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#ifdef GL_OES_standard_derivatives
# extension GL_OES_standard_derivatives : enable
#else
# define use_fallback
#endif
uniform highp mat4 mvp;
uniform highp float fontScale;
uniform int textureWidth;
uniform int textureHeight;
uniform highp vec2 shadowOffset;
attribute highp vec3 vCoord;
attribute highp vec2 tCoord;
attribute highp vec4 textureBounds;
varying highp vec2 sampleCoord;
varying highp vec2 shadowSampleCoord;
varying highp vec4 normalizedTextureBounds;
#ifdef use_fallback
varying highp vec2 alphas;
highp float thresholdFunc(highp float scale)
{
highp float base = 0.5;
highp float baseDev = 0.065;
highp float devScaleMin = 0.15;
highp float devScaleMax = 0.3;
return base - ((clamp(scale, devScaleMin, devScaleMax) - devScaleMin)
/ (devScaleMax - devScaleMin) * -baseDev + baseDev);
}
highp float spreadFunc(highp float scale)
{
return 0.06 / scale;
}
highp vec2 alphaRange(highp float scale)
{
highp float base = thresholdFunc(scale);
highp float range = spreadFunc(scale);
highp float alphaMin = max(0.0, base - range);
highp float alphaMax = min(base + range, 1.0);
return vec2(alphaMin, alphaMax);
}
highp float determinantOfSubmatrix(highp mat4 m, int col0, int col1, int row0, int row1)
{
return m[col0][row0] * m[col1][row1] - m[col0][row1] * m[col1][row0];
}
highp float determinantOfSubmatrix(highp mat4 m, int col0, int col1, int col2,
int row0, int row1, int row2)
{
highp float det = m[col0][row0] * determinantOfSubmatrix(m, col1, col2, row1, row2);
det -= m[col1][row0] * determinantOfSubmatrix(m, col0, col2, row1, row2);
det += m[col2][row0] * determinantOfSubmatrix(m, col0, col1, row1, row2);
return det;
}
highp float determinant(highp mat4 m)
{
highp float det = m[0][0] * determinantOfSubmatrix(m, 1, 2, 3, 1, 2, 3);
det -= m[1][0] * determinantOfSubmatrix(m, 0, 2, 3, 1, 2, 3);
det += m[2][0] * determinantOfSubmatrix(m, 0, 1, 3, 1, 2, 3);
det -= m[3][0] * determinantOfSubmatrix(m, 0, 1, 2, 1, 2, 3);
return det;
}
#endif
void main()
{
#ifdef use_fallback
highp float scale = fontScale * pow(abs(determinant(mvp)), 1.0 / 3.0);
alphas = alphaRange(scale);
#endif
highp vec2 textureSizeMultiplier = vec2(1.0 / highp float(textureWidth),
1.0 / float(textureHeight));
sampleCoord = tCoord * textureSizeMultiplier;
shadowSampleCoord = (tCoord - shadowOffset) * textureSizeMultiplier;
normalizedTextureBounds = highp vec4(textureBounds.xy * textureSizeMultiplier,
textureBounds.zw * textureSizeMultiplier);
gl_Position = mvp * vec4(vCoord, 1.0);
}
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