GroveEngine/modules/BgfxRenderer/Passes/TextPass.cpp

#include "TextPass.h"
#include "../RHI/RHIDevice.h"
#include "../Frame/FramePacket.h"

namespace grove {

TextPass::TextPass(rhi::ShaderHandle shader)
    : m_shader(shader)
{
    m_glyphInstances.reserve(MAX_GLYPHS_PER_BATCH);
}

void TextPass::setup(rhi::IRHIDevice& device) {
    // Initialize default bitmap font
    if (!m_font.initDefault(device)) {
        // Font init failed - text rendering will be disabled
        return;
    }

    // Create quad vertex buffer (unit quad, instanced) - same as SpritePass
    float quadVertices[] = {
        // pos.x, pos.y, pos.z,    r,    g,    b,    a
        0.0f, 0.0f, 0.0f,    1.0f, 1.0f, 1.0f, 1.0f,  // bottom-left
        1.0f, 0.0f, 0.0f,    1.0f, 1.0f, 1.0f, 1.0f,  // bottom-right
        1.0f, 1.0f, 0.0f,    1.0f, 1.0f, 1.0f, 1.0f,  // top-right
        0.0f, 1.0f, 0.0f,    1.0f, 1.0f, 1.0f, 1.0f,  // top-left
    };

    rhi::BufferDesc vbDesc;
    vbDesc.type = rhi::BufferDesc::Vertex;
    vbDesc.size = sizeof(quadVertices);
    vbDesc.data = quadVertices;
    vbDesc.dynamic = false;
    vbDesc.layout = rhi::BufferDesc::PosColor;
    m_quadVB = device.createBuffer(vbDesc);

    // Create index buffer
    uint16_t quadIndices[] = {
        0, 1, 2,
        0, 2, 3
    };

    rhi::BufferDesc ibDesc;
    ibDesc.type = rhi::BufferDesc::Index;
    ibDesc.size = sizeof(quadIndices);
    ibDesc.data = quadIndices;
    ibDesc.dynamic = false;
    m_quadIB = device.createBuffer(ibDesc);

    // Create dynamic instance buffer for glyphs
    rhi::BufferDesc instDesc;
    instDesc.type = rhi::BufferDesc::Instance;
    instDesc.size = MAX_GLYPHS_PER_BATCH * sizeof(SpriteInstance);
    instDesc.data = nullptr;
    instDesc.dynamic = true;
    m_instanceBuffer = device.createBuffer(instDesc);

    // Create texture sampler uniform
    m_textureSampler = device.createUniform("s_texColor", 1);
}

void TextPass::shutdown(rhi::IRHIDevice& device) {
    device.destroy(m_quadVB);
    device.destroy(m_quadIB);
    device.destroy(m_instanceBuffer);
    device.destroy(m_textureSampler);
    m_font.shutdown(device);
}

void TextPass::execute(const FramePacket& frame, rhi::IRHIDevice& device, rhi::RHICommandBuffer& cmd) {
    if (frame.textCount == 0 || !m_font.isValid()) {
        return;
    }

    // Set render state for text (alpha blending, no depth)
    rhi::RenderState state;
    state.blend = rhi::BlendMode::Alpha;
    state.cull = rhi::CullMode::None;
    state.depthTest = false;
    state.depthWrite = false;
    cmd.setState(state);

    m_glyphInstances.clear();

    // Convert each TextCommand into glyph instances
    for (size_t i = 0; i < frame.textCount; ++i) {
        const TextCommand& textCmd = frame.texts[i];

        if (!textCmd.text) continue;

        // Calculate scale factor based on font size
        float scale = static_cast<float>(textCmd.fontSize) / m_font.getBaseSize();

        // Extract color components
        uint32_t color = textCmd.color;
        float r = static_cast<float>((color >> 24) & 0xFF) / 255.0f;
        float g = static_cast<float>((color >> 16) & 0xFF) / 255.0f;
        float b = static_cast<float>((color >> 8) & 0xFF) / 255.0f;
        float a = static_cast<float>(color & 0xFF) / 255.0f;

        float cursorX = textCmd.x;
        float cursorY = textCmd.y;

        const char* ptr = textCmd.text;
        while (*ptr) {
            char ch = *ptr++;

            // Handle newline
            if (ch == '\n') {
                cursorX = textCmd.x;
                cursorY += m_font.getLineHeight() * scale;
                continue;
            }

            const GlyphInfo& glyph = m_font.getGlyph(static_cast<uint8_t>(ch));

            // Create sprite instance for this glyph
            SpriteInstance inst;

            // Position (top-left of glyph)
            inst.x = cursorX + glyph.offsetX * scale;
            inst.y = cursorY + glyph.offsetY * scale;

            // Scale to glyph size
            inst.scaleX = glyph.width * scale;
            inst.scaleY = glyph.height * scale;

            // No rotation
            inst.rotation = 0.0f;

            // UVs from font atlas
            inst.u0 = glyph.u0;
            inst.v0 = glyph.v0;
            inst.u1 = glyph.u1;
            inst.v1 = glyph.v1;

            // Texture ID (font atlas = 0)
            inst.textureId = 0.0f;

            // Layer
            inst.layer = static_cast<float>(textCmd.layer);

            // Padding/reserved
            inst.padding0 = 0.0f;
            inst.reserved[0] = 0.0f;
            inst.reserved[1] = 0.0f;
            inst.reserved[2] = 0.0f;
            inst.reserved[3] = 0.0f;

            // Color
            inst.r = r;
            inst.g = g;
            inst.b = b;
            inst.a = a;

            m_glyphInstances.push_back(inst);

            // Advance cursor
            cursorX += glyph.advance * scale;

            // Check batch limit
            if (m_glyphInstances.size() >= MAX_GLYPHS_PER_BATCH) {
                // Flush current batch
                device.updateBuffer(m_instanceBuffer, m_glyphInstances.data(),
                                   static_cast<uint32_t>(m_glyphInstances.size() * sizeof(SpriteInstance)));

                cmd.setVertexBuffer(m_quadVB);
                cmd.setIndexBuffer(m_quadIB);
                cmd.setInstanceBuffer(m_instanceBuffer, 0, static_cast<uint32_t>(m_glyphInstances.size()));
                cmd.setTexture(0, m_font.getTexture(), m_textureSampler);
                cmd.drawInstanced(6, static_cast<uint32_t>(m_glyphInstances.size()));
                cmd.submit(0, m_shader, 0);

                m_glyphInstances.clear();
            }
        }
    }

    // Submit remaining glyphs
    if (!m_glyphInstances.empty()) {
        device.updateBuffer(m_instanceBuffer, m_glyphInstances.data(),
                           static_cast<uint32_t>(m_glyphInstances.size() * sizeof(SpriteInstance)));

        cmd.setVertexBuffer(m_quadVB);
        cmd.setIndexBuffer(m_quadIB);
        cmd.setInstanceBuffer(m_instanceBuffer, 0, static_cast<uint32_t>(m_glyphInstances.size()));
        cmd.setTexture(0, m_font.getTexture(), m_textureSampler);
        cmd.drawInstanced(6, static_cast<uint32_t>(m_glyphInstances.size()));
        cmd.submit(0, m_shader, 0);
    }
}

} // namespace grove