGA_AVAIL_TRANSMODES)

returns an integer with the i-th bit set if i is a valid mode parameter for a vga_accel(ACCEL_SETTRANSPARENCY, mode, ...) call. The function lists only the supported enable functions (currently ENABLE_TRANSPARENCY_COLOR and ENABLE_BITMAP_TRANSPARENCY). It is assumed the corresponding disable functions will then exist as well.

vga_ext_set(VGA_EXT_AVAILABLE, VGA_AVAIL_FLAGS)

returns an int with one bit on/off flags. Bits that are set are supported refer to special features which can be enabled in the current mode.

Operations with one bit flags

You can always set flags, and their settings are remembered if not supported in the current mode. This is to avoid problems when switching VC's.

vga_ext_set(VGA_EXT_SET, int bitflags)

set all flags that are set in bitflags, do not touch any other flags. Returns previous setting of all flags.

vga_ext_set(VGA_EXT_CLEAR, int bitflags)

clear all flags that are set in bitflags, do not touch any other flags. Returns previous setting of all flags.

vga_ext_set(VGA_EXT_RESET, int bitflags)

set all flags to the corresponding bits of bitflags. Returns previous setting of all flags.

One bit flags for special features

VGA_CLUT8

which is set by calling vga_ext_set(VGA_EXT_SET, VGA_CLUT8). This makes the color lookup table for 16 and 256 color lookup table modes work with 8 bit per red, green, blue part instead of the ordinary 6 bits.

As of now this feature is only availabl for Mach32 cards with type 2 DAC's. 8 bit per red, green, blue wide in all (even VGA) 256 color modes. This mean, however, that all calls to vga_setpalette(3) and vga_setpalvec(3) need to be adjuste accordingly as well as that the interpretation of the return values of vga_getpalette(3) and vga_getpalvec(3) changes.

The testaccel(6) demos makes use of this to show a smooth 256 blue shades scale.

Miscanellous features

vga_ext_set(VGA_EXT_PAGE_OFFSET, int offset)

for all following vga_set*page(n) calls (even those implicitly done by svgalib drawing functions) do vga_set*page(n + offset) instead. This is very nice for drawing in an offscreen area. However, it requires the mode being able to use more than one page at all as well as not having called vga_setlinearaddressing(3).

A better approach would be to just use higher y values for all draw operations to have them end up in offscreen regions that may be displayed later (cf. vga_setdisplaystart(3)).

The previously set value for VGA_EXT_PAGE_OFFSET (which defaults to 0 at startup) is returned.

vga_ext_set(VGA_EXT_FONT_SIZE, int size)

sets the size of the buffer which the application passes to vga_gettextfont(3) and vga_puttextfont(3). Old versions of svgalib used a fixed size of 8192 which is still the default. Newer versions of svgalib use a larger size internally to properly support the extended font capabilities of newer kernels.

Calling vga_ext_set(VGA_EXT_FONT_SIZE, 0) returns the size of the internal buffers of svgalib. It is recommended to use this (or a larger size) for any font (re)storing application. If this differs from the size of the applications buffers set vga_gettextfont(3) and vga_puttextfont(3) truncate and zero-pad all buffers accordingly.

Otherwise the previously set buffer size is returned.