GLScaler.cc

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#include "GLScaler.hh"
#include "GLContext.hh"
#include "gl_vec.hh"
#include "strCat.hh"
#include "xrange.hh"
 
using std::string;
using namespace gl;
 
namespace openmsx {
 
GLScaler::GLScaler(const string& progName)
{
        for (auto i : xrange(2)) {
                auto header = tmpStrCat("#define SUPERIMPOSE ", char('0' + i), '\n');
                VertexShader   vShader(header, progName + ".vert");
                FragmentShader fShader(header, progName + ".frag");
                program[i].attach(vShader);
                program[i].attach(fShader);
                program[i].bindAttribLocation(0, "a_position");
                program[i].bindAttribLocation(1, "a_texCoord");
                program[i].link();
                program[i].activate();
                glUniform1i(program[i].getUniformLocation("tex"), 0);
                if (i == 1) {
                        glUniform1i(program[i].getUniformLocation("videoTex"), 1);
                }
                unifTexSize[i] = program[i].getUniformLocation("texSize");
                glUniformMatrix4fv(program[i].getUniformLocation("u_mvpMatrix"),
                                   1, GL_FALSE, &gl::context->pixelMvp[0][0]);
        }
}
 
void GLScaler::uploadBlock(
        unsigned /*srcStartY*/, unsigned /*srcEndY*/,
        unsigned /*lineWidth*/, FrameSource& /*paintFrame*/)
{
}
 
void GLScaler::setup(bool superImpose)
{
        int i = superImpose ? 1 : 0;
        program[i].activate();
}
 
void GLScaler::execute(
        ColorTexture& src, ColorTexture* superImpose,
        unsigned srcStartY, unsigned srcEndY, unsigned srcWidth,
        unsigned dstStartY, unsigned dstEndY, unsigned dstWidth,
        unsigned logSrcHeight, bool textureFromZero)
{
        if (superImpose) {
                glActiveTexture(GL_TEXTURE1);
                superImpose->bind();
                glActiveTexture(GL_TEXTURE0);
        }
        int i = superImpose ? 1 : 0;
        glUniform3f(unifTexSize[i], srcWidth, src.getHeight(), logSrcHeight);
 
        src.bind();
        // Note: hShift is pre-divided by srcWidth, while vShift will be divided
        //       by srcHeight later on.
        // Note: The coordinate is put just past zero, to avoid fract() in the
        //       fragment shader to wrap around on rounding errors.
        constexpr float BIAS = 0.001f;
        float samplePos = (textureFromZero ? 0.5f : 0.0f) + BIAS;
        float hShift = samplePos / dstWidth;
        float yRatio = float(srcEndY - srcStartY) / float(dstEndY - dstStartY);
        float vShift = samplePos * yRatio;
 
        // vertex positions
        vec2 pos[4] = {
                vec2(       0, dstStartY),
                vec2(dstWidth, dstStartY),
                vec2(dstWidth, dstEndY  ),
                vec2(       0, dstEndY  ),
        };
        // texture coordinates, X-coord shared, Y-coord separate for tex0 and tex1
        float tex0StartY = float(srcStartY + vShift) / src.getHeight();
        float tex0EndY   = float(srcEndY   + vShift) / src.getHeight();
        float tex1StartY = float(srcStartY + vShift) / logSrcHeight;
        float tex1EndY   = float(srcEndY   + vShift) / logSrcHeight;
        vec3 tex[4] = {
                vec3(0.0f + hShift, tex0StartY, tex1StartY),
                vec3(1.0f + hShift, tex0StartY, tex1StartY),
                vec3(1.0f + hShift, tex0EndY  , tex1EndY  ),
                vec3(0.0f + hShift, tex0EndY  , tex1EndY  ),
        };
 
        glBindBuffer(GL_ARRAY_BUFFER, vbo[0].get());
        glBufferData(GL_ARRAY_BUFFER, sizeof(pos), pos, GL_STREAM_DRAW);
        glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, 0, nullptr);
 
        glBindBuffer(GL_ARRAY_BUFFER, vbo[1].get());
        glBufferData(GL_ARRAY_BUFFER, sizeof(tex), tex, GL_STREAM_DRAW);
        glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 0, nullptr);
 
        glEnableVertexAttribArray(0);
        glEnableVertexAttribArray(1);
 
        glDrawArrays(GL_TRIANGLE_FAN, 0, 4);
 
        glDisableVertexAttribArray(1);
        glDisableVertexAttribArray(0);
        glBindBuffer(GL_ARRAY_BUFFER, 0);
}
 
} // namespace openmsx