libui/unix/drawtext.c

// 6 september 2015
#include "uipriv_unix.h"
#include "draw.h"

struct uiDrawFontFamilies {
	PangoFontFamily **f;
	int n;
};

uiDrawFontFamilies *uiDrawListFontFamilies(void)
{
	uiDrawFontFamilies *ff;
	PangoFontMap *map;

	ff = uiNew(uiDrawFontFamilies);
	map = pango_cairo_font_map_get_default();
	pango_font_map_list_families(map, &(ff->f), &(ff->n));
	// do not free map; it's a shared resource
	return ff;
}

int uiDrawFontFamiliesNumFamilies(uiDrawFontFamilies *ff)
{
	return ff->n;
}

char *uiDrawFontFamiliesFamily(uiDrawFontFamilies *ff, int n)
{
	PangoFontFamily *f;

	f = ff->f[n];
	return uiUnixStrdupText(pango_font_family_get_name(f));
}

void uiDrawFreeFontFamilies(uiDrawFontFamilies *ff)
{
	g_free(ff->f);
	uiFree(ff);
}

struct uiDrawTextFont {
	PangoFont *f;
};

uiDrawTextFont *mkTextFont(PangoFont *f, gboolean ref)
{
	uiDrawTextFont *font;

	font = uiNew(uiDrawTextFont);
	font->f = f;
	if (ref)
		g_object_ref(font->f);
	return font;
}

static const PangoWeight pangoWeights[] = {
	[uiDrawTextWeightThin] = PANGO_WEIGHT_THIN,
	[uiDrawTextWeightUltraLight] = PANGO_WEIGHT_ULTRALIGHT,
	[uiDrawTextWeightLight] = PANGO_WEIGHT_LIGHT,
	[uiDrawTextWeightBook] = PANGO_WEIGHT_BOOK,
	[uiDrawTextWeightNormal] = PANGO_WEIGHT_NORMAL,
	[uiDrawTextWeightMedium] = PANGO_WEIGHT_MEDIUM,
	[uiDrawTextWeightSemiBold] = PANGO_WEIGHT_SEMIBOLD,
	[uiDrawTextWeightBold] = PANGO_WEIGHT_BOLD,
	[uiDrawTextWeightUtraBold] = PANGO_WEIGHT_ULTRABOLD,
	[uiDrawTextWeightHeavy] = PANGO_WEIGHT_HEAVY,
	[uiDrawTextWeightUltraHeavy] = PANGO_WEIGHT_ULTRAHEAVY,
};

static const PangoStyle pangoItalics[] = {
	[uiDrawTextItalicNormal] = PANGO_STYLE_NORMAL,
	[uiDrawTextItalicOblique] = PANGO_STYLE_OBLIQUE,
	[uiDrawTextItalicItalic] = PANGO_STYLE_ITALIC,
};

static const PangoStretch pangoStretches[] = {
	[uiDrawTextStretchUltraCondensed] = PANGO_STRETCH_ULTRA_CONDENSED,
	[uiDrawTextStretchExtraCondensed] = PANGO_STRETCH_EXTRA_CONDENSED,
	[uiDrawTextStretchCondensed] = PANGO_STRETCH_CONDENSED,
	[uiDrawTextStretchSemiCondensed] = PANGO_STRETCH_SEMI_CONDENSED,
	[uiDrawTextStretchNormal] = PANGO_STRETCH_NORMAL,
	[uiDrawTextStretchSemiExpanded] = PANGO_STRETCH_SEMI_EXPANDED,
	[uiDrawTextStretchExpanded] = PANGO_STRETCH_EXPANDED,
	[uiDrawTextStretchExtraExpanded] = PANGO_STRETCH_EXTRA_EXPANDED,
	[uiDrawTextStretchUltraExpanded] = PANGO_STRETCH_ULTRA_EXPANDED,
};

