As independent programs, TealPrint printer drivers can still be launched from the Palm applications launcher. Normally, they only need put up some useful "About" information and perhaps offer options to do some debugging or print a test page.
TealPrint's print engine handles the majority of print-oriented tasks, including rendering, rotating, effects, and text wrapping. Drivers only need know how to send a prerendered bitmap raster row or text line (if applicable), and maintain current information about the current print mode and paper settings, and are responsible communicating with the printer hardware.
typedef struct {
// where to return success to the print engine.
// 0 = success
// nonzero = error or abort
long retval;
int cols; // total number of columns to print
int lines; // total number of text lines to print
int blank_lines; // number of blank lines before printed lines
int blank_cols; // number of blank columns before printed columns
// function pointer used by driver to fetch text for printing
void (*getline_func)(
char **text, // returned text pointer to text data
int line, // text line to get, starting at blank_lines
int *offset, // returned starting column where text goes
int *count, // returned count of text characters
void *data ); // pass copy of app_data, below
void *app_data; // data to pass through to getline_func()
long print_flags; // special print flags
int mode_number; // text mode to use
int paper_number; // paper number to use
} DriverPrintTextType;
A typical driver goes into a loop for each line of text after sending the blank lines to the
printer. For each line, it calls getline_func() to fetch the text for that
line and translates it, if necessary, and sends it to the printer. For most
printers, this routine can be nearly identical to that in the default drivers.
typedef struct {
// where to return success to the print engine.
// 0 = success
// nonzero = error or abort
long retval;
int width; // width in pixels of bitmap to render
int height; // height in pixels of the bitmap to render
int blank_lines; // number of blank rows to offset image from top
int blank_cols; // number of blank columns to offset image from left
// Call this function to get a row of pixel data
void (*getraster_func)(
unsigned char **targ, // returned pointer to bitmap data
int line, // index to pixel row, starting at blank_lines
int offset, // offset of pixel columen to get
int count, // count of pixels to get
void *data, // pass copy of app_data
unsigned char bgcolor ); // value for white, typically 0 or 255
void *app_data; // value to pass to getraster_func()
long print_flags; // print flags
int mode_number; // graphic mode to print
int paper_number; // paper number to use
} DriverPrintBitmapType;
A typical driver goes into a loop for each row of graphics after sending the blank rows to the
printer. For each line, it calls getraster_func() to fetch the bits for that
line and translates it, if necessary, then sending it to the printer. The
basic graphics routines send black and white graphical data one bit per pixel,
with the MSB (most significant byte) to LSB (least signicant byte). For printers
that expect the data in other formats, the bits may need to be processed and/or
reordered.
TealPoint Software Staff