MapLibreParticleLab/src/renderer/painter_text.cpp

#include <llmr/renderer/painter.hpp>
#include <llmr/renderer/text_bucket.hpp>
#include <llmr/style/style_layer.hpp>
#include <llmr/map/map.hpp>
#include <cmath>

using namespace llmr;

void Painter::renderText(TextBucket& bucket, std::shared_ptr<StyleLayer> layer_desc, const Tile::ID& id) {
    // Abort early.
    if (pass == Opaque) return;
    if (!bucket.hasData()) return;

    const TextProperties &properties = layer_desc->getProperties<TextProperties>();

    mat4 exMatrix;
    matrix::copy(exMatrix, projMatrix);
    if (bucket.properties.path == TextPathType::Curve) {
        matrix::rotate_z(exMatrix, exMatrix, map.getState().getAngle());
    }

    // If layerStyle.size > bucket.info.fontSize then labels may collide
    float fontSize = std::fmin(properties.size, bucket.properties.max_size);
    matrix::scale(exMatrix, exMatrix, fontSize / 24.0f, fontSize / 24.0f, 1.0f);

// TODO: figure out whether we actually need to account for this while painting; we might already have
// done this during label placement.
//    const mat4 &vtxMatrix = translatedMatrix(properties.translate, id, properties.translateAnchor);

    useProgram(textShader->program);
    textShader->setMatrix(matrix);
    textShader->setExtrudeMatrix(exMatrix);

    GlyphAtlas &glyphAtlas = *map.getGlyphAtlas();
    glyphAtlas.bind();
    textShader->setTextureSize({{static_cast<float>(glyphAtlas.width),
                                 static_cast<float>(glyphAtlas.height)}});

    // Convert the -pi..pi to an int8 range.
    float angle = std::round((map.getState().getAngle()) / M_PI * 128);

    // adjust min/max zooms for variable font sies
    float zoomAdjust = log(fontSize / bucket.properties.max_size) / log(2);

    textShader->setAngle((int32_t)(angle + 256) % 256);
    textShader->setFlip(bucket.properties.path == TextPathType::Curve ? 1 : 0);
    textShader->setZoom((map.getState().getNormalizedZoom() - zoomAdjust) * 10); // current zoom level

    // Label fading
    const timestamp duration = 300_milliseconds;
    const timestamp currentTime = util::now();

    std::deque<FrameSnapshot> &history = frameHistory.history;

    // Remove frames until only one is outside the duration, or until there are only three
    while (history.size() > 3 && history[1].t + duration < currentTime) {
        history.pop_front();
    }

    if (history[1].t + duration < currentTime) {
        history[0].z = history[1].z;
    }

    assert("there should never be less than three frames in the history" && (history.size() >= 3));

    // Find the range of zoom levels we want to fade between
    float startingZ = history.front().z;
    const FrameSnapshot lastFrame = history.back();
    float endingZ = lastFrame.z;
    float lowZ = std::fmin(startingZ, endingZ);
    float highZ = std::fmax(startingZ, endingZ);

    // Calculate the speed of zooming, and how far it would zoom in terms of zoom levels in one duration
    float zoomDiff = endingZ - history[1].z,
        timeDiff = lastFrame.t - history[1].t;
    float fadedist = zoomDiff / (timeDiff / duration);

#if defined(DEBUG)
    if (std::isnan(fadedist)) fprintf(stderr, "fadedist should never be NaN\n");
#endif

    // At end of a zoom when the zoom stops changing continue pretending to zoom at that speed
    // bump is how much farther it would have been if it had continued zooming at the same rate
    float bump = (currentTime - lastFrame.t) / duration * fadedist;

    textShader->setFadeDist(fadedist * 10);
    textShader->setMinFadeZoom(std::floor(lowZ * 10));
    textShader->setMaxFadeZoom(std::floor(highZ * 10));
    textShader->setFadeZoom((map.getState().getNormalizedZoom() + bump) * 10);

    // We're drawing in the translucent pass which is bottom-to-top, so we need
    // to draw the halo first.
    if (properties.halo_color[3] > 0.0f) {
        // TODO: Get rid of the 2.4 magic value. It is currently 24 / 10, with 24 being the font size
        // of the SDF glyphs.
        textShader->setGamma(properties.halo_blur * 2.4f / fontSize / map.getState().getPixelRatio());
        if (properties.opacity < 1.0f) {
            Color color = properties.halo_color;
            color[0] *= properties.opacity;
            color[1] *= properties.opacity;
            color[2] *= properties.opacity;
            color[3] *= properties.opacity;
            textShader->setColor(color);
        } else {
            textShader->setColor(properties.halo_color);
        }
        textShader->setBuffer(properties.halo_width);
        glDepthRange(strata, 1.0f);
        bucket.drawGlyphs(*textShader);
    }

    if (properties.color[3] > 0.0f) {
        // Then, we draw the text over the halo
        // TODO: Get rid of the 2.4 magic value. It is currently 24 / 10, with 24 being the font size
        // of the SDF glyphs.
        textShader->setGamma(2.4f / fontSize / map.getState().getPixelRatio());
        if (properties.opacity < 1.0f) {
            Color color = properties.color;
            color[0] *= properties.opacity;
            color[1] *= properties.opacity;
            color[2] *= properties.opacity;
            color[3] *= properties.opacity;
            textShader->setColor(color);
        } else {
            textShader->setColor(properties.color);
        }
        textShader->setBuffer((256.0f - 64.0f) / 256.0f);
        glDepthRange(strata + strata_epsilon, 1.0f);
        bucket.drawGlyphs(*textShader);
    }
}