// we need a context for a few things
// the documentation suggests creating cairo_t-specific, GdkScreen-specific, or even GtkWidget-specific contexts, but we can't really do that because we want our uiDrawTextFonts and uiDrawTextLayouts to be context-independent
// we could use pango_font_map_create_context(pango_cairo_font_map_get_default()) but that will ignore GDK-specific settings
// so let's use gdk_pango_context_get() instead; even though it's for the default screen only, it's good enough for us
#define mkGenericPangoCairoContext() (gdk_pango_context_get())

PangoFont *pangoDescToPangoFont(PangoFontDescription *pdesc)
{
	PangoFont *f;
	PangoContext *context;

	// in this case, the context is necessary for the metrics to be correct
	context = mkGenericPangoCairoContext();
	f = pango_font_map_load_font(pango_cairo_font_map_get_default(), context, pdesc);
	if (f == NULL) {
		// LONGTERM
		g_error("[libui] no match in pangoDescToPangoFont(); report to andlabs");
	}
	g_object_unref(context);
	return f;
}

uiDrawTextFont *uiDrawLoadClosestFont(const uiDrawTextFontDescriptor *desc)
{
	PangoFont *f;
	PangoFontDescription *pdesc;

	pdesc = pango_font_description_new();
	pango_font_description_set_family(pdesc,
		desc->Family);
	pango_font_description_set_size(pdesc,
		(gint) (desc->Size * PANGO_SCALE));
	pango_font_description_set_weight(pdesc,
		pangoWeights[desc->Weight]);
	pango_font_description_set_style(pdesc,
		pangoItalics[desc->Italic]);
	pango_font_description_set_stretch(pdesc,
		pangoStretches[desc->Stretch]);
	f = pangoDescToPangoFont(pdesc);
	pango_font_description_free(pdesc);
	return mkTextFont(f, FALSE);			// we hold the initial reference; no need to ref
}

void uiDrawFreeTextFont(uiDrawTextFont *font)
{
	g_object_unref(font->f);
	uiFree(font);
}

uintptr_t uiDrawTextFontHandle(uiDrawTextFont *font)
{
	return (uintptr_t) (font->f);
}

void uiDrawTextFontDescribe(uiDrawTextFont *font, uiDrawTextFontDescriptor *desc)
{
	PangoFontDescription *pdesc;

	// this creates a copy; we free it later
	pdesc = pango_font_describe(font->f);

	// TODO

	pango_font_description_free(pdesc);
}

// See https://developer.gnome.org/pango/1.30/pango-Cairo-Rendering.html#pango-Cairo-Rendering.description
// Note that we convert to double before dividing to make sure the floating-point stuff is right
#define pangoToCairo(pango) (((double) (pango)) / PANGO_SCALE)
#define cairoToPango(cairo) ((gint) ((cairo) * PANGO_SCALE))

void uiDrawTextFontGetMetrics(uiDrawTextFont *font, uiDrawTextFontMetrics *metrics)
{
	PangoFontMetrics *pm;

	pm = pango_font_get_metrics(font->f, NULL);
	metrics->Ascent = pangoToCairo(pango_font_metrics_get_ascent(pm));
	metrics->Descent = pangoToCairo(pango_font_metrics_get_descent(pm));
	// Pango doesn't seem to expose this :( Use 0 and hope for the best.
	metrics->Leading = 0;
	metrics->UnderlinePos = pangoToCairo(pango_font_metrics_get_underline_position(pm));
	metrics->UnderlineThickness = pangoToCairo(pango_font_metrics_get_underline_thickness(pm));
	pango_font_metrics_unref(pm);
}

// note: PangoCairoLayouts are tied to a given cairo_t, so we can't store one in this device-independent structure
struct uiDrawTextLayout {
	char *s;
	ptrdiff_t *graphemes;
	PangoFont *defaultFont;
	double width;
	PangoAttrList *attrs;
};

uiDrawTextLayout *uiDrawNewTextLayout(const char *text, uiDrawTextFont *defaultFont, double width)
{
	uiDrawTextLayout *layout;
	PangoContext *context;

