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I'm trying to render some text using FreeType and OpenGL:

text = "fghjRT-123VWYUGHJ$@%"

And have two questions:

1. Why there are so weird spaces between letters? (what wrong with advance?)


2. How to calculate top position (or origin position)? (there are some space between yellow border and characters. I want to attach it to the top border)

My render code:

/* top left position on screen to render text (yellow border) */
Vector<2> pos = params.rect.left_top();

/* adjust to bottom (how to get correct origin position?) */
pos.y() += font->char_size();

for (char ch : params.text)

 /* contains info after freetype FT_LoadGlyph */
 FontChar const* char_info = font->find_char(ch);

 RectF char_rect(
 pos - char_info->bearing(), /* left, top */
 char_info->glyph_rect().size() /* width, height */
 );

 /* convert screen coordinates to OpenGL coordinates */
 RectF dr = calc_coord(m_screen_size, char_rect);

 /* pack position of glyph and it's texture from bitmap
 * into one sequence of data
 */
 Vector<16> spr_coords = pack_spr_info(dr, char_info->rect());

 m_sprite_buffer.push_back(spr_coords);

 /* move pen by advance */
 pos.x() += char_info->advance();

Piece of my glyph loading code:

FT_GlyphSlot slot = face->glyph;

char_info->bearing() = 
 slot->metrics.horiBearingX / 64.0f,
 slot->metrics.horiBearingY / 64.0f
;

char_info->glyph_rect() = 
 slot->metrics.horiBearingX / 64.0f, /* left */
 slot->metrics.horiBearingY / 64.0f, /* top */
 slot->metrics.width / 64.0f, /* width */
 slot->metrics.height / 64.0f /* height */
;

char_info->advance() = slot->metrics.horiAdvance / 64.0f;

Ok, I found out the answer by myself.

There are was a mistake in my calculation for char_rect position. Correct way:

RectF char_rect(
 pos.x() + char_info->bearing().x(), /* left */
 pos.y() - char_info->bearing().y(), /* top */
 char_info->glyph_rect().size() /* width, height */
);

And the way to find baseline(origin) adjusted from top border:

Vector<2> pos = params.rect.left_top();
pos.y() += font->ascend(); /* move pen down on the screen */

Where:

FT_Face face = ...;
font->ascend() = face->ascender / 32;