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Add explanatory comments about text handling by Fl_Cairo_Graphics_Driver.

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ManoloFLTK 2022-07-11 12:11:04 +02:00
parent 79ce6547ce
commit 2327ede74c
1 changed files with 7 additions and 2 deletions
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9
src/drivers/Cairo/Fl_Cairo_Graphics_Driver.cxx
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@ -1076,11 +1076,15 @@ Fl_Cairo_Font_Descriptor::Fl_Cairo_Font_Descriptor(const char* name, Fl_Fontsize
// The factor of 0.75 below gives cairo-produced text the same size as // The factor of 0.75 below gives cairo-produced text the same size as
// Xft-produced text for the same FLTK font size. // Xft-produced text for the same FLTK font size.
sprintf(string + strlen(string), " %d", int(size * 0.75 + 0.5) ); sprintf(string + strlen(string), " %d", int(size * 0.75 + 0.5) );
//A PangoFontDescription describes a font in an implementation-independent manner.
fontref = pango_font_description_from_string(string); fontref = pango_font_description_from_string(string);
width = NULL; width = NULL;
//A PangoFontMap represents the set of fonts available for a particular rendering system.
static PangoFontMap *def_font_map = pango_cairo_font_map_get_default(); // 1.10 static PangoFontMap *def_font_map = pango_cairo_font_map_get_default(); // 1.10
//A PangoContext stores global information used to control the itemization process.
static PangoContext *pango_context = pango_font_map_create_context(def_font_map); // 1.22 static PangoContext *pango_context = pango_font_map_create_context(def_font_map); // 1.22
static PangoLanguage *language = pango_language_get_default(); // 1.16 static PangoLanguage *language = pango_language_get_default(); // 1.16
//A PangoFontset represents a set of PangoFont to use when rendering text.
PangoFontset *fontset = pango_font_map_load_fontset(def_font_map, pango_context, fontref, language); PangoFontset *fontset = pango_font_map_load_fontset(def_font_map, pango_context, fontref, language);
PangoFontMetrics *metrics = pango_fontset_get_metrics(fontset); PangoFontMetrics *metrics = pango_fontset_get_metrics(fontset);
ascent = pango_font_metrics_get_ascent(metrics); ascent = pango_font_metrics_get_ascent(metrics);
@ -1092,7 +1096,7 @@ Fl_Cairo_Font_Descriptor::Fl_Cairo_Font_Descriptor(const char* name, Fl_Fontsize
#endif #endif
pango_font_metrics_unref(metrics); pango_font_metrics_unref(metrics);
g_object_unref(fontset); g_object_unref(fontset);
//fprintf(stderr, "[%s](%d) ascent=%d descent=%d\n", name, size, ascent, descent); //fprintf(stderr, "[%s](%d) ascent=%d descent=%d line_height=%d\n", name, size, ascent, descent, line_height);
} }
@ -1122,7 +1126,8 @@ static Fl_Font_Descriptor* find(Fl_Font fnum, Fl_Fontsize size) {
* The pango_layout_ object is created relatively to the unscaled cairo context (scale() == 1). * The pango_layout_ object is created relatively to the unscaled cairo context (scale() == 1).
* Therefore, the cairo context is unscaled before calling pango_cairo_create_layout(), * Therefore, the cairo context is unscaled before calling pango_cairo_create_layout(),
* pango_cairo_show_layout(), and pango_cairo_update_layout(). * pango_cairo_show_layout(), and pango_cairo_update_layout().
* This way, the pixel width of a drawn string equals the sum of the widths of its characters. * This way, the pixel width of a drawn string equals the sum of the widths of its
* characters, except when kerning occurs.
*/ */
void Fl_Cairo_Graphics_Driver::font(Fl_Font fnum, Fl_Fontsize s) { void Fl_Cairo_Graphics_Driver::font(Fl_Font fnum, Fl_Fontsize s) {
if (!font_descriptor()) fl_open_display(); if (!font_descriptor()) fl_open_display();