	layout = uiNew(uiDrawTextLayout);
	layout->s = g_strdup(text);
	context = mkGenericPangoCairoContext();
	layout->graphemes = graphemes(layout->s, context);
	g_object_unref(context);
	layout->defaultFont = defaultFont->f;
	g_object_ref(layout->defaultFont);		// retain a copy
	uiDrawTextLayoutSetWidth(layout, width);
	layout->attrs = pango_attr_list_new();
	return layout;
}

void uiDrawFreeTextLayout(uiDrawTextLayout *layout)
{
	pango_attr_list_unref(layout->attrs);
	g_object_unref(layout->defaultFont);
	uiFree(layout->graphemes);
	g_free(layout->s);
	uiFree(layout);
}

void uiDrawTextLayoutSetWidth(uiDrawTextLayout *layout, double width)
{
	layout->width = width;
}

static void prepareLayout(uiDrawTextLayout *layout, PangoLayout *pl)
{
	PangoFontDescription *desc;
	int width;

	pango_layout_set_text(pl, layout->s, -1);

	// again, this makes a copy
	desc = pango_font_describe(layout->defaultFont);
	// this is safe; the description is copied
	pango_layout_set_font_description(pl, desc);
	pango_font_description_free(desc);

	width = cairoToPango(layout->width);
	if (layout->width < 0)
		width = -1;
	pango_layout_set_width(pl, width);

	pango_layout_set_attributes(pl, layout->attrs);
}

void uiDrawTextLayoutExtents(uiDrawTextLayout *layout, double *width, double *height)
{
	PangoContext *context;
	PangoLayout *pl;
	PangoRectangle logical;

	// in this case, the context is necessary to create the layout
	// the layout takes a ref on the context so we can unref it afterward
	context = mkGenericPangoCairoContext();
	pl = pango_layout_new(context);
	g_object_unref(context);
	prepareLayout(layout, pl);

	pango_layout_get_extents(pl, NULL, &logical);

	g_object_unref(pl);

	*width = pangoToCairo(logical.width);
	*height = pangoToCairo(logical.height);
}

void uiDrawText(uiDrawContext *c, double x, double y, uiDrawTextLayout *layout)
{
	PangoLayout *pl;

	pl = pango_cairo_create_layout(c->cr);
	prepareLayout(layout, pl);

	cairo_move_to(c->cr, x, y);
	pango_cairo_show_layout(c->cr, pl);

	g_object_unref(pl);
}

static void addAttr(uiDrawTextLayout *layout, PangoAttribute *attr, int startChar, int endChar)
{
	attr->start_index = layout->graphemes[startChar];
	attr->end_index = layout->graphemes[endChar];
	pango_attr_list_insert(layout->attrs, attr);
	// pango_attr_list_insert() takes attr; we don't free it
}

// these attributes are only supported on 1.38 and higher; we need to support 1.36
// use dynamic linking to make them work at least on newer systems
static PangoAttribute *(*newFGAlphaAttr)(guint16 alpha) = NULL;
static gboolean tried138 = FALSE;

// note that we treat any error as "the 1.38 symbols aren't there" (and don't care if dlclose() failed)
static void try138(void)
{
	void *handle;

	tried138 = TRUE;
	// dlsym() walks the dependency chain, so opening the current process should be sufficient
	handle = dlopen(NULL, RTLD_LAZY);
	if (handle == NULL)
		return;
	*((void **) (&newFGAlphaAttr)) = dlsym(handle, "pango_attr_foreground_alpha_new");
	dlclose(handle);
}

void uiDrawTextLayoutSetColor(uiDrawTextLayout *layout, int startChar, int endChar, double r, double g, double b, double a)
{
	PangoAttribute *attr;
	guint16 rr, gg, bb, aa;

	rr = (guint16) (r * 65535);
	gg = (guint16) (g * 65535);
	bb = (guint16) (b * 65535);
	aa = (guint16) (a * 65535);

	attr = pango_attr_foreground_new(rr, gg, bb);
	addAttr(layout, attr, startChar, endChar);

	if (!tried138)
		try138();
	// TODO what if aa == 0?
	if (newFGAlphaAttr != NULL) {
		attr = (*newFGAlphaAttr)(aa);
		addAttr(layout, attr, startChar, endChar);
	}
}