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Add explanatory comments about text size and vertical position.

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This commit is contained in:
ManoloFLTK 2022-04-29 16:34:47 +02:00
parent 1b513d3f00
commit 5341f0e45e
1 changed files with 5 additions and 1 deletions
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6
src/drivers/Cairo/Fl_Cairo_Graphics_Driver.cxx
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@ -1051,7 +1051,9 @@ int Fl_Cairo_Graphics_Driver::get_font_sizes(Fl_Font fnum, int*& sizep) {
Fl_Cairo_Font_Descriptor::Fl_Cairo_Font_Descriptor(const char* name, Fl_Fontsize size) : Fl_Font_Descriptor(name, size) {
char string[70];
strcpy(string, name);
sprintf(string + strlen(string), " %d", int(size * 0.75 + 0.5) ); // why reduce size?
// The factor of 0.75 below gives cairo-produced text the same size as
// Xft-produced text for the same FLTK font size.
sprintf(string + strlen(string), " %d", int(size * 0.75 + 0.5) );
fontref = pango_font_description_from_string(string);
width = NULL;
static PangoFontMap *def_font_map = pango_cairo_font_map_get_default(); // 1.10
@ -1122,6 +1124,8 @@ void Fl_Cairo_Graphics_Driver::font(Fl_Font fnum, Fl_Fontsize s) {
void Fl_Cairo_Graphics_Driver::draw(const char* str, int n, float x, float y) {
if (!n) return;
cairo_save(cairo_);
// The vertical offset size()/21. below vertically positions output text adequately
// relatively to the baseline (empirical observation).
cairo_translate(cairo_, x, y - height() + descent() + size()/21.);
pango_layout_set_text(pango_layout_, str, n);
pango_cairo_show_layout(cairo_, pango_layout_);