Calculate baseline for outline font.

getbaseline.c

#include <diskfont/diskfont.h>
#include <diskfont/diskfonttag.h>
#include <diskfont/glyph.h>
#include <proto/diskfont.h>
#include <stdio.h>

int main(int argc, char **argv) {
	struct OutlineFont *olf;
	const uint32 devdpi = (72 << 16) | 72;
	const uint32 ysize  = 16;
	uint32 charset;
	uint32 maptable[256];
	uint32 code;
	int32  error;
	int32  yorigin;
	int32  ascent, descent;
	int32  baseline;
	struct GlyphMap *gm;

	if (argc != 2) {
		printf("Usage: getbaseline <font>\n");
		return RETURN_ERROR;
	}

	/* Use system default charset */
	charset = IDiskfont->GetDiskFontCtrl(DFCTRL_CHARSET);

	/* Get mapping table */
	if (charset == 4) {
		/* ISO 8859-1 Latin1 */
		for (code = 0; code < 256; code++) {
			maptable[code] = code;
		}
	} else {
		const uint32 *src;
		src = (const uint32 *)IDiskfont->ObtainCharsetInfo(DFCS_NUMBER, charset, DFCS_MAPTABLE);
		if (src == NULL) {
			fprintf(stderr, "Mapping table not found for charset: %lu!\n", charset);
			return RETURN_ERROR;
		}
		for (code = 0; code < 256; code++) {
			maptable[code] = src[code];
		}
	}

	/* Open outline font */
	olf = IDiskfont->OpenOutlineFont(argv[1], NULL, OFF_OPEN);
	if (olf == NULL) {
		printf("Failed to open font '%s'!\n", argv[1]);
		return RETURN_ERROR;
	}

	/* Set DPI and point height */
	error = IDiskfont->ESetInfo(&olf->olf_EEngine,
		OT_DeviceDPI,   devdpi,
		OT_PointHeight, ysize << 16,
		TAG_END);
	if (error) {
		printf("Failed to set DPI and point height!\n");
		IDiskfont->CloseOutlineFont(olf, NULL);
		return RETURN_ERROR;
	}

	ascent = descent = 0;

	/* Set ascent and descent according to glyph dimensions */
	for (code = 0; code < 256; code++) {
		error = IDiskfont->ESetInfo(&olf->olf_EEngine,
			OT_GlyphCode, maptable[code],
			TAG_END);
		if (error)
			continue;

		error = IDiskfont->EObtainInfo(&olf->olf_EEngine,
			OT_GlyphMap8Bit, &gm,
			TAG_END);
		if (error)
			continue;

		if (gm->glm_BlackWidth) {
			yorigin = gm->glm_Y0;

			if (ascent < (yorigin - gm->glm_BlackTop))
				ascent = yorigin - gm->glm_BlackTop;

			if (descent < (gm->glm_BlackTop + gm->glm_BlackHeight - yorigin))
				descent = gm->glm_BlackTop + gm->glm_BlackHeight - yorigin;
		}

		IDiskfont->EReleaseInfo(&olf->olf_EEngine,
			OT_GlyphMap, gm,
			TAG_END);
	}

	/* Calculate baseline from ascent and descent */
	baseline = ascent - 1;
	if ((ascent + descent) > ysize)
		baseline -= (ascent + descent - ysize + 1) * 2 / 3;


	printf("Baseline: %ld\n", baseline);

	IDiskfont->CloseOutlineFont(olf, NULL);

	return RETURN_OK;
}