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Added auto hinting compensation to fix too wide gaps between small glyphs #1746

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merged 6 commits into from
Feb 10, 2021
Merged

Added auto hinting compensation to fix too wide gaps between small glyphs #1746

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1772846
Added glyph position compensation after autohinting
oomek Mar 8, 2020
1f9b3a3
Fix for fonts with no kerning tables
oomek Mar 8, 2020
2fb9bf2
Fixed unintialized variable
oomek Jan 20, 2021
d2406fc
Fixed unnecessary loadGlyph() calls
oomek Jan 20, 2021
cde120b
Fixed formating mistake
oomek Jan 21, 2021
ad734b2
Fixed naming convention mistakes
oomek Jan 21, 2021
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2 changes: 1 addition & 1 deletion include/SFML/Graphics/Font.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -217,7 +217,7 @@ class SFML_GRAPHICS_API Font
/// \return Kerning value for \a first and \a second, in pixels
///
////////////////////////////////////////////////////////////
float getKerning(Uint32 first, Uint32 second, unsigned int characterSize) const;
float getKerning(Uint32 first, Uint32 second, unsigned int characterSize, bool bold = false) const;

////////////////////////////////////////////////////////////
/// \brief Get the line spacing
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2 changes: 2 additions & 0 deletions include/SFML/Graphics/Glyph.hpp
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Expand Up @@ -52,6 +52,8 @@ class SFML_GRAPHICS_API Glyph
// Member data
////////////////////////////////////////////////////////////
float advance; //!< Offset to move horizontally to the next character
int lsb_delta; //!< Left offset after forced autohint. Internally used by getKerning()
int rsb_delta; //!< Right offset after forced autohint. Internally used by getKerning()
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FloatRect bounds; //!< Bounding rectangle of the glyph, in coordinates relative to the baseline
IntRect textureRect; //!< Texture coordinates of the glyph inside the font's texture
};
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21 changes: 16 additions & 5 deletions src/SFML/Graphics/Font.cpp
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Expand Up @@ -40,6 +40,7 @@
#include FT_STROKER_H
#include <cstdlib>
#include <cstring>
#include <cmath>


namespace
Expand Down Expand Up @@ -375,30 +376,37 @@ bool Font::hasGlyph(Uint32 codePoint) const


////////////////////////////////////////////////////////////
float Font::getKerning(Uint32 first, Uint32 second, unsigned int characterSize) const
float Font::getKerning(Uint32 first, Uint32 second, unsigned int characterSize, bool bold) const
{
// Special case where first or second is 0 (null character)
if (first == 0 || second == 0)
return 0.f;

FT_Face face = static_cast<FT_Face>(m_face);

if (face && FT_HAS_KERNING(face) && setCurrentSize(characterSize))
if (face && setCurrentSize(characterSize))
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{
// Convert the characters to indices
FT_UInt index1 = FT_Get_Char_Index(face, first);
FT_UInt index2 = FT_Get_Char_Index(face, second);

// Retrieve position compensation deltas generated by FT_LOAD_FORCE_AUTOHINT flag
float firstRsbDelta = getGlyph(first, characterSize, bold).rsb_delta;
float secondLsbDelta = getGlyph(second, characterSize, bold).lsb_delta;

// Get the kerning vector
FT_Vector kerning;
FT_Get_Kerning(face, index1, index2, FT_KERNING_DEFAULT, &kerning);
kerning.x = kerning.y = 0;
if( FT_HAS_KERNING(face))
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FT_Get_Kerning(face, index1, index2, FT_KERNING_UNFITTED, &kerning);

// X advance is already in pixels for bitmap fonts
if (!FT_IS_SCALABLE(face))
return static_cast<float>(kerning.x);

// Return the X advance
return static_cast<float>(kerning.x) / static_cast<float>(1 << 6);
// Combine kerning with compensation deltas and return the X advance
// Flooring is required as we use FT_KERNING_UNFITTED flag which is not quantized in 64 based grid
return std::floor((secondLsbDelta - firstRsbDelta + static_cast<float>(kerning.x) + 32) / static_cast<float>(1 << 6));
}
else
{
Expand Down Expand Up @@ -624,6 +632,9 @@ Glyph Font::loadGlyph(Uint32 codePoint, unsigned int characterSize, bool bold, f
if (bold)
glyph.advance += static_cast<float>(weight) / static_cast<float>(1 << 6);

glyph.lsb_delta = face->glyph->lsb_delta;
glyph.rsb_delta = face->glyph->rsb_delta;

int width = bitmap.width;
int height = bitmap.rows;

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4 changes: 2 additions & 2 deletions src/SFML/Graphics/Text.cpp
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Expand Up @@ -332,7 +332,7 @@ Vector2f Text::findCharacterPos(std::size_t index) const
Uint32 curChar = m_string[i];

// Apply the kerning offset
position.x += m_font->getKerning(prevChar, curChar, m_characterSize);
position.x += m_font->getKerning(prevChar, curChar, m_characterSize, isBold);
prevChar = curChar;

// Handle special characters
Expand Down Expand Up @@ -451,7 +451,7 @@ void Text::ensureGeometryUpdate() const
continue;

// Apply the kerning offset
x += m_font->getKerning(prevChar, curChar, m_characterSize);
x += m_font->getKerning(prevChar, curChar, m_characterSize, isBold);

// If we're using the underlined style and there's a new line, draw a line
if (isUnderlined && (curChar == L'\n' && prevChar != L'\n'))
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